Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session EA: Conference Experience for Undergraduates Poster Session (2:00-4:00PM) |
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Chair: Warren Rogers, Westmont College Room: Plaza Arbor |
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EA.00001: Higher-order Corrections in the Proton Radius Extraction Karl Medina Elastic electron-proton scattering is the primary technique used to extract proton electric and magnetic form factors. These form factors describe the electric charge and magnetization distributions inside the proton and at low energies allow for the extraction of the root-mean-square charge radius of the proton. Such extractions of the charge radius disagree with the value obtained using an alternate method involving muonic hydrogen. Corrections beyond the single-photon exchange model of the scattering are important in determining the form factors. The effect of the Coulomb interaction between the electron and proton has been estimated in the 2$^{nd}$ Born approximation, corresponding to the effect of a second soft photon exchange, but higher order effects are assumed to be negligible. We investigated the potential impact of higher order terms using a semi-classical calculation of the effect, which may become more important at extremely low energies. We find a correction that is small but not negligible, and which has a very different angular dependence from the previously-evaluated corrections. This examination suggests that the higher-order correction has the potential to impact the extraction of the proton's radius, pointing to the need for a more complete evaluation of the corrections. [Preview Abstract] |
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EA.00002: Exploration of Three-Body Decay using Jacobian Coordinates Mark Hoffmann, Kyle Williams, Nathan Frank Experiments on neutron-rich nuclei may result in the emission of one or more neutrons. Attempting to find a clear signature of two-neutron decay is possible in some systems, but more difficult in others. The goal in a two-neutron analysis is improving the algorithm for biasing toward true two-neutron events while removing one-neutron scatter. A continuing challenge is to find a better method to do this task. A contaminant beam of 32Mg produced isotopes of 30Na and 29Na with possible two-neutron coincidences during an experiment using the Sweeper-MoNA facility at the National Superconducting Cyclotron Laboratory (NSCL), located at Michigan State University. We analyzed these two isotopes by using Jacobian coordinate systems and comparing to typical gates that the research collaboration has used previously. The exploration of physical parameters to Jacobian coordinates will be presented. [Preview Abstract] |
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EA.00003: Active Target Simulation Nathan Smith, Peter Draznik, Nathan Frank We have simulated an existing experimental design to determine the resolution improvement upon energy measurements of neutron unbound nuclei. A number of experiments of this type have been performed at the National Superconducting Cyclotron Laboratory (NSCL), located at Michigan State University. An excited nucleus is typically produced with a radioactive beam interacting with a passive Beryllium target. Many different nuclei are produced in experiment, each of which immediately decays into a charged particle and neutron. The charged particles are detected and the neutrons interact in scintillation detectors such as the Modular Neutron Array (MoNA) and Large Multi-Institutional Scintillation Array (LISA). In our simulation, we have constructed an active target that provides additional information such that the point of nuclear interaction within the target may be determined. This information improves the resolution in decay energy measurements of neutron unbound isotopes. This presentation will cover some aspects of the simulation process, as well as showing some of the results that demonstrate the simulated improvement over a passive target. [Preview Abstract] |
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EA.00004: Analysis of J/Psi Production in Run 11 pp500 at PHENIX Louis Garcia Using the data from the most recent run of RHIC with proton-proton collisions at $\sqrt{500}$ GeV, we plan to measure the J/Psi cross-section in the forward direction with rapidity ($1.2 < |y| < 2.2$). By measuring dimuon pairs and then calculating the invariant mass spectrum, we will obtain a peak for the J/Psi at about 3.1 GeV/c. Currently, we are determining cuts based on the particles' flight path through the detectors to eliminate the background of non-muons within the dimuon continuum. After, we will run GEANT simulations of the detector and apply the same cuts to determine their efficiency. Finally, we will be able to apply these simulations to the real data and calculate the yield of the J/Psi for this run. The measurements of the J/Psi yield in this run are important for comparing against Au-Cu collisions where the J/Psi yield is thought to be suppressed due to color screening in the QGP. For my poster, I will include the background signals and their dependence on the cuts, along with their efficiency at reconstructing embedded simulation J/Psis. [Preview Abstract] |
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EA.00005: Calibrating the Muon Piston Calorimeter (MPC) MariAnne Skolnik The Muon Piston Calorimeter (MPC) is a subsystem of the PHENIX detector. The MPC, an electromagnetic calorimeter, is effective at measuring the energy of photons and electrons produced from collisions at the Relativistic Heavy Ion Collider (RHIC). The MPC outputs a voltage signal that we then convert into an energy reading. One common way to calibrate electromagnetic calorimeters is to use~photons from $\pi ^{0}$ decays. Since many of the photons that enter the detector are the result of natural pion decay, we can pair up the photons and create $\pi ^{0}$ candidates. We then plot their masses tower by tower and with the correct cuts a mass peak will appear close to the position predicted by the simulation PISA of the PHENIX detector. Then, we relate the mass peaks from the measured data to mass peaks from simulated data to adjust the gains. Once the MPC is calibrated we can use it to study Au+Au collisions. Previously, the detector has been used to study spin physics using data collected from p+p collisions, and cold nuclear matter effects using d+Au collisions. These new calibrations will allow us to measure new global variables such as transverse energy in both the forward and backward kinematic regions, 3.1$< \quad \vert \eta \vert \quad <$ 3.9. [Preview Abstract] |
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EA.00006: Efficiency Studies of the PHENIX Resistive Plate Chambers Aric Tate At Brookhaven National Laboratory the PHENIX experiment on the Relativistic Heavy Ion Collider (RHIC) studies polarized p+p collisions in an effort to better understand the contribution of sea quarks to the spin structure of the proton. To enable PHENIX to measure these contributions a trigger upgrade was needed to improve the ability of the data acquisition system to select single high transverse momentum muon events. A key component to the trigger upgrade was the addition of two stations of Resistive Plate Chambers (RPCs) in each muon arm. These chambers were installed and fully implemented prior to the last RHIC run. To ensure that the RPCs will continue to perform efficiently many tests have been done, both on the installed chambers and spare chambers on a cosmic test stand. An efficiency versus high voltage test was run with the cosmic stand as well as an efficiency versus threshold test to try and maximize efficiency without gaining noise. A noise versus threshold scan helped determine at what threshold the RPCs best perform. These tests help us to operate the RPCs at a high efficiency and low noise manner. The analysis and results of these tests will be presented. ~~~~~~~ [Preview Abstract] |
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EA.00007: Simulations for the PHENIX Muon Piston Calorimeter Measurement of Transverse Energy Christopher Zumberge The PHENIX detector's Muon Piston Calorimeter measures the energies of photons (most of which are the products of pion decay) in the collisions of particles at the Relativistic Heavy Ion Collider (RHIC). The data acquired from the collisions of gold ions at $\sqrt{s_{NN}}=200$~GeV will be used to measure the transverse energy over the kinematic acceptance of the detector. Corrections for the detector's hadronic response are needed to complete a measurement of the transverse energy and estimate systematic error. The PHENIX Integrated Simulation Application (PISA) is a software package that integrates both a GEANT3 simulation of the entire PHENIX detector and an event generator. In this case HIJING is being used as the event generator. Progress on the production of these simulations will be reported. [Preview Abstract] |
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EA.00008: sPHENIX Forward PYTHIA Jet Studies Lucas Flores sPHENIX is a proposed upgrade to the PHENIX detector at RHIC. It is a forward spectrometer covering the rapidity range $1 < ? < 4$, which is important for measuring hadrons, electrons, photons, and jets. Before completion, simulation studies will be made to determine if the intended location of the upgrade will allow for the measurement of jet events in both pp and heavy ion collisions. These studies incorporate a specific version of the PYTHIA event generator designed for PHENIX. Jet reconstruction is preformed on the simulated events in the ? interval of interest, and the transverse momentum of the jets is studied. [Preview Abstract] |
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EA.00009: Transverse Energy at RHIC in the forward/backward direction with the PHENIX Muon Piston Calorimeter Benjamin Schweid Progress in the measurement of transverse energy from RHIC Au+Au collisions at $\sqrt{s_{NN}}=200$~GeV will be reported. This measurement will be taken in the forward/backward directions. The pseudo-rapidity coverage of the PHENIX Muon Piston Calorimeter (MPC), an electromagnetic calorimeter, is $3.1<|\eta|<3.8$. Measurement of the transverse energy over this kinematic range will differ from that at mid-rapidity in that the baryon density is much higher. Ultimately, analysis of transverse energy fluctuations as a function of center of mass energy might help signal the existence of a critical point in the phase diagram of nuclear matter. [Preview Abstract] |
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EA.00010: Performance of the PHENIX Forward Trigger Resistive Plate Chambers Ramsey Towell The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory studies polarized proton-proton collisions to learn more about the spin structure of the proton. PHENIX's data acquisition system is able to record several thousand collisions each second. However, millions of collisions occur every second. So a forward trigger is required to select rare events of interest. To study the sea quark contribution to the spin structure of the proton, the interesting events are single high transverse momentum muons.~The muon trigger upgrade includes two sets of Resistive Plate Chambers (RPCs) in both muon arms.~Run 12 was the first run that had all of the RPCs installed. Now that the run is over, the performance of the RPCs under data-taking conditions can be analyzed. Initial studies indicate that the chambers performed extremely well. However, there were some noisy and dead channels identified. This careful systematic analysis has assisted in locating those channels so that they can be repaired before the next RHIC run. Results of the analyzed data showing the noisy and dead channels will be presented. [Preview Abstract] |
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EA.00011: Temperature study on PHENIX Resistive Plate Chamber 1 Mathew Solomon The PHENIX collaboration is investigating the results of polarized proton + proton collisions generated by the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Studying these collisions will help gain perspective on the overall spin structure of the proton. PHENIX has developed a trigger upgrade for the muon arms to select single high transverse momentum (p{\_}T) muons. A major part of this upgrade is the inclusion of 2 stations of Resistive Plate Chambers (RPC) in each arm of PHENIX. The RPCs are constructed with two gas gaps made of Bakelite and coated with linseed oil, which closely follows the CMS design. These materials are known to be sensitive to high temperatures and within PHENIX a station of RPC's are installed between two large magnets, which could cause the temperature environment to elevate. In order to gain a better understanding of the temperature of the gas gaps, we will compare the externally monitored temperature data from Run-12 to the temperatures acquired from a dedicated temperature profile study. Overall this will help the collaboration operate the RPCs in a manner that will improve their performance and extend their lifetime. [Preview Abstract] |
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EA.00012: ABSTRACT MOVED TO FC.00009 |
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EA.00013: Photon-Refracting Aerogel Daniel Rice A threshold aerogel Cherenkov detector is being constructed at CUA to allow for the study of kaons in experiments at the Jefferson Laboratory. These subatomic particles move faster than light through the aerogel material, emitting Cherenkov radiation. Photomultiplier Tubes (PMTs) convert the photons from the Cherenkov radiation into electrons and multiply the electrons sufficiently to get a readable electronic signal, which can be analyzed. An important part of a threshold aerogel Cherenkov detector is its use of aerogel material of several refractive indices to cover the full dynamic range over which one wants to detect the particles of interest (in this case the kaon). Uniform coverage in refractive index is important as the location of the incoming particle will not be constant throughout the testing. In addition to testing for uniform coverage, we must also verify these refractive indices to ensure that the particles we are detecting are in fact kaons. The last test on the aerogel that needs to be performed is the measurement of transparency. Although aerogel is highly transparent, it is still necessary to find the amount of light being absorbed, reflected, or scattered versus how much will actually be measured by the PMTs used. [Preview Abstract] |
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EA.00014: Aerogel Cherenkov Detector Prototype Experiments Laura Rothgeb Studying the additional flavor degree of freedom in the H(e,e'K$^{+})$ and H(e,e'K$^{+})$ reactions allows for exceptional insight into the transition from hadronic to partonic degrees of freedom in exclusive processes, specifically the reaction mechanism underlying strangeness production. To carry out strangeness physics experiments, the Nuclear Physics Group at Catholic University of America is building an Aerogel Cherenkov detector to be used at Jefferson Lab. To study the detector performance a prototype was built and experiments were carried out using several component configurations. One important aspect of the prototype is the photocathode uniformity of the large diameter photomultiplier tube: its effect on the detector is best studied with the prototype using the aerogel material and reflective detector box for Cerenkov photons in diffusive reflections. Another important aspect of the detector performance, therefore, is the effect of different reflective materials for the detector box wall lining. In this presentation I will present the results from these tests of the effect of the photomultiplier tubes and reflective surfaces on overall detector performance, as well as the modeling of the detector in the GEANT4 framework. [Preview Abstract] |
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EA.00015: Analysis of Jet Substructure to Identify Jets in Heavy Ion Collisions R.C. Malone Parton jets provide an excellent probe to study the properties of the quark gluon plasma. However, they are difficult to identify among the many particles created in a heavy ion collision. We seek to characterize the substructure of parton jets in order to distinguish these jets from showers of background particles. Jet characteristics and substructure are studied in the vacuum (p-p) case using a PYTHIA simulation. A thermal bath of background particles is then introduced to the simulation and the analysis is repeated. By studying differences between hard jets and jets composed mainly of background particles, hard jets are distinguished from soft background jets based on their substructure. The simulation is used to study the effectiveness of this method of jet identification. We then investigate if this method can be successfully applied to data from heavy-ion collisions measured by the ALICE experiment at the LHC. [Preview Abstract] |
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EA.00016: Recent analysis of a new class of proton correlation functions in Lattice QCD Mark Mace, Kostas Orginos Lattice QCD calculations have become increasingly more accurate due in large part to the refinement of the computational methods needed to calculate the correlation functions required for phenomenology. In this study, we analyze a new class of lattice QCD correlation functions for the proton in order for us to better calculate the ground and excited state masses. This new class is derived from a known class that works well for small volume. Previously efficiency deteriorates for larger volumes. For this reason we focus our study on the volume dependence of noise and the contamination from excited states. Our results indicate as the volume grows, noise is reduced, i.e. our method behaves better as volume grows (in our volume range). In addition the contamination from excited states becomes smaller as volume grows. Overall this method seems to scale well. [Preview Abstract] |
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EA.00017: The Qweak Experiment: Tracking Analysis Quinn Hailes The Qweak experiment is a search for new physics at the TeV scale through a measurement of the proton's weak charge, currently being conducted at Jefferson Lab. The experiment is a high precision measurement of the parity-violating asymmetry in elastic scattering at Q2 = 0.026GeV2 (Q2 = 4EE$'$sin2($\theta/2$)) using polarized electron beam on aluminum and liquid hydrogen targets. These polarized electrons will scatter universally but the forward angles are only analyzed due to the position of the detectors. Any deviation from the Standard Model would signal new physics. The Qweak group aims to carry out the first precision measurement of the weak charge: Q = 1 - 4sin2w. I have produced scripts, which provide knowledge on various kinematic variables: beam energy, scattering angle, scattering vertex, and momentum. These studies can determine whether the data analyzer is working properly and even corrects for different errors. Ultimately these scripts will analyze each and every run to determine a value for Q2. [Preview Abstract] |
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EA.00018: Correcting for Beam Effects in the Qweak Experiment David Specht Qweak is an experiment at Jefferson Lab to identify phenomena beyond the standard model by calculating the weak charge of the proton. A ring of quartz detectors measures the parity-violating asymmetry of polarized electronsS scattered against a liquid hydrogen target, a value proportional to the weak charge. The purpose of this research is to correct for effects of beam properties on measured asymmetries which affect the calculated weak charge. The beam slope, position, charge, and energy are known to affect measured asymmetries and are corrected for in a first pass through the data with linear regression. In a second pass, remaining correlations and associated errors are calculated between the corrected data and other beam properties, including linephase (phase of the AC power supply), beam position monitors, an additional quartz detector and bare photomultiplier tubes sensitive to backgrounds, raster position (where the beam is ``painted'' onto the target) and luminosity detectors. The corrected data are still correlated with some other beam properties, including luminosity, background detectors, and beam position monitors that are sensitive to beam energy. We are uncertain why these correlations remain and seek to determine if they should be the subject of future corrections. [Preview Abstract] |
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EA.00019: Particle Identification for Electron-Positron Pairs in Ultraperipheral Collisions at RHIC Jarrod K. Bang, J. Seger At RHIC (Relativistic Heavy Ion Collider), two atomic nuclei are accelerated to near the speed of light in opposite directions. Ultraperipheral collisions occur when these two nuclei interact in such a way that they have an impact parameter greater than twice their nuclear radius. While the nuclei continue along the beam line, particles are produced from the intense electromagnetic interaction. Studying direct electron-positron pairs can aid in understanding the quantum electrodynamics involved due to these intense fields. This talk will discuss different particle identification methods used by STAR in relation to electron-positron pair production in ultraperipheral interactions. [Preview Abstract] |
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EA.00020: Phi Meson Photoproduction in Ultraperipheral Collisions at RHIC Barak Gruberg We are studying ultraperipheral gold-gold collisions at 200 GeV/c collected with the STAR (Solenoidal Tracker at RHIC) detector. In these collisions, where the impact parameter is greater than twice the radius of the gold nuclei, the interactions are electromagnetic. We focus on $\phi$ meson photoproduction through its decay channel into $K^{+}$ and $ K^{-}$ mesons. Coherent photoproduction results in $\phi$ mesons with transverse momentum less than 0.15 MeV/c. However, the decay products from these are not within STAR's acceptance. $\phi$ mesons with momentum greater than 0.15 MeV/c, whose decay products are within STAR's acceptance, may come from incoherent photoproduction. We investigate the possibility of experimentally separating $\phi$ mesons produced from incoherent photoproduction from those produced in hadronic interactions. We compare our data with STARlight, a Monte Carlo simulator of the physics of ultraperipheral collisions. [Preview Abstract] |
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EA.00021: Constraints on Universal Extra Dimensions Theory from Dark Matter Direct Detection Christopher Lefky, Gintaras Duda The theory of Universal Extra Dimenions (UED) contains an excellent dark matter candidate, the B$^{(1)}$, which is the lightest Kaluza-Klein excitation/particle (LKP). Constraints can be placed on the two most fundamental parameters of UED Theory, R (the size of the extra-dimension) and $\Lambda $ (the cutoff scale of the theory) using recent dark matter direct detection results. Recent limits from the XENON experiment are used to calculate a generic WIMP-nucleon cross section for a range of masses. Using UED phenomenology, these cross section limits can yield limits on the mass splitting, $\Delta $ (the ratio of the Lightest Kaluza-Klein particle (LKP) to the Lightest Kaluza-Klein quark (LKQ)). This project builds upon previous work where constraints were placed on R and $\Lambda $ for fixed values of the mass splitting. The poster presentation will address constraints on the fundamental UED parameters as a function of mass splitting and will comment on the usefulness of direct detection bounds to restrict UED theory. Results obtained are compared against recent accelerator bounds, specifically the lower bound for 1/R from the ATLAS experiment. [Preview Abstract] |
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EA.00022: Measurements of 10B(p,a)7Be Cross-sections: A Reaction Relevant to Nuclear Fusion Energy Research Barbara Fisher, Adamos Kafkarkou, Mohammad Ahmed, Henry Weller, Luke Myers, Mark Sparker, William Zimmerman, Jon Mueller, Mark Sikora, Indral Mazumdar There is growing interest in aneutronic nuclear fusion reactors. One facility proposes to utilize the 11B(p,a)7Be reaction. The Radiative Capture Group at Triangle University Nuclear Laboratory (TUNL) has been engaged in a long-term study of this and related reactions. This poster will present preliminary data and analysis of the 10B(p,a)7Be reaction which is of interest because 10B is a potential reactor contaminant. Differential and total cross-sections will be presented for incident protons of 4.4 and 4.6 MeV. The data is necessary for simulations of an aneutrionic nuclear fusion reactor. [Preview Abstract] |
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EA.00023: Simulation Studies of the Helium and Lead Observatory (HALO) Nikki Sanford, Kate Scholberg Simulation studies for were conducted for the Helium and Lead Observatory (HALO), the supernova neutrino detector at SNOLAB, Sudbury, Ontario. HALO consists of 79 tons of lead, with 128 $^{3}$He counters which detect the scattered lead neutrons resulting from incoming neutrinos. Improvements were made to the Geant4 Monte Carlo simulation's geometry by the addition of water boxes and plastic baseboards, which serve to reflect scattered neutrons back towards counters, and shield against outside neutrons and gammas. Several box designs were created, and the resulting event detection efficiencies and labeling of 1n and 2n events were studied. It was found that these additions cause a 2{\%} efficiency increase, a slight improvement of correctly labeled events, and are a significant improvement to the HALO simulation. [Preview Abstract] |
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EA.00024: The ${}^{136} \mathrm{Xe} (n, n' \gamma ) {}^{136} \mathrm{Xe}$ Reaction at 8 MeV Joshua Bradt, Werner Tornow, Matthew Gooden An experiment was performed to look for $\gamma$-ray lines due to neutron inelastic scattering on ${}^{136}$Xe in order to identify potential background lines in the region of interest for neutrinoless double-beta decay searches like EXO and KamLAND-Zen. One clear line at 2414.7 keV was found which KamLAND-Zen cannot distinguish from the predicted neutrinoless double-beta decay signal at 2458 keV. In addition, a \textsc{Geant4} computer simulation of the 60 \% HPGe detectors used in our experiment was developed to model the detectors' efficiencies at various energies and distances from a radiation source, and we began to extend this simulation to model our entire experiment. [Preview Abstract] |
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EA.00025: Production of $^{38}$K Radioisotope for Plant Research Irene Zawisza, C.R. Howell, A.S. Crowell, C.D. Reid, D. Weisenberger Identifying and measuring the time scale of physiological responses to environmental changes provides information about mechanisms involved in the resource regulatory system of plants. Varying the amounts and types of nutrients and minerals available to a plant, the uptake and allocation of these resources are observed using Positron Emission Tomography (PET). Potassium is important to plant growth and maintenance in a number of areas. Among them is the K$^{+}$ and H$^{+}$ ion exchange provides the driving force for sugar loading into the phloem. A technique was developed for producing $^{38}$K in a chemical form that can be absorbed by plants. The $^{38}$K was created by the $^{35}$Cl($\alpha $,n)$^{38}$K reaction using 14 MeV $\alpha $-particles from the tandem accelerator at the Triangle Universities Nuclear Laboratory (TUNL). The target was a NaCl film about 20 mg/cm$^{2}$ thick that was evaporated onto a water-cooled tantalum disk. The irradiated NaCl film was dissolved in water and was transported to the Duke Plant Facilities (The Phytotron). The details of isotope production and demonstration of plant physiology measurement are presented. [Preview Abstract] |
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EA.00026: Evaluation of Hodoscope Rates and PMT Base Design at SeaQuest Kyle Bowling SeaQuest, FNAL E-906, is a fixed target Drell-Yan experiment that collides a proton beam from Fermilab's 120 GeV Main Injector with liquid hydrogen and liquid deuterium targets to study the antiquark structure of the light nucleon sea. We will also use solid targets of different elements to study other cold nuclear matter effects such as parton energy loss. SeaQuest has been constructed primarily of components from previous experiments that were optimized for different conditions. We are currently worried that our Photomultiplier tube (PMT) and base assemblies for the trigger hodoscopes will be unable to handle the high rates from our beam intensity. The 2012 data run is currently being analyzed to decide on any changes needed for full intensity running in 2013. This presentation will provide insight into the issues with our trigger hodoscopes, as well as discuss aspects of different PMT base designs. [Preview Abstract] |
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EA.00027: Measurement of Wire Tension for the New SeaQuest Drift Chamber Andrew Boles Fermilab E-906/SeaQuest is a fixed target experiment at Fermi National Accelerator Laboratory. The experiment uses a 120 GeV proton beam extracted from the Main Injector to measure the Drell-Yan di-muon cross sections for proton-proton and proton-deuterium collisions. One of the purposes of SeaQuest is to measure the anti-down to anti-up quark asymmetry in the nucleon sea. It will produce results up to a Bjorken x of ~0.45, much larger than its predecessor, NuSea (Fermilab E866). To increase precision of these measurements, a new drift chamber is being built for the SeaQuest spectrometer. The new chamber will increase our ability to measure anti-down to anti-up quark asymmetry by 5-20\%. The chamber is 3.4 meters long by 1.9 meters wide and has 19 planes of wires with 5,000 wires in total. In order for this chamber to work correctly, all of the wires must have tension values within a specified range. This poster will explain the method used to measure the tension and why having proper tension is necessary. [Preview Abstract] |
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EA.00028: New Drift Chamber for the SeaQuest Spectrometer Ryan Castillo SeaQuest (Fermilab E906) is a fixed target experiment that utilizes di-muons produced by the Drell-Yan process using the 120 GeV Main Injector at Fermilab. The main objective of SeaQuest is to measure the anti-down to anti-up quark asymmetry in the nucleon sea by determining total Drell-Yan p+p and p+d cross sections using liquid hydrogen and liquid deuterium targets. It will produce results up to a Bjorken x of ~0.45, much larger than its predecessor, NuSea (Fermilab E866). This is only one of several measurements the experiment will make. This presentation will focus on the function, construction, and defining features of a new drift chamber currently being built at Fermilab for the SeaQuest spectrometer. This chamber will replace an old drift chamber recycled from E866 located in the lower half of the spectrometer's third drift chamber station. [Preview Abstract] |
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EA.00029: Design and Construction of the Beam Intensity Monitors for SeaQuest Noah Kitts SeaQuest, Fermilab E906, is a fixed target experiment that measures the Drell-Yan cross-section ratio of proton-proton to proton-deuterium collisions in order to extract the sea anti-quark structure of the proton. SeaQuest will produce results far more precise than the previous E866/NuSea measurements and extend the results to higher Bjorken-x. SeaQuest receives a 120-GeV proton beam from the Fermilab Main Injector in 5 second pulses at an extremely high intensity of $1 \times 10^{13}$ protons per pulse. This beam intensity is too high to be measured directly. Therefore, it is monitored by a four element hodoscope counter that views the beam from the side, picking up scattering off a beam line component. This provides a low enough intensity to stay below the rate limits of each counter. The rates in the beam monitor hodoscope will be used to provide feedback to the accelerator operators and be used to determine the relative integrated luminosity for each target. This poster will describe the design, and construction of the improved beam monitor hodoscopes. [Preview Abstract] |
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EA.00030: W Boson Production Charge Asymmetry Ashley Huff, Susan Blessing We present a measurement of W Boson Production Charge Asymmetry in PP(bar) collisions through W $\to$ e-$\nu_e$ decays. The collision of a u quark and a d(bar)quark will produce a W+ Boson while the collision of an u(bar) quark and a d quark will produce a W- Boson. These particles decay rapidly but we are able to measure their asymmetry by studying the resulting electrons and neutrinos. These results will be used to further constrain PDF fits and improve the accuracy of future predictions for new physics. [Preview Abstract] |
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EA.00031: Lagrange Meshes in Hadronic Physics Taylor Hynds We examine different methods of solving the Schr\"{o}dinger equation for two and three-body systems. We begin by constructing variational wave functions, as expansions in a basis of orthogonal polynomials. This method has been found to give accurate results, given a sufficiently large basis. However, computationally this can become very cumbersome. We therefore employ the Lagrange-mesh method, which leads to a simple calculation of both potential and kinetic matrix elements that is both computationally efficient and results in little to no loss in accuracy. This method has been applied to several problems with well known analytical solutions, and has given excellent results. The effectiveness of this method in analyzing bound states of quarks has yet to be demonstrated. In the future this method will be applied to the quantum-mechanical three-body problem. [Preview Abstract] |
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EA.00032: Implementing a New Ion Chamber Design for Neutron Spin Rotation Hannah Gardiner, Eamon Anderson, Jason Fry, Adam Holley, Mike Snow The quark-quark weak interaction is difficult to measure due to the presence of the strong force. However, low energy neutrons passing through liquid Helium-4 can be used to probe the nucleon-nucleon weak interaction, which is induced by the quark-quark weak interaction. The neutron spin rotation experiment seeks to measure the spin rotation angle of neutrons due to their weak interaction with Helium-4 nuclei. This rotation angle is translated into a neutron flux asymmetry with a neutron polarizer/analyzer pair. A segmented Helium-3 gas ionization chamber was developed to measure the resultant neutron flux. We report on the design and initial tests of that ionization chamber. This work is supported by the National Science Foundation REU program and NSF grant {\#}PHY-0969490. [Preview Abstract] |
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EA.00033: MD simulations of electron and WIMP scattering from neutron star crust Jake Fish, Charles Horowitz Neutron star crust is composed of a crystal lattice of atomic nuclei embedded in a relativistic degenerate electron gas. We use molecular dynamics simulations to determine the crystal structure of neutron star crust material. From these simulations, we calculated the static structure factor S(q) that describes the scattering of electrons, neutrinos, or weakly interacting dark matter particles (WIMPs) from ions in the crust. The scattering of electrons determines the crust thermal conductivity, while WIMP scattering from the crust may allow dark matter particles to be trapped in neutron stars. [Preview Abstract] |
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EA.00034: Development of a GEM-based Imaging Detector for Small Field Dosimetry for Proton Therapy Beams Erin France, Alexander Klyachko, Dmitri Nichiporov In order to fully utilize the advantages of proton therapy, the beam range, the beam alignment with the tumor and the real-time dose distribution must be accurately known. Small proton fields (with characteristic sizes of less than 3 cm) are often used in radiosurgery, ophthalmic treatments, and as patch fields to augment dose distributions. Accurate planning and quality assurance of such fields are challenging. Gas electron multiplier (GEM)-based dose imaging detectors are capable of providing improved position resolution, dose rate linearity, fast response and accurate reproduction of depth-dose distributions. The purpose of this project is to develop a double-GEM dose imaging detector with the optical readout of scintillation light using a CCD camera, intended for small field measurements. The detector was tested in a 205 MeV proton beam at the Indiana University Cyclotron, during the Indiana University Physics 2012 REU funded by the NSF. It demonstrated linearity in dose rate up to 75 Gy/min. Lateral profiles measured with the GEM detector and radiochromic film agree within 0.4 mm (one pixel size) at 50{\%} isodose. After initial start-up, the detector response was stable within $\pm $5{\%} over a 40 hour time period. [Preview Abstract] |
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EA.00035: Hand scan results for NuMI events recorded in the NOvA near detector Teresa Lackey, Mark Messier The NOvA experiment at Fermilab will measure oscillations of 2~GeV muon neutrinos to electron neutrinos using two detectors and both neutrino and anti-neutrino beams. These oscillations are sensitive to the neutrino mass hierarchy and CP violation. Key to the experiment is the problem of neutrino particle identification and we are pursuing efforts to optimize pattern recognition to identify neutrino interactions as $\nu_\mu$ charged-current, $\nu_e$ charged-current, and neutral-current. To aid the development of these algorithms the experiment can use simulations, but additional valuable data are the real neutrino interactions recorded by the experiment prototype detector. These data events must be sorted into the three signal event categories. This was accomplished by a visual ``hand-scan" of the neutrino candidates. To trim the event sample for scanning to a manageable size a series of selection criteria were applied with the goal of minimizing the number of cosmic-ray events while efficiently retaining neutrino events. A training regimen and a method for testing the efficiency of each hand scanner were developed to maintain consistency between various scanners. The final sample contained 800 events of which roughly 1\% were electron-neutrino charged-current events. [Preview Abstract] |
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EA.00036: Testing of the integrated electronics and low-mass front-end board for the \textsc{Majorana Demonstrator} Sarah Bennedsen, Ryan Martin, Alan Poon The MAJORANA DEMONSTRATOR experiment will search for neutrinoless double beta decay in $^{76}$Ge. If this decay is observed, it will indicate that the neutrino is its own antiparticle---a Majorana particle---and reveal information about the mass of the neutrino. Along with a brief summary of the MJD experimental design, this poster will focus on the electronics developed by the group at Lawrence Berkeley National Laboratory (LBNL) to read out data from the experiment. A low-mass front-end board (LMFE) provides the first stage of signal processing. It is a fused silica board with a printed circuit designed for low background and low electronic noise performance. Mechanical studies of the LMFE were performed in addition to characterizations of the low noise behavior of the integrated electronics. These studies improve the performance and reliability of the LMFE. [Preview Abstract] |
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EA.00037: A Test Apparatus for the MAJORANA DEMONSTRATOR Front-end Electronics Harjit Singh, James Loach, Alan Poon One of the most important experimental programs in neutrino physics is the search for neutrinoless double-beta decay. The MAJORANA collaboration is searching for this rare nuclear process in the Ge-76 isotope using HPGe detectors. Each detector is instrumented with high-performance electronics to read out and amplify the signals. The part of the electronics close to the detectors, consisting of a novel front-end circuit, cables and connectors, is made of radio-pure materials and is exceedingly delicate. In this work a dedicated test apparatus was created to benchmark the performance of the electronics before installation in the experiment. The apparatus was designed for cleanroom use, with fixtures to hold the components without contaminating them, and included the electronics necessary for power and readout. In addition to testing, the station will find longer term use in development of future versions of the electronics. [Preview Abstract] |
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EA.00038: Identification of Fission Products using the large-acceptance VAMOS spectrometer Brent Glassman, Giacomo De Angelis, Jose Javier Valiente-Dob\'on The region of neutron rich Osmium isotopes exhibits a variety of nuclear phenomena such as K-isomeric states, triaxiality, and shape transitions across isotopic and isotonic chains. These phenomena have been considered highly important in demonstrating the accuracy of nuclear models and have been a considerable focus for both theoretical and experimental endeavor. Until recently knowledge in this region has been lacking due to the difficulty in populating these nuclei. An experiment has been performed in Ganil, France, using the EXOGAM-VAMOS setup, in order to study the prolate-oblate transition in neutron rich Os isotopes. In order to populate these nuclei a multi-nucleon transfer reaction was exploited, using a 1622MeV beam of $^{208}$Pb impinging on a 3mg/cm$^{2}$ self-supporting $^{198}$Pt target. Along with transfer channels, fission fragments were also detected. The current status of the investigation of these fission fragments will be discussed. [Preview Abstract] |
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EA.00039: Reducing Uncertainty of Neutron Capture Reaction Calculations for Stellar Nucleosynthesis Hannah Little, Toshihiko Kawano, Michael Bertolli Astrophysicists believe that all elements on Earth are derived from nucleosynthesis in stars, a process of creating new atomic nuclei from neutrons and protons that already exist. While one ultimate goal is to see the actual distribution of elements in stars line up with experimental results, thereby supporting the hypothesis, many necessary reaction rates cannot be measured empirically and thus we must rely on theoretical calculations to come up with data. Neutron capture reactions play a big role in nucleosynthesis, and the statistical Hauser-Feshbach model is often adopted to calculate the neutron capture rates. My objective is to reduce the uncertainty of the calculations by adjusting different parameters, such as the gamma-ray strength and the level densities. For a certain set of nuclides for which Maxwellian Averaged Cross Sections (MACS) have been experimentally determined, I found better descriptions of the gamma strength function and the level density parameters that well fit the experimental MACS values. By continuing to adjust parameters to make the calculation results align with experimental values, we expect the calculation will become more accurate so that we can extrapolate and calculate quantities that cannot be measured. [Preview Abstract] |
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EA.00040: Understanding Low Energy Gamma Emission from Fission and Capture with DANCE Grey Wilburn, Aaron Couture, Shea Mosby Los Alamos National Laboratory's Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 barium fluoride (BaF$_2$) detectors in a 4$\pi$~ array used to study cross-section measurements from neutron capture reactions. Further, recent studies have taken advantage of DANCE to study the gamma emission from fission, which is not well characterized. Neutron capture is studied because of its relevance to nuclear astrophysics (almost all elements heavier than iron are formed via neutron capture) and nuclear energy, where neutron capture is a poison in the reactor. Gamma ray cascades following neutron capture and fission include photons with energies between 100~keV and 10~MeV. DANCE uses a $^6$LiH sphere to attenuate scattered neutrons, the primary background in DANCE. Unfortunately, it also attenuates low energy gamma rays. In order to quantify this effect and validate simulations, direct measurements of low energy gammas were made with a high purity germanium (HPGe) crystal. HPGe's allow for high resolution measurements of low energy gamma rays that are not possible using the BaF$_2$~ crystals. The results and their agreement with simulations will be discussed. [Preview Abstract] |
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EA.00041: Building a Class-1 Glove Box for Use with the NIFFTE TPC William Lynn The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) uses a Time Projection Chamber (TPC) to measure the neutron-induced fission cross sections of actinides with unprecedented accuracy which will aid in the development of the next generation nuclear reactors. Charged particles, including fission fragments, create a trail of electrons within a fill gas through ionization, which then drift in an electric field towards the read-out electronics. Using a MicroMegas mesh, the signal is amplified and then detected by the TPC pad plane. Due to the delicate nature of the MicroMegas mesh, precaution must be taken to prevent damage to the mesh from airborne contaminants which can cause the mesh to short. To avoid radiological contamination, a glove box was chosen for the task of handling and installing actinide targets into the TPC. To protect the TPC electronics, a decision was made to modify the existing glove box to create a Class-1 cleanroom environment. Variables such as glove type, filter, and cleaning agent were tested independently to determine maximum cleanliness, and a procedure for creating an acceptable Class-1 environment inside the glove box for the TPC was developed. [Preview Abstract] |
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EA.00042: Data Acquisition and Calibration for MiniLENS Matthew Amrit The Low-Energy Neutrino Spectroscopy (LENS) Collaboration aims to precisely measure the entire energy spectrum of solar neutrinos through charged-current neutrino interactions using indium-loaded scintillator in a novel, optically-segmented detector architecture. The collaboration is currently constructing a prototype, miniLENS, that will demonstrate the performance and selectivity of the full-scale LENS instrument. Crucial to success of miniLENS is to develop a system and program of measurements to calibrate the performance of the instrument. We have performed measurements using a smaller prototype microLENS and developed a system for relative calibration of PMTs by injecting externally generated light from LEDs over fiber optic cables directly to each of the miniLENS PMTs. Here we present the design and testing of the calibration system. [Preview Abstract] |
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EA.00043: Development of a Position Sensitive Heavy Ion Detector for Nuclear Astrophysics Emily Need, J.C. Blackmon, C.M. Deibel, J. Lai, L.E. Lindhart, K.T. Macon, M. Matos, B.C. Rasco, G. Rogachev, I. Wiedenhover The Array for Nuclear Astrophysics Studies with Exotic Nuclei (ANASEN) is a charged-particle detector array used to study reactions with radioactive beams at FSU and the NSCL. One of the main goals is to improve our understanding of nuclear reactions important in stellar explosions. One important component of ANASEN is a heavy ion detector located downstream of the target that is used to identify the atomic number of heavy ions based upon their energy loss through the gas-filled chamber. We have developed a new version of this detector with major design changes to improve data collection and allow much greater selectivity for the reactions of interest. These changes include anodes based on custom printed circuit boards that provide position sensitivity, larger grids to provide greater acceptance, and a change in wire spacing on the grids to improve transmission. We will present the new design and results from initial tests. [Preview Abstract] |
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EA.00044: A Heavy Ion Recoil Detector for the HELIcal Orbit Spectrometer (HELIOS) Cedric Williams, J.C. Blackmon, C.M. Deibel, J. Lai, L.E. Lindhart, K.T. Macon, M. Matos, B.C. Rasco The helical orbit spectrometer (HELIOS) is an instrument for studying nuclear reactions in inverse kinematics with radioactive ion beams at the Argonne Tandem Linac Accelerator System (ATLAS) facility at Argonne National Laboratory. We have developed a gas filled Ionization chamber for use with HELIOS to detect heavy reaction products in coincidence at forward angles. Detection of coincident heavy ions will help distinguish the reaction channel of interest from fusion evaporation and reactions induced by beam contaminants. The counter provides high acceptance and allows for counting rates over 1e5 ions/s with good particle identification. Construction of the counter and results from initial test will be presented. [Preview Abstract] |
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EA.00045: Gain Calibrations for the BUNI Large-Volume NaI(Tl) Detector at MAX-lab Olivia Campbell Quantum Chromodynamics (QCD) provides a framework for understanding the properties of the nucleon. Predictions from QCD-based theories combined with experimental results can provide important tests of these theories. A measurement of $\gamma n \rightarrow p \pi^-$ close to threshold was performed in 2011 using the tagged photon facility at MAX-lab in Lund, Sweden. Using a LD$_2$ target, the $\pi^-$ had insufficient energy to escape the target to be detected directly but were captured in the target producing a nominal 128-MeV gamma-ray through the $\pi^- d \rightarrow nn \gamma$ channel. These high-energy gamma-rays were detected in three large-volume NaI(Tl) detectors located around the target. The NaI(Tl) detectors consist of a core surrounded by a segmented annulus. The core energy calibration was performed by placing each detector directly in the tagged photon beam which has a known energy and was monitored using cosmic-ray measurements throughout the experiment. During the data acquisition period, the gain of the annulus segments were measured daily using a Th-C $\gamma$-ray source. These calibrations ensured that changes in the detector gains were accurately monitored and corrected for during the analysis of the data. Results from the gain calibrations will be presented. [Preview Abstract] |
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EA.00046: Development of a Polarized Helium-3 Ion Source for RHIC Charles Epstein, Richard Milner, James Maxwell, James Alessi, Alexander Pikin, Anatoli Zelenski A polarized Helium-3 beam in RHIC would enable new, unique, high-energy QCD studies of neutron structure with existing polarized proton beams, as well as fundamental tests of the standard model in a future electron-ion collider eRHIC. An MIT-BNL collaboration is developing a polarized Helium-3 ion source for RHIC, and initial construction is underway. Helium-3 atoms will first be polarized through metastability exchange optical pumping and then transferred to the RHIC Electron Beam Ion Source (EBIS). Fully stripped Helium-3 ions would be extracted from EBIS and their polarization measured at low energies before acceleration in RHIC. [Preview Abstract] |
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EA.00047: Optical model parameters extracted from elastic deuteron scattering Cathleen Fry Nuclear incompressibility is an important ingredient of the equation of state of nuclear matter. Isoscalar Giant Monopole Resonance (ISGMR), a compressional mode oscillation of the nucleus, serves as an experimental tool in extracting the nuclear incompressibility. In order to make measurements on the ISGMR strength distributions in the nuclei far from stability, experiments have to be done in the inverse kinematics. This is now made possible with the advent of new radioactive ion beam facilities. $^{2}$H can serve as a target in such reactions. However there the no available Optical Model Parameters (OMP) for this probe at the energies required to study ISGMR. With this in mind an experiment was performed with 100 MeV/A $^{2}$H beam at Research Center for Nuclear Physics (RCNP). Elastic scattering data were obtained for $^{58}$Ni, $^{90}$Zr, $^{116}$Sn, and $^{208}$Pb, over a wide range of angles. The OMP extracted from the analysis of these elastic cross-sections would be presented. [Preview Abstract] |
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EA.00048: ASIC Readout System for use with a Silicon Detector Array (SAND) Ian Marsh, Shelly Lesher, Wanpeng Tan, Mallory Smith, Mike Robbe, Ani Aprahamian Silicon (Si) detectors are widely used throughout the scientific community, particularly in nuclear physics. Modern versions of Si detectors are getting larger and increasingly segmented, requiring many electronic channels to process the signals. NIM and VME modules have traditionally been used to process signals from various types of detectors. Applying this traditional method to a large array of Si-detectors, segmented or otherwise, would be very expensive and in most cases highly impractical. To handle this high density of signals from state-of-the-art Si detector arrays we have explored an Application Specific Integrated Circuit (ASIC) approach in collaboration with University of Washington in St. Louis. This involves ASIC chips developed for simultaneous signal processing with charge sensitive preamplifiers, shaping amplifiers, and constant fraction discriminators built in for 16 channels. One ASIC box is capable of housing 32 of these chips and thus processing signals directly from detectors through a total of 512 channels. Analog energy and timing signals are digitized through a pipeline ADC for the NSCL DAQ software to readout. I was a part of the ND effort to implement such an ASIC system. I conducted energy and timing calibrations as well as linearity, threshold, and resolution tests on the system. In collaboration with Indiana University at Bloomington the ASIC system will be applied to a silicon detector array (SAND) at ND for the study of nuclear astrophysics. [Preview Abstract] |
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EA.00049: Exploring the Neutron Channel of Carbon Burning at Stellar Energies Terri Poxon-Pearson The $^{12}$C($^{12}$C,n)$^{23}$Mg fusion reaction could be an important neutron donor to the weak s-process which is the stellar process responsible for forming most of the elements between iron and strontium. Carbon burning in this scenario occurs at low energies, around 3 MeV center-of-mass, where the nuclear reaction cross section is both small and difficult to predict. Recently, an experiment was conducted at University of Notre Dame's Nuclear Science Laboratory using direct neutron detection in order to determine the cross section at the lowest energy ever measured. This June, we used an independent experimental method which involved the detection of $\beta ^{+}$ particles from $^{23}$Mg decay in order to validate the results from the previous experiment. Results from this experiment show overall agreement, but indicated that a newly discovered resonance at 3.4 MeV may not have been as strong as originally thought. Along with these results, I will discuss possibilities and limitations for future investigations of $^{12}$C($^{12}$C,n)$^{23}$Mg at astrophysically relevant energies. [Preview Abstract] |
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EA.00050: St. George Recoil Mass Separator Time of Flight and Position Sensitive Detector Luis Morales, Sunil Kalkal, Jerry Hinnefeld, Manoel Couder The St. George recoil mass separator at the University of Notre Dame will be used to study ($\alpha$, $\gamma$) reactions of astrophysical interest. A detection system being developed for St. George at Indiana University South Bend and Notre Dame will utilize energy, time-of-flight and position to separate reaction products from residual unreacted beam particles. Two designs for the timing detectors have been investigated -- an electrostatic mirror design and a combination of electrostatic plates with magnetic deflection. Both designs deflect secondary electrons produced by the passage of an ion through a thin carbon foil onto a microchannel plate (MCP) detector, which registers timing and position measurements. A detailed analysis of position and timing resolution for the two designs was conducted using the ion optics simulation software SIMION, in order to identify the configuration best suited for the challenges presented by these low energy and low count rate experiments. [Preview Abstract] |
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EA.00051: Sensitivity of Carbon Synthesis in Accreting Neutron Stars to Reaction Rate and Network Parameter Variations Jeremy Stevens, Hendrik Schatz, Richard Cyburt, Ed Brown, Andrew Cumming Superbursts from accreting neutron stars represent an opportunity for probing nuclear processes at densities ($\rho \approx 10^{9} \ {\rm gr \ cm^{-3}}$) and temperatures ($T>10^9 {\rm K}$) only available in a few other astrophysical locations. These $10^{42} \ {\rm erg}$ bursts are most likely triggered by unstable ignition of carbon in an otherwise inert sea of heavy nuclei made during the rp-process of regular type I bursts (where the accumulated hydrogen and helium are burned). An open question is the origin of sufficient amounts of carbon, which is largely destroyed during the rp-process in X-ray bursts. We explore carbon production in steady state burning via the rp-process, which might occur together with unstable burning in systems showing super bursts. We determine carbon production for a range of accretion rates and helium mass fractions. We then examine the sensitivity of this production of carbon to steady state model parameters as well as reaction rate variations and identify critical nuclear reaction rates. [Preview Abstract] |
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EA.00052: Feasibility of Q-value Determinations Using a Thick Ge Detector Brittany Abromeit, Sean Liddick, Alexander Chemey, Nicole Larson, Chris Prokop, Scott Suchyta The rapid-neutron capture process is responsible for the creation of about half of the neutron-rich heavy elements above Fe. The path of the r-process depends sensitively on the nuclear masses of the isotopes involved. To better constrain the r-process path, experimental masses can be determined and compared with theoretical calculations. The relative mass between two members of an isobaric chain can be calculated from the beta-decay Q value inferred from a measurement of the beta-decay electron energy distribution. The National Superconducting Cyclotron Laboratory has a successful beta-decay spectroscopy program exploring the characteristics of the decay of neutron-rich nuclei which was recently upgraded with a 1-cm thick central implantation Ge detector. To determine the feasibility of using a thick planar Ge detector to determine relative masses based on Q-value determinations, a measurement of the beta-decay electron distribution was performed. A cocktail of radioactive ions were implanted into the detector around 67Fe and their subsequent beta-decays were monitored. To further examine the beta-decays of these radioactive ions and the feasibility of using a planar Ge detector to obtain relative masses from Q-value measurements, the system will be compared with Geant4 simulations and previously measured mass differences. [Preview Abstract] |
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EA.00053: Visualization of Scattering in Two Dimensions Savannah Logan This presentation examines two-dimensional scattering for three potentials in both classical mechanics and quantum mechanics. The connection between classical mechanics and quantum mechanics in scattering theory is explored through two-dimensional visualizations of scattering and comparisons of classical and quantum cross sections. We have used the program Mathematica to calculate cross sections and create figures. [Preview Abstract] |
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EA.00054: Simulating Neutron Interactions in the MoNA-LISA/Sweeper Setup with Geant4 Magdalene McArthur The sweeper magnet is a superconducting dipole designed to bend charged particles of 4 Tm rigidity 43 degrees at a radius of approximately one meter. In a typical experiment neutron-unbound states are populated in a reaction in front of the magnet and emitted neutrons are subsequently detected with the high-efficiency position sensitive neutron detector arrays, MoNA and LISA. Before the neutrons interact in MoNA or LISA, they have to pass through the walls of the sweeper magnet chamber. A Monte Carlo simulation was written using Geant 4 which included MoNA and LISA, as well as the geometry of the sweeper magnet and the chamber. In a recent experiment LISA was positioned at large angles were the neutrons passed through the sidewalls of the chamber. The impact of the sidewalls on the neutron spectra was explored for neutrons from the decay of 12Li $\rightarrow$ 11Li + n produced from 50 MeV/u 14B beams on a beryllium target. [Preview Abstract] |
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EA.00055: Uncertainties in production of stellar 26Al Ronaldo Ortez, Christopher Wrede, Micheal Bennet, Marco Santia, Alice Bowe While most of $^{26}$Al content is believed to be produced in supernovae, as much as 20{\%} may come from novae whose favorable energies enable the precise study of the production mechanism of $^{26}$Al in novae. This study achieves greater importance because $^{26}$Al is one of the critical isotopes that governs the path by which nucleosynthesis takes to heavier species and would also indirectly constrain the $^{26}$Al content produced by supernovae thereby impacting the ratio of stellar $^{26}$Al/$^{60}$Fe, an important benchmark in supernovae nucleosynthesis. Despite significant progress on the subject there remains large uncertainties in one of the competing $^{26}$Al production channels which relies on the $^{25}$Al(p,$\gamma$)$^{26}$Si transition. This uncertainty is primarily characterized by the undetermined energy of the excited 3$^{+} \quad ^{26}$Si state which decays to the ground state of $^{25}$Al+p. To determine the resonance strength and energy of this transition an experiment is planned at the NSCL, which populates $^{26}$Si through the beta decay of $^{26}$P. Using an array of Ge clover detectors to measure the energies of the beta-delayed photons and their intensities, one could then determine $\Gamma_{\gamma}$, which then allows the calculation of the resonance strength (since $\Gamma_{p}$ is known), completing the decay scheme of the $^{25}$Al(p,$\gamma)^{26}$Si transition. [Preview Abstract] |
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EA.00056: Fits of Geant4 simulations of GRETINA to source and in-beam spectra Bryan Sadler In preparation for an experiment with GRETINA at the NSCL planned for spring of 2013, we traveled to the National Superconducting Cyclotron Laboratory to collect source spectra and in-beam data from GRETINA. We have compared Geant4 simulations with measured photopeak efficiencies and fits to measured spectra with the aim of improving the accuracy of the simulation code. Fits of simulations to source and in-beam spectra will be presented. [Preview Abstract] |
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EA.00057: Digital Data Acquisition for the Low Energy Neutron Array (LENDA) at NSCL Matthew Solt, Remco Zegers, Shumpei Noji, Chris Sullivan, Michael Scott, Sean Liddick, Masaki Sasano The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight spectrometer developed at the National Superconducting Cyclotron Laboratory (NSCL) for use in inverse kinematics experiments with rare isotope beams at intermediate energies ($>$100MeV/u) [1]. Consisting of 24 plastic scintillators, LENDA is capable of measuring the energy and angle of recoiled neutrons with high detection efficiency. It was first used in an inverse-kinematics 56Ni(p,n) experiment at 110 MeV/u [2]. In this project, we implemented a digital data acquisition system (DDAS) in LENDA, which was originally developed for germanium detectors [3]. The digital acquisition system will provide easier setup which in turn will allow for easier addition of bars in the future. We studied the detection threshold and linearity of the DDAS using gamma-ray sources of 22Na and 241Am. We also performed TOF measurement of neutrons from a 252Cf fission source. In this presentation, we will report the results from the source tests. \\[4pt] [1] G. Perdikakis, et al., NIMA 686 (2012) 117.\\[0pt] [2] M. Sasano, et al., PRL 107, 202501 (2011).\\[0pt] [3] K. Starosta, et al., NIMA 610 (2009) 700. [Preview Abstract] |
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EA.00058: Field cage development for a time-projection chamber to constrain the nuclear symmetry energy J. Estee, J. Barney, Z. Chajecki, M. Famiano, J. Dunn, F. Lu, W.G. Lynch, A.B. McIntosh, T. Isobe, T. Murakami, H. Sakurai, R. Shane, A. Taketani, S. Tangwancharoen, M.B. Tsang, S. Yennello The SAMURAI time-projection chamber (sTPC) is being developed for use in the dipole magnet of the newly-commissioned SAMURAI spectrometer at the RIBF facility in Japan. The main scientific objective of the sTPC is to provide constraints on the nuclear symmetry energy at supra-saturation densities. The TPC allows for tracking and identification of light charged particles such as pions, protons, tritons and $^{3}$He. The sTPC must have a Cartesian geometry to match the symmetry of the dipole magnet. The walls of the field cage (FC) detector volume consist of sections of rigid, two-layer circuit boards. Inside and outside copper strips form decreasing equipotentials via a resistor chain, and create a uniform electric field with a maximum of 400 V/cm. The FC volume is hermetically sealed from the enclosure volume to create an insulation volume which can be filled with dry N$_{2}$ to inhibit corona discharge. I will be presenting the current status of the design and assembly of the sTPC field cage. [Preview Abstract] |
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EA.00059: Calibration of Charged-Particle Detectors for the LISA Commissioning Experiment S. Garrett, N. Taylor, A. Barker, W.F. Rogers The Modular Neutron Array (MoNA) and the Large area multi-Institutional Scintillator Array (LISA), housed at the National Superconducting Cyclotron Laboratory at Michigan State University, were constructed by students at primarily undergraduate institutions. Each array consists of 144 2-m long scintillator detectors with PMTs attached to each end and are used for the detection of neutrons resulting from the breakup of exotic neutron-unbound nuclear states. The commissioning run for LISA was conducted during summer 2011 (in conjunction with MoNA and the Sweeper Magnet) to investigate unbound excited states of the neutron-rich nucleus 24O that breakup via sequential 2-neutron decay. In order to do this the energies and trajectories of both the charged fragments and neutrons need to be determined precisely, which require careful energy, position, and time calibration of the Sweeper Chamber charged particle detectors. Then careful separation of the individual Oxygen isotopes is necessary so that gates can be produced to be used in the calculation of individual decay energies. Results to be presented. [Preview Abstract] |
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EA.00060: Analysis of LISA Commissioning Run Data for Study of 24O Excited State Decay Energies N. Taylor, S. Garrett, A. Barker, W.F. Rogers The commissioning run for the Large-area multi-institutional Scintillator Array (LISA), located at the National Superconducting Cyclotron Laboratory at Michigan State University (and built by undergraduates from 9 primarily undergraduate institutions) was conducted over summer 2011. Used along with the Modular Neutron Array (MoNA) and the Sweeper Magnet, the purpose of this run was to study the neutron-unbound excited states of 24O by measuring the energies and trajectories of the charged fragments and the neutrons resulting from the breakup. Careful calibration of all detectors is necessary, including correction for time drifts and absolute time calibration of all charged-particle and neutron detectors. In the Sweeper chamber, the two Cathode-Readout Drift Chamber detectors experienced significant drift in the vertical direction over the course of the experiment, requiring particular care in calibration. Absolute time calibration of all detectors is also necessary before clean isotope separation and decay energies can be determined. Additionally, a variety of isotopes produced in the secondary target interactions for possible future study was made. Results will be presented. [Preview Abstract] |
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EA.00061: Materials Testing and Performance Optimization for the SAMURAI-TPC K.D. Long, W.G. Lynch, J. Barney, Z. Chajecki, J. Estee, R. Shane, S. Tangwanchareon, M.B. Tsang, J. Yurkon The SAMURAI time-projection chamber (TPC) will be used to make measurements of pion spectra from heavy ion collisions at RIBF in Japan. Such research provides an opportunity to study supra-saturation density neutron-rich matter in the laboratory, and is critical to understanding the structure of neutron stars. It will provide a complete, 3D picture of the ionization deposited in a gas volume, from which particle types and momenta can be determined. The gas-containment volume is composed of surfaces of aluminum and plastic, as well as halogen-free printed circuit board. During multiplication of the ionized electrons at the anode wire plane of the TPC, UV photons are produced. These cause unwanted discharges when they interact with oxidized aluminum surfaces, which have low work functions. This problem can be addressed by application of a suitable conductive paint or epoxy. Paints were investigated to insure they did not contain any materials capable of inhibiting the performance of the detector gas. These investigations were cross-checked by tests carried out using an existing BRAHMS-TPC. Details on these tests and the materials chosen will be shown. The design and optimization of the gating grid, used to limit data collection to triggered events, will also be discussed. [Preview Abstract] |
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EA.00062: Calibration of the E Si detector in a DE-E telescope with a $^{212}$Pb pin source Ka Pang Chan In nuclear physics experiments, telescopes composed of two or more large area silicon strip detectors are used to identify charged particles. To use the energy loss method for particle identification, a thin ($\sim $0.065mm) silicon detector (DE) is mounted in front of a thicker E detector ($\sim $1.5 mm). The DE Si detector can be calibrated with 8.785, 6.778, 6.288, 5.685 and 5.423 MeV alpha particles emitted from a $^{228}$Th source. However, this method cannot be used to calibrate the E detector as the alpha particles cannot penetrate the front DE detector. We have developed a method to calibrate the E detector by inserting a small irradiated dowel pin between the two Si detectors. The pin source is electroplated with $^{212}$Pb nuclei which emit alpha particles with 8.785 MeV, 6.090 and 6.051 MeV. Insertion of the dowel pin is designed and guided so that the head of the pin lies near the center of the detector at a distance of 2.72 mm away from the surface of the E detector. In addition to providing two strong alpha peaks for calibrations, the close distance and high pixilation of the E detector allows accurate determination of the front dead layer of the E Si strip detector. This technique has been implemented successfully in calibrating the E Si detectors in the NSCL High Resolution Array (HiRA) consisting of 20 closely pack DE-E-CsI telescopes. [Preview Abstract] |
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EA.00063: Reducing Cosmic Background in the NSCL SuN Detector Anne Kyner, Artemis Spyrou, Anna Simon, Stephen Quinn, Mikayla Seeber The Summing NaI(T1) detector, SuN, was developed by the Nuclear Astrophysics group at NSCL (National Superconducting Cyclotron Laboratory) to explore important reactions in the p-process, a process involved in stellar nucleosynthesis. Using inverse kinematics with the detector allows for the investigation of experiments with radioactive beams. A problem arising from these experiments is that the background rate is high compared to the expected reaction of interest. The high background peak is due to the cosmic rays, high energy muons, that hit the detector. By using two plastic scintillators above and below the SuN detector, cosmic ray background may be reduced. This project was conducted in order to understand one of the two plastic scintillators. Characterizing the detector and coupling it with a CsI crystal aided in understanding the plastic scintillator and the cosmic ray distribution that is detected. By taking background runs and eliminating signals that occurred in both the plastic scintillator and the CsI crystal, a rejection region of over 60\% was observed. This background reduction shows how the plastic scintillators can be used in correlation with the SuN detector to reduce the cosmic background and improve results from reaction measurements in inverse kinematics. [Preview Abstract] |
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EA.00064: Characterization of NE-110 Plastic Scintillator as a Cosmic Ray Veto Detector Mikayla Seeber, Artemis Spyrou, Anna Simon, Stephen Quinn, Anne Kyner Explosive astrophysical environments cause the nuclear reactions that fuel the synthesis of many isotopes seen in the universe. The reaction rates and cross sections of these reactions involved in stellar nucleosynthesis can be measured with devices like the SuN (Summing NaI(Tl)) detector, a 4$\pi$ gamma-summing detector recently acquired by the Nuclear Astrophysics group at the National Superconducting Cyclotron Laboratory. The NE-110 plastic scintillator is being developed as cosmic ray veto for SuN when studying (p, $\gamma$) and ($\alpha$, $\gamma$) reactions. The present work was focused on characterizing the veto detector using a Cesium Iodide detector and standard gamma ray sources $^{127}$Cs, $^{60}$Co, and $^{22}$Na. The results were compared to GEANT4 simulations developed for this particular experimental setup. [Preview Abstract] |
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EA.00065: Characterization of Zr-V-Fe Non-Evaporable Getter Strips for use in a Miniature Penning Trap Robert Baker, Georg Bollen, David Lincoln, Matt Redshaw, Ryan Ringle, Stefan Schwarz, Adrian Valverde The Low Energy Beam and Ion Trap (LEBIT) group at the National Superconducting Cyclotron Laboratory (NSCL) performs high-precision mass measurements using a Penning trap. The current method involves measuring reference ions of known mass in order to calibrate the magnetic field. Because the reference measurements require us to stop the measurement of a rare isotope, we will optimize the use of beam time by installing a magnetometer to directly measure the magnetic field while conducting a rare isotope measurement. A miniature Penning trap (MiniTrap) will be mounted adjacent to the measurement trap to serve as a magnetometer. To reach the desired precision, the MiniTrap must be operated in very low pressures. We investigate using the SAES St707 (Zr-V-Fe) non-evaporable getter to pump out the MiniTrap to achieve an ultra-high vacuum. Excess hydrogen will be ionized into $H_2^+$ and serve as the reference mass. We report a pumping speed for the activated getter material, partial pressures for the background gases after different pumping intervals, and discuss further work with the MiniTrap. [Preview Abstract] |
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EA.00066: Composition of the $^{24}$O Ground State Wave Function R.A. Scotten, E. Traynor, P.A. DeYoung, N.T. Islam, R.A. Haring-Kaye Recent experimental and theoretical evidence points to a closed shell at $N = 16$ for the neutron-rich oxygen isotopes based on the measured and predicted excitation energy of the first-excited 2$^+$ state in $^{24}$O and the energy gap between the $\nu$(0$d_{3/2}$) and $\nu$(1$s_{1/2}$) single-particle states. This work seeks to test this assertion by measuring the cross section for neutron knockout from the $^{24}$O ground state to the ground and first-excited states of $^{23}$O (which immediately decays to the ground state of $^{22}$O through neutron emission). From this we can infer the composition of the $^{24}$O ground state wave function. $^{24}$O nuclei were produced at the National Superconducting Cyclotron Lab (NSCL) at Michigan State University via fragmentation of a $^{48}$Ca beam on a 1316 mg/cm$^2$ Be target, and bombarded a 481 mg/cm$^2$ Be target downstream to induce knockout reactions. Fragment nuclei (neutron decays) were detected by a system of charged-particle detectors (the Modular Neutron Array (MoNA)). The current status of the analysis will be discussed, including the identification of oxygen fragments, the calibrations for timing and position measurements using MoNA, and the determination of the relevant spectroscopic factors of interest. [Preview Abstract] |
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EA.00067: Intensities of yrast transitions in the $^{95}$Mo(d,p$\gamma$)$^{96}$Mo$^{\ast}$ reaction Sean Burcher, Andrew Ratkiewicz, Jolie Cizewski, Brett Manning, Callum Shand, Samantha Rice, Jason Burke, Robert Casperson, Matt McCleckey, Bill Peters, R.A.E. Austin, T.J. Ross, R.O. Hughes Direct neutron transfer reactions preferentially populate nuclear excitations with single--particle strength that decay by gamma-ray emission. Using the 88-Inch Cyclotron at Texas A\&M and the STArLiTe (Silicon Telescope Array Livermore Texas) Detector Array, the $^{95}$Mo(d,p$\gamma$)$^{96}$Mo$^{\ast}$ reaction was measured for the first time. Gamma rays that correspond to energies of known level transitions, particularly the yrast transitions of 6$^{+}$$\to$4$^{+}$, 4$^{+}$$\to$2$^{+}$, and 2$^{+}$$\to$0$^{+}$ have been identified. The gamma-ray peaks were identified in coincidence with protons to select the $^{95}$Mo(d,p) channel. Results from this study will be presented in the form of a gamma-ray spectrum showing the energies of transitions between states in $^{96}$Mo, as well as the corresponding level scheme. These data will be useful in the understanding of the nuclear structure of $^{96}$Mo and could aid efforts to validate the (d,p$\gamma$) reaction as a surrogate method of studying neutron capture. [Preview Abstract] |
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EA.00068: Source Calibration for Neutron Flux Measurement Kayla Craycraft The NPDGamma experiment is currently running at the Fundamental Neutron Physics Beamline (FNPB) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The goal of the experiment is to measure the parity-violating asymmetry between the incident neutron spin and emitted photon direction for the capture of neutrons on protons. The gamma-rays are detected in a CsI array. We need to know the neutron flux accurately to verify that we are running at counting statistics. We measure the neutron flux from the gamma signal produced by capturing all neutrons on a black boron target. The detectors were calibrated with a known gamma-ray source (Cesium-137) to high precision using a High Purity Germanium (HPGe) detector. I will present the methodology and results of this calibration, and how it affects our measurement of the statistical precision of NPDGamma. [Preview Abstract] |
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EA.00069: Detection of Correlations in Stellar Isotopic Abundances K.A. Thomsen, M.S. Smith The composition of a star changes with time via sequences of thermonuclear reactions. These sequences strongly couple the abundances of all elements to each other. The resulting complex interdependencies often make it difficult to ascertain which isotopic abundances most influence one another. To investigate this, a FORTRAN program has been written which analyzes these abundances over time as predicted by a simulation to determine if they may be correlated. This is accomplished via a looping over all possible pairs of tracked isotopes, quantitatively ascertaining the shapes of the abundance versus time curves for each, and assigning numerical scores to determine if these pairs of curves are correlated, anticorrelated, or uncorrelated. Preliminary results from this study will be presented. [Preview Abstract] |
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EA.00070: Assembling, Characterizing, and Measuring the Efficiency of VANDLE Ran Ikeyama, S.R. Lesher, W.A. Peters, J.A. Cizewski, M.E. Howard, D.W. Bardayan, Ran Grzywacz, M. Madurga, S.V. Pauluskas, Z.J. Bergstrom The Versatile Array of Neutron Detectors at Low Energy (VANDLE) has been developed to study ($d,n$) transfer reactions and beta delayed neutron spectroscopy using unstable isotope beams. These experiments are important for our understanding of nuclear structure and stellar nucleosynthesis. VANDLE is a modular array composed of two different size plastic scintillator bars coupled with PMTs at each end and designed to detect neutrons with energies in the range between 100 keV and 20 MeV. This allows VANDLE to be mounted in a variety of geometries to achieve high detection efficiency for particular experimental requirements. The light response from cosmic-ray muons and gamma-ray sources was used to measure the resolution and gain match the VANDLE modules. The intrinsic efficiency of VANDLE was determined, using a $^{252}$Cf source, for various thresholds. Details of the assembly of large VANDLE modules, possible experimental configurations, and the measured intrinsic efficiency will be presented. [Preview Abstract] |
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EA.00071: Preparation for MoNA/LISA VANDLE $^{56}$Ni($d,n$) Experiment at the NSCL Z.J. Bergstrom, R.L. Kozub, W.A. Peters, J. A. Cizewski, M.E. Howard, D.W. Bardayan, R. Ikeyama, S.V. Paulauskas, M. Madurga, R. Grzywacz, P.A. DeYoung, T. Baumann, J. Smith, M. Thoennessen The rp-process is the explosive nucleosynthesis process in novae by which ions rapidly capture hydrogen nuclei, forming heavy, proton-rich nuclei. Most of the rp-process reactions are believed to pass through the $^{56}$Ni($p,\gamma$)$^{57}$Cu reaction which cannot presently be measured directly. An experiment to be performed at the NSCL employs the method of ($d,n$) proton transfer reactions in inverse kinematics to determine pertinent properties of this reaction via $^{56}$Ni($d,n$)$^{57}$Cu at 30 MeV/nucleon. The experiment will be carried out using two neutron detector arrays of plastic scintillator bars. The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is able to detect neutrons in the 100 keV to 20 MeV range; however, when used in conjunction with MONA/LISA and the Sweeper detectors at the NSCL, the combined arrays allow for the detection of a wider range of neutron energies. Recently, the trigger logic was tested for the VANDLE-Sweeper coincidences and for the left-right coincidence trigger for MoNA/LISA. Results from these tests will be presented along with details of the approved ($d,n$) experimental setup. [Preview Abstract] |
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EA.00072: SuperORRUBA Test Results A.J. Burkhart, S. Ahn, D.W. Bardayan, R.L. Kozub, S.D. Pain Transfer reactions in inverse kinematics with radioactive ion beams are needed to provide nuclear structure information far from stability to aid in the development of nuclear models and in the understanding of astrophysical processes. Highly granular, low threshold detector arrays are needed to perform such experiments. The SuperORRUBA (Oak Ridge Rutgers University Barrel Array) was created to measure lower threshold reactions with better energy resolution than the original ORRUBA detectors. The new array consists of 18 silicon detectors, each with a 64 non-resistive strip front side and a 4 non-resistive strip back side. To collect the data from these 1224 channels, the ASICs (Application-Specific Integrated Circuits) are used for timing, triggering, shaping, and digitizing the signals, with each chip handling 32 channels. Utilizing the ASICs system and a triple-alpha source, SuperORRUBA detectors were tested to ensure proper function. In addition, all preamps and ASICs elements were tested. The depletion voltage of each detector was found, and the detectors were tested for any shift in gain over time. Finally, issues with crosstalk causing poor resolution on particular channels were investigated. A detailed description of the system and the test results will be presented. [Preview Abstract] |
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EA.00073: Effective Sea-level Cosmic Ray Exposure of Copper During Transportation Timothy Berguson, John Orrell, Estanislao Aguayo, Austen Greene The Majorana Project aims to observe neutrinoless double beta decay utilizing high purity germanium detectors enclosed in a low-background shield. Germanium and copper, which are to be used in the detector assembly, are susceptible to cosmogenic activation, which produces isotopes within the materials whose decay generates signals in the energy region of interest of neutrinoless double beta decay, thus serving as an unwanted background. In order to assure that the materials have not been exposed to cosmic radiation beyond the established acceptable limits, a muon detector, the Muon-Witness, was used to track the integral muon count rate. This muon rate can be used to estimate the activation levels of the materials relative to the cosmic background at sea level. Other Majorana collaborators have previously estimated the activation using another method, and the two results varied significantly. An analysis of the two methods, including simulations and measurements with the Muon-Witness checking for its efficiency to muons, seeks to understand this discrepancy. [Preview Abstract] |
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EA.00074: Vibration Measurements of the Wire Scanner for the SwissFEL Prajwal Mohanmurthy, Gian Luca Orlandi, Rasmus Ischebeck The SwissFEL is an X-Ray ($0.1nm-7nm$) Free Electron Laser user facility which is being planned for the Paul Scherrer Institute in Switzerland. At the SwissFEL, view screens will be used to monitor the transverse profile of the electron beam. Wire scanners are also to be employed as the high beam densities of the electron beam will hamper the standard diagnostics. Wire scanners will be tested on the $250MeV$ SwissFEL Injector Test Facility with a $200pC$ electron beam whose transverse diameter is typically about $100 \mu m$. The portion of the electron beam that is unscattered from the wire will be measured to determine the beam loss. The wire scanner is driven by a stepper motor and the wire position is obtained using a digital encoder. The wire scanner may be susceptible to vibrations which may lead to erroneous encoder positions. The variation in position of the wire, with the motor being driven at a number of different speeds, was studied using a concentrator back-light and a 1MPixel high speed camera. The camera was triggered using the $10Hz$ SwissFEL Injector Test Facility timing signal. A typical vibration with an amplitude of about $0.5\mu m$ was observed. Dependence of vibration of the wire on the motor driving speed and ways of optimizing the operational parameters. [Preview Abstract] |
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EA.00075: Modeling the Partonic Structure of the Nucleon Through Semi-Inclusive Deep Inelastic Scattering Daniel Banks, Leonard Gamberg The focus of this research is to model the transverse spin and momentum partonic structure of the nucleon. Using hard scattering processes such as semi-inclusive deep inelastic scattering (SIDIS) as a means to access this sub-structure it is evident that precise knowledge of the transverse degrees of freedom of partons (momentum and spin angular momentum) are essential to unfold a comprehensive description of the nucleon. Of particular importance are transverse momentum dependent parton distribution and fragmentation functions (TMD PDFs/FFs). By observing the experimental single-spin asymmetries of produced pions for a longitudinally polarized electron beam on an unpolarized nucleon we explore the spin-orbit correlations in the beam-spin asymmetry [1]. Considering these single-spin asymmetries we then model the twist-three TMD PDF, $g^\perp(x,\mathbf{k}_T)$. We also study the factorization of the SIDIS cross sections for twist-3 TMD PDFs [2] by studying the issue of light cone divergence in the quark-target model.\\[4pt] [1] M.~Aghasyan {\it et al.}, Phys. Lett B {\bf 704}, 397 (2011).\\[0pt] [2] L.~P.~Gamberg {\it et al.}, Phys. Lett B {\bf 639}, 508 (2006). [Preview Abstract] |
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EA.00076: Design and Development of a Cryogenic Preamplifier for the MuSun Experiment Eisen Gross, Stanley Goston, Matthew Gubanich, Jeffrey Stroud, Frederick Gray The MuSun Collaboration is working to measure the rate of muon capture on the deuteron with high precision. A pad plane TPC filled with cryogenic deuterium gas detects muons and nuclear recoils. In previous experimental runs the preamplifiers for the TPC were located outside its vacuum chamber at a distance of 80 cm. This additional cable added interference, capacitance and noise, which decreased the energy resolution. A design for a preamplifier was developed that could be placed inside the vacuum at low temperatures. Components for the preamplifier were tested and characterized, and a prototype was constructed. Measurements of energy resolution as a function of detector capacitance are in progress, and they will be presented along with the design of the preamplifier. [Preview Abstract] |
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EA.00077: Measurements of the $g$-factors of the 2$^+_1$ states in $^{82}$Sr (25.3 d) and $^{90}Sr$ (28.8 y) Samantha Rice, Samuel Naimark, Gerfried Kumbartzki, Noemie Benczer-Koller Magnetic moments and lifetimes of the 2$^+_1$ states in $^{84-88}$Sr isotopes were measured via the transient field technique and Coulomb excitation in inverse kinematics. The pending experiment will use $^{78,86}$Kr beams from the TAMU Cyclotron to induce ${\alpha}$-capture reactions on a $^{12}$C target and produce the unstable isotopes of interest, $^{82,90}$Sr. A new beam line, consisting of a target chamber, target cooling device, and external magnetic field, is being assembled at Rutgers. The $^{12}$C target was evaporated on a substrate of gadolinium backed by a copper foil. A PIPS Si detector will detect ${\alpha}$-particles exiting the target after the $^8$Be breakup, and ${\gamma}$-rays will be detected by four Ge clover detectors. A digital data acquisition system will record ${\alpha}$-${\gamma}$ coincidences. The angular correlation of the emitted ${\gamma}$-rays with respect to the beam direction will be determined from appropriate combinations of ${\gamma}$-ray intensities observed in various elements of the clover detectors. The measurement of the precession angles of the 2$^+_1$ magnetic moments yield the experimental $g$-factors. The results will be compared to shell model calculations based on $^{88}$Sr as a core nucleus. [Preview Abstract] |
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EA.00078: Construction of the MAJORANA DEMONSTRATOR Logan Rice The \textsc{Majorana Demonstrator} aims to demonstrate the feasibility of searching for nuetrinoless double beta decay of 76-Ge at the tonne scale. The \textsc{Demonstrator} will consist of an array of 30 kg of enriched 76-Ge and 10 kg of natural high purity Ge detectors that serve as both source and detector. It is currently being constructed at the Sanford Underground Research Facility in Lead, SD. Searching for such a rare process with a halflife of at least 10$^{25}$ years requires a detector with correspondingly low background rates. Cosmologically induced backgrounds are reduced by shielding the detector 4850 feet underground and inside a layered shield of Cu, Pb, and neutron absorbing plastic. Additional background reduction is provided by using an inner shield of electroformed copper that is fabricated in a controlled underground environment to reduce U and Th contaminants by a factor of $\sim$1000 over OFHC copper. Backgrounds can be reduced further by using data analysis methods to reject multi-site events, events consistent with a decay chain series, and other events likely to have occurred because of contaminants. These methods are expected to allow \textsc{Majorana Demonstrator} to achieve backgrounds 3.0 counts in the region of interest per tonne year of exposure. [Preview Abstract] |
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EA.00079: Contribution of Form Factors to the Pion Cloud of the Proton Feras Aldahlawi, Kayla Furukawa, Kara Merfeld We have investigated the contribution of the pion cloud to the excess of $\bar{d}$ over $\bar{u}$ in the proton sea. In the pion cloud model, the number of pions produced depends on the splitting function $f_\pi (y)$, the cutoff form factor $F_{\pi N} (t)$, and the parton distribution functions of the pion. We have studied how these factors affect the pion cloud and, therefore, the excess of $\bar{d}$ over $\bar{u}$. We examine the effects of $Q^2$ evolution. We compare our theoretical results to the HepData parton distributions provided by Durham University and to the experimental E866 data from Fermilab. [Preview Abstract] |
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EA.00080: Pion Cloud Contributions to the Proton Sea Kayla Furukawa, Feras Aldahlawi, Kara Merfeld A proton may split into a meson and a baryon as allowed by the Heisenberg uncertainty principle. This process and the possible meson-baryon combinations have been studied by several theoretical models. In this study, we investigate the proton and its constituents through the pion cloud model. The pion cloud model depends on the splitting function, f$_{\pi B}$(y), which represents the probability of a proton splitting into a pion and a baryon, and the pion parton distribution function, q$_{\pi }$(z). The goal of our research is to examine the way the proton antiquark distributions depend on q$_{\pi }$(z) and the form factors and cutoffs of f$_{\pi B}$(y). We have studied functional forms for the dbar and ubar quarks given by the Durham HepData Project, compared their difference and ratio to the E866 experimental data from FermiLab and have studied a simplified pion cloud model. For Henley and Miller's f$_{\pi N}$(y) we show how different q$_{\pi }$(z) affect the proton antiquark distribution. We consider the pion parton distribution function of Sutton et al., as well as Aicher et al., and other forms of q$_{\pi }$(z). [Preview Abstract] |
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EA.00081: Splitting Functions for the Pion Cloud Model of the Proton Sea Asymmetry Kara Merfeld, Kayla Furukawa, Feras Aldahlawi The proton contains three valence quarks of different types: two up quarks and a down quark, as well as a sea of quarks, antiquarks, and gluons. Due to Heisenberg's uncertainty principle, it is possible for these constituents to fluctuate into a pion and a nucleon, a phenomenon that contributes to the downbar-upbar asymmetry in the proton sea. The probability of a proton splitting into a meson and a baryon is represented by the splitting function, f$_{MB}$. We investigate the asymmetry in the proton sea using the pion cloud model, and study how the downbar and upbar distributions depend on the forms of the splitting function, for the pion-nucleon and pion-delta terms. [Preview Abstract] |
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EA.00082: Radon Emanation System Deborah Noble 222Rn is a significant contributor to radioactive backgrounds. We are constructing a radon emanation system that includes several chambers which would emit the lowest levels of 222Rn possible and be almost completely airtight, minimizing 222Rn contributions from both inside and outside the chambers. This system includes several electropolished stainless steel chambers, copper gaskets, and weldless metal seals. This system makes it possible to more accurately determine the amount of 222Rn emanated from a sample or the amount present in a particular gas. A sample is placed inside one of these chambers and the system is then purged using a boil-off gas such as Helium. Any residual radon is reduced to negligible levels using a low-radon charcoal trap. After allowing the sample to emanate radon for around a week, the chamber's contents are pumped through a nitrogen cold trap, which collects the radon. The system is heated, allowing radon to expand into another detection chamber, this one containing a Si PIN diode that will collect the 218Po and 214Pb daughters of 222Rn. This system can also be used to determine the amount of radon in a sample of gas, however the gas would be released directly into the detection chamber, and is useful in many applications. [Preview Abstract] |
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EA.00083: Removal of Long-Lived Radon Daughters by Electropolishing Thin Layers of Stainless Steel James White, Richard Schnee, Raymond Bunker, Michael Bowles, Priscilla Cushman, Matthew Epland, Mark Pepin, Vince Guiseppe Long-lived alpha and beta emitters in the Radon decay chain on detector surfaces may be limiting background in many experiments attempting to detect dark matter or neutrinoless double beta decay. To screen detector surfaces for this radioactive contamination, a low-radiation, multi-wire proportional chamber (the BetaCage) is under construction. Removal of Pb-210 implanted on its 25-micron stainless steel wires without causing significant variation in the diameter of the wires is critical to the BetaCage's ultimate sensitivity. An apparatus to perform electropolishing trials to remove roughly a micron of material has been assembled. These trials have shown promising results. Stainless steel square samples implanted with Pb-210 have shown counts with a reduction factor greater than 10 after electropolishing according to gamma assay. Furthermore, alpha counting has produced similar results, with a reduction factor greater than 100. Lastly, the diameters of wires after electropolishing have remained sufficiently uniform, with reduction in thickness consistent with expectations. [Preview Abstract] |
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EA.00084: Experimental studies of the nuclear Symmetry Energy Giacomo Bonasera Nuclei, are quantum Fermi systems that exhibit many interesting features that depend on temperature and density. At zero temperature and ground-state density, nuclei are charged quantum drops; that is, they have Fermi motion due to their quantum nature, and the nucleons interact through both a short range attractive force and a long range Coulomb force. The goal of this proposal is to study the dependance of the nuclear Hamiltonian on the Symmetry Energy, in other words the difference in energy seen by the protons and the neutrons. This term is very important for the sability of neutron rich nuclei and neutron stars. [Preview Abstract] |
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EA.00085: Optimization of the Extraction Efficiency of a Gas Stopper using a Th-228 Source Michael DeVanzo, Marisa C. Alfonso, Charles M. Folden III A gas stopper, or Recoil Transfer Chamber (RTC), for heavy element research has been fabricated at the Cyclotron Institute at Texas A{\&}M University and characterized offline using a Th-228 source. The RTC features a laminar He gas flow and a series of ring and spherical electrodes to efficiently transport heavy ions through an extraction nozzle to an appropriate chemistry set up. Applying a decreasing potential difference across the ring and spherical electrodes creates potential gradients which act as a means of guiding and focusing heavy ions, respectively. By systematically altering potential gradients in the RTC, a determination can be made of the most efficient RTC configuration by using the radioactive recoils from a Th-228 source as a measure of extraction efficiency. An efficiency of up to 70 percent was obtained with the most effective electrode configuration, based on recent offline measurements. This poster will elaborate on RTC experimentation and propose electrode settings for which maximal extraction efficiency may be achieved. [Preview Abstract] |
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EA.00086: Spectral Medium Effects on Hadronic Densities Rodolfo Gonzalez, Ralf Rapp, Paul Holher Quarks and leptons are the basic building blocks of the ``visible'' matter in the universe. Quarks are confined into hadrons but it may be possible to release them for a short moment by smashing two heavy ions together at ultra-relativistic speeds. The product from doing this collision is possibly a Quark-Gluon Plasma (QGP). The goal of my research is to find the hadronic density for three specific hadrons as temperature increases. The problem with the density model I began with is it assumes mass is fixed but we know mass can change in a medium depending on the momentum and energy of a particle. In order to correct for this we add a spectral function to our density equation that has a distribution for mass depending on its momentum, energy and vacuum width. The newly added spectral function for density was first implemented with a vacuum width, but then allowed to be changing as temperature increases by including an in-medium width. My results find that with this new spectral functions the densities increase faster than in the original fixed-mass equation; the effect is particularly pronounced for the small-mass pion, but less so for the heavier resonances. [Preview Abstract] |
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EA.00087: Precision Measurement of the Internal Conversion Coefficient of 119Sn Isomer Molly Maguire, N. Nica, J.C. Hardy We made a preliminary measurement of the K-shell internal conversion coefficient, $\alpha_K$, for the 65.7 keV \emph{M4} transition from $^{119m}$Sn, with the result 1645$\pm$27. This result agrees with 1618, the value obtained with the ``Frozen Orbital'' method to describe the electron vacancy when calculating the ICC. If the vacancy is not included, the calculated value of the ICC is 1544, nearly four standard deviations away from our preliminary result. Our value was achieved by a measurement of the $\gamma$-ray and K x-rays from $^{119m}$Sn with an efficiency-calibrated high-purity Germanium detector. However, work is still needed to include the effects of scattering in our detector's efficiency calibration in the range of the K x-rays. Despite this, our preliminary measurement indicates better agreement with the calculation that includes the vacancy, as is physically expected. [Preview Abstract] |
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EA.00088: Monte Carlo Simulation of Partons in Ultra-Relativistic Heavy Ion Collisions Travis Salzillo, Rainer Fries, Guangyao Chen Quantum Chromodynamics (QCD) is the theory behind interactions of quarks and gluons through the strong nuclear force, and it is often studied experimentally through ultra-relativistic collisions of heavy ions. Hydrodynamics is a transport theory which describes the flow of these partons during a collision when they are in a state known as Quark Gluon Plasma (QGP). However, one of the primary unsolved problems in QCD is the evaluation of initial conditions to be used in hydrodynamics. The purpose of this project was to use the theory of Color Glass Condensate (CGC) to create a model which would simulate the initial phase of these collisions while maintaining accuracy to empirical data. The initial positions of quarks and other partons were established through the random sampling of their distribution functions in nuclei. The average color charge density of the incoming nuclei was then determined. Using CGC, the color charge density was used to calculate the energy-momentum tensor of the system. The results were visualized through plots of components of the energy-momentum tensor as a function of the rapidity and transverse coordinates of the system. The energy-momentum tensor may then be used in hydrodynamics. [Preview Abstract] |
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EA.00089: Automated Gas Distribution System Allen Starke, Henry Clark The cyclotron of Texas A{\&}M University is one of the few and prized cyclotrons in the country. Behind the scenes of the cyclotron is a confusing, and dangerous setup of the ion sources that supplies the cyclotron with particles for acceleration. To use this machine there is a time consuming, and even wasteful step by step process of switching gases, purging, and other important features that must be done manually to keep the system functioning properly, while also trying to maintain the safety of the working environment. Developing a new gas distribution system to the ion source prevents many of the problems generated by the older manually setup process. This~developed system can be controlled manually in an easier fashion than before, but like most of the technology and machines in the cyclotron now, is mainly operated based on software programming developed through graphical coding environment Labview. The automated gas distribution system provides multi-ports for a selection of different gases to decrease the amount of gas wasted through switching gases, and a port for the vacuum to decrease the amount of time spent purging the manifold. The Labview software makes the operation of the cyclotron and ion sources easier, and safer for anyone to use. [Preview Abstract] |
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EA.00090: $^26$Al Beam Production and its Application to Nuclear Astrophysics Brad Richard Presumably produced during the supernova stage of stellar evolution, $^{26}$Al offers unique opportunities to better understand the processes of nucleosynthesis occurring in pre-SN phases of stellar evolution and within the Galactic disk. When decaying to $^{26}$Mg, $^{26}$Al emits a unique 1.8MeV gamma ray, detectable by satellite telescopes. The production and destruction pathways of $^{26}$Al is a key portion of understanding the on-going stellar nucleosynthesis. In order to measure the cross-section of $^{26}$Al(n, p) $^{26}$Mg at the astrophysical relevant energies, an indirect method, called the Trojan Horse Method(THM), is utilized. The THM allows the study of neutron induced reactions at astrophysical energies via the d break-up. This method requires the three-body cross section for the $^{26}$Al(d, p $^{26}$Mg)H reaction to be measured at a beam of 60 MeV. This requires that the $^{26}$Al secondary beam is produced by the MARS facility at Cyclotron institute of Texas A{\&}M University from a primary $^{26}$Mg beam (E$\approx $16MeV/u) impinging on a H$_{2}$ target. $^{26}$Al beam was then degraded to 2.25MeV/u energy by means of a Beryllium foil. The obtained results will be shown and discussed in details together with the features of the obtained intense and pure beam. [Preview Abstract] |
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EA.00091: New Developments on Target Mass Corrections Matthew Brown, Wally Melnitchouk We consider the consistency of factorization of deep-inelastic nucleon structure functions in the presence of target mass corrections (TMCs) at low $Q^{2}$. After reviewing the standard operator product expansion derivation of TMCs in both $x$- and moment-space, we compare the results with those based on collinear factorization and assess their convergence. We discuss the limitations of the various TMC prescriptions, including attempts to alleviate the threshold problem for the behavior of structure functions as $x\to $ 1. The results are used to analyze recent high-precision structure function data from experiments at Jefferson Lab. [Preview Abstract] |
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EA.00092: High Voltage Slow Controls for the Silicon Vertex Tracker Minnae Chabwera The slow controls program developed at Thomas Jefferson National Accelerator Facility, JLab, for the Silicon Vertex Tracker, SVT, controls and reports high voltage and reads back the current drawn. The SVT is a large acceptance spectrometer designed to detect charged particles and reconstruct their paths in order to determine their momentum. It consists of 66 identical modules, each of which is connected to a High Flex Circuit Board, HFCB. Each HFCB requires 2 high voltage channels. The slow controls LabVIEW program designed for the SVT allows the user to set the threshold settings at 75V required for the HFCB to operate. If the threshold settings for voltage or current are detected outside of the operating range the channel will shut-off at a ramp rate of 5V/sec to preserve the detector. The program includes features for real-time data monitoring and offline data analysis. It will be expanded to control 132 high voltage channels to be used in Hall B at JLab and will expand to measure more parameters such as temperature and humidity. [Preview Abstract] |
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EA.00093: Low Voltage Slow Controls for the Silicon Vertex Tracker Kalee Hammerton Nuclear physics research requires the use of detectors, like the Silicon Vertex Tracker (SVT) being developed at Thomas Jefferson National Accelerator Facility, to understand the fundamental properties of particles. This detector is designed to reconstruct the paths of charged particles, aiding in the determination of their momentum. Each of the SVT's 66 individual modules is connected to a High Flex Circuit Board (HFCB). A HFCB requires 4 low voltage channels. A slow controls program was developed to control the voltage. The program allows the user to set the voltage at the 2.5 V required for the HFCB. The program is also capable of reading back the voltage and current. It includes features for real-time data monitoring and offline data analysis. The program will be expanded to control all 264 channels used for the final SVT as well as measure more parameters such as temperature and humidity. [Preview Abstract] |
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EA.00094: Consistency Constraints on Pion Momentum Distributions in the Nucleon Khalida Hendricks, Wally Melnitchouk The effects of the pion cloud of the nucleon can be parametrized in the form of pion momentum distributions (PMDs) in the nucleon. Previous efforts have used the naive pseudoscalar formulation to calculate PMDs; however, the pseudovector formulation arises more naturally from chiral field theory and explicitly respects chiral symmetry. We used pseudovector theory to calculate PMDs using several different form factors commonly used in the literature. It was found that the pseudovector formulation introduces terms that have a profound effect on the resulting PMDs. Terms that had values only at zero pion momentum had important consequences for the physical interpretations of the results. Form factors that explicitly suppress these terms may introduce significant error into calculations. In addition, suppressing terms at zero pion momentum requires that contributions previously treated separately be considered together in order to maintain a physical, probabilistic interpretation. One form factor is shown to violate gauge invariance not just in the pseudovector but also in the pseudoscalar formulation, calling into question the validity of using this form factor at all. These results will provide guidance for more accurate effective theories to describe the long-range structure of the nucleon. [Preview Abstract] |
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EA.00095: Simulating Pressure Profiles for the Free-Electron Laser Photoemission Gun Using Molflow+~ Diego Song, Carlos Hernandez-Garcia The Jefferson Lab Free Electron Laser (FEL) generates tunable laser light by passing a relativistic electron beam generated in a high-voltage DC electron gun with a semiconducting photocathode through a magnetic undulator. The electron gun is in stringent vacuum conditions in order to guarantee photocathode longevity. Considering an upgrade of the electron gun, this project consists of simulating pressure profiles to determine if the novel design meets the electron gun vacuum requirements. The method of simulation employs the software Molflow+, developed by R. Kersevan at the Organisation Europ\'{e}ene pour la Recherche Nucl\'{e}aire (CERN), which uses the test-particle Monte Carlo method to simulate molecular flows in 3D structures. Pressure is obtained along specified chamber axes. Results are then compared to measured pressure values from the existing gun for validation. Outgassing rates, surface area, and pressure were found to be proportionally related. The simulations indicate that the upgrade gun vacuum chamber requires more pumping compared to its predecessor, while it holds similar vacuum conditions. The ability to simulate pressure profiles through tools like Molflow+, allows researchers to optimize vacuum systems during the engineering process. [Preview Abstract] |
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EA.00096: Cresting Algorithm Using Fourier Analysis of Beam Position for CEBAF Accelerator Ryan Roussel, Yves Roblin The Continuous Electron Beam Accelerator Facility (CEBAF) accelerator contains two linear accelerators with Radio frequency (RF) cavities to accelerate electrons. For this to happen, the maxima of the sinusoidal electric fields in each cavity must be precisely matched to the timing of the particle's trajectories. Optimization of the beam energy is achieved by modulating the phase of cavities one at a time until the electrons are observed have the maximum energy. The focus of this project is to improve the process of finding the crest (maxima) phase of multiple cavities by modulating several cavities simultaneously. This was done by modulating the phase of each cavity at a different frequency and observing the position of the beam. The position of the beam over the period of modulation was then Fourier Transformed, producing peaks at the frequencies that corresponded to the different cavities. This was repeated with different amplitudes of modulation to fit a relationship between the amplitude of modulation and the Fourier Transform spike amplitude, which contained phase information. It has been shown that multiple cavities can be crested at the same time through the phase modulation of cavities at different frequencies and Fourier transforming the positions of the resulting beam. This has ramifications for accelerator operation because it dramatically decreases tuning time needed for beam optimization. [Preview Abstract] |
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EA.00097: Pulse Digitization: Distinguishing between single and multiple gamma ray events with Sodium Iodide Crystals Neal Anderson, Art Champagne, Stephen Daigle Gamma ray detection using analog signal processing techniques retains energy information at the expense of information about the type of interaction. However, by digitizing signals from gamma-ray detectors, we can distinguish events on the basis of interaction type, which can be used to reduce background noise. In particular, we would like to isolate single gamma-ray events from multiple gamma-ray events, which may sum in coincidence. We used a 14 bit 100MS/s digitizer to store time, energy, and waveform information from a position sensitive NaI detector, using a Co-60 source to provide both single- and double- gamma-ray events. We compared the waveforms from the individual cascade lines and the waveforms of the associated sum-peak to explore the difference in pulse shape between single- and double- gamma-ray events. [Preview Abstract] |
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EA.00098: Instrumentation Development for Plant Research at the Triangle Universities Nuclear Laboratory Nathan Tripp, Calvin Howell, Alex Crowell, Chantal Reid, Drew Weisenberger Plant physiology studies at TUNL use a variety of short-lived isotopes in radiotracing measurements. Two recently developed capabilities for this research are production of nitrogen-13 (N-13) in a water target and pulsed-loading of carbon-11 (C-11). Administering N-13 as a solution of aqueous nitrate ions allows researchers to observe plant uptake of nitrogen through the roots. The nitrogen tracer is produced through proton bombardment of a natural water target. Two main species of isotopes form during irradiation: the desired N-13 and a fluorine-18 (F-18) contaminant. A scrubber containing alumina pellets reduces the F-18 contamination by about an order of magnitude. C-11 administered as gaseous carbon dioxide allows researchers to observe plant uptake of carbon from the atmosphere. A system was constructed to deliver C-11 tagged air in bursts of adjustable width. The radioactive signatures of such pulses have sharp leading and trailing edges. This differs from the usual loading technique where the gradual exponential decay of C-11 dominates the trailing edge. This poster will include descriptions of the C-11 pulsing and N-13 production systems, their technical performance, and demonstrations of their use in plant physiology research at TUNL. [Preview Abstract] |
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EA.00099: Calculating Effective Operators of Double Beta Decay in an Algebraic Model Anthony Charles The shell model is one of the most commonly-used tools in calculating matrix elements of double-beta decay. However, the shell model does not account for certain physical phenomena, causing some inaccuracy in these matrix element calculations. Much work has gone into constructing effective Hamiltonians in order to compensate for these flaws, but very little work has gone into calculating other kinds of effective operators. We explore how to make shell model calculations of double-beta decay more accurate by finding effective double-beta decay transition operators. We use a solveable model of double-beta decay that accounts for two valence shells of nucleons. In this model, we carry out the Lee-Suzuki method in order to find effective double-beta decay operators in a smaller, one-shell space that reproduce the full result for small numbers of nucleons. We are the first to calculate any kind of effective three-body operators in this way, and we compare the relative significance of two-body and three-body effects in these effective operator calculations. [Preview Abstract] |
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EA.00100: Neutron Activation Analysis of Trace Elements in Lava Ross Meyer, Jordan Sabella, Keenan Thomas, Eric Norman, P. Guillamon, I. Goldman, A. Smith The elemental compositions of lavas vary with the locations of the volcanoes from which they emerged. We have used neutron activa- tion analysis to measure the abundances of approximately 32 different elements in lava samples collected from three different Hawaiian islands and from the summit of Mt. Kilimanjaro. Two different neutron ir- radiations were performed at the McClellan Nuclear Radiation Center to optimize our sensitivities to both short- and long-lived radioisotopes. Gamma-ray counting was done at McClellan, UC Berkeley, and LBNL using large-volume high-purity Ge detectors. Results from the mea- surements will be presented and comparisons will be made between the trace-element compositions of the lavas from these different sites. [Preview Abstract] |
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EA.00101: Use of Silicon Photomultiplier in LBL Cosmic Tay Detector Leo Osornio During a summer internship program at Hartnell Community College our team successfully constructed two complementary cosmic ray experiments. The first employed NIM electronic modules the second constructed as per specifications of a circuit board designed by the Berkeley Lab Cosmic Ray Telescope Project (http://cosmic.lbl.gov/). During the following summer at Lawrence Berkeley National Laboratory, we worked on optimizing the performance of a group of Berkeley Lab Detector and developed tools to measure its performance. The next phase was exploring whether Silicon Photomultiplier (SiPM) can be used to replace the phototube of the Berkeley Detector. Data will be presented from both summers including the dependence of the cosmic ray flux on the separation and polar angle of scintillator paddles, as well as the results from our SiPM tests. Finally, I will include prospects for curriculum development using the cosmic ray experiments. [Preview Abstract] |
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EA.00102: Analysis of J/Psi Production in Run 12 pp200 at PHENIX Will Usher PHENIX recorded 4.5 billion proton-proton collisions at $\sqrt{s}=200$ GeV during the most recent RHIC run. Using the data recorded from these collisions, we plan to measure the J/psi cross-section in the forward direction ($1.2 < |y| < 2.2$) by measuring pairs of muons and calculating the invariant mass spectrum. The J/psi mass peaks close to 3.1 GeV/c. Currently, we are working toward determining cuts which are used to reduce the non-muon backgrounds in di-muon continuum. Next, we embed muons simulated in Geant with a model of the detector into real events to determine the efficiency of our cuts. Finally we can apply the best cuts we've found to the real data and determine the J/psi yields for this year's data. Measurement of the J/psi yield in pp collisions at 200 GeV is valuable when comparing to yield in CuAu collisions where its production is expected to be suppressed as a result of color screening in the hot dense QGP. In my poster I will show the dependence of the J/Psi and background signals on the cuts applied, along with the cut's effeciency at reconstructing embedded simulation J/Psis. [Preview Abstract] |
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EA.00103: STAR measurements of elliptic flow in U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV Thomas Callister The hot, dense nuclear medium created in Au+Au collisions at RHIC has exhibited strong, anisotropic collective motion, characterized by the elliptic flow v\_2. v\_2 has been extensively studied, and is thought to be related to the initial eccentricity of the colliding system and the parton density, quantified by 1/S*dN/dy. Collisions of heavier, deformed uranium nuclei will introduce different eccentricities, and will increase the achievable value of 1/S*dN/dy by 13\% [1]. Simulations therefore predict central U+U collisions to yield a significant increase in v\_2 over central Au+Au collisions [2], and also predict a cusp structure in v\_2 vs. multiplicity due to the deformation of uranium [3]. STAR has taken data of U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV in RHIC run2012. In this poster we present preliminary STAR measurements of v\_2 from these collisions. Physics implications of our measurements will also be discussed.\\[4pt] [1] C. Nepali, G. Fai, and D. Keane, Phys. Rev. C73 (2006) 034911.\\[0pt] [2] H. Masui, B. Mohanty, N. Xu, Phys. Lett. B679 (2009) 440.\\[0pt] [3] S. Voloshin, Phys. Rev. Lett.105 (2010) 172301. [Preview Abstract] |
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EA.00104: $\Lambda$-hadron azimuthal correlations in Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV at STAR Matthew Chu Parity-odd domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in non-central relativistic heavy ion collisions [1]. A measurement consistent with several theoretical expectations has been reported by STAR [2]. The measurement, which is based on a three particle azimuthal correlator -- a $P-$even observable, is sensitive to the charge separation effect. The published results analyzed the correlations between all charged particles. A replacement of the first particle with a neutral particle, $\Lambda$ ($\bar{\Lambda}$), will provide an important systematic check. In RHIC run2010, high statistics of Au+Au collisions at 39 GeV have been taken by STAR, and that enables us to carry out the beam-energy scan of the correlation measurement. In this poster, we present the preliminary measurement of $\Lambda$-hadron azimuthal correlations as a function of centrality for Au+Au collisions at 39 GeV, and we will also discuss possible physics implications of the measurement.\\[4pt] [1] D. Kharzeev, Phys. Lett. B 633, 260 (2006).\\[0pt] [2] B. I. Abelev et al., Phys. Rev. C81 (2010) 54908. [Preview Abstract] |
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EA.00105: Neutron Capture Rates and the r-Process in a Range of Possible Environments Christopher Allen, Sean Collison, Ana Mikler, Rebecca Surman We examined the role of neutron capture rates in the r-process by running and analyzing sensitivity studies. The sensitivity studies were composed of r-process simulations in which we chose successful r-process conditions, ran a baseline simulation, and then repeated the simulation thousands of times with the neutron capture rate of each nucleus individually modified by a factor of 100. We then looked at the effects of the final abundance patterns and found the nuclei whose capture rates make the biggest changes to the patterns. Previous research focused on specific regions of the nuclear chart - A~130 region, the rare earth region, or the A~195 region - and examined only a small set of r-process conditions. For our research we expanded the range of nuclei considered to all of the isotopes of elements with $40 <$ Z $< 99$, and we studied ten trajectories that had very different environmental conditions. We found that many of the same neutron capture rates were important even in very different conditions. [Preview Abstract] |
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EA.00106: Distinguishing early-time and late-time effects of neutron capture rates in r-process nucleosynthesis simulations Sean Collison, Christopher Allen, Ana Mikler, Rebecca Surman Simulations of r-process nucleosynthesis need neutron capture rates for thousands of nuclei far from stability. We performed r-process nuclear network simulations with the aim to determine the most important neutron capture rates for further examination. We started with a baseline simulation then altered the neutron capture rate of each isotope and repeated the simulation for every nucleus in the network. By comparing these abundance patterns with the baseline, we were able to determine the nuclei whose neutron capture rates have the greatest effect on the final abundance pattern. Previous studies have shown two ways that neutron capture rates can influence the r-process pattern: an early-time photodissociation effect and a late-time neutron capture effect. For each important nucleus, we determined the mechanism that was causing the discrepancy, either neutron capture or photodissociation. [Preview Abstract] |
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EA.00107: Prototype Development for the sPHENIX Hadronic Calorimeter Shawn Beckman The sPHENIX detector proposal, for precision jet measurements in heavy ion collisions at RHIC, requires a large coverage hadronic calorimeter. The design must be compact and incorporate the magnetic field flux return, thus requiring the electronics to operate in a magnetic field. The current design incorporates alternating plates of steel and plastic scintillator, with wavelength shifting fiber optic cables embedded in the scintillator to transmit photons to silicon photomultipliers (SiPMs). We report on tests involving machining scintillator, embedding fiber optics, and light collection into SiPMs. It is our aim to optimize the light collection and ensure uniformity in the prototype hadronic calorimeter. [Preview Abstract] |
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EA.00108: Design and Fabrication of Calibration Device for Scintillating Fibers of Tagger Microscope: For use in GlueX's QCD Experiment Emily Briere For decades, scientists have struggled to understand the chromo-electromagnetic field which confines quarks and gluons within the hadron. GlueX is a QCD experiment centered at Jefferson Lab, Virginia, seeking to better understand this gluonic field by exciting it and mapping the spectrum of exotic hybrid mesons that it generates. The experiment uses coherent bremsstrahlung radiation to produce a beam of photons, which due to their polarity act as virtual vector mesons. When incident on a liquid hydrogen target, these mesons are expected to form exotic hybrid mesons. Such particles quickly decay into new particles which are captured in a solenoid detector. The decays can then be reconstructed to examine the properties of the original exotic hybrid meson, although the initial energy of the photon is required to draw meaningful conclusions. The post-bremsstrahlung degraded electrons are bent from the main beam into the tagger microscope where they strike an array of scintillating optical fibers. Given the correlation between momentum and radial bend, the Silicon Photmultiplier sensors attached to the optical fibers are able to ``tag'' the electrons', and thus the photons', initial energies based on which fibers were hit. Providing central data for GlueX, the tagger microscope must be accurate. This paper details the design and fabrication of a scintillating fiber calibration device that moves horizontally above fiber bundles, using a green laser diode to direct light pulses into the fibers. This calibration method has been tested mechanically and via a Monte Carlo Matlab simulation, and has proven to be effective. [Preview Abstract] |
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EA.00109: Simulation Studies of the COMPASS DC56 Drift Chambers Ran Bi Measurements of single transverse spin asymmetries in pion induced Drell-Yan production will be carried out with the COMPASS spectrometer at the M2 beam line of the Super Proton Synchrotron (SPS) at CERN. For this measurement the COMPASS spectrometer requires two new large area tracking chambers. GARFIELD simulations were carried out in order to optimize the position resolution of the detector and to characterize the detector signal as input to the front end electronics development. The simulation of the gas transportation coefficients, electrical fields, electron and ion drift and signal development will be presented. [Preview Abstract] |
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EA.00110: Analysis and Selection of Materials for the COMPASS DC56 Drift Chamber Prototypes Marie Blatnik The development of two new large area drift chambers is necessary to replace the current failing straw chambers at the COMPASS spectrometer at the M2 beam line of the Super Proton Synchrotron (SPS) at CERN, whose purpose is to measure single transverse spin asymmetries in pion-induced Drell-Yan productions. In order to build drift chambers that can operate in the expected high background environment, the materials used in the detector must be studied and chosen carefully. A prototype detector was designed and constructed. Results from the detector material studies and the prototype tests will be presented. [Preview Abstract] |
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EA.00111: Resistive Plate Chamber Efficiency {\&} Rate Capability Analysis Max Candocia Bakelite-based resistive plate chambers (RPCs) are particle detectors commonly used in muon trigger systems for high-energy physics experiments. Bakelite RPCs combine fast response, sufficient position resolution and low cost, and they can be operated at instantaneous background rates up to approximately 1.5 kHz/cm$^{2}$. Current and future collider experiments will demand operation of trigger RPCs under background rates higher than what is currently achieved. The rate capability is related to the bulk and surface conductivities of the Bakelite material used for the plates bordering the active gas volume in the RPCs. At the LHC and RHIC, these surfaces are coated with linseed oil, which lowers the surface resistivity of the Bakelite, which, to a point, improves the rate capability of the detectors. We have doped our own plates with various concentrations of carbon black. Over the past year we have tested RPCs with Bakelite plates of different resistivity using cosmic ray muons and radioactive Fe55 sources to emulate different levels of background in the detector. Results on the RPC efficiencies at different background rates and for different Bakelite coatings will be presented. [Preview Abstract] |
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EA.00112: Investigation of low-spin states in Gd nuclei following (p,t) and (p, d) reactions Kristen Gell, Cornelius Beausang, Erin Good, Richard Hughes, Timothy Ross, Thomas Tarlow The low to medium spin structures of a variety of Gd nuclei with N $\sim$ 90 were studied following the $^{154,155,158}$Gd(p, d) and (p, t) reactions. The 27 MeV proton beam was provided by the 88-Inch Cyclotron at LBNL. The Silicon Telescope Array for Reaction Studies (STARS) was utilized to detect the outgoing charged particles (providing both reaction selectivity and excitation energy in the residual nucleus) while the clover Ge detectors of the Liberace array measured coincident gamma-rays. Using the energies of known directly populated states in Gd nuclei, the charged particle spectra were internally calibrated. In addition, the data was analyzed in order to determine which energy states in the respective nuclei were directly populated. Furthermore, angular distributions of gamma-rays emitted from $^{154Gd}$(p,t-$\gamma$) were studied in order to make spin assignments to levels directly populated by the reactions. The next step in this research will be to further refine spin assignments and to measure the relative cross sections for direct population. This work was partly supported by the US Department of Energy via grant numbers DE-FG52-09NA29454 and DE-FG02-05-ER41379. [Preview Abstract] |
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EA.00113: Exploring The Level Schemes of Nuclei in the Z=38 to 40 Range Erin Good, Kristen Gell, Tom Tarlow, Richard Hughes, Tim Ross, Con Beausang Nuclei in the vicinity of $^{89}$Y are of interest for a variety of reasons including their use as RadChem markers in the 1950s and 60s. To improve our knowledge of the nuclear structures in the vicinity of $^{89}$Y, high to medium spin excited states in nearby nuclei were populated following the $^{74}$Ge + $^{18}$O reaction. The $^{18}$O beam, at beam-energy of 65 MeV, was delivered by the ESTU tandem Van de Graaff accelerator at Yale University's Wright Nuclear Structure Laboratory. Gamma-rays from the product nuclei (mainly Z =38 to 40, N = 48 to 50) were detected using the YRAST Ball's array of Ge clover detectors. Coincident gamma-rays were sorted into a cube which was analyzed using the Radware XmLevit8r software. The existing level schemes for several of these nuclei were re-evaluated and expanded during this analysis. Preliminary results will be discussed. This work was partly supported by the US Department of Energy via grant numbers DE-FG52-09NA29454 and DE-FG02-05-ER41379. [Preview Abstract] |
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EA.00114: Extracting the Fifth Structure Function of the $\rm ^2H(e,e^\prime p)n$ Reaction Liam Murray, Gerard Gilfoyle We have measured the imaginary part of the longitudinal-transverse interference term (the fifth structure function) of the $^2{\rm H}(e,e^\prime p)n$ reaction to test the hadronic model of nuclear physics. At Thomas Jefferson National Accelerator Facility, a 2.6-GeV electron beam was incident on a deuterium target. The beam polarization was rapidly and pseudo-randomly flipped parallel or anti-parallel to the beam momentum. Using a large-solid-angle, magnetic spectrometer, the CEBAF Large Acceptance Spectrometer (CLAS), we obtained two sets of data in the range $\rm Q^2=0.2-2.0 ~(GeV/c)^2$ using opposite polarizations of the toroidal magnetic field in CLAS. To extract the fifth structure function, we formed the helicity asymmetry $A^\prime_{LT}$. We start by taking the ratio of the difference of events for the two beam polarizations divided by their sum as a function of their missing momentum $p_m$ and $\phi_{pq}$, the out-of-plane angle between the scattering and reaction planes. The data in each $p_m$ bin were fitted as a function of $\phi_{pq}$ to a sinusoidal curve over the range $p_m = 0-0.7 ~ \rm GeV/c$. The amplitude of the fit is $A^\prime_{LT}$. The results were consistent with other methods for extracting $A^\prime_{LT}$. [Preview Abstract] |
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EA.00115: Simulation of the Scintillator Geometry in the Electromagnetic Calorimeter in the CLAS12 Detector Keegan Sherman, Gerard Gilfoyle We have modified the geometry of the electromagnetic calorimeter (EC) in a simulation of the CLAS12 detector at Jefferson Lab (JLab). The goal of JLab is to understand how quarks and gluons form nucleons and nuclei. It is being upgraded with a higher energy beam and new detectors including CLAS12 in Hall B. To prepare for CLAS12's operation, we use the code {\it gemc} that is based on Geant4 to simulate particle tracks. The EC is one of the CLAS12 components and it is used to measure the energy and position of charged and neutral particles. It is composed of alternating layers of lead and scintillating plastic. Each layer of scintillator is, in turn, composed of 36 parallel strips that form a triangle about 4.7 m on a side. Adjacent layers are rotated 120 degrees so the crossed strips can be used to determine the position of a hit. In the past the scintillators have been defined as a large slab instead of stips to reduce computation time. We have redefined them as the more realistic strips in {\it gemc}. Using the UNIX ``time'' command we observe about a 5\% increase in CPU time in the EC simulation. To test the effect on the interactive graphics in {\it gemc} we use {\it glxgears} and see about a 25\% decrease in frame rate. [Preview Abstract] |
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EA.00116: GRETINA commissioning and engineering run resolution analysis Thomas Tarlow, Con Beausang, Tim Ross, Richard Hughes, Kristen Gell, Erin Good GRETINA, the first stage in the full Gamma Ray Energy Tracking Array (GRETA), consists of seven modules covering approximately 1 solid angle. Each module is made up of four large, highly-segmented germanium detectors capable of measuring the interaction points of individual gamma-rays. GRETINA has recently been assembled and commissioned in LBNL via a series of engineering and commissioning runs. Here we report on an analysis of data from the first engineering run (ER01) which was intended to probe the response of the data acquisition system to high multiplicity gamma-ray cascades. For this experiment the 122Sn(40Ar, 4n) reaction at a beam energy of 210 MeV was utilized to populate high spin states in 158Er. A variety of beam currents, targets and trigger conditions were utilized to test the acquisition. Here we report on the measured energy resolution, both with calibration and in-beam sources as well as a gamma-gamma coincidence analysis to confirm the known level scheme and the capability of the data acquisition system for high fold coincidence measurements. This work was partly supported by the US Department of Energy via grant numbers DE-FG52-09NA29454 and DE-FG02-05-ER41379. [Preview Abstract] |
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EA.00117: Measurement of spin and parity of high spin rotational bands and the de-orientation effect in $^{178}$Hf Chengzhe Zhou, Douglas Cline, Adam Hayes Coulomb-excited rotational bands including the high K-isomer K=16+ ($\tau_{\frac{1}{2}}$=31yr), have been populated in $^{178}$Hf. The excitation mechanism, which requires 14 times K-forbidden transitions from the ground state band, is not understood. A 0.5 mg/cm$^{2}$ $^{208}$Pb target was bombarded by a $^{178}$Hf beam at 985 MeV to investigate how the 16+ isomer is Coulomb-excited. Particles in coincidence with $\gamma$-rays were detected by CHICO and Gammasphere. Several new bands, including an a-band and t-band, were seen to high spins. These could contribute to the population of the K=16+ band. The spins, parities, as well as the mixing ratios of decaying transitions (E2/M1 or E1/E3), were deduced for the a-band and t-band based on the particle-$\gamma$ angular correlation. The Coulomb excitation code GOSIA was used to fit to the experiment data. In this experiment, the ground-state band angular distribution of E2 decays was accurately reproduced by GOSIA. Best $\chi^{2}$ fits of $\gamma$-$\gamma$ angular correlation led to the assignment of positive parity for both the a-band and t-band. The spin assignments of both bands were confirmed with reasonable measurements on the mixing ratio of their decaying transitions to the ground state band. [Preview Abstract] |
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EA.00118: Study of Mobility for Germanium Crystals Steven Harding, Dongming Mei The study of mobility for n-type germanium crystals expands our capability of improving electron drift velocity and hence the time resolution of germanium detectors. With a higher mobility, we could develop a new generation of HPGe detectors for sensitive experiments like that of searching in rare event physics. Free electrons in semiconductor material move randomly with no particular average direction. Inducing a low electric field, the equation of motion for these electrons includes a resistive term, a result of the scattering processes involved with impurities and lattice vibrations of the crystal, which establishes a constant charge carrier drift velocity. The scattering mechanisms within HPGe material at 77K significantly reduce the averaged relaxation time and, thus, define the mobility. These include ionized and neutral impurity along with acoustical and optical deformation potential. Theoretical calculations were derived from first principles with reasonable assumptions and then compared with experimental data. Results show that the neutral impurity density within the acceptable range strongly affects the overall mobility. Therefore, a large reduction in neutral impurity as well ionized impurity density is necessary for high-quality mobility. [Preview Abstract] |
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EA.00119: Characterization of High-purity Germanium Crystals for Rare Event Physics Program Miranda Smith Germanium detectors are made with high-purity crystals grown in a hydrogen atmosphere at the University of South Dakota. Before these crystals can be effectively utilized, they need to be characterized for their purity, dislocation density and carrier mobility. These measurements will provide feedback to improve the crystal growth process. X-ray diffraction is used to determine the orientation of grown crystals and quality of crystalline structure. Dislocations occur when the crystal lattice structure of the germanium does not stay uniform throughout the layers. Dislocation density should be within a range of 100-10,000/cm$^{3}$ in order to avoid hydrogen-bonding issues. Our group has achieved acceptable dislocation densities of 3294/cm$^{2}$ and 7361/cm$^{2}$. The crystals have reached purity levels of 99.99999999999{\%}, but remaining unintentional impurities need to be identified to verify their nature and source. We used Photothermal Ionization Spectroscopy to determine shallow level impurities. These results are incorporated with the Van Der Pauw Hall Effect measurement, which is used to determine whether the crystal is n-type or p-type, as well as the carrier concentration and mobility. The dominant impurities are Al, B, and P. We show an entire calibration program in our research group. [Preview Abstract] |
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EA.00120: Calibration of the first Low-Background Counting Facility for SURF Mitchell Wagner, Dongming Mei, Jason Goon, D'Ann Barker Material assay, screening, and low background counting capabilities are critical to the success of the planned SURF experiments. For the next generation low-background experiments, the contamination level of the materials in the detector need to be many orders of magnitude lower than the current generation of detectors. Measuring such low activities is a challenging task that will be best accomplished by using large, high-purity germanium (HPGe) detectors, which have become commercially available in large detector volumes. Because of their extremely high purity, outstanding energy resolution and sound detection efficiency, the low-background HPGe detectors can provide the screening measurements with desired sensitivity in an underground setting. To effectively assay material at this level of sensitivity requires that the assay detector, itself, be exceptionally low in radioactivity and be deployed in a well-shielded and low background environment. We propose a phase-approached method to build the capacity that will meet the requirement for the planned SURF experiments. Phase 1 is a generic low background counter located at Davis Cavern with a sensitivity of 0.1 parts per billion for both U and Th. Phase 2 will utilize a large volume intrinsic, N-type Ge detector aiming a sensitivity of 10 parts per trillion for both U and Th. Phase 3 proposes using a GeMPI type detector that has a target sensitivity of 1 part per trillion for both U and Th. The calibration results will be discussed for the phase 1 detector will be the first low-background counting facility at SURF. [Preview Abstract] |
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EA.00121: Depletion of 39Ar in Natural Argon Gas Using a Multiple-Port Thermal Diffusion Column David Smith This project aims at providing argon depleted of~39Ar by utilizing established thermal diffusion methods for isotopic separation.~ The depleted argon can then be used as a target material for next generation large-scale dark matter detectors.~ Thermal diffusion exploits an established temperature gradient to produce a concentration gradient along the length of a vertical column.~ In this concentration gradient, heavier isotopes will accumulate at the bottom of the column, while the lighter isotopes will rise to the top. Though this technique has existed for over 50 years, little research has been conducted on investigating the distribution of concentration gradient along the length of a thermal diffusion column. A three-meter thermal diffusion column with seven sample ports has been assembled and operated at the University of South Dakota. With this column, information is being gathered about how the isotope separation factor varies along a three-meter length and how fast the separation will reach an optimal level. Preliminary tests have shown that this multi-port column can produce separation factors similar to a thermal diffusion column of the same length without multiple ports. The experimental results are being compared to a theoretical model. [Preview Abstract] |
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EA.00122: Analysis of Alpha Background from the Sudbury Neutrino Observatory Using Wavelet Analysis Jarrett Moon The Sudbury Neutrino Observatory (SNO) was a solar neutrino detector that differed from previous detectors in that it was equally sensitive to all flavors of neutrinos, which allowed SNO to obtain evidence for the oscillation of solar neutrinos. A neutrino incident on a deuteron in the heavy water used in the detector could break apart the deuteron producing a neutron. The neutron was detected by an array of proportional counters filled with $^{3}$He. The voltage vs. time, referred to as a waveform, was recorded from each proportional counter. These proportional counters were sensitive to both neutrons and alpha particles. Any alphas detected were background due to the presence of radioisotopes in the detectors. Therefore, in order to reduce the number of alpha events contributing to this background it was necessary to be able to distinguish between neutron and alpha events. Since neutrons and alphas interact differently in the detector some differences were expected in their waveforms. I attempted to eliminate confusion between neutrons and alphas by establishing a cut between them. This was done by denoising the waveforms using a stationary wavelet transform and then comparing the integrated waveforms. I will present the results of this method of distinguishing waveforms of neutrons and alphas in SNO and compare it with previous methods used. [Preview Abstract] |
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EA.00123: Development and Testing of a Novel Thermalization Mechanism for the CUORE Detector Calibration System Natania Wolansky The Cryogenic Underground Observatory for Rare Events (CUORE) will search for the signature of neutrinoless double beta decay from Tellurium-130 using an array of large crystals of Tellurium Oxide that operate as both a source of radiation and bolometric detectors, kept in a 10mK dilution refrigerator. Energy deposited in the detectors will be detected as a temperature rise in the crystals. Non-linear detector response from the bolometers with respect to time and temperature necessitates a calibration system which allows the individual calibration of each bolometer with a radioactive Th-232 source. The low-background environment of the detector requires the calibration sources to be inserted into the cryostat for each calibration campaign. A thermalization mechanism to cool the calibration source capsules from 300K to 4K before entering the 10mK chamber was designed and tested to operate within the constraints of the cryostat system. I report on the mechanical and cryogenic temperature tests of the system. [Preview Abstract] |
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EA.00124: Geant4 simulations of the GRETINA array Benjamin Roberts The GRETINA array, recently installed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University, is a powerful new tool for gamma ray spectroscopy. Early next year we are scheduled to use it to study the shell structure of exotic calcium nuclei. In summer of 2012 we visited the NSCL to assist with the preliminary testing of GRETINA at the NSCL. We took on the task of improving an existing simulation of GRETINA using the Geant4 library developed at CERN. We began with an early build of the simulation which included only the target, the beam pipe, and the detectors, and added a substantial amount of the dead material around the detectors in order to better model the Compton continuum in measured spectra. We present comparisons of simulations with gamma-ray spectra collected during our visit to the NSCL. [Preview Abstract] |
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EA.00125: Spectroscopy of $^{161}$Yb with ATLAS/Gammasphere J. Gaison, J. Carroll, M. Litz, X. Wang, M. Riley, J. Baron, S. Miller, J. Simpson, E. Paul, A. Boston, H. Boston, J. Nolan, M. Rees, J. Revill, R. Janssens, M. Carpenter, F. Kondev, T. Lauritsen, S. Zhu, L. Riedinger, D. Hartley, A. Ayangeakaa, U. Garg, C. Chiara An experiment was performed at Argonne National Laboratory's ATLAS accelerator using the Gammasphere array ($\sim $100 HPGe detectors) whose primary aim was to investigate the collective bands beyond band termination in $^{160}$Yb via the $^{120}$Sn($^{44}$Ca,4n) fusion-evaporation reaction. The high spin yield of the 4n channel was enhanced significantly by selecting a beam energy of 222 MeV and a considerable amount of data of 3n and 5n channels were also obtained. Here is presented the preliminary result of an initial spectroscopic analysis of $^{161}$Yb, the product of the 3n channel. The RadWare (coincidence analysis) software package was utilized and the possibility of revised level placements has been suggested by the analysis, in comparison with previous level schemes. [Preview Abstract] |
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EA.00126: Experimental System to Study the $\alpha$ Decay of $^{178}$Hf$^{m2}$ K.A. Netherton, J.J. Carroll, M.S. Litz, S.A. Karamian The nuclide $^{178}$Hf possesses a second isomer that is notable in its spin (I$^{\pi }$ = 16$^{+})$, lifetime (T$_{1/2}$~=~31 years) and excitation energy (E$_{m}$ = 2.446 MeV). It is this high excitation energy that permits $\alpha $ decay of the nucleus from the isomeric state, although the $^{178}$Hf nuclide is stable in its ground state. The $\alpha $ decay was detected (PRC 75, 057301, 2007) through the use of a track detector and the associated half-life was deduced to be (2.5 \underline {+} 0.5) $\times $ 10$^{10}$ years, compared with the previously-known half-life for IT decay of 31 years. The most probable decay sequence was predicted to be $\alpha $ decay with E$_{\alpha }$ = 3.91 MeV to the I$^{\pi }$ = 6$^{+}$ member of the $^{174}$Yb ground-state band. However, so far no spectroscopic study of this rare decay has been performed. An experimental system to accomplish this has been constructed using a silicon surface barrier (SSB) charged-particle detector and a high purity Germanium (HPGe) $\gamma $ detector, with the aim of recording both $\alpha $ decays and $\alpha -\gamma $ coincidences. The experimental design, instrumentation and preliminary testing will be discussed. [Preview Abstract] |
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EA.00127: Development of calibration sources for the CUORE detector calibration system Jess Clark CUORE, the cryogenic underground observatory for rare events, is a search for neutrinoless double beta decay(0$\nu\beta$$\beta$) that utilizes 988 TeO$_2$ bolometers at a temperature of 10 mK within a cryogen-free cryostat. Periodic precise energy calibration, particularly in the energy region surrounding the double beta decay Q-value of $^{130}$Te (2527 keV), is required to reliably establish and maintain an understanding of the bolometer responses. The detector calibration system (DCS) uses 12 gamma-source strings that are lowered into the detector region of the cryostat through a series of internal guide tubes for monthly calibration. The main constraints on our source string design are radiopurity of the production materials, mechanical reliability, and the load introduced into the cryostat from friction, thermal conductance, and radiation. We discuss the design, fabrication, and quality assurance of the radioactive source strings for the CUORE calibration system. [Preview Abstract] |
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EA.00128: Neutral Pion Background Analysis at STAR Adam Clark The STAR detector at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory takes measurements of polarized proton collisions which can then be used to extract cross sections and spin asymmetries. The Endcap Electromagnetic Calorimeter (EEMC) in STAR allows measurements of electromagnetic particles in the forward direction, $1<\eta<2$. The EEMC will be used to determine the neutral pion ($\pi^0$) cross section and the double longitudinal spin asymmetry ($A_{LL}$) which gives us information about the gluon contribution to the proton's spin. The $\pi^0$ cross section is an important supporting measurement to verify our signal reconstruction and the background characterization for the $\pi^0$ asymmetry. In order to measure the $\pi^0$ cross section and asymmetry, the backgrounds must be well understood (such as those from photon conversions and reconstruction errors where one photon reconstructs as two clusters). Efforts toward the $\pi^0$ cross section and asymmetry measurements and, specifically, those to understand $\pi^0$ backgrounds will be discussed. [Preview Abstract] |
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EA.00129: Stability of the Gains of the STAR Endcap Calorimeter from 2006 to 2011 Kayla Kutz The Solenoid Tracker at RHIC (STAR) experiment, based at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC), uses polarized-proton collisions to investigate sea quark and gluon contributions to the known proton spin. The STAR detector's Endcap Electromagnetic Calorimeter (EEMC) measures the energy of particles produced by those collisions using a lead-scintillator sampling calorimeter, consisting of several layers that include pre-shower, shower maximum, tower, and post-shower detectors. In these detectors, the energy gains, which convert a measured pulse into an energy deposition, have been determined using data taken from the years, 2006, 2009 and 2011. Changes in the gains over time may result from known high voltage changes or deterioration of the detector, such as from radiation damage. A comparison of the gains from the three years will be presented. [Preview Abstract] |
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EA.00130: An event-by-event comparison of clustering algorithms for photon detection in the STAR Endcap Calorimeter William Pochron The STAR detector at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory uses polarized proton collisions to determine the origin of the proton spin, using measurements such as neutral pion asymmetries. The Endcap Electromagnetic Calorimeter (EEMC) in the STAR detector is especially useful for detecting photons from $\pi^0$ decays at forward angles. This latter measurement is obtained from the Shower Maximum Detector (SMD) in the EEMC where narrow crossed scintillator strips measure the energy deposited in them and can be used to identify the location of the photon shower. The electromagnetic shower most often deposits energy in a small number of adjacent strips that collectively form a ``cluster.'' This work has focused on a qualitative and quantitative comparison of two different clustering algorithms that were developed to reliably identify $\pi^0$ events and to effectively discriminate against background cluster selection that produce false $\pi^0$ signals. This comparative analysis will be presented and the strengths and weaknesses of the algorithms will be discussed. [Preview Abstract] |
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EA.00131: Alpha-decay of exited states in 12C Juan Manfredi, Robert Charity, Kevin Mercurio, Rebecca Shane, Lee Sobotka, Alan Wuosmaa, Adriana Banu, Livius Trache, Robert Tribble Recently it was suggested that the state in $^{12}$C at an excitation energy of 7.65 MeV ($J^\pi = 0^+$), the Hoyle state, can decay via a mechanism that produces three $\alpha$-particles of almost equal energy. High-resolution triple-$\alpha$ coincidence data were used to reconstruct the decay of the excited states in $^{12}$C at 7.65 MeV ($J^\pi = 0^+$) and 9.64 MeV ($J^\pi = 3^-$). These data were gathered at the Texas A\&M University K500 cyclotron facility, where a $^{10}$C beam impinged on a Be target and reaction products were detected using four Si $E-\Delta E$ detectors. The results of this experiment are consistent with the $\alpha$-particle decay of both levels proceeding exclusively through $^8 Be _{g.s.}$. In the first of these cases, the Hoyle state, upper limits of 0.45\% and 3.9\% (at the 99.75\% confidence level) are set for an equal-energy $\alpha$-particle decay process and a process uniformly spanning three-body phase space (respectively). The limit for the equal-energy $\alpha$-particle decay is much lower than claimed in the previous result. [Preview Abstract] |
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EA.00132: Coincidence Efficiency Measurement Using 11B(p,n)11C Megan Russ, Stephen Padalino, Danae Polsin, Michael Krieger, Collin Stillman, Mollie Bienstock, Drew Ellison, Angela Simone, Mark Yuly, Keith Mann, Tyler Reynolds, Craig Sangster An attempt to measure the 12C(n,2n)11C cross section for high energy neutrons in the range of 20-30 MeV was conducted using Ohio University's accelerator facility as a fast neutron source. The neutrons were incident on a graphite target and the $\beta $+ decay of the activated carbon-11 nuclei were observed in an on-axis gamma ray detector pair. To pre-determine the efficiency of this gamma ray detector system, a boron-11 activation experiment was performed. Using SUNY Geneseo's 1.7 MV tandem pelletron accelerator, 3.1 MeV protons were incident upon the 11B foil inducing the 11B(p,n)11C reaction to occur at a high rate of activation. The 11C decays via $\beta $+ emission, then upon annihilation with an electron creates characteristic 511-511 keV photon pairs which were counted using coincidence methods. Since the 11B(p,n) cross section is well defined, a calculation was performed to determine the expected number of activations and later compared to the total number of decays observed in the counting system. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics. [Preview Abstract] |
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EA.00133: Cross Section of the (n, 2n) Reaction in $^{12}$C in the Energy Interval 20-30 MeV Danae Polsin, Steven Padalino, Megan Russ, Michael Krieger, Mollie Bienstock, Drew Ellison, Angela Simone, Collin Stillman, Mark Yuly, Keith Mann, Tyler Reynolds, Craig Sangster The behavior of the (n, 2n) reaction in $^{12}$C and other light nuclei is known with much less certainty than for heavy nuclei. The published cross section data for the $^{12}$C(n, 2n)$^{11}$C reaction is bifurcated in the energy range of 20-30 MeV. An experiment to measure the $^{12}$C(n, 2n)$^{11}$C cross section for these neutron energies has been performed using the Ohio University Tandem Accelerator. Deuterons from the accelerator struck a tritium foil releasing neutrons via the T(d, n)$^{4}$He reaction. Deuteron bombarding energies between 3.3-8.7 MeV resulted in neutrons with energies between 20-26 MeV. The geometry of the experiment was chosen so that the incident neutron energy would not vary by more than 0.5 MeV across the graphite target. After neutron bombardment, the decay of the $^{11}$C nuclei by positron emission was measured with an array of NaI detectors to determine the activity of the carbon sample. The neutron fluence through the carbon was measured using a particle telescope to detect protons from the $^{1}$H(n, p) reaction in a polyethylene target, allowing the absolute cross section for the $^{12}$C(n, 2n)$^{11}$C reaction to be determined. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics. [Preview Abstract] |
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EA.00134: In Situ Calibration for Proton Particle Telescope Collin Stillman, Stephen Padalino, Danae Polsin, Megan Russ, Michael Krieger, Mollie Bienstock, Drew Ellison, Angela Simone, Mark Yuly, Keith Mann, Tyler Reynolds, Craig Sangster Neutrons produced via the 3H(2H,n)4He reaction at the Ohio University Accelerator Lab were used to activate a graphite sample via the $^{12}$C(n,2n)$^{11}$C reaction in an attempt to measure the (n,2n) reaction cross section. Before striking the graphite, the neutrons struck a thin polyethylene foil and elastically scattered protons in to a surface barrier detector telescope. The recoiling protons were used to determine the energy and number of neutrons which struck the $^{12}$C activation sample. To verify that the particle telescope's predicted response function for 15 to 27 MeV protons was correct a calibration of the detector telescope was performed in air on the SUNY Geneseo tandem Pelletron accelerator. High energy protons were created via the $^{2}$H($^{3}$He, p)$^{4}$He reaction by bombarding a deuterated polyethylene target with 4.5 MeV $^{3}$He ions. The high-energy protons then pass through a Kapton window from vacuum into air where they were detected by the particle telescope. The dependence of the detector response on various proton energies was then investigated for various detector geometries. This data was extremely useful when performing the graphite activation experiment at the Ohio University accelerator lab. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics. [Preview Abstract] |
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EA.00135: Design and Characterization of a Collimated Neutron Beam User Facility at SUNY Geneseo Michael Krieger, Stephen Padalino, Megan Russ, Danae Polsin, Mollie Bienstock, Drew Ellison, Angela Simone The Collimated Neutron Beam (CNB) Facility at SUNY Geneseo provides users an opportunity to perform neutron experiments that require a low neutron background. Neutrons with energies up to 10 MeV are produced by a Plutonium-Beryllium (Pu-Be) source and are collimated to form a well characterized beam. A six foot high, 18 inch thick shielding wall made of water-bricks was built to reduce neutron background in the target area. Neutron and gamma radiation were extensively mapped throughout the facility using a calibrated Bonner sphere, Geiger counter, plastic scintillator and an HPGe detector. Potential uses for the CNB include neutron activation, time-of-flight, attenuation and neutron detector calibration experiments. A detailed description and layout of the facility will be displayed on the poster. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics. [Preview Abstract] |
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EA.00136: A Method to Normalize the NPDGamma Data Forrest Simmons The NPDGamma Experiment measures the parity-violating asymmetry in the $\vec{n} + p \rightarrow d + \gamma$ reaction. In the measurement, polarized cold neutrons interact with liquid parahydrogen target and the spatial asymmetry of the gamma-rays is measured. The neutrons are produced in pulses by the Spallation Neutron Source, where 1 GeV proton pulses are interacting with circulating liquid mercury target producing neutrons that then are moderated and guided to experiments. The delivered proton beam intensity per pulse varies producing varying neutron fluxes in the experiment. The signal from the NPDGamma detector needs to be normlized to remove the beam intensity fluctuations in the measurement. There are two ways to do this, either by measuring the neutron flux out from the neutron guide or by measuring the flux of protons delivered to the mercury spallation target. I will present a method of reading the proton current for each proton pulse into a data file, which can then be used for the normalization. [Preview Abstract] |
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EA.00137: Search for $^{90}$Sr from the Fukushima Reactor Accident in San Francisco Bay Area Rainwater B.T. Lo, P.A. Chodash, K.J. Thomas, E.B. Norman Shortly after the Fukushima reactor accident, we collected rainwater samples in the San Francisco Bay area. Subsequent gamma-ray counting revealed the presence of volatile short-lived fission fragments such as $^{131, 132}$I, $^{132}$Te, and $^{134,137}$ Cs [1]. Recently, we have searched for the presence of the long-lived fission fragment $^{90}$Sr in these same rainwater samples. To chemically separate Sr, a small amount of stable Sr carrier was dissolved in each rainwater sample. Potassium carbonate was then added to precipitate SrCO$_{3}$. The precipitate was filtered, dried, and then beta counted using a planar Ge detector. Results from these measurements will be presented and compared to the levels of other fission fragments previously observed in the rainwater. \\[4pt] [1] E. B. Norman, C. T. Angell, P. A. Chodash, PLoSONE 6(9): e24330. Doi:10.1371/journal.pone.0024330. [Preview Abstract] |
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EA.00138: Neutron Activation Analysis of Trace Elements in Lava R.E. Meyer, J.L. Sabella, K.J. Thomas, E.B. Norman, P.V. Guillamon, I.D. Goldman, A.R. Smith The elemental compositions of lavas vary with the locations of the volcanoes from which they emerged. We have used neutron activation analysis to measure the abundances of approximately 32 different elements in lava samples collected from three different Hawaiian islands and from the summit of Mt. Kilimanjaro. Two different neutron irradiations were performed at the McClellan Nuclear Radiation Center to optimize our sensitivities to both short- and long-lived radioisotopes. Gamma-ray counting was done at McClellan, UC Berkeley, and LBNL using large-volume high-purity Ge detectors. Results from the measurements will be presented and comparisons will be made between the trace-element compositions of the lavas from these different sites. [Preview Abstract] |
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EA.00139: Nuclear properties associated with the unitary limit Dan Fu, Aram Mekjian The unitary limit occurs when scattering lengths become very large compared to inter-particle spacings. In this limit properties of the system become independent of the details of the underlying force. Various features acquire a behavior that is universal which therefore manifest themselves in other systems under the unitary limit. Cold atoms and Fermi and Bose quantum gases are studied in the unitary limit. The nuclear case has an S-wave spin 0 scattering length for two neutrons which is -17.4fm (virtual state). The S-wave spin 0 neutron --proton scattering length is -23.7fm (virtual state) while the spin 1 bound state (the deuteron) is weakly bound. The unitary limit is approximately realized in a nuclear system. Some departures from the unitary limit exist and the effective range of the nuclear force appears in expressions. A square well potential adjusted to give experimentally observed properties is used. Our study focusses on the finite temperature thermodynamic properties of nuclei. These properties include the nuclear equation of state and associated compressibility, the nuclear viscosity and the entropy. The issue of near perfect fluid behavior is remarked on. Dan Fu research was supported by the Aresty undergraduate research program at Rutgers. This work was also supported by a DOE grant- DOE FG02-96Er40987. [Preview Abstract] |
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EA.00140: Lagrange Meshes in Nuclear Physics Taylor Hynds We examine different methods of solving the Schr\"{o}dinger equation for two and three-body systems. We begin by constructing variational wave functions, as expansions in a basis of orthogonal polynomials. This method has been found to give accurate results, given a sufficiently large basis. However, computationally this can become very cumbersome. We therefore employ the Lagrange-mesh method, which leads to a simple calculation of both potential and kinetic matrix elements that is both computationally efficient and results in little to no loss in accuracy. This method has been applied to several problems with well known analytical solutions, and has given excellent results. The effectiveness of this method in analyzing bound states of quarks has yet to be demonstrated. In the future this method will be applied to the quantum-mechanical three-body problem in an effort to better understand the structure of various nuclei. [Preview Abstract] |
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