Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session DA: CEU Poster Session (14:00 - 15:48) |
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Room: Lobby |
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DA.00001: E906 Experiment: Study of Background Rates with a Solid Magnet Obiageli Akinbule Fermilab (Fermi National Accelerator Laboratory) E906 is an experiment to determine the ratio of d-bar to u-bar quarks in the nucleon sea. The experiment measures the di-muon pairs that are produced via the Drell-Yan process, which is when a quark and anti-quark annihilate, creating a di-lepton pair. With a goal of extending the E866/NuSea measurements to higher Bjorken x, it will help reveal the structure of the proton. The results to be presented focus on using GEANT4 Monte Carlo simulations to investigate spectrometer acceptance and background rates if a solid iron magnet is used, as opposed to the original plan of an open magnet filled with hadron absorbers. A solid iron magnet would be relatively low cost, since the coils and iron can be taken from parts of the E866/NuSea detector apparatus. Results of these simulations will be shown to demonstrate that the solid iron magnet will give acceptable results. Results will also be shown on ideas to reduce the background from in-flight pion decays from the liquid hydrogen and deuterium targets. [Preview Abstract] |
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DA.00002: Developing an Efficient Read-Out System for the A2 Pair Spectrometer at Mainz Amal Al Katrib, William Briscoe The scientific program at the Mainz Microton (MAMI) is based on polarized electron and photon beams from the MAMI A-B-C accelerator complex. The scientific program at the Mainz Microtron (MAMI) is based on polarized electron and photon beams from the MAMI A-B-C accelerator complex with energies up to 1.5GeV. In order to deal with the energy increase, the photon tagger system has been extended and refurbished by the Glasgow University Nuclear Physics Group. It is now available for real photon experiments in the A2 hall. For experiments with real photons in the A2 hall, the Crystal Ball detector is being used regularly together with an inner detector for tracking and a forward crystal calorimeter (TAPS) for 4pi gamma coverage. A new data acquisition system with high-rate performance is in operation. Experiments are currently running using a liquid hydrogen/deuterium target. The Pair Spectrometer in the A2 hall is not providing timing information efficiently due to the various disadvantages of using photomultiplier tubes in high magnetic fields. This poster will include the current status of the experimental equipment in Mainz and the role of student involvement in the program at MAMI. Student will discuss the project given in hand, which is replacing photomultipliers in the Pair Spectrometer with avalanche photodiodes that are not affected by the 1 Tesla magnetic field. The output of 2 detectors, a large area avalanche photodiode and a multi-pixel photon counter, is observed and compared for better rise time and detection of electron-positron pair as the photon beam hits matter. For testing purposes, the photodiode is attached to a scintillator and is connected to a pre-amplifier (ORTEC 142A) followed by a timing amplifier (ORTEC 474) and then a pulse shape discriminator (model 2160A). [Preview Abstract] |
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DA.00003: Metal Oxide Films Produced by Polymer-Assisted Deposition (PAD) for Nuclear Science Applications~ Mazhar Ali, Mitch Garcia, Noel Chang, Tashi Parsons-Moss, Jacklyn Gates, Paul Ashby, Liv Stavsetra, Kenneth Gregorich, Heino Nitsche The preparation of homogenous metal oxide films (100 to 750 nm) is of interest to nuclear science for use as targets in nuclear reactions. Metal oxide targets, prepared for nuclear science applications, are conventionally made by molecular plating. However, the method suffers from poor adhesion to the backing material and lacks homogeneity at target thicknesses less than about 300 nm. Polymer-assisted deposition (PAD) produces crack-free homogeneous metal oxide films with uniform thicknesses between 20 and 400 nm and was investigated as a new method for preparing targets. Metal oxide films of europium, thulium, and hafnium were prepared as models for actinide oxides. Films produced by a single application of the PAD method were homogenous and uniform and ranged in thickness from 30 to 320 nm. Targets were then prepared on silicon nitride backings (thickness of 1000 nm) and were irradiated with an 40Ar beam at a laboratory frame energy of approximately 210 MeV. Atomic force microscopy and scanning electron microscopy of the irradiated target reveals no significant difference in surface homogeneity when compared to imaging prior to irradiation. Future plans with the PAD method will also be presented. [Preview Abstract] |
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DA.00004: Searching for a Betatron Tune Working Point for the Proposed Electron-Ion Collider at Jefferson Laboratory Scott Alton The mechanics of relativistic particles in storage rings are well understood. The particles oscillate around the intended orbit in the transverse X and Y directions--called the betatron oscillations. The number of oscillations per orbit is known as the betatron tune. If the betatron tune is an integer or a special resonance value, the oscillations will build in amplitude due to constructive interference and the beam will become less focused. This becomes complicated in the proposed ELectron-Ion Collider at Thomas Jefferson National Accelerator Facility (ELIC). The ELIC will be similar to a storage ring except that there will be beams of particles in both directions through each other several times every turn around the ring. When the beams pass through one another, they give each other a ``kick'' which alters the betatron tune often causing it to become one of the resonance values and degrading the beam quality and luminosity, which is a measure of the number of collisions per turn around the ring. This narrows down the range of betatron tunes that are available to operate the collider with a well focused beam. The purpose of this research was to find a betatron tune working point, or a set of betatron tunes in both transverse directions, which optimize the luminosity for both beams. A tune map shows which areas of the tune space are far from resonance values. The tune map was used to choose some betatron tune working points far from resonance. The region that was used was near half integer, because there was a large space on the tune map that was far from the regions of resonance. Simulations were run that broke down the collider rings into a series of linear maps around the ring and elementary forces at the point where the two beams interact. The goal was to find a betatron tune point where the beams stayed focused after many turns. An effort was made to separate the different tunes to find out how each one affected the luminosity but due to the highly nonlinear nature of the forces involved, this was ineffective. A stable working point has been found in the half integer region of the tune map. The point maintained about 65{\%} of its peak luminosity after 30000 turns. This compares well with some of the best working points that have been found which top out at around 70{\%} of the peak luminosity. It was found that there are certainly stable working points in the half integer region, and more points should be explored in this promising region of values. With a good working point, it will be possible to build a high luminosity collider allowing new experiments involving quantum chromo dynamics. [Preview Abstract] |
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DA.00005: Signal Readouts in a PHENIX RPC Keller Andrews The PHENIX collaboration at RHIC studies polarized proton-proton and heavy ion collisions to better understand the structure of the proton. PHENIX is in the process of upgrading the muon trigger to improve their capabilities of studying the production of W-bosons. By triggering on single, high transverse momentum muons among a background of low transverse momentum muons, new observations on the inner structure of a proton can be obtained. The trigger upgrade will consist of six stations of Resistive Plate Chambers (RPCs), three stations on each side of the interaction region. Inside an RPC, there are several copper strips, called a signal plane. When a charge is induced on them by a charged particle (a muon) traveling through an adjacent gas gap, it passes a charge from the strip, into a readout wire. The wire runs to a card that transitions from the signal plane to the readout electronics (a transition card). In the readout electronics, the signal is amplified and sent to a discriminator that produces a digital record of the charged particle's path. This poster will explain how RPCs work and how the signal is generated in the prototype PHENIX detectors. [Preview Abstract] |
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DA.00006: The High Voltage System for the PHENIX RPC Test Stand Phil Bailey PHENIX is an experiment at RHIC designed to probe the spin structure of the proton by observing high energy polarized proton-proton scattering. Observing W boson production is an effective way to make this measurement. The W bosons are identified by detecting their decay into muons. In order for these rare events to be effectively measured, however, the muon trigger requires an upgrade that will allow the higher rejection rate required by higher luminosities at RHIC. The upgrade will allow PHENIX to trigger only on the high pT muons and ignore the lower pT background muons. The actual hardware that will provide the triggering is called an RPC. In order to test the working condition of the RPCs, they will be placed on a test stand in order to gain assurance that cosmic muons are seen by the detectors. The high voltage systems, including cabling and data logging software, that operate the RPCs in the cosmic test stand will be presented. [Preview Abstract] |
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DA.00007: Evidence for Multiple Negative-Parity Band Structure in $^{71}$Se N.R. Baker, R.A. Kaye, S.R. Arora, J.K. Bruckman, S.L. Tabor, T.A. Hinners, C.R. Hoffman, S. Lee, J. D\"oring The negative-parity bands of $^{69}$Se and $^{73}$Se indicate a stark contrast between strong single-particle ($^{69}$Se) and collective ($^{73}$Se) behavior over a wide range of spins. However, only one negative-parity band has been observed so far in $^{71}$Se, making it difficult to see where it lies between these two very different cases. Thus, the goal of the present work was to extend the level scheme of $^{71}$Se as much as possible, with an emphasis on finding new negative-parity states. $^{71}$Se nuclei were produced at high spin following the 80-MeV $^{54}$Fe ($^{23}$Na, $\alpha pn$) reaction at Florida State University. $\gamma-\gamma$ coincidences were measured using an array of 10 Compton-suppressed Ge detectors which included three Clover detectors. From the coincidence relationships, new states were found that formed candidates for perhaps two new negative-parity bands. Cranked-shell model calculations indicate that one new band is associated with rigid- body rotation at high spin. [Preview Abstract] |
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DA.00008: Forward RPC Trigger Design and Integration at PHENIX Austin Basye PHENIX is a general purpose particle physics experiment at the Relativistic Heavy Ion Collider (RHIC) studying polarized proton and heavy ion collisions. One of PHENIX's goals is to define the sea quark contribution to proton spin by using W boson asymmetries arising from quark-antiquark interactions in polarized proton collisions. This analysis is dependent on the reconstruction of single, high transverse momentum (pT) muons. The Forward Resistive Plate Chamber (PRC) Upgrade will allow PHENIX's muon arms to trigger on probable W boson events despite a significant low pT muon background. To that end, the RPC design team was tasked with designing and installing four stations of detectors (each $\sim$80 m$^2$ in surface area) into the existing PHENIX architecture. This poster will discuss our approach to balance cost, practicality and complexity on the one hand with efficiency, resolution and acceptance on the other hand using RPC detector technology. [Preview Abstract] |
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DA.00009: Gamma Ray Spectroscopy of Heavy Elements using GAMMASPHERE Marco Bonett-Matiz The project involves data analysis to study excitations in heavy nuclei in and around the nucleus 209Bi. The data is from an experiment that was carried out to study heavy nuclei in the 248Cm region. The experiment consisted of a 209Bi beam from the ATLAS heavy-ion accelerator at Argonne National Laboratory incident on a 248Cm target. The beam energy was 1450 MeV, 15{\%} above the Coulomb barrier. Excited states in both target-like and beam-like nuclei were populated. While the primary focus of the experiment was to study isomers in 248Cm, this complementary project was to study excitations of 209Bi and neighboring nuclei around the doubly magic 208Pb. The gamma rays were detected by the GAMMASPHERE array of 100 germanium detectors. Level schemes were analyzed through gamma matrices and cubes using the standard RADWARE suite of programs. Angular correlations were analyzed for multipolarity information. Isomer halflives in the nanosecond to microsecond range were studied. New isomers in 209Bi, expected through the coupling of an extra proton to the 208Pb core, were searched for. Results of the above spectroscopic studies will be presented. [Preview Abstract] |
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DA.00010: Electron Identification for Jet Finding Algorithms in ALICE Brandon Boswell, Christopher Brown, J.L. Klay Particle jets emitted by heavy ion collisions in the ALICE experiment at the LHC can be measured with jet-finding algorithms that have been adapted to account for the large heavy ion backgrounds. Energy hits collected from the Electromagnetic Calorimeter (EMCAL) are coupled with tracks from the Time Projection Chamber (TPC) to identify jets. By comparing the properties of jets in Pb+Pb to those found in p+p collisions we can study the energy lost by partons before they fragment into jets. In order to study the color, flavor and mass dependence of partonic interactions within a quark gluon plasma, we must isolate jets that have been created by heavy quarks. These fragment to heavy mesons that through semi-leptonic decay can produce high $p_T$ electrons within the jets. We have combined the ALICE JetFinder with the electron identification from the EMCAL+TPC to try to tag heavy quark jets. This poster will present the status of our analysis of heavy quark jets produced in PYTHIA and HIJING simulations within the ALICE software framework, AliRoot. [Preview Abstract] |
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DA.00011: GRETA Pile-Up Recovery Whitney Brooks The proposed Gamma Ray Energy Tracking Array uses Ge detectors to track interactions by each gamma ray detected. Tracking determines which interactions belong to which gamma rays using the energy and position of the interaction found properties of Compton scattering. Detectors are connected to a pre-amplifier which puts out a pulse signal when a gamma ray is detected. The pre-amplifier is connected to a Digital Signal Processor which digitizes the pulse shape using a 10 ns sampling time, showing an image of the pulse. The rise time for the signal is 100-200 ns. The signal decays with a time constant of about 50 microseconds. The height of the pulse is proportional to the energy of the gamma ray. Sometimes a second gamma ray is detected before the pulse signal of the first one has fully decayed, creating a pile-up of pulse signals. LBNL's current data analysis system performs ``Pile-Up Rejection'' where it discards any data not deemed a single pulse. My code performs Pile-Up Recovery, enabling us to get more data instead of rejecting useful data. The code uses derivatives and regression lines to tell if a pulse is a single pulse or a pile-up pulse. If a pile-up is detected, the two are separated and the energy of each is found. [Preview Abstract] |
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DA.00012: Performance of the STAR Heavy Flavor Silicon Tracker in Measuring the Charged B Meson through B $\rightarrow$ J/$\Psi $ + X Decay Elizabeth Brost The STAR detector, located at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, gathers data from particle collisions. STAR's main task is to study the properties of the matter produced in these collisions, particularly the quark-gluon plasma (QGP), which is expected to have been created a few microseconds after the ``Big Bang''. Among all probes used to study the properties of the QGP, heavy quarks are unique, and ideal for studying the QGP because of their large mass. One particularly interesting way to study heavy quarks is through the B $\rightarrow$ (J/$\Psi \rightarrow$ e$^{+ }$+ e$^{-})$ + X decay channel, since there is very little background. Using simulated central Au+Au collision data containing electron-positron pairs from B $\rightarrow$ J/$\Psi $ decay and from prompt J/$\Psi $ decay, I was able to reconstruct the displaced vertices (L$_{xy})$ for the J/$\Psi $ particles. Then, I made a distribution of L$_{xy}$ for B decay (signal) and prompt (background) J/$\Psi $ particles. Finally, after making successive cuts of L$_{xy}$, I created signal-to-background and efficiency distributions for measuring the charged B mesons in central Au+Au collisions through this decay channel. [Preview Abstract] |
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DA.00013: Study of Carbon 16 Within the Three-Body Model H.J. Brown, F.M. Nunes In this study the Carbon 16 nucleus has been examined within a three-body model Carbon 14 + n + n. The valence neutrons interact with a realistic n-n force while the Carbon 14 - neutron interaction was fitted to reproduce the low-lying single particle spectrum of Carbon 15. Two shell model pictures of Carbon 15 were considered, each differing in the treatment of the p-wave orbitals. The main results presented assume the Carbon 14 core is inert but we also will mention preliminary results including core deformation and excitation. Our findings indicate that in order to build a more realistic Carbon 16, one must account for the inversion of the p-wave resonances in Carbon 15. Our model is in fair agreement with experimental values for the Carbon 16 ground state three-body binding energy and RMS radius. This calculation predicts the lowest 0.0+ and 2.0+ states in Carbon 16 with the proper ordering but excitation energies are a bit smaller than experiment. [Preview Abstract] |
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DA.00014: Assembly and Quality Assurance Tests of Gas Gaps for the PHENIX Muon Trigger Upgrade David Broxmeyer The RHIC ``spin'' program investigates the spin of a proton by looking at collisions between polarized protons. W bosons are sometimes created in these collisions. The parity violating decay of W bosons can be used to identify the underlying quark-quark and quark-antiquark interaction. The PHENIX muon trigger upgrade will utilize resistive plate chambers (RPCs) to distinguish the muons that decay from W bosons from other muons. The RPCs use 95{\%} Freon 134A, 4.5{\%} isobutene, and 0.5{\%} sulfur hexafluoride (SF$_{6})$. In order for these gas gaps to be used, checks are performed on the gaps. The gas gaps must contain no leaks. Approximately 10kV are placed across the 2mm gaps and therefore the gaps require spacers to insure that there is uniform separation between the surfaces. Popped spacer tests are performed to insure that the spacers are properly attached. [Preview Abstract] |
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DA.00015: Evolution of Collective Structure in Odd-Odd $^{70}$As J.K. Bruckman, R.A. Kaye, S.R. Arora, N.R. Baker, S.L. Tabor, T.A. Hinners, C.R. Hoffman, S. Lee, J. Doering Excited states in $^{70}$As were produced via the $^{23}$Na($^{54}$Fe, $\alpha 2pn)^{77}$Rb reaction at 80MeV. Gamma-ray transitions between the excited states were collected in coincidence using a high-resolution array of 10 Ge detectors. From the coincidence relationships, a candidate for the missing odd-spin negative-parity sequence was found, with spins and parities assigned tentatively using systematic arguments. All other high-spin level sequences found previously were confirmed. The kinematic moments of inertia for the new band and those observed previously, calculated within the context of the cranked-shell model, show that $^{70}$As is likely dominated by collective behavior at high spin, making it more similar in this regard to $^{72}$As than $^{68}$As. Collectivity and deformation also seem to increase with neutron number in the light proton-rich arsenic isotopes. [Preview Abstract] |
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DA.00016: Design and Construction of a Drift Chamber for RPC Detector Development Alex Burnap Currently, the PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Lab is developing resistive plate counters (RPC) to be used as one component of the Level 1 trigger for high p$_{T}$ muons produced in the decay of W-bosons. The single spin asymmetries of W-bosons in polarized p-p collisions can be used to measure sea quark spin contributions to the proton spin. RPC prototypes are tested at UIUC by utilizing cosmic rays. Drift chambers are placed in planes parallel with resistive plate counters for cosmic ray track reconstruction. The drift chamber design was updated with novel improvements, optimized using Garfield simulation, and a prototype was built and tested. In this poster we present results from the simulation, details of the design and construction, as well as test results obtained from the drift chamber prototype. [Preview Abstract] |
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DA.00017: Parton Distributions of the Kaon and the Tetraquark Bonnie Canion The goal of this research is to describe parton distributions for the $K^+$ meson (kaon) and the tetraquark. We used the statistical model of Zhang et al. [1,2], which describes a particle as an expansion in quark-gluon Fock states, assumes detailed balance, and does not use any free parameters. The $K^+$ meson and tetraquark are each made up of a set number of valence quarks, and a sea of light quark-antiquark pairs and gluons. The $K^+$ meson has two valence quarks, $u$ and $\bar{s}$. The tetraquark, an exotic meson recently discovered [3] by the Belle collaboration at KEKB, is composed of four valence quarks, $u$, $\bar{d}$, $c$ and $\bar{c}$. To find the parton seas for these particles, three processes were considered, $g \leftrightarrow qg$, $g \leftrightarrow q\bar{q}$, and $g \leftrightarrow gg$. Similar to the proton, there is an asymmetry in the parton sea of the $K^+$ meson, which was found to be $\bar{d}-\bar{u}\approx 0.264$. The tetraquark light quark sea was found to be symmetrical. These mesons are further described by their parton momentum distributions, which were determined by using a Monte Carlo code. Understanding the parton distributions of particles is increasingly important as we approach the opening of the LHC. This research has been supported in part by the Research in Undergraduate Institutions Program of the National Science Foundation, Grant no. 0555706. \textbf {References} [1] Y-J. Zhang et al, Phys. Lett. B 523 (2001) 260. [2] Y-J. Zhang et al, Phys. Lett. B 528 (2002) 228. [3] S. -K. Choi et al. (Belle collaboration), Phys. Rev. Lett. 100 (2008) 142001. [Preview Abstract] |
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DA.00018: Position determination of fragile objects in nuclear physics experiments Hoi Kit Cheung, M. Betty Tsang To study the single particle nature of unstable nuclei, inverse kinematics with radioactive beams in transfer reactions have to be used. In such experiments, it is important to determine the exact positions of the beam and detected particles. A Laser Based Alignment System (LBAS) has been successfully used in several nuclear physics experiments. LBAS is designed to determine positions of sharp edges with sub-millimeter accuracy without physical contact with the measured object. In the recent p($^{34,46}$Ar,d) transfer experiments, the beam positions at the target are reconstructed with Channel Plate Detectors, the emitted deuteron particles are detected with the High Resolution Array (HiRA) and the recoil particles are measured with the S800 spectrometer. The HiRA device consists of multiple telescopes, each of which consists of 1024 pixels, with the dimension of 1.95x1.95mm$^{2}$ for each pixel. We use LBAS to determine the positions of the target, the channel plate detectors, and the pixels positions of HiRA. We then map these elements to the global positions of the S800 spectrometer and its magnetic elements. [Preview Abstract] |
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DA.00019: Developing a computer code simulating recoil-beta decay tagging of fission products Berta Darakchieva Neutron-rich nuclei far from stability exhibit insightful structural patterns and deformations, and can be used for testing existing nuclear theories. However, experimental information on many such nuclei is lacking, because they are hard to produce directly or through fusion-evaporation reactions. One way to populate light neutron-rich nuclei is by exploiting the fission process. Since these nuclei are primarily beta emitters, a technique of recoil beta tagging can be employed. A gas-filled separator, such as SASSYER (WNSL) or BGS (LBNL), can be used to select a mass window of fission fragments, which will be implanted on a DSSD detector located at the focal plane of the separator. By selecting high beta-endpoint energies, characteristic for the nuclei of interest, decays at the DSSD can be correlated to emitted gamma rays for further spectroscopy studies. An essential step in planning this project would be the development of a computer simulation of count rates at the DSSD. The program works by reading in files of half-lives and fission yields and uses a step-by-step iteration process. The role of the code is two-fold: to help identify a suitable nucleus for study and to optimize a mass window for its highest count rate. To test the method, experiments are planned with a fission source, such as Cf-252, placed at the target position of a recoil separator. If successful, the technique could be extended to in-beam experiments. [Preview Abstract] |
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DA.00020: Optimization of a Drift Chamber for Cosmic Ray Tracking Using Garfield Simulations. George Deinlein The PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory seeks a precise measurement of the spin contribution from sea quarks to the proton spin. This is accomplished by measuring the asymmetry in W-boson production in longitudinally polarized proton-proton collisions, where W-decays are signaled through the presence of high transverse momentum muons. The first level trigger in the detection of these muons will employ resistive plate counters (RPCs). As part of the research and development of these RPCs, at UIUC, drift chambers assist with cosmic ray tracking. Improvements have been made to the current drift chamber design, and are being implemented and tested in PHENIX's cosmic ray test stand. In this poster, specific improvements will be discussed, as well as the design process, which involved detailed Garfield simulations. [Preview Abstract] |
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DA.00021: Experimental system to search for induced depletion of $^{166m}$Ho Ben Detwiler, Shane Downing, Nathan Caldwell, James Carroll, Nino Pereira, Marc Litz, George Merkel, Joe Schumer Known nuclear data indicate that incoming photons below 300 keV might cause an induced depletion of the 1200 year isomer of $^ {166}$Ho. This process would be identified by an excess of ground state activity after irradiation with bremsstrahlung or by excess activity in any excited state that was part of the depletion cascade. A unique sign of depletion in $^{166}$Ho would be radiation emitted near 136 keV from a level above the isomer, but part of the expected depletion cascade. A detection system has been developed using a gated fast inorganic scintillator to observe gamma rays after pulsed irradiation of an isomeric sample containing $^{166}$Ho using an electron linac. [Preview Abstract] |
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DA.00022: Determination of the $^{11}$B($\alpha $,$\alpha )^{ 11}$B Cross Section below 7 MeV Chelsey Driessen, M.W. Ahmed, S.S. Henshaw, B.A. Perdue, P.-N. Seo, S. Stave, H.R. Weller, R.M. Prior, M.C. Spraker, P. Martel, A. Teymurazyan, R.H. France, E. Sand, A. Smith The use of $^{11}$B as a fusion energy resource using the $^{11}$B(p,$\alpha )$2$\alpha $ reaction has been studied for over 50 years. Recently TUNL has been requested to investigate discrepancies in previous measurements of the cross section of $^{11}$B($\alpha $,$\alpha )$. The cross sections were measured using silicon surface barrier detectors at 45, 60, 75, 90, 90, 110, 130, 150 degrees. The target used for the measurement of the cross section of $^{11}$B was composed of 2-3 $\mu $g/cm$^{2}$ of pure $^{11}$B with two surrounding thicker layers of gold. The alpha source and the tandem accelerator at TUNL were used to create a beam with a maximum energy of 7 MeV. Preliminary cross sections as a function of energy and angle will be reported and compared to previous results. [Preview Abstract] |
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DA.00023: Structural investigation of the nuclei in Z=52 to Z=78 region by E-GOS method Kelsey Dudziak, D.A. Meyer The E-GOS (E-Gamma Over Spin) method allows us to empirically determine the structure of a nucleus as a function of its angular momentum through a comparison to the ideal limits of perfect harmonic vibrator and axially symmetric rotor. Unique to the E-GOS method, no preconceived notion of nuclear structure is necessary. It differs from other common models by analyzing structural evolution as a function of angular momentum rather than as a function of nucleon number. In this project, we applied E-GOS method to the yrast bands of nuclei in the region Z=52 to Z=78 by plotting the ratio of Gamma Ray Energy divided by spin against that spin. Afterwards, we arranged the plots in order of increasing nucleon number. Mapping the E-GOS curves in this manner shows a clear transition from vibrational to rotational motion. [Preview Abstract] |
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DA.00024: Spatial Reconstruction of Co-60 Radiation Sources Using Goodness-of-Fit Tests on Spectra Obtained from an HPGe Detector Lenny Evans The effect of the position of a Co-60 point source on the shape of spectra was observed in both Monte Carlo and HPGe detector measurements. HPGe detectors are used in numerous low background assay systems and this spatial reconstruction could be used to locate unwanted backgrounds. Spectra taken with the radiation source placed at points on the face and side of the detector were compared in peak areas and were compared using the Kolmogorov-Smirnov goodness-of-fit test. We will discuss the position reconstruction accuracy of this statistical method. [Preview Abstract] |
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DA.00025: Calibration of the Shower Maximum Detector in the Barrel EMC at STAR Kara Farnsworth, Saskia Mioduszewski, Martin Codrington The STAR detector at RHIC was designed to measure properties of the quark-gluon plasma (QGP), a deconfined medium of quarks and gluons produced in high-energy heavy-ion collisions. The measurement of $\gamma $-jet (in which a direct photon is produced back-to-back with a jet) is a particularly good probe of the density of the produced medium. However background photons, like those from $\pi ^{0}$ decays, can contribute to the selection of high-energy direct photon trigger particles. To distinguish between direct and decay photons, the shower profile in the Barrel Shower Maximum Detector (BSMD) of the Barrel Electromagnetic Calorimeter (BEMC) is analyzed. The BSMD has very good spatial resolution ($\Delta \phi \sim $0.007 rad $\times \quad \Delta \eta \sim $0.007), and a refined calibration promises to improve its performance in $\gamma $/$\pi ^{0}$ discrimination. A summary of the quality assurance and calibration performed on the BSMD strips will be presented. [Preview Abstract] |
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DA.00026: The Joint Institute of Nuclear Astrophysics Virtual Journal Ryan Ferguson We have developed a weekly, online system for collecting and distributing scholarly articles of interest to researchers in nuclear astrophysics, a virtual journal (VJ), through the Joint Institute of Nuclear Astrophysics (JINA). The articles are gathered from a variety of well-known publications, and our database of both current and past issues is easily searchable by topics, chosen by the editors, or by keywords. Subscribers are notified of each new VJ issue through an email-list server. The VJ is a source for experimental and theoretical data for the JINA reaction rate database, and the references to review and popular level articles are a convenient way to introduce students to the literature. There are two related journals: the JINA VJ and the SEGUE VJ. Both the journals and support information are available at http://groups.nscl.msu.edu/jina/journals. [Preview Abstract] |
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DA.00027: Probing 23{\%} of the Universe at the Large Hadron Collider Will Flanagan With recent astronomical measurements, we know that 23{\%} of the Universe is composed of dark matter, whose origin is unknown. Supersymmtery (SUSY), a leading theory in physics, provides us with a cold dark matter candidate, the lightest supersymmetric particle (LSP). SUSY particles, including the LSP, can be created at Large Hadron Collider (LHC) at CERN. We perform a systematic study to characterize the SUSY signals in the ``focus point'' region, one of a few cosmologically-allowed regions in our SUSY model. We also present a methodology for extracting the dark matter signals at the LHC, and show the accuracy to which we can measure the dark matter relic density and the SUSY parameters. [Preview Abstract] |
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DA.00028: Geant4 Simulation of MoNA A. Fritsch, M. Heim, T. Baumann, S. Mosby, A. Spyrou The Modular Neutron Array (MoNA) is a neutron detector array consisting of 144 plastic scintillator detector modules at the National Superconducting Cyclotron Laboratory (NSCL). The detailed simulation of the neutron interaction with the detector is a crucial tool for optimizing detector configurations and analyzing experimental data. For this purpose the MoNA collaboration is developing a simulation package based on Geant4, a state-of-the-art C++ toolkit for the simulation of the passage of particles through matter. Our work this past summer involved introducing detector geometry into the Geant4 code, as well as determining how the program handles simulations of different physical interactions inside of the detector. By upgrading from Geant3 to Geant4, we are able to better simulate the physics of our experiments. [Preview Abstract] |
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DA.00029: Dalitz Plot for $\eta \rightarrow \pi^+ \pi^- \pi^0$ Miguel Garcia I present a preliminary Dalitz plot analysis of the decay $\eta \rightarrow \pi^+ \pi^- \pi^0$. The data used in this analysis were taken by the CLAS Collaboration during the g1c running period. A physical interpretation of the Dalitz plot is provided. Extraction of parameters related to the shape of the Dalitz plot is compared to theoretical predictions, as well as previous experimental values. Comparison of the data with these theoretical predictions might shed light on the double-quark mass ratio for the SU(3) constituent quarks. This important subject will be discussed briefly. [Preview Abstract] |
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DA.00030: Investigation of Neutron Scattering in the Modular Neutron Array (MoNA) Michael Gardner, Warren F. Rogers The MoNA Collaboration consists of scientists from several primarily undergraduate institutions and from MSU and FSU that investigate the properties of light neutron-rich nuclei in the vicinity of the neutron dripline. The MoNA array consists of 144 organic scintillator detectors stacked in 9 columns of 16 detectors each, used to determine the energy and trajectory of neutrons resulting from nuclear breakup reactions. When MoNA is used in conjunction with the Sweeper magnet kinematic reconstruction of the breakup is made possible. We are currently developing algorithms to enable MoNA to discriminate neutron multiplicity resulting from breakup. This process is significantly complicated by elastic and inelastic neutron scattering from carbon nuclei in the scintillator, which not only changes the neutron trajectories predominantly below the energy threshold of the detectors, but can also produce additional neutrons. By investigating the relative time and distance between multiplicity-two neutron events occurring in the first two layers of the array, we have been able to obtain slightly different signatures for data sets involving one- and two-neutron decays. Results will be presented. [Preview Abstract] |
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DA.00031: The Effects of a Late Decaying Scalar on Dark Matter Density Katherine Garrett, Stephanie Schuk, Gintaras Duda The neutralino as dark matter has yet to be discovered, either through direct detection of its interaction with detectors here on Earth, or through indirect detection of the products of neutralino self-annihilation processes. Dark matter searches have pushed limits of the neutralino's cross section so far down that only a handful of theoretical models with carefully constrained parameters can fit the experimental data. This seems unnatural; a correct model of neutralino dark matter should not have to be finely tuned to serve as a solution. The addition of a late decaying scalar particle, which essentially decays into the Lightest Supersymmetric Partner, has been shown to give neutralino densities in a more natural range needed for dark matter for a wide range of parameter space. We have implemented the addition of the scalar field in the code of DarkSUSY, run models, probed the parameter space, and compared the results of this modification with results from standard cosmological models. We also compared results from the simulations with the bounds set on dark matter from detection experiments; this let us place limits on properties of the scalar field and on non-standard cosmology scenarios. [Preview Abstract] |
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DA.00032: Bit-Error Ratio Testing of Xilinx FPGAs Using Pseudo-Random Binary Sequences Andy Goers With RHIC collision rates reaching orders of a MHz in pp reactions, it is vital that detector electronics are able to process the massive influx of data received every second. Much of this data processing is done by field programmable gate arrays (FPGAs). However, with any experimental setup, one must know the limitations of the apparatus. High speed electronics often see bit errors due to attenuation or simply from hardware failures. Bit errors in detector electronics can show up as bad data and even ``fake'' particles, so it is important to know how often these bit errors occur. Pseudo-random binary sequences (PRBS) are often used to test high speed electronics' bit-error ratios (BER), or errant bits per bits received. A PRBS is generated using polynomials creating a seemingly random sequence of binary numbers. A BER can be measured by sending out and receiving a known PRBS and checking for errors in the received sequence. I will present results of BER testing of gigabit transceiver protocols on Xilinx Virtex 5 LXT50T and LXT110T FPGAs for PHENIX detector electronics upgrades. [Preview Abstract] |
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DA.00033: Measuring Rate Capability of a Bakelite-Trigger RPC Coated with Linseed Oil Leah Goldberg The PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory intends to study proton spin structure through the detection of high $p_{T}$ muons produced from W-Boson decay. Such measurements will require an upgrade of the first level muon trigger using Resistive Plate Chambers (RPCs). RPCs are gas detectors in which high voltage is applied across two resistive electrodes (bakelite plates) spaced $2~$mm apart. The resistivity of the electrodes and possible coatings on the surface of the electrodes determine the rate capability of RPCs. We tested the performance of a double gap RPC in avalanche mode under gamma radiation from an Fe55 source. In this paper we present the rate capability of a bakelite RPC with a coating of linseed oil applied to the bakelite electrode surfaces. [Preview Abstract] |
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DA.00034: CUORE: The Three Towers Test Alison Goodsell, Laura Sparks CUORE (Cryogenic Underground Observatory for Rare Events) will be part of the next generation of detectors used to search for neutrinoless double beta decay ($0\nu\beta\beta$). Located in Assergi, Italy at the Gran Sasso National Laboratory (LNGS), CUORE will be a large cryogenic bolometer composed of 988 tellurium dioxide (TeO$_2$) detectors with a total mass of 750 kg, and will search for $0\nu\beta\beta$ in $^{130}$Te. The intermediate upgrade, CUORE-0, first involves the disassembly of Cuoricino, CUORE's smaller counterpart in operation since 2003, and the readying of the Three Towers test, a diagnostic detector configuration. As the experiment will monitor the extremely rare event of $0\nu\beta\beta$, all factors contributing to background need to be minimized to effectively increase the sensitivity. We assisted the LNGS researchers over the summer of 2008 by supporting R\&D work with the Three Towers test to reduce the radioactive background of the experiment. Activities involved decontaminating the copper frame of radon daughters, and chemically etching and lapping the TeO$_2$ crystals with nitric acid and silicon dioxide, respectively, to remove surface contaminants which contribute to background counts. This work was supported in part by NSF grant PHY- 0653284 and the California State Faculty Support Grant. [Preview Abstract] |
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DA.00035: The Interaction of Nuclei in the Gravitational Fields of Mini Black Holes Lauren Greenspan The goal of this research was to find solutions to the Schrodinger equation that describe particle scattering around black holes around eighteen orders smaller and less massive than our sun. Black holes of this kind could have formed in density irregularities in primordial space just after the big bang and can answer cosmological questions as well as providing a setting for research in quantum-gravity. Black holes go along with the theory of general relativity, but since mini black holes can be comparable in size to nucleons, the project also considers the limit at which the black hole must obey Quantum Mechanical law. A large emphasis was placed on the choice of a coordinate system and its implications on general relativity and the curvature of space-time. To get rid of unwanted singularities we chose the Eddington-Finkelstein metric and used it to evaluate the Klein-Gordon equation. From this we derived the potentials for the black hole and used them to calculate the absorption cross-section in the non-relativistic limit. As an additional exercise, we calculated the possible bound states of a particle with the black hole and the amount of mass it could gain based on the expected cross-section. [Preview Abstract] |
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DA.00036: Slow Controls Using the Axiom M5235BCC Tyler Hague The Forward Vertex Detector group at PHENIX plans to adopt the Axiom M5235 Business Card Controller for use as slow controls. It is also being evaluated for slow controls on FermiLab e906. This controller features the Freescale MCF5235 microprocessor. It also has three parallel buses, these being the MCU port, BUS port, and enhanced Time Processing Unit (eTPU) port. The BUS port uses a chip select module with three external chip selects to communicate with peripherals. This will be used to communicate with and configure Field Programmable Gate Arrays (FPGAs). The controller also has an Ethernet port which can use several different protocols such as TCP and UDP. This will be used to transfer files with computers on a network. The M5235 Business Card Controller will be placed in a VME crate along with VME card and a Spartan-3 FPGA. [Preview Abstract] |
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DA.00037: Experimental Observation of Decay Energy of $^{12,13}$Li C.C. Hall, P.A. DeYoung, S. Mosby, A. Spyrou, M. Thoennessen Observation is made, for the first time, of unbound states of $^{12}$Li and $^{13}$Li. The $^{12}$Li and $^{13}$Li were created using $^{14}$B and $^{14}$Be beams, respectively, from the coupled cyclotrons at the National Superconducting Cyclotron Laboratory. $^{12,13}$Li decays very rapidly (10$^{-21}$ s) to $^{11}$Li and a neutron for $^{12}$Li and $^{11}$Li and two neutrons for $^{13}$Li. The $^{11}$Li fragments were carried by the Sweeper, a 4 T superconducting magnet, through a series of charged particle detectors while the coincident neutrons were detected using the Modular Neutron Array (MoNA). Work is currently being done to simulate the resonances observed in the decay spectrum for $^{12}$Li with Breit-Wigner line-shapes. Initial results for $^{13}$Li will be shown. [Preview Abstract] |
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DA.00038: A study of continuum contribution to dielectron mass spectra at RHIC energies. Valerie Hanger The invariant mass distribution of electron-positron pairs is a crucial tool to account for particles which decay in a lepton-like manner such as J/$\psi$, $\psi$', and $\Upsilon$. Most of the background in the measurement of invariant mass comes from combinatorial pairs and can be removed with mixed event or like-sign electron pair distributions. This still leaves some background composed of unlike-sign electron pairs from correlated D and B mesons and from Drell-Yan. In this poster I will present a systematic study of these contributions, known as continuum. I calculated the continuum contribution to the dielectron mass spectra at RHIC energies using the PYTHIA event generator, studying changes in continuum by varying several of the PYTHIA input parameters. [Preview Abstract] |
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DA.00039: Event Display for the RPC Test Stand at PHENIX Caitlin Harper The Pioneering High Energy Nuclear Interaction Experiment (PHENIX) is located on the Relativistic Heavy Ion Collider (RHIC) ring at Brookhaven National Laboratory. One of the ultimate goals at RHIC is to obtain a more accurate understanding of a proton's intrinsic spin structure through polarized proton-proton collisions. The parity violating decay of W-bosons created in some of these collisions allows for the determination of flavor separated quark distribution functions. Recently, PHENIX has been focusing on the building and installation of Resistive Plate Chambers (RPC's). These RPC's are useful in the selection of high transverse momentum muon events from a background of low transverse momentum muon events. However, before the installation of these RPC's, it is essential to test their efficiency. We have assembled the RPC modules in a cosmic ray test stand and collected data. In order to better analyze the data and reconstruct the events, an event display was produced. The primary focus of this poster is the development of the track reconstruction and event display software. [Preview Abstract] |
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DA.00040: New measurements of $\gamma $-ray branching ratios in the $\beta ^{+}$ decay of $^{32}$Cl Mark Hernberg, Dan Melconian We have determined the $\gamma $-ray branching ratios in the $\beta ^{+}$ decay of $^{32}$Cl using a high-purity Germanium (HPGe) detector at the Texas A{\&}M University Cyclotron. Our experiment was motivated by a recent measurement of isospin symmetry breaking correction ($\delta _{c})$ in $^{32}$Ar which has implications for the extraction of V$_{ud}$ from other superallowed decays. The experimental result for this superallowed decay [$\delta _{c}$ = (2.0 +/- 0.8){\%}] agrees with the theoretical predictions but is not a stringent test of theory. By measuring the $\gamma $-ray branching ratios in the $\beta ^{+}$ decay of $^{32}$Cl (a decay product of $^{32}$Ar) the detector efficiencies can be better determined allowing for a more precise determination of $\delta _{c.}$ Furthermore these branching ratios are important in the study of various nuclear decay schemes and transition rates. Previous measurements of the $\beta ^{+}$ decay of $^{32}$Cl are 35 years old and contain uncertainties of up to 40{\%}. Our preliminary results agree with past data and additionally we've identified previously unseen branches and reduced the uncertainties by an order of magnitude. [Preview Abstract] |
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DA.00041: Jet Conversion in a Hadronic Gas Aaron Hernley, Rainer Fries It has been proposed that flavor conversion of leading jet partons could be used as a probe for the Quark-Gluon Plasma. In order to check the validity of this proposition, the case of a hadronic gas needs to be considered. If the two cases produce different results, flavor conversions could be used to make a stronger case for the creation of a Quark-Gluon Plasma at RHIC. Here we investigate the case of fragmented jets interacting with a hadronic medium and compare with previous results from quark and gluon jets interacting with Quark-Gluon Plasma. We compute the drag coefficients and conversion widths for pions and kaons and use these values to calculate their nuclear modification factor R$_{AA}$ and their elliptic flow v$_{2}$ at high transverse momentum. We find there is much less suppression in a hadronic gas than in a Quark-Gluon Plasma, but there is still a net conversion of pions into kaons, leading to kaon R$_{AA} >$ 1 not expected for Quark-Gluon Plasma. This significant difference between a hadronic medium and a Quark-Gluon Plasma means that jet conversion could be a unique probe for heavy-ion collisions. [Preview Abstract] |
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DA.00042: An Energy Calibration of the FN Tandem Accelerator Magnet Analyzing System at Notre Dame Ansel Hillmer This work established the groundwork for a proper calibration of the magnet analyzing system for the FN Tandem accelerator at the University of Notre Dame. The calibration utilized (p.n) reactions with well-known threshold energies to correlate NMR Frequency with beam energy. A neutron detector composed of three 3He proportional counters with moderating polyethylene has been constructed to detect the neutrons. To maximize detection efficiency, GEANT4 was employed to determine the optimal dimensions of the moderator. The maximum efficiency was found to occur with a 3-inch moderator half-length, with the efficiency varying by 2.2\% over an 11keV proton beam energy range. A preliminary analysis of data from the 27Al(p,n)27Si yields a result of 5.803MeV corresponding to a frequency of 14.64$\pm$.01MHz. [Preview Abstract] |
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DA.00043: Modern Energy Density Functional for Nuclei and Nuclear Matter Alberto Hinojosa We search for a modern energy density functional for nuclei and nuclear matter, based on the Skyrme type effective interaction. This interaction has been widely used for decades and many parameterizations have been realized to best reproduce binding energies, charge root mean square radii, and other properties of nuclei. Now that more experimental data is available, we are able to fit our results to a broader collection of nuclei at and far from the stability line. We implement the Simulated Annealing Method to search for the particular set of Skyrme parameters that best reproduces a collection of nuclear data. The data consist of binding energies, charge root mean square (rms) radii, rms radii for valence neutrons, spin-orbit splittings and breathing mode energies. The results we obtain using this new parameterization are in good agreement with a wide range of experimental measurements. [Preview Abstract] |
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DA.00044: Laser System and Optical Cavity for the Hall C Compton Polarimeter Eric Holland At Jefferson Lab a polarized electron beam is used to study the properties of nuclei. Currently, in Hall C a M{\o}ller Polarimeter is used to measure the electron beam polarization. This process is accurate but measurements cannot be made simultaneously with the main experiment and this leads to the assumption that the polarization remains constant between measurements. To supplement the M{\o}ller Polarimeter, Hall C is constructing a Compton Polarimeter, which performs non-destructive electron beam polarization measurement by Compton scattering. The purpose of this research is to optimize the laser component of the Compton Polarimeter. A fiber optic pulsed laser, with the same radio frequency as the electron beam (499MHz), was chosen to improve the luminosity and thus the number of Compton events. The current choice of the laser alone would be adequate for Hall C; however, a higher power system would provide two obvious benefits: the time needed for a measurement would decrease, and the signal to background noise ratio would increase. An optical cavity was proposed to achieve a gain in the laser power. Due to cavity conditions and geometrical restraints, it was determined that a cavity of length 1.2 meters would satisfy the needs of the Compton Polarimeter best. Experimentally, an external cavity could not be coupled to the radio frequency non-mode locked pulsed laser. [Preview Abstract] |
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DA.00045: Laser System for Jefferson Lab's Hall C Compton Polarimeter Eric Holland At Thomas Jefferson National Accelerator Facility a polarized electron beam is used to study the properties of nuclei. Currently, in Hall C a M{\o}ller Polarimeter is used to measure the electron beam polarization. This process is accurate but during measurements the experiment is interrupted (destructive measurement). Since M{\o}ller measurements can only be done at low beam current $<$ I microAmp and the experiments typically run near 100 microAmps, one has to assume that the polarization remains constant between measurements. To supplement the M{\o}ller Polarimeter, Hall C is constructing a Compton Polarimeter, which performs non-destructive electron beam polarization measurement by Compton scattering. The purpose of this research is to optimize the laser component of the Compton Polarimeter. A fiber optic pulsed laser, with the same radio frequency as the electron beam (499MHz), was chosen to improve the luminosity and thus the number of Compton events. The current choice of laser alone would be adequate for Hall C; however, a higher power system would provide two obvious benefits: the time needed for a measurement would decrease, and the signal to background ratio would increase. A Fabry-Perot optical cavity was proposed to achieve a gain in the laser power. Due to cavity conditions and geometrical restraints, it was determined that a cavity of length 1.2 meters would best satisfy the needs of the Compton Polarimeter. Our results strongly suggest that a gain switched pulsed laser cannot be coupled to an external optical cavity. A possible explanation is that the process of gain switching does not produce a mode-locked pulse train. Within each pulse it is possible that the Gaussian may be coherent but from pulse to pulse the coherence does not held. Mode locking is necessary for realizing a successful optical cavity. . [Preview Abstract] |
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DA.00046: PHENIX RPC Production Database Timothy Jones The Pioneering High Energy Nuclear Interaction eXperiment (PHENIX) is located on the Relativistic Heavy Ion Collider (RHIC) ring at Brookhaven National Laboratory. A primary physics goal that can be studied by PHENIX is the origin of the proton spin. One of the types of rare events looked for in the moun arms at PHENIX are single high transverse momentum mouns, which tend to result from the decay of a W bozon. Resistive Plate Chambers (RPCs) will be used as a level 1 trigger to select these events from a large background of low transverse momentum muons. As these RPCs are assembled it is necessary to keep track of the individual parts of each RPC as well as data from various quality assurance tests in a way that will allow the information to be easily accessible years to come as the RPCs are being used. This is done through the use of a database and web page interface that can be used to enter data about the RPCs or to look up information from tests. I will be presenting on how we keep track of the RPCs, their parts, and data from quality assurance tests as they are being assembled as well as how we can retrieve this data after it has been stored in the database. [Preview Abstract] |
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DA.00047: Analysis of Out-of-Plane Measurments of the Fifth Structure Function of the Deuteron Matthew Jordan, Gerard Gilfoyle We have measured the $D(\vec e,e^\prime p)n$ reaction and the asymmetry $A_{LT}^\prime$ associated with the fifth structure function in quasi-elastic electron scattering from deuterium at a beam energy of 2.56 GeV and over the range $\rm Q^2 = 0.1-2.0 ~ GeV^2$ with the CLAS detector at Jefferson Lab. The data were collected using both magnet polarities to explore different $\rm Q^2$ regions. We extracted $A_{LT}^\prime$ as a function of missing momentum ($p_m$) using spectra weighted by $\sin \phi_{pq}$ where $\phi_{pq}$ is the angle between the electron scattering plane and the plane defined by the ejected proton and 3-momentum transfer. We compared the measured $A_{LT}^\prime$ with a calculation by Jeschonnek and Van Orden by averaging over the $\rm Q^2$ distribution of the CLAS data. The theoretical curves largely agree with the 2.56-GeV data at $\rm Q^2=0.6-2.0~ GeV^2$, but diverge from the data for low $\rm Q^2$ ($\rm 0.1-1.0~ GeV^2$) and high $p_m$ (greater than 0.4 GeV). To understand the systematic uncertainties on $A_{LT}^\prime$ we varied the positions of the kinematic cuts used to define quasielastic scattering and the final state proton. The results showed systematic uncertainties of about 1\% or less in regions of high statistics. [Preview Abstract] |
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DA.00048: A high resolution scintillation detector for nuclear reactor monitoring via antineutrino interactions Jonathan Kessler, Rex Tayloe We have constructed a prototype detector employing a novel method using wave-length shifting fibers and liquid scintillator. We evaluate the performance of a 1 cubic-meter device using this technique as a detector of electron antineutrinos from a nuclear reactor. These antineutrinos are measured via the inverse beta decay interaction. We have simulated the device to determine the efficiency and reaction rates for the device placed near a nuclear reactor. We propose that this type of detector will more efficiently veto backgrounds and track antineutrino interactions more effectively than detectors with lesser spatial and energy resolution. This will allow for a more accurate measurement when determining whether a critical amount of plutonium has been removed from the reactor core. [Preview Abstract] |
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DA.00049: A Systematic Study of RPC Spacer Bond Strength for PHENIX Joseph Kish The Pioneering High Energy Nuclear Interaction eXperiment at Brookhaven National Laboratory is currently undergoing a forward muon trigger upgrade by incorporating large Resistive Plate Chamber tracking stations. The upgrade will make it possible to determine the spin contributions of sea and valence quarks to the spin of the proton. Many aspects of the PHENIX RPC design were borrowed from the Compact Muon Solenoid experiment at CERN. Unfortunately, approximately 5\% of CMS gas gaps had gas leaks or failed spacer integrity testing. In order to address the problem of spacer failure, a systematic study of spacer-epoxy-Bakelite bond strength was conducted. Several tests were performed in order to determine the relationship, if any, between various surface treatments, curing temperature, spacer geometry and bond strength. The methods, results and improvements will be discussed. [Preview Abstract] |
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DA.00050: TPC tracking software for NIFFTE: the Neutron Induced Fission Fragment Tracking Experiment Ryuho Kudo, J.L. Klay Ever since the scientific community started analyzing and filtering data using computers, programming has become a crucial part for the success of many projects. The NIFFTE Collaboration, which is building a Time Projection Chamber (TPC) to study neutron-induced fission of the major actinides, naturally requires a comprehensive software framework to analyze the high volume of data it will collect. Following the traditional TPC reconstruction model, we have written a set of offline analysis algorithms to reconstruct tracks left by the fission fragments in the TPC and determine their (A,Z). We accomplish this by organizing the raw TPC voxel data into 2 dimensional planes, performing cluster and hit-finding within those planes and then connecting the hits to create 3-D tracks. Finally, track fitting and error correction are performed and the fragment A,Z are determined from the distribution of specific ionization along the track. Since one of the goals of this project is to create a re-usable library of TPC reconstruction code that can be adapted to other TPC projects, the software uses open source tools and is built as an object-oriented package in C++. This poster will present the current status of the TPC reconstruction algorithms and discuss the motivations behind our specific programming choices. [Preview Abstract] |
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DA.00051: Cosmic Ray Study with the Nose Cone Calorimeter Thomas Langin The Nose Cone Calorimeter (NCC) is a proposed upgrade detector for the PHENIX experiment at Brookhaven National Lab. The NCC will be useful for a variety of measurements in polarized p+p, d+A, and A+A collisions at the Relativistic Heavy Ion Collider (RHIC). The NCC is a tungsten-silicon sampling calorimeter, made up of 3 mm tungsten plates sandwiched by $1.5\times1.5 cm^2$ silicon pads. The NCC would add a new capability to measure the $\chi_C$ meson and electrons from W-boson decays in PHENIX, as well as adding acceptance for the $\pi^0$ and $\gamma$-jet and many other measurements. Since it uses tungsten plates which have a very small Moliere radius of 0.9 cm, the NCC is capable of distinguishing photons down to very small separations, which is essential for the high densities in the heavy ion collisions and for decay photons from very high energy $\pi^0$'s. The performance of the most recent NCC prototype was tested using cosmic rays, which deposit close to the lowest energies the NCC needs to measure. We find that the dynamic range of the NCC is within design specifications. Additionally, different methods to reconstruct the energy from the measured signal pulses were studied which will help in optimizing the pulse shaping for the next prototype. [Preview Abstract] |
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DA.00052: Gamma-Ray Spectroscopy of $^{101}$Pd Justin LeBlanc, D.A. Meyer, A. Heinz, H. Ai, R.J. Casperson, B. Huber, R. Luttke, E.A. McCutchan, J. Qian, B. Shoraka, J. Smith, R. Terry, J.L. Hugon, E. Williams Structural evolution is frequently characterized as a function of varying neutron or proton number. The E-Gamma Over Spin (E-GOS) method is a simple way to describe changes in the shape of a specific nucleus as a function of its angular momentum. We performed an experiment using the ESTU tandem Van de Graaff accelerator at the Wright Nuclear Structure Laboratory at Yale University. In the experiment, $\sim $10 different isotopes in the A=100 region were synthesized. This work focuses on $^{101}$Pd and considers it within the framework of the E-GOS method. A summary of the results obtained and an interpretation of their implications in the context of the region will be presented. [Preview Abstract] |
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DA.00053: Reducing DAC noise to sub-millivolt level in an effort to lock a high gain Fabry-Perot cavity Lawrence Lee Several pending experiments at JLAB Hall A require Compton polarimetry at a higher precision than currently obtainable in the hall, requiring $\sim1\%$ error electron polarization measurements. As the frequency of light scattered from the electron beam is increased, the longitudinal asymmetry is decreased as understood within the framework of QED, lowering experimental error. The goal of the project is to create a cavity that resonates with more power and at a higher frequency than the currently implemented setup. Obtaining a PDH-locked, high gain Fabry-Perot cavity that resonates at $1.5$ $kW$ of green ($532$ $nm$) laser is desired. To combat mechanical fluctuations of the cavity at atomic scales, the feedback loop used tunes the frequency of the input laser. Many upgrades to our hardware and software are required to lock the cavity over long time periods. To this effect, a digital-to-analog converter upgrade was performed to implement a 16-bit DAC setup over the current 12-bit DACs to reduce the effect of bit-noise, which currently rivals the bandwidth of the high-gain cavity. The reduction of noise to a level well within the cavity's bandwidth should allow a more stable lock of the cavity. [Preview Abstract] |
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DA.00054: Development and Testing of the LED Calibration System for the Daya Bay Antineutrino Detectors Brian Lester The Daya Bay Neutrino Experiment requires extremely precise measurements of the antielectron-neutrino rate and spectrum from the Daya Bay nuclear reactors to produce an accurate measure of the neutrino mixing angle $\theta _{13}$. Such precise measurements require rigorous calibration of each antineutrino detector (which use liquid scintillator in the detecting regions) using both radioactive and LED calibration sources. This project aims to test the feasibility that, by comparing the detector response in a dry run to the liquid run, we can determine the attenuation length of the liquid interior of the detector. Using two photomultiplier tubes (PMTs) attached to the ends of 5 meters of 4" inner diameter PVC pipe, we mock up the interior of the detector with 2" calibration PMTs at the top and bottom of the detector. We then place an LED diffuser ball inside of the PVC pipe via various access holes to model the LED calibration units inside of the detector and pulse the LED as we would for calibration of the detector. We record the response of the PMTs for various positions along the PVC pipe, both with the pipe filled with liquid and with only air inside of the pipe. Comparing the PMT detection ratio for runs in liquid and runs in air we measure the attenuation length of the liquid. [Preview Abstract] |
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DA.00055: Using Lithium 6 in measureing Giant Monopole Resonance Anthony Licata Finding the Isoscalar Giant Monopole Resonance (ISGMR) is one of the ways to determine the compressibility of nuclear matter (Knm). This Knm is used to find the equation of state for nuclear matter and in astrophysics concerning supernova and neutron stars. To determine this Knm more accurately, we need to survey the ISGMR for many nuclei. To study unstable isotopes the inverse reaction has to be studied. Finding the ISGMR has been done in the past with alpha scattering. For the inverse reaction using a 4He gas as a target is problematic so a Lithium (6Li) target could be a solution. For this reaction to be studied a new detector needs to be built which can measure the different products of the reaction in the test chamber. Thanks to the Youngblood Group at the Cyclotron Institute, TAMU. [Preview Abstract] |
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DA.00056: Preparatory Low-Background Assay Analysis Alex Long Confirmation of previous observational claims of neutrino-less double-beta decay (0$\nu \beta \beta )$ made by Klapdor and Kleingrothaus could have tremendous physical implications. This includes: violation of lepton number conservation in the Standard Model, measurement of the 0$\nu \beta \beta $ decay-rate, improved limits in the measurement of the Majorana mass of the electron neutrino, and support for the theoretical consideration that the neutrino is its own antiparticle. The Majorana Collaboration will use enriched Ge-76 crystals in a low-background environment, to probe below the current upper limits of the neutrino-mass region. Our sub-group is performing a materials assay for the Majorana experiment, using two High Purity Germanium (HPGe) coaxial detectors located in the Kimbalton Underground Research Facility (KURF). My contribution is primarily in the quantitative analysis and identification of prominent contaminants found in the construction materials being used in the Majorana experiment. This is achieved by comparison of Gamma-ray spectra to known radioactive decay-chains and creating consistent methods for computing the absolute activities of contaminants using efficiencies found from Monte Carlo simulation. [Preview Abstract] |
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DA.00057: Activity Calculations using HPGe Detectors and Monte Carlo Efficiencies Kevin Macon The next generation of experiments in particle astrophysics will require extremely low and well-known backgrounds. This requires performing experiments with low activity materials and going underground to escape the ubiquitous cosmic-ray background. Current radiometric assays using low background HPGe detectors at the recently established Kimballton Underground Research Facility for Low Background Counting (KURF LBC ) examine the bulk activity of materials that will be used in direct dark matter searches such as Mini-CLEAN and in the search for 0$\nu$$\beta$$\beta$ by the MAJORANA Collaboration. Finding the bulk activity from the spectra of a measured sample is involved. To account for branching ratios, geometry effects, and attenuation in the sample and non-active parts of the detector-- Monte Carlo calculations of peak acceptances were made using the MaGe/GEANT4 simulation package in addition to modeling the affect of energy resolution on peak height to continuum ratio from fitted data. [Preview Abstract] |
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DA.00058: Cosmic Ray Background Analysis for MuLAN Michael Mangialardi The goal of the MuLAN experiment is to make a measurement of the muon lifetime to a precision of 1 ppm so that a 5 ppm value of the Fermi coupling constant can be calculated. To do this, a beam of positive muons is stopped in a target surrounded by 340 scintillating detectors arranged in a geodesic around the target. Once the muons stop in the target, they decay, and the product positrons are emitted outward, where they are detected by the scintillators. By examining the spectrum of decay times, the lifetime of positive muons can be calculated. One of the myriad factors affecting this measurement is the background of cosmic ray muons constantly showering upon the detector. To study this background, an angular distribution of the cosmic rays was found, and the rate at which cosmic rays muons ``rain'' upon the detector was calculated. In addition, the cosmic rays were used to examine the timing differences between the individual scintillators. [Preview Abstract] |
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DA.00059: Search for the $2^{+}_{3}$ to $0^{+}_{2}$ Transition in $^{158}$Gd M.C. Marshall, R.J. Casperson, V. Werner, A. Heinz, A. Schmidt, J. Qian, J.R. Terry, E. Williams, R. Winkler, Z. Berant, M. Bunce, G. Henning, M. Smith Interacting Boson Model 1 (IBM) calculations on Gadolinium nuclei indicate that the quadrupole deformation undergoes a phase transition. The IBM predicts that the deformation of the first excited $0^{+}_{2}$ state in $^{158}$Gd rises beyond that in $^{156}$Gd in a first order phase transition, while remaining smaller than that of the ground state [1]. This can be tested via measurement of quadrupole shape invariants. Coulomb excitation in conjunction with the YRAST-Ball array was used at the Yale ESTU tandem accelerator to excite the $2^+_3$ state in $^{158}$Gd and detect its transition of 63 keV to the $0^{+}_ {2}$ state. The intensity of this low-energy $\gamma$-ray has to be measured relative to decays around 900 keV. Therefore, an efficiency calibration with multiple sources covering the entire energy range was performed. \\ \noindent [1] V. Werner et al., Phys. Rev. C (R), submitted (2008).\\ [Preview Abstract] |
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DA.00060: Commissioning Measurements of ORRUBA Detectors C.T. Matthews, J.A. Cizewski, P.D. O'Malley, S.D. Pain The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a silicon detector array being developed by the Center of Excellence for Stewardship Science at Oak Ridge National Laboratory. The array is comprised of two rings of position-sensitive detectors in a cylindrical setup designed to maximize solid angle coverage for (d,p) measurements in inverse kinematics. Each detector has 4 resistive strips, with readout from each strip-end. At forward angles, detector telescopes are used, comprised of a thin non-resistive detector (65$\mu$m) for transmission backed by the thicker resistive detector (1000$\mu$m) for stopping, allowing particle identification in addition to measurement of the angle and energy of the detected particles. For commissioning, the profile of each detector must be tested to insure that it is functioning properly, and to understand its optimal bias voltage and energy resolution. Measurements of leakage current profiles, full-depletion voltages and energy resolution measurements have been completed. The details of the array, its motivation and these commissioning measurements will be reported. [Preview Abstract] |
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DA.00061: Determination of Observables from Double-Polarization Photoproduction Randall McClellan A key technique in the study of poorly established and unobserved baryon resonances is polarization observables in meson production experiments. These asymmetries, sensitive to weak resonance contributions, will provide additional constraints and therefore eliminate ambiguous solutions characteristic of unpolarized data. In addition, the majority of our ``baryon'' knowledge is based on pion-nucleon scattering experiments. By employing photoproduction, states that have proved elusive due to weak coupling to pion-nucleon interactions may be more easily seen. The combination of a polarized photon beam and polarized target provides a unique and unprecedented look into the excited states of the nucleon. The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, Newport News, Virginia, is an excellent tool for observing circularly and linearly polarized light incident on a longitudinally-polarized frozen spin butanol target (FROST). CLAS has accumulated double-polarization data from November 2007 to February 2008 and the debut of the butanol target has exceeded expectations. The FROST data provide (nearly) complete experiments for a variety of different photoproduction reactions. This contribution will present the status of the experiment and outline plans for the determination of polarization observables in double-pion production. [Preview Abstract] |
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DA.00062: New results on the excited states in $^{32}$Mg A.J. McGauley, H. Mach, L.M. Fraile, O. Tengblad, R. Boutami, C. Jouliet, W. Plociennik, D.Z. Yordanov, M. Stanoiu $^{32}$Mg is located at the center of a region known as the ``island of inversion,'' a region in which the classic picture of stable shell structure was shattered when the energy of the 2$^{+}$ state in $^{32}$Mg was found to be only 885 keV, much lower than expected for a nucleus with a closed neutron shell. The collapse of the $N=20$ shell closure has been extensively studied, yet very little information exists on the excited states in $^{32}$Mg, which is the critical nucleus. We have studied the levels in $^{32}$Mg populated from the beta-decay of $^{32}$Na at the ISOLDE facility at CERN. We have established a new level scheme which includes 9 excited states and 18 transitions based on the gamma-gamma coincidences. The statistics exceeded by about 2 orders of magnitude statistics collected in previous measurements of $^{32}$Mg [1]. We do not confirm two levels previously proposed, while two new levels and five new transitions are included in the level scheme. [1] G. Klotz \textit{et al}., Phys. Rev. C\textbf{47, }2502 (1993), C.M. Mattoon \textit{et al}., Phys. Rev. C\textbf{75,} 017302 (2007), and V. Tripathi \textit{et al}., Phys. Rev C\textbf{77,} 034310 (2008). [Preview Abstract] |
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DA.00063: Determination of Impact Parameter for Fermi Energy Heavy Ion Collisions Using the HIPSE Event Generator Michael Mehlman, Zach Kohley, Sherry Yennello In order to determine the impact parameter of a nuclear collision (a quantity that cannot be observed directly), one must first verify the method for doing so. This is only possible using a theoretical model that provides realistic observables associated with a known impact parameter, such as the HIPSE (Heavy-Ion Phase-Space Exploration) event generator. For four systems, HIPSE-generated observable distributions were mapped to the geometrical impact parameter distribution, providing probable event impact parameter ranges, which were then compared with the theoretical impact parameter. Numerous quantities were considered for correlation, several of which ultimately proved useful, such as charged particle, neutron, and total particle multiplicity, as well as total event transverse momentum. Four observables, charged particle and neutron multiplicities, intermediate to light fragment ratio, and total event transverse momentum, were then chosen to train a Neural Network to refine the impact parameter prediction. The output of the Neural Network showed better correlation than the distribution mapping method, and is expected to prove useful for analysis of data currently (July 2008) being taken on the NIMROD detector. Results are presented for correlations stemming from both the mapping and Neural Net analyses. [Preview Abstract] |
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DA.00064: REACLIB: A Reaction Rate Library for the Era of Collaborative Science Zachary Meisel Thermonuclear reaction rates and weak decay rates are of great importance to modern nuclear astrophysics. They are critical in the study of many topics such as Big Bang Nucleosynthesis, X-ray bursts, Supernovae, and S-process element formation, among others. The Joint Institute for Nuclear Astrophysics (JINA) has been created to increase connectivity amongst nuclear astrophysicists in our modern age of highly collaborative science. Within JINA there has been an effort to create a frequently updated and readily accessible database of thermonuclear reactions and weak decay rates. This database is the REACLIB library, which can be accessed at the web address: http://www.nscl.msu.edu/$\sim$nero/db/. Here I will discuss the JINA REACLIB Project, including a new procedure to fit reaction rates as a function of temperature that takes full advantage of physicality. With these updated reaction rates, astrophysical modelers will no longer have to worry about the adverse effects of using obsolete reaction rate libraries lacking physical behavior. [Preview Abstract] |
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DA.00065: Precision Measurement of Target Mass in the Antineutrino Detectors of the Daya Bay Reactor $\theta_{13}$ Experiment Patrick Mende Of the parameters within the neutrino mixing matrix, the reactor neutrino experiment at Daya Bay seeks to determine the yet unknown neutrino mixing angle $\theta_{13}$ to a sensitivity of 0.01 or better in sin$^22\theta_{13}$. The experiment utilizes the inverse beta-decay reaction of electron antineutrinos on protons to measure the flux of reactor antineutrinos at different distances from the reactors and measure the disappearance of $\overline{\nu}_{e}$. In the experiment it is important to measure the target mass to a high degree of accuracy to determine the number of free protons in the detector target. My work focuses on evaluating sensors for a high-precision measurement of the target mass in the Daya Bay antineutrino detectors to $<$ 0.1\%. The resolution and long-term stability of ultrasonic and capacitance sensors have been characterized and found to meet the precision requirements of the experiment. [Preview Abstract] |
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DA.00066: Experimental system to search for induced depletion of 108mAg Isaac Mills, Thomas Harle, Geoffrey Trees, James Carroll Nuclear isomers may provide high density energy storage media for specialized batteries. The key would be to identify a way to release the stored energy when desired, by depleting the isomer population. Existing nuclear data [1] suggest that an induced depletion of the 418 year isomer $^{108m}$Ag may be possible, caused by providing an input of 255 keV or 413 keV. The result would be production of additional ground state nuclei with a half-life of 2.37 minutes, leading to beta decay. An experiment has been designed to measure beta decay of $^{108m}$Ag after exposure of an isomeric sample to 450 keV bremsstrahlung. Because beta particles are attenuated by air, a clean vacuum chamber was assembled with which to use a Si(Li) detector. The aim of this experiment is to observe an increased rate of beta decay after several minutes of direct exposure to bremsstrahlung radiation. $\\$ $\\$ [1] F. R. Espinoza-Quinones, et al., Phys. Rev. C 52, 104 (1995). [Preview Abstract] |
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DA.00067: Double beta decay Q-values of $^{130}$Te, $^{128}$Te, and $^{120}$Te Jessica Mintz, Eric Norman, Nicholas Scielzo The observation of neutrinoless double-beta decay would constrain the absolute neutrino mass scale, determine whether or not the neutrino is its own antiparticle, and imply that lepton number is not conserved. In order to search for this elusive decay, the CUORICINO and CUORE experiments at Gran Sasso National Laboratory use $^{nat}$TeO$_{2}$ bolometers to measure the temperature increase from radioactive decays in the crystals. Since the signature of neutrinoless double-beta decay is a peak at the full decay energy Q-value, it is critical to measure this energy to a very high precision. The three isotopes of natural Te which undergo double beta decay are $^{130}$Te to $^{130}$Xe, $^{128}$Te to $^{128}$Xe, and $^{120}$Te to $^{120}$Sn. Mass differences between each of these parent and daughter nuclei have been measured using the Canadian Penning Trap Mass Spectrometer at Argonne National Laboratory to within 0.5 keV. The method by which nuclear masses are measured with the Penning trap will be described. Preliminary results for the double beta decay Q-values of $^{130}$Te, $^{128}$Te, and $^{120}$Te will be presented. [Preview Abstract] |
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DA.00068: Study of Inelastic Background for Quasielastic Scattering from Deuterium at 11 GeV Mark Moog, Gerard Gilfoyle The magnetic form factor of the neutron is a fundamental quantity of nuclear physics that describes the distribution of charge and magnetization within the neutron, yet there are only limited data for this form factor in the $\rm Q^2$ range 5-14 $\rm GeV^2$. Experiment E12-07-104 at Jefferson Lab is planned to measure $G_M^n$ in this $\rm Q^2$ range after the 12-GeV Upgrade using the ratio method. This technique uses the ratio of quasielastic $e-n$ to $e-p$ scattering on deuterium, knowledge of the well-known proton elastic cross section, and accurate calculations of nuclear effects to extract $G_M^n$. The effect of the neutron elastic form factor is small. The method has worked well at lower $\rm Q^2$. To further study this future experiment we simulate the Fermi motion of nucleons in the deuteron and use the known behavior of the nucleon elastic form factors to calculate the quasielastic cross section. For inelastic events we use the same model for the deuteron and the GENEV program to calculate the number of events. We have simulated the experiment at the limit of the anticipated $\rm Q^2$ range, studied the effects of various cuts, and investigated strategies for reducing the inelastic background in the quasielastic region. [Preview Abstract] |
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DA.00069: An interactive website for the nuclear shell model: Concordia David Morris, Alexander Volya The nuclear shell model has become a standard theoretical approach to study nuclear many body systems. Shell model calculations using well-established interactions provide a powerful tool for nuclear experiments. Although some shell model results are tabulated, on demand calculations are increasingly important. In order to facilitate extensive calculations, result storage, and analysis, we have developed a web-based interactive interface\footnote{http://cosmo.volya.net} for the shell model code CoSMo.\footnote{ A. Volya, \textit{Applications of Continuum Shell Model}, in \textit{Opportunities with exotic beams} (WorldScientific, Singapore, 2007), p. 132; http://arxiv.org/abs/nucl-th/0605034} The web portal allows calculation of nuclear levels with a number of interactions and valence spaces. It also permits analysis of occupation numbers, spectroscopic factors, and electromagnetic transition rates. [Preview Abstract] |
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DA.00070: Impact of Polycarbonate Spacers on Resistive Plate Chamber Efficiencies Nicholas Mucia The PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory will measure the flavor dependent quark and anti-quark polarizations in the proton through parity violating W-production. A new dedicated muon trigger spectrometer is being built to select high momentum muons from the decay of W bosons. The muon spectrometer relies on Resistive Plate Chambers (RPCs) developed for the CMS experiment at the Large Hadron Collider. PHENIX continues to pursue detailed studies of CMS RPC technology to ensure that these detectors will be optimally deployed and operated in PHENIX. In this poster we present two dimensional efficiency measurements with cosmic rays in RPC prototypes. In particular we have studied the impact polycarbonate spacers used to define the 2 mm wide RPC gas gaps have on the detector efficiency. We will present two dimensional efficiency measurements in the region adjacent to the spacers including the radial dependence of the efficiency with respect to the center of the spacer. [Preview Abstract] |
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DA.00071: Gamma Detection Efficiency of a State-of-the-Art Ge Detector Erika Navarro, Carl Gagliardi, Adriana Banu An experiment to determine the ground state spin of the exotic nucleus $^{23}$Al is presented. By analyzing the spectra of the emitted gamma rays of the core nucleus $^{22}$Mg arising from the reaction $^{22}$Mg(p$^{+}$, $\gamma )^{23}$Al, the higher energy levels of the $^{22}$Mg and their associated spin (j) values are determined. Subsequently, the need to precisely calibrate the EXOGAM Ge clovers to accurately determine these gamma ray energies, and therefore draw conclusions about the separation between nuclear shell levels, is met. Using careful analysis of gamma ray spectra and precise calibration of Ge detectors, resulting momentum distributions indicate a ground state spin of 5/2$^{+}$. This both rejects the theory of halo structure of the $^{23}$Al exotic nucleus, and is consistent with previous experimental results strengthening the case for the use of mirror symmetry in nuclear astrophysics in systems otherwise not accessible. [Preview Abstract] |
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DA.00072: Development of the Low Energy Neutron Detector Array(LENDA) for the Study of Charge-Exchange Reactions at the NSCL Du Nguyen, S.M. Austin, D. Bazin, C. Caesar, J.M. Deaven, C.J. Guess, G.W. Hitt, R. Meharchand, G. Perdikakis, R.G.T. Zegers Charge-exchange reactions have long been used as a probe of the spin-isospin response of stable nuclei, in particular the Gamow-Teller transitions. Gamow-Teller strengths can be extracted model-independently, providing detailed information on nuclear structure and key inputs for astrophysical scenario that involve weak transitions. Therefore, it is important to extend the charge-exchange studies to unstable nuclei. The Low Energy Neutron Detector Array (LENDA) is currently in development at the NSCL and is designed to facilitate the study of ($p,n$) charge-exchange reactions in inverse kinematics using unstable beams. The energy and angle of the recoiling neutrons from these reactions can be measured by LENDA and used for kinematical reconstruction of charge-exchange each event. For this purpose, good timing and position resolutions should be achieved in LENDA. Currently, an initial array consisting of three 30cmX4.5cmX2.5cm plastic scintillators has been developed. The final LENDA array will consist of 24 such scintillators designed to detect neutrons with energies as low as 100 keV. In addition, the proper light output function must be extracted to determine the correct efficiency of the detectors. Results from ongoing work on the development of the array will be presented. This work was supported by the US NSF, grants PHY-0606007 and PHY 0216783(JINA). [Preview Abstract] |
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DA.00073: Determining the polarization of $^{3}$He by means of an optical technique Timothy Nichols An experiment now being developed will increase the accuracy of the current neutron electric dipole moment (EDM) measurement by a factor of 100. In order to obtain this new level of accuracy, a system of polarized ultra-cold neutrons (UCN) and $^{3}$He is being used. The UCN's and $^{3}$He are placed in a combined magnetic and electric field where their relative precession rate is measured using the spin-dependent n-$^{3}$He capture reaction. Any change in the precession rate when the electric field is reversed is attributable to an EDM. The polarization of the $^{3}$He must be maintained at as high a level as possible, and a variety of materials are being tested to determine their wall depolarization probabilities. In order to understand the ultimate sensitivity of these measurements, the initial polarization of the $^{3}$He, produced by optical pumping of a discharge, must be known. In this paper we present a measurement of the circular polarization of light from the 667 nm transition in He in a standard pumping cell. The polarization in this transition is induced by the nuclear polarization via the hyperfine interaction; the degree of polarization has been previously calibrated by comparing with absolute nuclear magnetic resonance measurements. [Preview Abstract] |
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DA.00074: Precise measurements of $\alpha_{k}$ for the 346.5 keV M4 transition from $^{197}$Pt$^{m}$: A test of internal conversion theory J. Nolan, N. Nica, J.C. Hardy, M. Hernberg, J.R. Goodwin, V.E. Iacob Precise values for internal conversion coefficients (ICCs) are important in the study of nuclear decay schemes; they are also useful for detector efficiency calibration. A recent survey revealed that few measured ICCs are known to a high precision ($\sim $ 1{\%}); in addition, there is some theoretical uncertainty over how to deal with the atomic vacancy left by the departing electron during the internal conversion process. Texas A{\&}M has previously precisely measured the ICCs for $^{193}$Ir, $^{137}$Ba, and $^{134}$Cs as a test of internal conversion theory; we now consider the ICC for $^{197}$Pt$^{m}$ as a further test. The $^{197}$Pt$^{m }$was produced by thermal neutron activation of separated $^{196}$Pt (97.43{\%} pure). Two separate sources were produced; x-ray and gamma-ray emissions from each source were recorded by a High Purity Germanium Detector (+/- 0.20{\%} absolute efficiency uncertainty). After impurity subtraction and attenuation correction, preliminary results for the $\alpha _{k}$ value for the two sources have now been obtained. The $\alpha_{k}$ from source one is 4.24 (13); the $\alpha _{k}$ from source two is 4.26 (8). While these values are still tentative, the results show agreement with the theory that considers the atomic vacancy. [Preview Abstract] |
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DA.00075: Neutron-Deuteron Breakup and Quasielastic Scattering Alice Ohlson, June Matthews, Wilbur Franklin, Brian Daub, Taylan Akdogan, Mark Yuly, Steven Wallace, Stephen Thomson, Daniel Haas Quasielastic scattering in the 200 MeV region is studied by impinging a pulsed neutron beam on a deuterium target at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center. The scattered neutrons from the \emph{d(n,np)n} reaction are detected by a wall of neutron time-of-flight scintillators, and scattered protons are detected by a permanent magnet spectrometer with two sets of wire chambers. This setup allows for measurement of incident neutron energy, scattered neutron energy, and scattered proton energy, as well as scattering angle and position for all scattered particles. The results of the experiment are compared with a Monte Carlo simulation of quasielastic scattering, to observe the differences between two-body elastic and three-body quasielastic collisions. [Preview Abstract] |
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DA.00076: Investigating Background Sources in the DIANNA Experiment using GEANT4 and MCNPX Catrish Pagan, Richard Showalter-Bucher, David Yager-Elorriaga, Bret Crawford, Sharon Stephenson The DIANNA collaboration is pursuing a direct measurement of the $^{1}S_{0}$ neutron-neutron scattering length at the YAGUAR reactor. The neutron background is predicted to depend linearly on the neutron flux, while the neutron-neutron signal should have a quadratic dependence, and therefore, variation in the pulse power of the reactor provides a mechanism for separating the signal from the background. Initial measurements show a non-linear contribution to the background, which could be from both desorption in the aluminum vacuum pipe as well as physical movement of the moderator during the reactor pulse. To study the background effects of various desorption processes, GEANT4 was used. MCNPX was used to model the possible background effects of the moderator movement during the YAGUAR reactor pulse. Results will be presented. [Preview Abstract] |
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DA.00077: RF Quadrupole Ion cooler for negative ions Jacques Pape, Yuan Liu, Tom Lewis In order to improve the quality of radioactive ion beams (RIBs), radio frequency (RF) quadrupole ion coolers are being developed for reducing the energy spreads and, consequently, the emittances of negative RIBs. RF quadrupole ion coolers are RF-only quadrupole ion guides filled with a buffer gas. The ions can be cooled by collisions with lighter buffer gases and their radial trajectories can be reduced to a small region near the axis of the device while the ions are inside the RF quadrupole ion cooler. Studies have been conducted to determine the operation parameters and the transmission of two ion coolers of quadrupole rod size of 11.48 mm diameter and 8 mm diameter, which are equipped with provisions for both retarding energetic negative ion beams to energies below thresholds for electron detachment at injection and re-accelerating negative ion beams to high energies after the cooling process. After mass separation, the ions of a selected mass are focused into the ion coolers where they are slowed by collisions with He buffer gas. At the exit of the cooler, the ions are re-accelerated to their original energies and measured with a Faraday cup detector. The performances of the two coolers are characterized with O$^{-}$, OH$^{-}$, F$^{-}$, S$^{-}$, Cl$^{-}$, Ni$^{-}$, Co$^{-}$ and Cu$^{-}$ ions. The analysis results gathered from the two RF quadrupole ion coolers will be presented. [Preview Abstract] |
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DA.00078: Simulation of d(7Be,t)6Be with Fresco, and investigation of resonant states of 6Be Timothy Pelham An ongoing study is presented into the resonant states of 6Be via simulation of d(7Be,t)6Be with Fresco to investigate the results of ``Searching for resonances in the unbound 6Be nucleus'' a paper by K.Y. Chae [1]. In this paper the d(7Be,t)6Be reaction was studied to search for resonances in the 6Be nucleus that may be used to increase our knowledge of the 3He(3He,2p)4He reaction. A 100-MeV 7Be beam from the Holifield Radioactive Ion Beam Facility (HRIBF) was used to bombard CD2 targets, and tritons were detected by the Silicon Detector Array (SIDAR). It was concluded that a combination of reaction mechanisms are necessary to account for the observed triton energy spectrum. This will be further investigated by simulating the various reaction mechanisms with Fresco to try to reproduce and explain these results. Preliminary Results will be presented. [Preview Abstract] |
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DA.00079: The Astrophysical $^{187}$Re/$^{187}$Os Ratio: Measurement of the $^{187}$Re(n,2n)$^{186m}$Re Destruction Cross Section Eric Pooser, A. Hutcheson, H. Karwowski, J. Kelley, E. Kwan, C. Huibregtse, A. Tonchev, W. Tornow, F. Kondev, S. Shu We have continued a program to measure (n,2n) reaction cross sections on $^{187}$Re with an emphasis on population of the $^{186m}$Re isomer with half-life 2 x 10$^{5}$ y. We produced 12 MeV quasi-monoenergetic neutrons with the TUNL Tandem Van de Graaf accelerator and a deuterium gas cell, and we measured the $^{187}$Re(n,b)Y cross sections using activation techniques. While various reaction channels were populated in the activation, our emphasis is on the (n,2n) reaction channels, where $^{186}$Re is populated. Of specific interest is the population of $^{186m}$Re, which has an extremely long lifetime, which complicates the measurement intended. This data is intended to reduce uncertainties in the $^{187}$Re/$^{187}$Os cosmochronometer. [Preview Abstract] |
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DA.00080: Storing Data from Qweak--A Precision Measurement of the Proton's Weak Charge Timothy Pote The Qweak experiment will perform a precision measurement of the proton's parity violating weak charge at low Q-squared. The experiment will do so by measuring the asymmetry in parity-violating electron scattering. The proton's weak charge is directly related to the value of the weak mixing angle--a fundamental quantity in the Standard Model. The Standard Model makes a firm prediction for the value of the weak mixing angle and thus Qweak may provide insight into shortcomings in the SM. The Qweak experiment will run at Thomas Jefferson National Accelerator Facility in Newport News, VA. A database was designed to hold data directly related to the measurement of the proton's weak charge such as detector and beam monitor yield, asymmetry, and error as well as control structures such as the voltage across photomultiplier tubes and the temperature of the liquid hydrogen target. In order to test the database for speed and stability, it was filled with fake data that mimicked the data that Qweak is expected to collect. I will give a brief overview of the Qweak experiment and database design, and present data collected during these tests. [Preview Abstract] |
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DA.00081: Production and Quality Control Improvements in the Fabrication of Diamond-Like-Carbon Guides David Richardson, Russell Mammei, Bruce Vogelaar, Mark Pitt Stemming from the search for physics beyond the Standard Model, the goal of the UCNA collaboration is to obtain the value of Vud. The weak and axial vector coupling constants provide an effective means of determining Vud but require knowledge of the angular correlation between the spin vector of the neutron and the momentum vector of the electron during beta-minus decay. Due to their superiority in minimizing systematic errors, Ultra-Cold Neutrons (UCN) were adopted for UCNA experiments. UCN require transport guides exhibiting the properties of being minimally depolarizing, nonmagnetic, nonconductive, possessing a high Fermi potential and high specularity. Experiments have shown that quartz tubes coated with Diamond-Like Carbon (DLC) are exceptional in the aforementioned categories. Recent improvements in the production process at Virginia Tech, including a refined cleaning procedure, the installation of a target rastering system, improved monitoring diagnostics, and a new drive mechanism have been implemented yielding improved guide quality. Furthermore, the use of X-ray spectroscopy has been employed to determine the quality of the DLC guides. Results of these improvements along with analytical results from X-ray spectroscopy will be presented. [Preview Abstract] |
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DA.00082: Separating the Spin States of a Free Electron Beam Neil Rifkin In 1922 Otto Stern and Walther Gerlach set out to test the spacial quantization of the electron by passing a beam of neutral silver atoms through a transverse magnetic field. The interaction of the two projections of the electron's magnetic moment with the magnetic field resulted in a splitting of the beam. However, for some sixty years it was generally accepted that the spin of free electrons, and thus their magnetic moment, could not be measured with an experiment similar to that of Stern and Gerlach. The reason being that the lorentz force on charged particles is far greater than the force due to the magnetic moment of the electron, thus blurring any desired results. To reduce the lorentz force, the electrons could be passed through a magnetic field whose gradient is in the direction of the electrons' momentum. This longitudinal Stern-Gerlach device, with a superconducting magnet, could polarize the tails of a low energy electron beam. [Preview Abstract] |
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DA.00083: Simulation of Velocity Filters in the Daresbury Recoil Separator at the HRIBF J.P. Rogers, R.L. Kozub, S.D. Pain, M.S. Smith, D.W. Bardayan, Y. Liu, M. Matos The Daresbury Recoil Separator (DRS) at Oak Ridge National Lab's (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF) is used for the study of nuclear reactions of astrophysical importance. For example, the DRS enables direct measurements of proton capture reactions on radioactive ions which occur in stellar explosions such as novae and X-ray bursts. The DRS uses velocity filters (Wien filters) that are tuned to transmit the reaction products with a specific velocity while deflecting the unreacted primary beam particles away from the optical axis, where they are stopped on adjustable slits. Data from earlier calculations of the electromagnetic fields inside and around the filters has been implemented into a FORTRAN program to provide accurate calculations and graphic representations of particle trajectories through the Wien filters. This information can be used to predetermine optimum positions of the slits for future experiments. The program will be used as an experimental setup tool for the DRS. [Preview Abstract] |
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DA.00084: Neutron damage tests of a GRETINA prototype detector T.J. Ross, C.W. Beausang, I.Y. Lee, A.O. Macchiavelli, S. Gros, M. Cromaz, R.M. Clark, P. Fallon, Henrik Jeppesen, J.M. Allmond Gamma ray energy tracking arrays such as GRETINA/GRETA and AGATA are the latest evolution in gamma ray detection. By locating the interaction points, in 3-dimensions, of individual gamma ray interactions such arrays allow the energies of gamma rays to be reconstructed. This leads to excellent energy resolution, superior peak-to-total ratio and photo peak efficiency and resolving powers up to a thousand times superior to the best current generation array. The position information is extracted from the detailed pulse shapes recorded in each segment. It is anticipated that these tracking-detectors will experience significant neutron fluxes during in beam experiments. Thus it is important to test the response of highly-segmented Ge detectors when subjected to high-energy neutrons. In a one week test carried out at the 88-Inch Cyclotron at LBNL the P3 prototype detector for the GRETINA array was exposed to a neutron flux equivalent to at least one and a half years normal use. The detector was then successfully annealed. Preliminary results for the energy and position resolution, prior to and after neutron damage, and after annealing, will be presented. [Preview Abstract] |
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DA.00085: Crosstalk Studies of a Time Projection Chamber Jonathan Ryer The crosstalk between various pads of a Time Projection Chamber (TPC) developed for the experiment MuSun was studied. Crosstalk between TPC pads must be studied and understood in order for proper muon path reconstruction to be obtained. A printed circuit board was developed to use capacitive coupling to transmit a signal pulse onto the TPC, where the crosstalk of the transmitted signal was studied. [Preview Abstract] |
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DA.00086: Transmission Line Properties of Nickel-Bodied Proportional Counters Jennifer Ryu Simultaneous measurements of neutral current and charged current neutrino scattering events allowed the Sudbury Neutrino Observatory (SNO) to demonstrate definitively neutrino oscillation. The three phases of the SNO detector are distinguished by different techniques of detecting the neutrons produced by neutral current neutrino scattering. In the final phase, nickel-bodied proportional counters filled with $^{3}$He were used as neutral current detectors (NCDs) by observing the charged particles produced by neutron capture on $^{3}$He. If we can understand the electrical transmission properties of the NCDs, we can use the different pulse shapes produced by neutron captures compared to those of alphas to distinguish these events and gain more sensitivity to the neutral current events. We found that because of the ferromagnetism of the nickel, standard calculations provided for proportional counters are not accurate enough. To obtain a better calculation, we directly measured the electrical properties of the transmission line as a function of frequency. This is a presentation of our results. [Preview Abstract] |
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DA.00087: Analyzing power and yield measurements of the $^{13}$C(d,n$_{0})^{14}$N Reaction between 280-460 keV Evan Sand, R. France, S. Stave, M.W. Ahmed, S.S. Henshaw, H.R. Weller, R.M. Prior, M.C. Spraker One of the poorly understood reactions that may contribute to heavy element inhomogeneous nucleosynthesis is the $^{13}$C(d,n$_{0})^{14}$N reaction. To understand the dynamics of this reaction, we have measured the yield and vector analyzing power of the n$_{0}$ group in the deuteron energy range from 280 keV to 460 keV. Neutrons were produced by a deuterium beam from the atomic beam polarized ion source, accelerated through the TUNL mini tandem onto a thick and enriched $^{13}$C target. Eight organic liquid scintillator neutron detectors were placed at angles from 0\r{ } to 150\r{ }. Results for the angular distributions of the yield and analyzing power were extracted and will be shown. [Preview Abstract] |
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DA.00088: Fusion reactions using the new and improved focal plane of SASSYER A. Schmidt, A. Heinz, R. Winkler, J. Qian, G. Henning, J.R. Terry, Z. Berant, M. Bunce, R.J. Casperson, R.F. Casten, V. Werner, E. Williams The Small Angle Separator System at Yale for Evaporation Residues (SASSYER) is a gas-filled magnetic separator used to transmit recoils from fusion-evaporation reactions to detectors at the focal plane. Improvements to the focal plane of SASSYER, including the addition of a Multi-Wire Avalanche Counter (MACY) as well as two 2400-pixel Double-sided Silicon Strip Detectors (DSSDs) with multiplexed electronics, were completed in the spring of 2008. Recoils can now be identified at the DSSDs by time-correlated alpha decays. The observed alpha decays are then correlated to prompt gamma events detected at the target position. The physics program at SASSYER is aimed at the study of the structure of neutron-deficient trans-lead and actinide nuclei. We present the results of the first experiments performed with the improved focal plane investigating $^{208}$Rn, $^{215}$Ac and $^{216}$Th. [Preview Abstract] |
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DA.00089: Discovery of Isotopes A. Schuh, A. Shore, A. Bury, A. Fritsch, J.Q. Ginepro, M. Heim, J. Snyder, M. Thoennessen We started a project to document the discovery of all known isotopes. The information for the isotopes are summarized for each element, including the discoverers, the laboratory and year in which it was first observed, the production method and the method of mass assignment used. Only refereed publications were considered, but unpublished reports and other various discrepancies pertaining to the discovery of individual isotopes are also discussed. The project began only recently and we will present the discoveries of the first elements summarized: arsenic, barium, cerium, einsteinium, gold, iron, krypton, silver, and vanadium. [Preview Abstract] |
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DA.00090: Simulations of $^{12}$C Break Up In A Twin Ionization Chamber C.B. Segal, N.R. Patel, U. Greife, K.E. Rehm, C.M. Deibel, J. Greene, D. Henderson, C.L. Jiang, B.P. Kay, H.Y. Lee, R. Pardo, M. Notani, S.T. Marley, X.D. Tang In stellar explosions the triple $\alpha$ decay process is key to forming the life-giving $^{12}$C . This experiment is to further investigate the energy region in $^{12}$C around 10 MeV where a theoretically predicted 2$^{+}$ state has yet to be observed. The motivation for studying this is to better understand the $^{12}$C nucleosynthesis process that occurs in red giant stars where the short lived $^{8}$Be interacts with alphas at extreme temperature and pressure scenarios which then in turn creates $^{12}$C. We study the particle-unbound states by implanting $^{12}$B into a twin Frisch grid ionization chamber and following the decay into $^{12}$C and subsequently into three $\alpha$ particles. The response of this ionization chamber to the detection of multiple $\alpha$ particles was studied using various simulation programs. Results of these simulations and limits for the predicted 2$^{+}$ state will be presented. [Preview Abstract] |
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DA.00091: Track Reconstruction for the NIFFTE TPC Sarvagya Sharma The Global Nuclear Energy Partnership (GNEP) has funded the construction of a Time Projection Chamber (TPC) to be used for precision fission cross-section measurements through the Nuclear Energy Research Initiative (NERI). This poster shall illustrate the status of algorithms intended for intelligent track finding and track fitting using raw data obtained TPC simulations will be presented. The track fitting effort in this experiment has borrowed a number of ideas from high-energy physics along with other pattern recognition techniques not previously affiliated with experimental physics. Two track-finding techniques have been investigated. The Hough Transform is a brute force attempt at finding tracks. The second paradigm for track reconstruction, Binary Space Partitioning (BSP), was found to be less computationally expensive. BSP however had to be used in conjunction with a multilayer perceptron to rejoin tracks that were overly partitioned. To determine track fit parameters, an iterative Kalman Filter has been implemented that allows multiple scattering and energy losses to be taken into account to obtain unbiased errors. [Preview Abstract] |
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DA.00092: Target Implantation for Inverse ($^{3}$He,d) Reaction Studies D.J. Sissom, R.L. Kozub, D.W. Bardayan, D.W. Stracener Proton transfer reactions such as ($^{3}$He,d) can provide valuable structure information on proton single particle states and resonances, some of which are very important for the rp process in explosive nucleosynthesis. In stellar explosions, the reactants are often radioactive, so radioactive ion beams and inverse kinematics are needed for such studies. These ($^{3}$He,d) experiments in inverse kinematics require localized $^{3}$He targets. Since helium gas jet targets are difficult and expensive to produce, implanted targets may be the more practical solution. Helium implanted Al foil targets have been successfully produced in other facilities\footnote{J. E. McDonald {\em et al.}, Journal of Instr.\ {\bf 1}, 09003 (2006).} up to densities of $\sim$$4\times10^{17}$ ions/cm$^{2}$. The UNISOR facility at the HRIBF at ORNL can be utilized to implant $^{3}$He ions, but modifications to the UNISOR collection chamber are needed. A new assembly has been designed to accommodate a linear motion feedthrough that attaches to a target ladder on which aluminum foils and a slit for beam profile analysis can be mounted. The targets produced will be used in a number of experiments with stable and unstable beams. A detailed update of the project will be presented. [Preview Abstract] |
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DA.00093: A Geant4 simulation for DSAM lifetime measurements at low recoil velocities Mallory Smith, J. Russell Terry Lifetimes of low-spin excited states can be determined by populating such states in light-ion fusion-evaporation reactions. Reduced transition probabilities derived from these measurements provide a sensitive test for low-energy nuclear structure models. The Doppler shift attenuation method (DSAM) is a common, flexible technique used to resolve lifetimes for stable and unstable isotopes on the order of hundreds of femtoseconds. DSAM is typically employed in heavy-ion fusion-evaporations, in which nuclei have high recoil velocities and introduce high angular momenta to the compound system. However, these reactions generally populate high-spin and yrast states. We explore the possibility of using DSAM to extract lifetimes from low-spin, non-yrast states, using light-ion-induced fusion-evaporation, where the nuclear recoil velocity is small. A Geant4 simulation was created to test the viability of using light ions to measure lifetimes. From the simulation, the minimum required bombarding energy was ascertained. [Preview Abstract] |
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DA.00094: Cross-sections of alpha scattering on Boron 11 Andrew Smith There has been a recent renewal in the interest of aneutronic fusion as a power source using the $^{11}$B(p,$\alpha )$2$\alpha $. In light of this, TUNL has been requested to measure accurate cross sections for the $^{11}$B(p,$\alpha )$2$\alpha $ reaction as well as $^{11}$B($\alpha $,$\alpha )$. To measure the cross section of $^{11}$B($\alpha $,$\alpha )$ the capture group at TUNL has collected data using a target with a 2-3 $\mu $g/cm$^{2}$ layer of isotopically pure $^{11}$B between two layers of gold. A beam was generated using the TUNL alpha source and accelerated with the tandem accelerator producing beam energies up to 7 MeV. Silicon surface barrier detectors were placed at angles 45, 60, 75, 90, 90, 110, 130, 150 degrees. There are some discrepancies between the present data and the previous data that have yet to be resolved. Preliminary results as a function of energy and angle will be shown and compared to previous measurements. [Preview Abstract] |
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DA.00095: Assembling Nine Resistive Plate Chamber Prototype Modules for PHENIX Thalassa Sodre The Pioneering High Energy Nuclear Interaction eXperiment, located at the RHIC ring at Brookhaven National Laboratory, is designed to examine direct probes from proton-proton and heavy ion collisions. One of the goals of PHENIX is to discover how the components of the proton contribute to its intrinsic spin. Specifically, the muon trigger upgrade at PHENIX focuses on flavor separated quark and anti-quark contributions to proton spin. The goal of the upgrade is to enhance our ability to collect and analyze muons that decay from W-bosons produced in polarized proton-proton collisions. To achieve this, Resistive Plate Chambers (RPCs) and new front-end electronics will be employed that will enable us to discern high PT muons from the low PT muon background. This poster will focus on the assembly and quality assurance procedures of the RPC modules. Over the summer nine RPC prototypes were assembled and tested on a cosmic ray stand. Two half octants--made up of three RPC prototypes each--will be installed on the south arm of the PHENIX detector this fall. [Preview Abstract] |
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DA.00096: NIFFTE Overview and Goals Scott Stewart The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) will make fission cross section measurements for next generation nuclear reactors using a Time Projection Chamber (TPC). Collaborating institutions are Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Idaho National Laboratory, Georgia Institute of Technology, Abilene Christian University, Oregon State University, Cal Poly San Luis Obispo, Colorado School of Mines, and Ohio University.~ It is funded under the Global Nuclear Energy Partnership (GNEP) in order to increase the precision needed for the design of a new generation of fast neutron reactors.~ The TPC is a new tool to improve the existing measurements that used fission chambers.~ The TPC will allow an overall view of the fission event and will distinguish it from background processes; primarily alpha decay. The experiments are planned at the Los Alamos Neutron Scattering Center (LANSCE) utilizing neutron beams from 10 keV to 10 MeV where existing fission cross sections have typical uncertainties of 5{\%}. [Preview Abstract] |
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DA.00097: Testing a luminosity detector for the BRAN project at the LHC Johannes Stiller Two pairs of segmented ion chambers, called BRAN, are used at CERN's LHC. One pair is located at the ATLAS interaction region while the other is at CMS. The detector itself is a pressurized gas ionisation chamber. It is segmented into four multi-gap quadrants which are able to function independently. This device will measure the bunch by bunch luminosity and crossing angle of the beam at both locations. Recently, the device was tested at CERN's SPS with 300 GeV protons using its final electronic design. The performance of the BRAN was studied as a function of pressure, absorber thickness, and voltage. We have compared these test results to that of Monte Carlo simulations. These results as well as the current status of this detector will be presented. [Preview Abstract] |
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DA.00098: Temporal Variation in Cosmic Ray Muon Flux Steven Stroberg, Kalya Evans, Bethany Lyles-Goldblum, Erik Swanberg, Eric Norman Plastic scintillator detectors are often used in homeland security applications that look for high energy photons, such as active interrogation of cargo containers. In these applications, the background due to cosmic ray muons is assumed to be constant. However, there appears to be potentially significant variation in the muon flux over time. The muon flux was measured over a period of several months using two plastic scintillator detectors (122x61x15 cm and 30x30x10 cm). The data from these detectors were compared to data from cosmic ray neutron detectors in Kiel, Calgary, Moscow, Thule and Beijing collected during the same time period. The response function of the two detectors was also compared with a model developed in MCNPX code using the CRY simulated cosmic ray background. Preliminary data suggest that the temporal variation in muons is significantly greater than that of the cosmic ray neutrons. [Preview Abstract] |
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DA.00099: Quality Control for the RPC Upgrade for PHENIX Dillon Thomas The PHENIX detector is located at Brookhaven National Laboratory on the Relativistic Heavy Ion Collider (RHIC) ring where it studies both heavy ion and polarized proton-proton collisions. One of the primary goals of the polarized proton program is to improve our understanding of the proton's spin structure. A level 1 trigger upgrade is currently being constructed for PHENIX. This will involve the installation of Resistive Plate Chambers (RPCs). These new chambers will improve our ability to trigger on high transverse momentum single muons that are produced in the decay of W bosons. After these chambers are constructed, they must be carefully and completely checked to ensure they operate properly, before they are installed in the PHENIX spectrometer. These chambers are assembled as modules and then tested in our cosmic ray test stand while they are hooked up to data acquisition and gas systems. From cosmic ray muons, we can carry out tests to learn the efficiency and performance of each RPC. These tests ensure that only fully efficient chambers will be used in the final installation in the PHENIX spectrometer. Data and graphs of the efficiencies and performance will be presented. [Preview Abstract] |
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DA.00100: Simulation of NIFFTE TPC Remington Thornton The Global Nuclear Energy Partnership (GNEP) has funded the construction of a Time Projection Chamber (TPC) to be used for precision fission cross-section measurements through the Nuclear Energy Research Initiative (NERI). One important requirement of the TPC project is to have an accurate simulation of the physical volume and realistic data flow. GENAT4 is multi-purpose 3-D Monte Carlo simulation package that has bee chosen for this effort. The sensitive volume of the TPC has been created in GENAT4 along with simulation of the detector response, which includes: 3-D ion diffusion, pedestal fluctuations, charge sharing and digital latching noise. In this poster, results from the initial simulation will be described in detail. [Preview Abstract] |
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DA.00101: Systematic Trends in Nuclear Reactions Luke Titus A systematic study of elastic scattering is performed to test global optical potentials. Many global optical potentials exist in the literature. Here, three popular potentials were used to predict cross sections of proton elastic scattering: Perey and Perey, Chapel Hill and Koning and De la Roche. The predicted cross sections are compared with experimental data for accuracy. In addition to the elastic studies, transfer (d,p) reactions are also calculated using the adiabatic method to construct the deuteron optical potential. Two methods for constructing the deuteron optical potentials are tested for accuracy, the first consisting on the Johnson and Soper approximation and the second on the finite-range correction by Wales and Johnson. Systematic trends in the predicted cross sections are analyzed as neutrons are added to the target and projectile energies are changed. Our calculations have shown that some well established potentials may lose their predictive power over certain mass and energy ranges, while others are more consistent. [Preview Abstract] |
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DA.00102: Design of an in-beam gamma coincidence measurement to study K-forbidden transitions in $^{178}$Hf induced by bremsstrahlung Geoffrey Trees, James Carroll Recent experiments [1] have suggested that several K-forbidden transitions exist that feed the 31-year isomer $^{178m2}$Hf from the ground state band, with surprisingly large transition probabilities. Further study is needed, however, to confirm this result and to more accurately measure the probabilities. One approach would be to excite these transitions using real photons (bremsstrahlung) incident on an isomeric target, and to search for resulting emission of gamma emission within the ground-state band that do not occur during natural decay of the isomer. This poster will describe an experiment in development to investigate one of the reported K-forbidden transitions, at 331 keV, by in-beam coincidence gamma spectroscopy using two Ge clover detectors.$\\$ $\\$ [1] A. B. Hayes, et al., Phys. Rev. C 75, 034308 (2007). [Preview Abstract] |
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DA.00103: The Effects of Measurement Errors on Neutrino Angular Resolution in the IceCube Neutrino Detector Leslie Upton The IceCube collaboration is actively pursuing neutrino detection to study astrophysical sources. These neutrinos are identified by the secondary muons detected within the IceCube detector array. The muon track is reconstructed using the information provided by the time information of Cherenkov photon illuminated digital optical modules (DOMs) within the detector. However, it is imperative to calculate how different measurement errors affect the reconstruction of the muon. A Monte Carlo simulation was developed in order to study these effects on the resolution of the muon reconstruction. The simulation, developed in ROOT, creates a muon in an array detector and uses time information from illuminated DOMs and Minuit to reconstruct the parameters of the muon without any knowledge of the original coordinates of the muon. Minuit provides precise results, with spikes around zero for the space angle between the original and reconstructed muon tracks. There are correlations between the number of illuminated DOMs, muon track length, and the angular resolution of the reconstructed track. Further work includes exploring photon statistics, energy dependence and more precise DOM information. [Preview Abstract] |
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DA.00104: Using a Geant4 Simulation to Model E906 Marissa Walker The goal of E906 at FNAL is to further explore the anti-quark distribution in the nucleon sea using a 120 GeV proton beam and fixed liquid hydrogen and deuterium targets. The resulting particles pass through a spectrometer of two magnets, three stages of scintillator and wire chambers, and layers of absorber designed to absorb and deflect as much of the background noise as possible, isolating pairs of muons produced by the Drell-Yan process. The design of the first magnet previously involved an open aperture with a number of layers of hadron absorbers inserted. However, in order to reduce cost, the plan is now to have a solid iron magnet. Geant4 based simulations were used to determine if this magnet would be able to especially in minimize background rates adequately. Based on simulation results, the solid iron magnet should be sufficient. Various possibilities for the geometry of this magnet, as well as the layout of the target and absorbers, have been evaluated. [Preview Abstract] |
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DA.00105: Investigation of extensions to the Glauber model of nuclear collisions Ryan Ward, J.L. Klay The Glauber model of nuclear collisions describes the geometrical distribution of interacting nucleons. Monte Carlo versions of the Glauber model have been very successfully applied to data from the Relativistic Heavy Ion Collider. This poster will describe how it is used to model the collisions of nuclei at high energy particle accelerators such as RHIC and the LHC, as well as possible quark level extensions to the model. A computer simulation of the model written in Java with full visualization and outputs to ROOT will be demonstrated. [Preview Abstract] |
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DA.00106: B$^0$ Meson Reconstruction Through the J/$\psi$ Decay Channel with the Heavy Flavor Tracker at STAR Joshua Weiner The Solenoidal Tracker at RHIC (STAR) is an ongoing experiment at the Relativistic Heavy Ion Collider (RHIC) located at Brookhaven National Laboratory. Its goals are to observe and study the characteristics of the quark-gluon plasma produced by nuclear collisions. The Heavy Flavor Tracker (HFT) is a new high-resolution vertex detector that has been proposed by STAR. The HFT will allow high-resolution tracking of charged particles, enabling the identification of particles containing charm and bottom quarks that decay hundreds of microns from the primary interaction vertex. The B$^0\rightarrow$ J/$\psi$ X and J/$\psi\rightarrow e^+e^-$ decay channels form a good candidate for B$^0$ meson detection due to the presence of the dielectron pair generated at a large distance from the primary vertex. Reconstruction of B$^0$ events mixed with Au-Au 200 GeV events was performed with HIJING, GEANT, and the STAR software library. We will show how the HFT can identify the B$^0$ events and what can be learned by identifying the B mesons. [Preview Abstract] |
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DA.00107: Silicon Detector Deadlayer Measurements Meagan White, Kate Jones, Ryan Kapler, Brian Moazen, Kyle Schmitt The Oak Ridge Rutgers Universities Barrel Array (ORRUBA) is a large silicon detector array for measuring ejectiles from transfer reactions [ref]. A large component of ORRUBA is made up of position sensitive silicon strip detectors which use a resistive readout to give position information. The ejectile energy is found by summing the signals on the two ends. This method assumes that the complete energy of the particle is recorded. However, before the particle reaches the active part of the detector, there is a thin layer in which the particle loses energy before it is detected. This layer of the detector is the deadlayer, and to get an accurate ejectile energy for the particle, the energy lost in the deadlayer prior to detection has to be known. We have developed a technique to measure the thickness of the deadlayer using an alpha source and rotating the detector. I will present this technique and the results we have obtained with it. [Preview Abstract] |
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DA.00108: Effects of Two-Nucleon Correlations in the Formation of Multiquark Clusters in Nuclei Paul W. Wiecki, Drew A. Fustin, James P. Vary, Athanasios N. Petridis If the wavefunctions of two or more 3-valence-quark nucleons bound in a nucleus overlap sufficiently, quark clusters made of 6, 9 or more valence quarks may be created. The quark cluster probabilities depend on the single-body nuclear densities and correlations. The radial single-particle nuclear density is approximately calculated analytically, using a harmonic oscillator mean potential with spin-orbit coupling, or, more accurately, by numerically diagonalizing the Hamiltonian with potentials, such as Woods-Saxon, in the Independent Particle Model. These theoretical results are compared to scattering data to isolate the two-body nuclear correlations. The resulting single-particle density and two-nucleon correlation function are incorporated into a quasi-classical Monte-Carlo algorithm, using network theory, which calculates the multi-quark cluster formation probability for several nuclei. The parton momentum distributions in quark clusters differ from those in single nucleons. The calculated cumulative cluster probabilities together with appropriate parton distributions are sufficient to describe the EMC effect for all Bjorken-x, dilepton production off nuclei, and $J\Psi$ suppression. [Preview Abstract] |
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DA.00109: Simulations of a HELIOS Recoil Detector Jack Winkelbauer The Helical Orbit Spectrometer (HELIOS) is a new type of light-charged particle spectrometer, designed to study inverse kinematic nuclear reactions with unstable beams. HELIOS is based around a 3T superconducting solenoid with the magnetic axis aligned with the beam axis. The ejected light nuclei undergo helical motion, transporting them from the target to a hollow array of silicon detectors. The heavy recoil nuclei scatter at small angles in the forward direction. HELIOS will require heavy recoil detection. Possibilities for recoil detection include an ionization chamber or an annular silicon detector. A full three dimensional field map has been measured and incorporated into the existing Monte Carlo simulations. These simulations have been used to investigate the transport properties of the HELIOS spectrometer for the heavy recoil nuclei. The acceptance of these recoil detection methods, as well as details on the placement and operation of a HELIOS recoil detector will be presented. Work supported by the U. S. Department of Energy, Office of Nuclear Physics under grant numbers DE-FG02-04ER41320 and DE-AC02-06CH11357. [Preview Abstract] |
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DA.00110: Calculating dilepton production from pions interacting with a disoriented chiral condensate Shawn Witham Recent data by the PHENIX collaboration at RHIC show an enhancement of low invariant-mass dilepton production in Au-Au collisions at 200 GeV [1]. In this project we study whether the formation of a Disoriented Chiral Condensate (DCC) could explain (part of) this dilepton enhancement. In particular, we compute dilepton production by means of annihilation of DCC domains [2], and compare it to baseline calculations where two thermal pions are annihilating via a rho meson. Using an in-vacuum rho meson line shape, the DCC-DCC annihilation is the dominant source at very low mass ranges. However, it is shown that using an in-medium rho meson [3] the thermal pion-pion annihilation drowns out the effects of the DCC-DCC annihilation. The calculation of dilepton production from thermal pions interacting with a DCC will also be looked at in continued work. [1] PHENIX Collaboration, ``Enhancement of the dielectron continuum in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV.'' arXiv:0706.3034v1 (2007). [2] Huang, Z., Wang, X. 1996. ``Dilepton and Photon Productions from a Coherent Pion Oscillation.'' Phys. Rev. B, Vol. 383:4, 457-462. [3] R. Rapp, 2007. J. Phys. G 34, 405. [Preview Abstract] |
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DA.00111: TPC Pad Structure and Track Reconstruction for the Muon Capture on Deuterium Lukasz Wojtaszek The MuSun experiment proposes to measure the rate $\Lambda _{d}$ for the muon capture on the deuteron to better than 1.5{\%} precision. The measurement will provide the low-energy constant representing the coupling of the axial current to the two-nucleon system necessary in describing weak interaction processes in two-nucleon systems such as solar pp fusion and \textit{$\nu $ + d} reactions observed by the Sudbury Neutrino Observatory. The desired precision requires a cryogenic Time Projection Chamber (TPC) to be designed and built. A Monte Carlo simulation of muon tracks was used to determine the optimal geometry and size of the TPC pads, taking into account noise and crosstalk. A track reconstruction program was developed to determine the three dimensional path of the muon to within a fraction of the pad size. The drift time of the electrons gives the height above the pad. The energy deposited on the TPC pads, following the Bragg curve, allows determination of the muon stopping position to within a fraction of the pad size. The information will be combined to reconstruct the three dimensional path of the muon in the chamber. Progress on this project will be reported. [Preview Abstract] |
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DA.00112: Neutron Pulse Shape Discrimination in Long Liquid Scintillator Counters Bradley Wood, Jeff Blackmon, Savarnik Dixit, Laura Linhardt, Edward Zganjar Efficient and selective neutron detection is important for nuclear physics research and for applied areas like homeland security. Counters based upon some varieties of liquid scintillator have the significant advantage that neutrons can be discriminated based upon pulse shape analysis. Large counters are desired to achieve high efficiency, but the effectiveness of pulse shape discrimination is compromised in some large geometries by light propagation and reflections that distort the signal shape. We are studying signal distortion in long (lengths up to 2 m) counters based upon the EJ301 scintillator. Digital signal processing and waveform analysis are being applied in an effort to improve neutron discrimination despite signal distortion. The approach and preliminary results will be presented. [Preview Abstract] |
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DA.00113: Testing Different Materials to Produce Gas Gaps in High Rate RPCs Ryan Wright The PHENIX experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory uses polarized proton-proton collisions to study the spin of the proton. This study is made by reconstructing muons produced in the proton collisions. As RHIC moves to higher energies, the existing trigger is not sufficient to select the events of interest such as single high $p_T$ muons that are a result of W-Boson production. To aid the current muon triggering system, fast Resistive Plate Chambers made from Italian Bakelite are being added to the detector system. At the University of Illinois Urbana-Champaign, a test stand has been built to help understand different factors that affect the RPCs performance and rate capabilities. The test stand uses open gas gap RPCs which are ideal for testing different materials and their rate capabilities of these different materials. Various materials and their data will be presented. [Preview Abstract] |
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DA.00114: Testing and classification of various silicon detectors Kenneth Wunder In order to truly understand the techniques used in nuclear physics experiments and radiation detection, it becomes necessary to explore the basic interactions between the energy quanta and the detector itself, the way in which the detector signals and captures this energy, the methods of electronic signal processing, and, finally, the analysis of the data recorded during the testing. The testing explored three different types of silicon detectors, focusing on the most often used categories for classification and the tests used to get the results. [Preview Abstract] |
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DA.00115: Static Magnetic and Quadrupole Moments of Excited States of Nuclei Sean Yeager, Larry Zamick, Yitzhak Sharon The gyromagnetic ratio $(g)$ is the ratio of $\mu$ to J. We have noticed that many isoscalar $g$ factors of excited states in both even-even and odd-odd nuclei have values close to 0.5 nuclear magnetons. It should be noted that both the collective model and the single $j$ shell model (in the limit of large orbital angular momentum $l$) predict this result. We also note the importance of the ``$l$ forbidden" $[Y^2 \sigma ]^1$ term for magnetic moments. For quadrupole moments we define the quadrupole ratio, $\frac {Q_0(S)}{Q_0(B)}$ i.e. the ratio between the intrinsic quadrupole moment deduced from $2^+$ states and from $B(E2)_{0 \rightarrow 2}$. Ideally, the rotational model predicts a value of one for the quadrupole ratio while the simple vibrational model predicts zero. The poster will show a graph plotting this ratio against mass number. There are small regions where the ratio is close to zero and $\frac{E(4)}{E(2)} $ is close to two. Also, there are regions where the quadrupole ratio is close to one and $\frac{E(4)}{E(2)}$ is close to $\frac{10}{3}$. Yet there are intermediate regions which lie in between these two limits. This theoretical analysis is of relevance to the experimental program of Prof. Noemie Koller at Rutgers University. [Preview Abstract] |
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DA.00116: Simulation of Bottom Measurement with the STAR HFT Detector Xiaoyu Zhu STAR (Solenoidal Tracker At RHIC) is a working experiment at RHIC (Relativistic Heavy Ion Collider) to study properties of Quark-Gluon Matter under extreme energy density and temperature. Bottom quark production and propagation is a unique probe of the dense matter created at RHIC. The HFT (Heavy Flavor Tracker) is a proposed detector upgrade of STAR, capable of reconstructing open charm/bottom hadrons at midrapidity. We present a study of B meson reconstruction via the semi-electronic channel using GEANT simulations of HFT performance. We carried out two approaches to separate B from D mesons: the impact parameter method and the displaced vertex method. First, B mesons have mean proper decay lengths of ~500 microns, so their decay electrons have large impact parameters with respect to the interaction vertex. Second, the secondary vertex (daughter D decay) displacement is in the direction of the B meson, and close to the direction of the decay electron, so the flight distance (the scalar product of the secondary vertex displacement and the daughter electron momentum) provides a good measure for the B meson reconstruction. Preliminary results on STAR HFT B measurement performance will be discussed. [Preview Abstract] |
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