Session HA: Conference Experience for Undergraduates Poster Session (4:00 - 6:00 pm)

Scrutinizing contaminants via beta spectra and lifetimes in the He6-CRES experiment

We are doing careful analysis searching for possible contaminants that could affect the He6-CRES experiment. The latter

looks at producing high-precision measurements of the beta spectra of 6He and 19Ne. These are produced via

7Li(d,3He) and 19F(p,n). We will present our plan and initial data to search for possible contaminants that could affect

the experiment. The main tools are measurements of halflifes and thick-scintillator data to identify the contaminants.   

Reconstructing 10Li Neutron-unbound States using a Compact Detector System

The study of neutron-unbound states requires measuring properties of the emitted charged fragments and neutrons, which may be made more complicated if the emitted charged particles are in a bound excited state. This is because the de-excitation of these bound excited states emit gamma rays, which causes an energy misassignment of the neutron-unbound states. An additional detection system is therefore required to measure these gamma rays. The MoNA collaboration recently ran an experiment to determine if the 0⁺ bound excited state of ¹²Be is populated following neutron emission from ¹³Be rather than the 0⁺ ground state. There were several secondary beams available in the experiment, including ¹¹Li, ¹⁵B, and ¹⁴Be, the latter of which was used for the main experiment. The neutron-unbound states in this experiment were reconstructed by using a stack of five silicon PINs and one CsI detector to measure the energy of the charged fragment, the MoNA-LISA detector to measure the momentum of neutrons, and the CAESAR detector to measure gamma rays. A reconstruction of ¹⁰Li neutron-unbound states produced by neutron knockout with the ¹¹Li beam may be used as a test of this experimental setup. The comparison of this data with prior experimental results will be presented.   

Investigation of Be and Li ion production via laser ablation for future high precision 7Be EC Q-value measurements

The investigation of neutrinos is an important part of understanding physics beyond the Standard Model. Experiments that employ beta decay can provide information on the particle nature of the neutrino, its absolute mass, and on the existence of sterile neutrinos. One such experiment is the BeEST, which uses electron capture decay of ⁷Be to search for signatures of keV scale sterile neutrinos via precise measurements of the recoil energy of the ⁷Li daughter. A precise and accurate Q value is needed for a determination of the recoil energy to help evaluate the BeEST measurement. We have performed such a Q value measurement via Penning trap mass spectrometry with the LEBIT facility at the NSCL, and have reduced the Q value uncertainty by a factor of about three. At Central Michigan University, we are investigating the use of our laser ablation ion source as a means of producing Be⁺ and Li⁺ ions for future measurements with the CHIP-TRAP Penning trap at CMU that aim to improve upon this precision.   

Radioactivity from Welding Processes, Compare Amateur Welds with Commerial welds

Many nuclear physics research projects require the fabrication of custom-built hardware which often includes welding. Especially for small-scale setups, these hardware components could be produced in-house by amateur welders or in student labs. Low-background experiments, such as High Purity Germanium (HPGe) gamma spectroscopy setups, have stringent requirements on the radiopurity of materials in and around the experimental setup. In this summer student project we investigate the radioactive background introduced by different welding techniques, including non-perfect amateur welds. 

We use 2% thoriated tungsten electrodes and Gas Tungsten Metal Arc Welding (GTAW) to create sample welds on a 3’’x3’’ mild steel base plate. We perform a deliberately poor welding technique, dipping the electrode into the molten puddle. This creates tungsten inclusions a welding defect of the GTAW process. We measure the welded plate with a HPGe detector to determine ²³²Th and ²³⁸U contaminants introduced by the “poor” welding process. We also compare the radioactivity of different commercial welding electrodes containing thorium, lanthanum, and cesium. Additionally, we compare our poor welds with welds created by a certified welder.

We also study different stick electrodes used in the Shielded Metal Arc Welding process. We also use deliberately poor welding technique to create slag inclusions, a defect where slag is included in the weld. We measure the radioactivity and compare with welds created by a certified welder.

    

New Method for Self-Absorption: Demonstrating Utility of a Polarized Beam

A newly proposed self-absorption experiment was performed following nuclear resonance fluorescence (NRF) of ²⁴Mg at the High-Intensity γ-Ray Source using photon beam energies of 9.82, 9.97, and 10.71 MeV. For this project, preparatory analysis was carried out focusing on determining the efficiency of the 32 clover-detector channels of the Clover Array and the analysis of NRF spectra, important steps toward extracting photoabsorption cross sections. Data from a radioactive source were analyzed, in order to optimize the simulation of the entire Clover Array setup such that computed efficiencies match measured ones. This experiment turned out to be very sensitive to weak decay branches of the states produced by NRF. Thus far, three new, weak decay branches, not reported in the literature, have been observed.   

Commissioning of the neutron+charged-particle coincidence setup at FSU. Valarie Milton, Sergio Almaraz-Calderon, Ashton Morelock Department of Physics, Florida State University.

Many of the nuclear reactions important for explosive nucleosynthesis scenarios in the cosmos proceed through resonant states in exotic nuclei. In order to calculate the rate of these reactions and linked them with observables like for example, energy generation, light curves, isotopic and elemental abundances in the stars; information on the properties of the relevant resonances is needed. Such information includes the energy of the resonance, spin-parity, and partial and total widths.

At the John D. Fox accelerator laboratory at Florida State University, we are developing a setup that will allow us to measure charged particles from the decay of resonant states in exotic nuclei. States of interest will be populated via (³He,n) reaction. The states of interest will be tagged using the CATRiNA neutron array which consists of 32 deuterated benzene liquid scintillators. Charged particles decaying from states above the particle threshold will be measured in a compact array of silicon detectors in coincidences with the neutrons from the reaction. In this talk, the commissioning of the experimental setup will be discussed as well as preliminary results.

    

Testing Mirror Symmetry

Certain nuclei of astrophysical interest can be difficult to study experimentally. In such cases, mirror nuclei are sometimes used to estimate quantities such as spectroscopic factors. A study to examine the accuracy of mirror symmetry in attaining these quantities was completed at Florida State University using the Super-Enge Split Pole Spectrograph and associated focal plane detector. Accelerated beams of 3He and deuterons impinged targets of 28Si and 24Mg to study mirror pairs via the 28Si(3He, d)29P, 28Si(d, p)29Si, 24Mg(3He, d)25Al and 24Mg(d, p)25Mg reactions. The resulting light reaction particles were measured in the focal plane detector.  Data were taken at laboratory angles of 10° - 45° in 5° increments. The excitation energy range was up to and beyond the proton and neutron separation energies for each reaction: 0 mev to 8 MeV in all cases. The resultant proton and deuteron spectra were analyzed to find the angular distributions of pairs of mirror states and their relative spectroscopic factors. Preliminary results will be presented and their impact on determining reaction rates discussed.    

β-Decay of the 74,75Ni Istopes

The process of element synthesis beyond Fe is an open question in modern physics largely because this synthesis happens exclusively in stars. We know that the rapid neutron capture process, also known as the r-process, is accountable for the production of nearly half of the isotopes of these heavier elements. Therefore, it is imperative that the isotopes resulting from the r-process are studied. A beam of isotopes with atomic masses close to 75amu was produced at the National Superconducting Cyclotron Laboratory (NSCL) and was embedded into a Double Sided Silicon Strip Detector. The Summing NaI detector (SuN), a large volume detector surrounding the Double Sided SIlicon Strip Detector at the NSCL, was able to detect the gamma rays emitted in the β-decay of  74,75Ni, which provides information about both the populated levels and individual gamma ray in the daughter nuclei. Using the Total Absorption Spectroscopy (TAS) technique, these measurements can provide new information like beta decay intensities in 74,75Ni and their daughter nuclei 74,75Cu. The conclusions drawn from this experiment will be extremely beneficial to the study of unstable isotopes along the r-process path.

    

Design concepts of a Cherenkov detector at the Facility for Rare Isotope Beams

The mechanical design of a Cherenkov detector for the MoNA Collaboration scientific program at the Facility for Rare Isotope Beams is under study by the MoNA Collaboration. Such detector will complement the existing charged detector system to improve its particle identification capability as exotic ion beams will now reach relative velocities of b » 0.5. The Fusion360 software was used to optimize several configurations from triangular to hexagonal shapes to detect ions across a large area while minimizing losses between tiles. Hybrid devices that include diamond and semiconductors (Si and Ge), as well as single silicon carbide sheet were investigated. We will discuss the various designs including their advantages and deficiencies. This work was done in collaboration with CEMHTI (UPR 3079 CNRS) and Université d'Orléans in France.

    

Investigation of various material properties for a Cherenkov detector at the Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams located on the campus of Michigan State University in the United States started its scientific program in May 2022, becoming the most powerful facility to study exotic nuclei with energies up to 200 MeV/u. Over the past two decades, the MoNA Collaboration has established a strong program for the understanding of the reaction mechanism and spectroscopy of extreme neutron rich nuclei along the dripline using the invariant mass technique. These nuclei decay by emitting a charged fragment and one or multiple neutrons. At FRIB energies, properly identifying the charged fragments will become a challenge due to their high velocities. A Cherenkov detector is under study to complement the existing charged detector system and improve its particle identification. The optical properties (transmittance, specular reflectance, diffuse reflectance) of several materials (4H SiC, GaN, multilayer graphene (MLG), single layer graphene (SLG), silicon diamond like carbon (Si-DLC), and Si) were investigated before and after hydrogen implantation. Ion-implantation induced defects in the different semiconductors studied, and their formation and evolution with fluence and thermal annealing will be presented and compared. This work was done in collaboration with the CEMHTI (UPR 3079 CNRS) and Université d'Orléans in France.   

Probing the limits of nuclear excited state lifetime measurement using fast rare isotope beam and doppler-shift attenuation method with a single active target.

Precise lifetime measurements of excited states provide valuable information for the structure of nuclei. Using Geant4 simulation software, we are able to analyze how different factors such as beam energy, beam composition, and reaction target thickness affect the sensitivity of lifetime measurements. Here, we analyze the properties of fast heavy ion beams with regard to the limits of what measurements are possible using a doppler shift attenuation method. Simulation parameters are set to a single fixed target with the Gretina γ-ray tracking HPGe array measuring decays. The effects of varying thickness of a Carbon target are explored and 1mm thickness is determined to be optimal for lifetimes in the range of 0.5ps to above 5.0ps. Furthermore, it is determined that the use of an active diamond target can allow for more precise lifetime measurements as well as greatly extend the lower bound of what lifetimes can be measured with this method down to ~0.2ps.   

Absolute Proton Detection Efficiency

Many neutron lifetime experiments have been performed following one of two methods, the storage method and the beam method. Currently there is approximately a 4σ, or 8 second, discrepancy between the measured lifetimes of the two methods. The Sussex-ILL-NIST beam method measures neutron lifetime by detecting protons released from decaying neutrons. Absolute proton detection is essential to the beam experimental approach. The absolute detector efficiency is not currently known for existing experiments and could be a source of a hidden systematic error. The proposed calibration technique seeks to determine absolute detector efficiency and can also be used to calibrate new particle detectors for use in future experiments. The method as well as the results of recent Geant simulations will be presented.

    

Simulating a Multi Reflective Time of Fight Device for uses in Heavy Element Chemistry Experiments

The heaviest elements on the periodic table are interesting to study for investigations of both their nuclear and chemical properties. Unfortunately, these studies can be extremely challenging as these elements need to be produced in nuclear reactions and most have very short half-lives. This means that traditional chemistry techniques cannot be used to probe their chemical behavior. However, nuclear physics techniques are now being employed for these chemistry measurements. Such experiments have already been conducted with the Berkeley Gas-Filled Separator and FIONA devices at the Lawrence Berkeley National Laboratory 88-inch cyclotron facility. Individual ions of heavy elements are trapped and then exposed to reactive gases such that a chemical reaction could take place. Then products of that chemical reaction can be directly identified from their mass-to-charge ratio. In the future, it is believed that the addition of a Multi-Reflective Time-of-Flight device to the setup may aid these chemistry experiments, as products of the chemical reaction can be detected over a broader-mass range than what is currently possible with FIONA alone. Simulations of the device for this use have been performed. Preliminary results will be presented.

    

Gain Mapping of a Micromegas Detector by Localized Beta Emissions

The Texas Active Target detector is a time projection chamber used for Rare Isotope Beam experiments conducted at the Cyclotron Institute at Texas A&M University [1]. A primary component of the TexAT is a micromegas detector, which amplifies and detects electrons resulting from charged particle interactions in the tracking region. This allows for particle track reconstruction, which requires high precision in both energy measurement and position of impact. The micromegas manufacturing process, primarily sheet stretching and curing [2,3] results in mechanical deformities in amplification gap distance. Variations in the gap length exponentially affect the detector response. Therefore, it is important to characterize variations in the gap uniformity. In this work, this uniformity was studied by measuring detector energy response to a localized Sr-90 beta source. The resulting gain map for each detector can then be used to improve the data quality in future experiments.   

Data Analysis of 34Mg

³⁴Mg is of interest, as it is near the magic number N=20. Looking into ³⁴Mg, it decays into ^34,33,32Al via beta decay, beta-delayed neutron emission, and beta-delayed two-neutron emission. Each of these isotopes decay into ^34,33,32Si, which decay into ^34,33,32P, respectively.  An additional phenomenon that occurs in ³⁴Si is the release of an additional electron due to E0 transition. With these additional electrons, the scintillator detectors collect more data than should be accounted for from the beta-decay electrons. Data is then collected and analyzed from these decays. What is being evaluated is the half-life values of each isotope and the beta-delayed neutron emission branching ratio.

In this study, we specifically watch the decay chain of ³⁴Mg. The ³⁴Mg decay data is fitted with the use of the Bateman Equations. Throughout each of these different iterations, ³⁴Mg and its decay chain are given different values and ranges to see what gives the best fit for the data. This analysis takes many trials to reach proper conclusions. These conclusions are made with the expectations from previous experiments within their respective errors. The goal of the fit is to extract the beam intensity which would then give an absolute decay rate to help determine the decay feeding intensity.    

Low Energy Anomalies Identification in the St. George Detection System

The St. George recoil mass separator at the University of Notre Dame is used to study the process of nucleosynthesis during the stellar helium burning phase by measuring the cross sections of alpha-capture reactions. These reactions are induced by using a beam of heavy nuclides in inverse kinematics to collide with a lighter target, for instance, the reaction 14N(α,γ)18F would have a 14N beam and a target of α particles. The St. George detection system uses a 16-pad silicon strip detector (SSD) to measure the energy of the particles and a pair of transmission detectors utilizing microchannel plates to measure the time-of-flight (TOF). Reaction products are separated from residual unreacted beam particles on a plot of TOF vs. energy. The measured energy is too low for a small number of events, and the identification is unclear. This work investigates the possibility of using hit location on the SSD, in combination with energy and TOF, to aid in identifying these low-energy events.  

    

Thorium Dioxide Nanoscale Materials and Thin Films Prepared by Combustion Synthesis

Thorium dioxide (ThO₂) is a highly considered nuclear fuel for generation IV breeder reactors and  ThO₂ thin film target materials are needed for basic nuclear science measurements. Here, we report on a novel solution combustion synthesis (SCS) method for ThO₂ nanoscale materials and thin films. An exothermic chemical reaction in thorium nitrate-2-methoxyethanol-acetylacetone solutions is investigated to prepare these materials. First, thermodynamic modeling of this system was completed to optimize conditions for SCS. Next, the effects of various process parameters, such as furnace temperatures and holding times, on the structure and morphology of ThO₂ nanopowders were investigated. The nanopowders are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), showing that the crystallinity and morphology of the products can be controlled by tuning processing conditions. Finally, SCS is combined with the spin coating method to create thin films of tunable thicknesses on different backings (e.g. carbon, aluminum). X-ray fluorescence analysis, electron microscopy, and alpha spectroscopy prove that films are highly uniform.

 

This method is a significant advance in targetry for nuclear science studies and has broad applications including stockpile stewardship.   

Production and Characterization of Bismuth Targets

Targets are an important part of nuclear physics. In heavy element research, targets are a source of nucleons and set the location for the reaction to happen. For our reactions of interest, the target provides nucleons that the beam can interact with to produce the desired heavy element. This summer, our group worked to make bismuth targets via physical vapor deposition for use in the cyclotron for heavy element research. In particular, these evaporated targets will be compared to the novel bismuth incorporated graphene targets our group is currently investigating for their possible higher sustainability against beams. After commissioning new components to our thermal evaporator, we evaporated 500 μg/cm² Bi onto a carbon substrate through resistive heating. After finalizing the data and sensor used to measure the thickness of the bismuth, we were able to start the production of carbon backed bismuth targets to be used in the cyclotron. After finalizing our targets, we will take them up to LBNL to test out in their cyclotron. The reaction we are hoping for is ²⁰⁹Bi + ⁴⁸Ca → ²⁵⁴Lr + 3n⁰.   

Calibration of the Berkeley Gas-filled Separator Through Beam Spot Image Analysis

Super heavy elements (SHEs) are the heaviest elements in the periodic table. They do not naturally exist on Earth and must be created in the lab through complete-fusion neutron-evaporation reactions at particle accelerators. Along with the desired isotope, these collisions primarily produce unwanted reaction products, which must be filtered out. To do this filtering, the SHE research program at Lawrence Berkeley National Lab uses a machine called the Berkeley Gas-filled Separator (BGS). The BGS consists of one quadrupole magnet (Q1), two dipole magnets (M1 and M2), and a vacuum chamber filled with a trace amount, ~0.5 torr, of helium gas. This separates the products of interest from the unwanted reaction products based on different magnetic rigidities in He gas. Each reaction product has its own magnetic rigidity, which is determined by its mass, velocity and the number of electrons that it is missing. The BGS is optimized to send ions of a given magnetic rigidity to a detector. Calibrating the BGS magnets to determine the precise magnetic rigidity for each isotope of interest is a necessary step to take before embarking on the search for the next heaviest element.   

McStas simulations of neutron beam transport for the Nab experiment

The Nab experiment aims to accurately measure the little a and little b correlation parameters in free neutron decay. For the ‘a’ parameter, the beam must be completely unpolarized as it passes through the decay volume. Two He3 cells (polarizer and analyzer) in combination with an accompanying collimation scheme will be used to measure the beam’s polarization. It must be verified that the beam polarization with the current collimation scheme can be generalized to the larger beam used in the Nab experiment. This verification was completed with McStas, a monte carlo neutron ray tracing software package. Neutron guide scattering events were simulated for all proposed collimation schemes, comparisons will be presented between the beam phase space for the polarimetry measurement and the full Nab experiment.

    

Studying the response of a novel Hexagonal Boron Nitride Solid State neutron detector with Geant4

Nuclear nonproliferation is one of the pillars of nuclear safety. To prevent the acquisition of unauthorized nuclear material, new technology for its early detection must be created. One way to do so is by measuring the neutrons emitted by some radioactive isotopes. Graphene hexagonal Boron Nitride (GhBN), is being proposed as a novel material in the use of solid state neutron detectors. GhBN comprises layers of hexagonal boron nitride encapsulating a layer of graphene. The boron nitride serves to act as a very effective neutron trap, where the 10B isotope traps slow neutrons, following the nuclear reaction: 10B + n –> 4He + 7Li. Both daughter particles,4He and 7Li, then ionize atoms in the hBN layer creating an electron-hole pair that could be drifted to an electrode under an electric field. Geant4 Monte Carlo simulations of the GhBN detector were performed in this work, which showed a detector efficiency consistent with values reported in the literature for scalable hexagonal boron nitride. Polymethyl methacrylate (PMMA) was layered on top of the GhBN to moderate high energy neutrons; simulations showed that a thickness of 10mm was effective at increasing the efficiency of the detector at higher neutron energies, >1.0 MeV, and resulted in minor increases to efficiency for all neutron energies between 0.0253 eV and 18 MeV. To simulate a possible advanced geometry for the novel neutron detector, GhBN and PMMA were then layered to determine the effective limit of efficiency increase, which showed the most effective geometry being 5 layers each of GhBN and PMMA. In this contribution, we are going to show the results of the simulation work, which will contribute to the determination of the final, optimal design for this novel detector.    

Analysis of Neutron Dark Scattering from Plastic Scintillators

Background:

Plastic scintillators are widely used for detecting energetic particles in nuclear physics applications. The MoNA Collaboration uses these detectors to measure the neutrons emitted from neutron-rich nuclei. Detailed simulations are needed to interpret the data.  Dark scattering - events when the neutron scatters from a plastic scintillator but doesn’t produce enough light to be detected - needs to be studied more as these events make the interpretation of the data more challenging as the neutrons scatter from one site without record to another.

Purpose:

The purpose of the work is to observe neutron dark scattering off of plastic scintillator detectors. The observations are compared to two different simulation packages in Geant4, a simulation toolkit that simulates the interaction of particles through matter.

Methods:

An experiment was performed at the Los Alamos Neutron Science Center with a beam of neutrons ranging from 20 to 400 MeV. The neutrons were scattered off of plastic scintillators. Properties of the incident and scattered neutrons like beam energy, scattering angle, and the kinetic energy of the scattered neutron are calculated from recorded data like x, y, z coordinates, time of flight of the particles, and the light output in the scintillators. A variety of analysis techniques were required to eliminate sources of background such as cosmic muons and neutrons scattered at the collimator.

Results:

The different versions of scaling for background allowed us to analyze dark scattering and compare it to predictions from simulations up to 100 MeV. We observed that scattering angles from dark scatter in lower energies have a very good correlation but the measure angles start to shift higher as the energy gets higher compared to both Geant4 and MenateR simulations.

    

Accuracy Correlation in Neutron Resonance Reclassification

Collecting accurate neutron resonances is essential for application in practical nuclear systems and understanding astrophysical processes. Current methods for finding the resonance quantum numbers associated with angular momenta and spin are subjective and irreproducible, often leading to incorrect spin assignments. To solve this problem, we have employed a machine learning (ML) method to train an algorithm for identifying and reclassifying incorrect neutron spin assignments. Currently, the algorithm operates with varied successes depending on the isotope. For this project, we are examining the properties of the algorithm on polarized In-115. We build synthetic data that mimics the statistical properties of real resonances to train the algorithm. We then validate the trained algorithm with a set of real In-115 data and observe the correlation between the two sets. However, for unpolarized data, we cannot guarantee the given resonances as accurate, so we also test the trained algorithm on an In-115 set with jumbled resonance assignments. We can then improve the validation accuracy by adjusting the ML classifier's parameters. We also explored an iterative method in which successive reclassifications could incrementally improve the quality of any misclassified resonance sequence.   

Nuclear Resonance Spectroscopy of Engineered Ferritin Samples

Ferritin consists of a protein shell encapsulating an iron biomineral core¹. The shell is composed of 24 amino acid chains of two types, H and L². Mӧssbauer spectroscopy³ based on the recoil-free emission and absorption of nuclear γ-rays in solids can uniquely characterize the structure of the core⁴. It uses radioactive ⁵⁷Co that decays into ⁵⁷Fe at an excited energy state with subsequent emission of a 14.4 KeV γ-ray. The lifetime of the 14.4 KeV excited state is 10^-7 s making the γ-ray extremely sharp. Resonant absorption of the γ-ray by the ferritin sample is achieved by using the Döppler Effect. The absorption spectrum reports on the electronic charge density, the iron coordination symmetry and magnetic order in the material. The Mӧssbauer spectra of L-rich and H-rich ferritins reconstituted to 1000⁵⁷Fe/protein in the presence of phosphate were recorded at RT. The spectra were analyzed in terms of the core/shell model of the iron core⁵. The results show the H-rich cores to be more crystalline than the L-rich, while TEM studies indicate that the L-rich proteins form somewhat larger cores than the H-rich under similar iron reconstitution conditions. These observations can be traced to differences in H- and L-chain molecular structures and their influence on core growth ^6,7. 

    

Measurement of Outgassing Properties for Potential nEXO Materials

Neutrinoless double beta decay is a hypothetical rare nuclear decay process that can occur if neutrinos are Majorana particles. nEXO is a worldwide collaboration that aims to detect this decay with 5 tonnes of isotopically enriched Xenon (Xe-136) in a high voltage time projection chamber (TPC). nEXO reconstructs energy deposits through measurement of the ionization electrons and scintillation photons produced by a decay within the xenon. The more efficiently nEXO can detect these electrons, the more accurately the energy can be reconstructed. However, the presence of electronegative impurities in the TPC, which may diffuse out of the detector materials, reduces the number of collected electrons. In order to select ideal detector materials, we investigate potential nEXO samples by studying their diffusion coefficient associated with pertinent gaseous impurities as a function of temperature and time. These data are used to develop a model that compares the diffusion coefficient of various gasses through each nEXO sample. 

    

Simulation of Jet Production at the Future Electron-Ion Collider

The Electron-Ion Collider (EIC) is planned to be built at Brookhaven National Laboratory. The EIC will enable the study of the internal structure of nucleons and nuclei with unprecedented precision. Jets in high energy, high luminosity particle collisions at the EIC will allow for detailed studies of Quantum Chromodynamics (QCD) and the three-dimensional hadron structure in transverse momentum dependent parton distribution functions (TMD PDFs). Jets are useful channels to probe the partons produced in these collisions. Jet charge measurements can be used to differentiate between quark flavors and increase u- and d-quark flavor sensitivity. This flavor sensitivity is essential for understanding the TMD PDFs since there are cancellations between different flavors. Here Pythia 8 and Fastjet are used to simulate electron-proton collisions, and jet properties are used to study the quarks and gluons in the initial and final states.

    

Charm hadron production and hadronization in electron-nucleus collisions at the future Electron Ion Collider

One of the main physics goals of the future Electron-Ion Collider (EIC) is to study the hadronization mechanism in high energy electron-proton and electron-nucleus collisions. In particular, measurement of charm hadron production will allow us to study heavy quark transport and hadronization inside the cold nuclear matter. Here we characterized the statistical significance of charm hadron measurements by reconstructing D⁰ mesons and Λ_c baryons. This was accomplished using interactions simulated with the BeAGLE and PYTHIA event generators factoring in the expected detector effects and luminosity of the EIC. As this measurement is highly sensitive to the efficiency of charm hadron selection cuts and detector characteristics, we carefully studied the optimal analysis selection criteria with the proposed detector designs for the EIC. In this poster we will present the projected precision of D⁰ meson and Λ_c baryon multiplicity measurements in electron-nucleus collisions relative to proton at the EIC, the differentiating power of related charm hadron measurements on existing hadronization models, and the implications on understanding nuclear modification mechanisms.   

COHERENT: Use of Photodetectors for Neutrino detection in Liquid Argon

The COHERENT Collaboration first observed CEvNS (coherent elastic neutron-nucleus scattering) in 2017 with a 15 kg CsI(Na) detector with confirmation in a 24 kg liquid argon detector in 2021.  Since that time, numerous detectors have been developed using a variety of nuclei with the goal of observing more CEvNS events for better sensitivity to beyond-standard-model physics.  COH-Ar-750, a 610 kg (fiducial mass) liquid Argon nuclei detector, is currently under development. Calibrated 3-inch photomultiplier tubes with sufficiently low dark rate will allow for detection of scintillation within the argon chamber. Dark rates, single-photoelectron spectra, and gain values from tested PMTs have been measured and will be presented along with a description of the apparatus.  We will also describe the design and calibration of a liquid cryogen level detector that weas used to monitor the liquid nitrogen levels in the test chamber.

 

    

On the sensitivity of modern neutrino oscillation experiments to flavor-changing matter effects

We investigate the sensitivity of modern neutrino oscillation experiments to novel flavor-changing neutrino-matter interactions. Specifically, we fit non-standard interaction (NSI) parameters in the electron-tau sector to combined appearance data from the NOvA and T2K long-baseline experiments and compare our results to the standard model fit. Finally, we explore the implications of this fit for the solar electron neutrino survival probability by comparing our long-baseline fit to data from the SNO experiment.   

Interpretable Machine Learning Model Development for Background Rejection in LEGEND

Neutrinoless Double Beta Decay (0νββ) is the hypothetical process which, if discovered, would shed light on persistent puzzles in the Standard Model. Detecting 0νββ is a major research interest in nuclear physics and is the primary task of the Large Enriched Germanium Experiment for Neutrinoless ββ Decay (LEGEND). LEGEND aims to utilize an array of High-Purity Germanium (HPGe) detectors with a novel inverted-coaxial point-contact (ICPC) design to detect 0νββ. Due to the requirement for unambiguous discovery of 0νββ, background rejection methods play a critical role in LEGEND. We have developed a Machine Learning algorithm to reject some of the most prominent backgrounds. Using an interpretable Boosted Decision Tree model, multiple pulse shape parameters can be analyzed simultaneously to improve rejection performance. Additionally, the interpretability of the model makes it a useful tool for discovering new correlations between parameters. By learning from the machine, we can gain a better understanding of detector microphysics.   

Updates from NuDot: Double-Beta Decay with Direction Reconstruction in Liquid Scintillator

Future neutrinoless double beta-decay experiments using kiloton-scale liquid scintillator detectors will require new background-reduction techniques. Otherwise irreducible backgrounds such as ⁸B solar neutrino scattering can be identified by their event topology using Cherenkov light signals. NuDot is a half-ton prototype aiming to demonstrate this technique, using precision timing to separate Cherenkov and scintillation signals in 1 to 2 MeV beta particles. In the coming months, NuDot will undergo upgrades and move from its current location, at the MIT Bates Research and Engineering Center, to continue its surface operation phase at Triangle Universities Nuclear Laboratory. The goal of this surface data-taking campaign is to demonstrate Cherenkov light-based directional reconstruction with a collimated beta calibration source. Updates will be presented on NuDot's commissioning and the design and implementation of magnetic shielding for the experiment. Updates will also be presented on a new testing campaign of perovskite-based quantum-dot-loaded liquid scintillators.   

Nitrogen Vacancy Optically-Detected Magnetometry for Characterization of Systematic Effects in Precision Ultracold Neutron Experiments

A magnetometer with large dynamic range is potentially useful in the UCNτ experiment at Los Alamos National Laboratory for magnetic field mapping, needed to constrain experimental systematics. Nitrogen Vacancy (NV) centers in a diamond lattice provide a possibility for one such system. The simplest approach is based on an optically-detected magnetic resonance (ODMR) effect. A green laser is beamed into the diamond, causing NV centers to fluoresce and emit red light. In the presence of ~3 GHz microwaves, the emitted red light intensity will sharply decrease at several frequencies corresponding to a zero field splitting and a Zeeman shift in the NV quantum system, the latter of which is dependent on the magnetic field. By determining the frequency of these resonances, the magnetic field can be determined. An NV center-based magnetometer using ODMR was constructed and tested to characterize its sensitivity over a range of field values from μT to T, which includes the characteristic range of magnetic fields important for UCNτ. Data were taken in a Halbach field identical to the one used in UCNτ. Results will be presented describing the performance of this magnetometer.   

Normalizing Flows for Generative Modeling of the Nucleon-Nucleon Interaction

Over the past decade, chiral effective field theory has been extensively used to derive models of nuclear many-body forces. Choice of resolution scale and the associated high-momentum regulating function in chiral nuclear interactions are in principle arbitrary and represent a source of uncertainty in the calculation of nuclear many-body observables. Systematically accounting for uncertainties due to the regulating function is challenging, so in the present work we explore the use of generative modeling to propose new regulated interactions based on a set of training samples. Using normalizing-flow models (NFs) from machine learning, we seek to create a model that can learn a distribution of matrix elements for any appropriate cutoff value, from which we can sample new potentials at different cutoffs. We attempt two NF architectures, the Glow model [1] and a similar model without multi-scale architecture, which we call cFlow. As a test case, the models are trained on a set of low-momentum and similarity renormalization group evolved potentials. We show the effectiveness of the NF models by reconstructing the initial potentials and generating new matrix elements for validation samples. Future work will involve testing the models on a set of high-precision chiral nuclear forces.   

Investigating jet charge for heavy and light quark jets in LHCb kinematics

In high-energy proton-proton collisions, quarks and gluons can escape the strong force bond and produce conical sprays of new hadrons called jets. Jet charge is an observable which is calculated as a momentum-weighted sum of the electric charges of the hadrons in the jet. It was developed to try to determine the flavor of quark initiating a jet, in particular for light quark jets, based on Monte Carlo simulations of how light quarks hadronize. It is extremely difficult in data to obtain a high-purity sample of light quark jets of a particular flavor, which is why Monte Carlo simulations are relied on. However, if we see in the detector a jet with a hadron containing a heavy quark, we can confirm using actual data that the jet was initiated by that specific heavy quark produced in the proton-proton collision. In this project, we study how well the jet charge observable performs to successfully identify the specific electric charge and flavor of the quark for heavy quark jets in LHCb kinematics, where we have both Monte Carlo and high-purity real data samples available. In this way, we try to verify the accuracy and range of applicability of the jet charge observable.   

Measurement of b quark fragmentation and hadronization properties in jets using the decay B± → (J/ψ) K± → (μ+μ-) K± in proton-proton collisions at √s = 13 TeV with the LHCb detector

The fragmentation and hadronization properties of scattered b-quarks within jets are analyzed using the decay B^± → (J/ψ) K^± → (μ⁺μ⁻) K^± in proton-proton collisions at √s = 13 TeV. The distributions of B mesons are obtained using Pythia 8.2 Monte Carlo simulations in order to make correlations between B mesons and geometrically associated jets. Jets are clustered with the radius parameter, R = 0.5, using the anti-k_T algorithm. The goal of this analysis is to study the longitudinal momentum fraction, the transverse momentum profile, and the radial profile of the B hadrons with respect to the jet axis. Another goal of this project is to replicate this study implementing various event generators with different parton shower and hadronization models. Ultimately, the Monte Carlo predictions will be compared to data from Run 2 at the LHCb experiment for this particular process.  The results from this study will be compared to a similar analysis done using the ATLAS detector; however, some complementary information, such as the radial profile of B mesons within jets, will be included.  The study will complement a list of hadronization and fragmentation properties of heavy and light quarks measured by the University of Michigan-Ann Arbor group at the LHCb experiment.   

Study of Momentum Tensor Observables in Heavy-Ion Collisions

Event shape variables in heavy-ion collisions have been an important tool for QCD studies. They provide a measure of the hadronic energy-momentum flow in the final state and play an important role in determining the strong coupling constant and hadronic effects. In this study, we explore the properties associated with the momentum tensor, which does not require the determination of the event plane, to characterize geometrical features of participants from colliding nuclei. The eigenvalues of the tensor yield two observables, known as Sphericity (S) and Coplanarity (C), which can be used to quantify the event shape. Historically these observables have been used in e⁺e^- annihilation studies, and now we apply them to 200 GeV Au+Au events simulated by a multi-phase transport model (AMPT), and present the S and C values for various centrality intervals.   

Simulating Antihydrogen Annihilation Distributions in ASACUSA's Cusp Trap

The hyperfine structure of hydrogen is known very precisely, and if charge, parity and time reversal (CPT) symmetry holds, antihydrogen will have the exact same spectrum. CPT violation may help explain the baryon asymmetry, the mysterious and presently unexplained fact that the universe contains much more matter than antimatter. The Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) Collaboration aims to measure the ground state hyperfine structure of antihydrogen in a magnetic field-free region with a precision of 1 ppm. Antiproton and positron plasmas, which are produced further upstream, are combined in the Cusp trap. We use SIMION to simulate antihydrogen trajectories in the spatially varying magnetic field of ASACUSA's Cusp trap. We use the resulting annihilation distributions as a look-up table in a Python routine which accounts for plasma rotation, thermal velocity distribution, magnetic moment probability, and our panel detectors. This work provides a guide for the interpretation of future experimentally detected antihydrogen annihilation data. This will help us to optimize plasma properties for producing more antihydrogen.

    

Resonance systematics for capture reactions using Machine Learning

Nuclear data is used for a variety of purposes in our daily life, from basic science to advanced usages like nuclear power. Nuclear reaction data must be evaluated for all these purposes that require a detailed knowledge of the neutron-nucleus cross section. Below 1MeV incident energy, such cross sections show fluctuations, or resonances, that are not predictable and are characterized by several parameters like the resonance spacing, the distance in energy between two resonance peaks, and the resonance width, the width of the resonance peaks. These parameters can be measured experimentally, but for specific energies of the incident neutron this is not possible, because they cannot be resolved experimentally. Thus, all we can do is to calculate the average values of such parameters. The goal of my project is to study the average resonance widths, and I have developed a code to extract the average widths from the Atlas of Neutron Resonances, for all elements given their atomic species and mass number. Using machine learning, I have developed code that learns the average capture width and the capture degrees of freedom from the capture width survival function and the results show survival functions for each combination of allowed quantum numbers of orbital (L) and total (J) angular momentum. Problems related to small widths and deficient data in the Atlas have been also corrected using machine learning techniques to compare the resonance systematics for capture reactions and help to fill in the information to correct the misassignment. We identified and corrected several errors in the Atlas. The current goal is to use the extracted resonance widths and tabulated L and J assignments from the Atlas and so that we can produce average resonance widths for specific materials.

    

Investigating a multiparticle cumulant method for measuring fluctuations in energy loss at high transverse momentum in heavy-ion collisions

Jets are often used to probe the QGP produced in heavy-ion collisions, due to their interactions with the medium at various length scales resulting in energy loss. The Fourier harmonics for anisotropies in the high p_T particle yield v_n(p_T)  are useful for measuring energy loss, because they are sensitive to the path length for jets traveling through the QGP, and are thus sensitive to the angular dependence of energy loss. These quantities and their fluctuations can be measured experimentally by differential multiparticle cumulant estimates v_n{2k}(p_T), that correlate the angular yield of high p_T particles with the net angular yield of particles. The average value for energy loss can be measured accurately, but those measurements are not sensitive to event by event fluctuations in energy loss, which could be caused by the QGP’s changing geometry, parton shower, or other variables. To measure fluctuations in v_n(p_T), we present a set of experimental observables to estimate the difference between central moments of cumulant estimates for reference and differential flow. We show these quantities are sensitive to differences in the central moments for various distributions of v_n(p_T) with a Monte Carlo simulation.

    

Development of the photon readout electronics for nEXO

Neutrinos have continually surprised physicists, and the recent discoveries that they have mass and oscillate between different states definitively points towards physics beyond the Standard Model. One of the best ways to test whether neutrinos are Majorana particles is to search for neutrinoless double beta decay. Double beta decay is a special decay mode where two beta-decays occur simultaneously in a nucleus, and if the neutrino is Majorana they can annihilate each other, leaving zero neutrinos to escape. nEXO is a 5 ton liquid Xenon time projection chamber operating at cryogenic temperatures that is being proposed to search for such a decay. Brookhaven National Laboratory is developing readout electronics for the photon detectors in nEXO. I will contribute to developing the nEXO photon readout by evaluating the performance of prototypes of the readout. In order to achieve this I have used Python code to create a Monte Carlo to simulate the maximum bit error rate and not lose any good events. Along with simulating the max bit error rate, I have analyzed data gathered from a prototype of the readout electronics to determine how to test the Silicon PhotoMultipliers at room temperature, where the noise reaches very high levels.   

Feasibility Studies for Ultraperipheral Collision Physics in sPHENIX

Ultraperipheral Collisions (UPC's) are collisions where two ions in a collider are separated by more than the ion radius. Instead of a direct collision between the two ions, the particles interact via electromagnetic and photonuclear exchanges. The sPHENIX experiment is an upgrade of the PHENIX experiment which will increase the data acquisition (DAQ) rate capability. sPHENIX will collect significantly more data about the Quark Gluon Plasma, which is created in RHIC's particle smashups. To best exploit this capability, triggers need to be devised so that we can accurately identify special events such as the creation of UPC J/Psi particles and record those events. I analyzed simulations of UPC events in the sPHENIX detector to devise triggers that have good efficiency and low noise. Additionally, I have studied the feasibility of sPHENIX to measure various UPC physics channels. I have determined the acceptance for the UPC J/Psi events in the sPHENIX detector, establishing that sPHENIX will have substantial statistics for a UPC J/Psi analysis. These feasibility studies will promote research towards the understanding of photoproduction in heavy ion collisions.   

Cosmic Ray Testing of the New sPHENIX Event Plane Detector

sPHENIX is a state-of-the-art detector currently under construction at Brookhaven National Laboratory. It will study strongly interacting quark gluon plasma using jet and heavy-flavor observables. A crucial part of the sPHENIX design is the Event Plane Detector (sEPD), which measures the orientation of charged particles emitted at small angles with respect to the particle beam line. It consists of two wheels of scintillator made of 12 sectors, with each sector divided into 31 tiles. Each of these tiles requires extensive testing to look at qualities such as tile isolation, uniformity, and efficiency. To test for tile efficiency, I set up a cosmic ray test stand using a leading edge discriminator and pairs of paddle scintillators connected to photomultiplier tubes as the trigger. This test requires a muon coincidence, which indicates a muon passed through both paddles, and therefore the sEPD tile placed in between them. The light output of each sEPD tile is read via a silicon photomultiplier and optical fibers connected to an oscilloscope. The distribution of this voltage is then analyzed.   

Evaluation of Jet Substructure Observables for sPHENIX

The sPHENIX collaboration at RHIC aims to understand the quark-gluon plasma (QGP) that emerges during heavy ion collisions. Jets, cones of final state particles produced by parton hadronization, are effective probes of the QGP. Jet quenching refers to the observed energy differences between jets resulting from proton-proton (pp) collisions and those resulting from heavy ion collisions. Embedding simulated pp collisions in a heavy ion background suggests that quenching is likely due to the traversal of jets through the QGP, rather than multiplicity effects.

This analysis focuses on jet substructure by analyzing subjets,  jets of smaller cone size contained within jets of larger cone size. Specifically, we examine the momentum fraction and opening angle of each event’s leading larger jet. Using simulated collision data from the sPHENIX Mock Data Challenge 2 along with background subtraction methods, these observables are calculated for truth pp collision data and reconstructed sPHENIX calorimeter data. The calculated observables are compared across data sets to assess whether those for the sPHENIX data set accurately reflect the true structure of the jets and can thus be analyzed by sPHENIX.    

Constraining Quark and Gluon Momentum Fractions Accessed by Observables in Polarized pp Collisions at PHENIX and sPHENIX

Observations of transverse single-spin asymmetries (TSSAs) in polarized proton-proton collisions at the Relativistic Heavy Ion Collider (RHIC) have proven useful for probing quark and gluon dynamics inside the proton. Such observations are made in proton collisions in the Pioneering High Energy Nuclear Interaction Experiment (PHENIX) and the upcoming sPHENIX experiment at RHIC. Individual quarks and gluons, collectively known as partons, carry some fraction of the proton momentum, denoted x. Parton distribution functions (PDFs), at leading order, describe the probability of finding a given quark or gluon at a given x. Analyses of TSSAs for direct photon, eta meson, and open heavy-flavor hadron production, as well as open heavy-flavor decays, provide access to spin-dependent quark and gluon PDFs. A Monte Carlo study of these events is done using the PYTHIA event generator. After the appropriate kinematic cuts are applied, final state particles are traced back to their quark or gluon ancestors, and their respective momentum fractions are plotted. This procedure therefore tells us what range of momentum fractions and mix of partonic flavors can be accessed by each existing or planned measurement.   

The Effect of Neutrino Flavor Oscillations on The Supernova Early Warning Pypeline (SNEWPY)

The observation of the next supernova in our Galaxy will greatly advance our understanding of how massive stars die. The value of an early supernova alert cannot be overstated because it is a once-in-a-generation event. The earliest indication of the explosion is the arrival of the neutrino burst which will lead to a simultaneous increase of the number of neutrino events in all the neutrino detectors around the globe. In order to prepare for such a burst, detectors first have to know what that looks like. Enter SNEWPY. The SNEWPY code is a data pipeline that connects supernova simulation data with the SNOwGLoBES code, which computes event rates for different interaction types in neutrino detectors, then collates the data into observable channels. Using this pipeline, we can explore the landscape of different types of supernovae, thus enhancing the supernova early warning system. As neutrinos travel to Earth, they undergo flavor oscillations modulated by their environment. I will explain how SNEWPY enhances the use of SNOwGLoBES, and discuss the upgrade to SNEWPY that will involve new time and energy dependent flavor transformations.   

On the possibility of darkening epoxy due to radiation damage in the STAR EPD

The STAR EPD (event plane detector) is a subsystem of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) whose purpose is to probe the geometry of a heavy ion collision by examining the distribution of forward-going charged particles exiting the collision. The EPD consists of two wheels of scintillators wound with wavelength shifting fibers, each composed of 12 "supersectors," which are themselves connected to a Silicon photomultiplier (SiPM) via an optical fiber connection. To hold the wavelength shifting fibers in their place within each supersector, Eljen EJ-500 optical epoxy was used. The goal of this study was to determine if this epoxy darkened appreciably throughout RHIC's operation from 2018 - 2021 due to radiation damage. Analysis was performed on measurements of output (ADC) vs. bias voltage to investigate this phenomenon. The epoxy was demonstrated not to darken appreciably on this time scale due to radiation damage.   

Infinite volume radius extrapolation for two body bound states in finite volume

Simulations of quantum systems in finite volume have proven to be a useful aid in calculating physical observables. Most notably finite volume effects on the energy of a variety of systems have already been investigated in great depth. The aim of this project is to derive finite volume relations for the radius of a system analogous to those that exist for the energy. We report the volume dependence of the mean square radius for two body bound states. We verify this result by demonstrating a robust method for extracting the infinite volume radius from finite volume simulation data in a cubic box with periodic boundary conditions.   

Numerical Study of Single-Inclusive Longitudinal-Transverse Double-Spin Asymmetries in Electron-Proton and Proton-Proton Collisions

High-energy collisions allow us to probe the interaction of quarks and gluons, which make up the internal structure of hadrons.  In the aftermath of these collisions, other particles are formed, such as pions. These pions are produced in different quantities and directions depending on the type of collision and the orientation of the spins of the initial-state particles involved.  These asymmetries can be measured in experiments. Our research focuses on the asymmetry A_LT involving a longitudinally polarized electron or proton colliding with a transversely polarized proton, with a single pion detected in the final state. We have provided updated, more rigorous numerical predictions using new information on the functional form of parton distribution functions (PDFs) and fragmentation functions (FFs) involved in calculating A_LT. Predictions have been made for Jefferson Lab, COMPASS, RHIC, and the future Electron-Ion Collider. By generating these predictions, we hope to gain more insight into the quark-gluon-quark interactions that occur inside of hadrons.

This work is supported by the National Science Foundation under Grant No. PHY-2011763.   

Smart Experiment Control at FAIR Phase 0

As a part of the international accelerator facility FAIR project in Germany, a study was conducted into the viability of implementing machine learning (ML) based algorithms for realignment of the HADES' forward Straw Tracking System (STS). All models tested were forward feeding regression models, utilizing a custom loss function which calculated the minimum residual distance between the model's adjusted hit location and the provided track. Output layers and loss functions were modified depending on if the model's purpose was to test translational realignment, track parameter correction or both simultaneously. The models were trained and tested on Monte Carlo simulated data where translational misalignments were introduced into the two modules of the STS and aligned, misaligned and generated tracks were used. It was found that the models designed for translational realignment could learn and correct for numerous simultaneous shifts in both modules of the STS, but could not correct for misalignments not present in their training datasets. The models could learn how to adjust the location to better fit hits to misaligned tracks, but were unable to correct simultaneously for both misaligned track and detector parameters. In this poster presentation, I will present the status of the current work and discuss the plan for future work.   

6He-CRES: The mapping and error analysis of the superconducting magnet field

The ⁶He-CRES collaboration at the University of Washington CENPA aims to measure the Fierz-interference coefficient from the beta decay of ⁶He with high precision in the pursuit of finding signatures of new physics. The experiment uses cyclotron radiation emission spectroscopy (CRES) of the beta particles trapped inside a waveguide by a magnetic field. A superconducting solenoid surrounding the waveguide generates a magnetic field that can be shimmed to improve uniformity. An NMR probe with a rotatory mount is deployed to measure the magnetic field non-uniformity around the inner bore. From the measurements of the unshimmed field, the magnet can be adjusted to have better uniformity. The probe mount is improved with a spring locking system and vernier scale to decrease the propagated error. The final error analysis shows an error of approximately 1 ppm from the probe measurement. This result lowers the possible systematic errors for further measurements.   

Calculating the reaction rate 37Cl(a,n)40K to constrain the destruction rate of 40K in stars

⁴⁰K is one of the key isotopes that manipulate the radiogenic heating of a planet’s mantle due to the isotope’s radioactive decay. The heating in turn may facilitate the formation of continents and tectonic plate activity, the latter of which is associated with a habitable environment on a planet. Our group recently constrained the reaction rate of ⁴⁰K(n,p)⁴⁰Ar experimentally for the first time. A preliminary measurement of the ³⁷Cl(a,n)⁴⁰K reaction cross section was also completed in March of 2021. A final measurement of the same reaction is planned for later this year. With these measurements and by studying the reaction ³⁷Cl(a,n)⁴⁰K using the statistical model we can constrain the reaction rate and further reduce the uncertainty in the production of ⁴⁰K. Constraining the destruction rate of ⁴⁰K in stars may further our understanding of its effect on a planet's mantle and its association with the habitability of a planet.   

Unsupervised Learning to Build Pretrained Models for the AT-TPC

Using PointNet, a trained unsupervised model whose latent space can be used for tasks such as event selection and track selection in the Active Target Time Projection Chamber (AT-TPC) was developed. The AT-TPC is a charged particle tracking detector that is used to study rare isotopes and is located at the Facility for Rare Isotope Beams at Michigan State University.

PointNet is a machine learning architecture that is specially developed for point clouds. The model was made by first voxelating each event, translating each voxel to a different location on the grid, then constructing the model by training to unscramble the events. It will be used to investigate the latent representations for event and track identification using the point and global feature layer. Preliminary results will be presented and discussed.   

Identifying Radioisotopes in Soil Samples of Lake Norman

We are constantly exposed to radiation from naturally existing radioisotopes, but human activity can artificially introduce radioisotopes too. Lake Norman, located near Davidson College, has both coal and nuclear power plants. Improper management of waste products from these plants can deposit potentially harmful isotopes into the environment. Thus, the radioisotopes present and their activity were analyzed to evaluate the lake’s radioactivity. To identify and calculate the activity of radioisotopes present, soil samples were collected across the lake. The radioactive content in the samples were analyzed using gamma ray spectroscopy, specifically using two NaI detectors to conduct coincidence gamma ray spectroscopy. Coincidence spectroscopy only classifies events where two or more gamma rays emitted within a short time frame. This procedure reduces background radiation, and allows for clearer identification of emitted gamma rays. Single emissions were also recorded to calculate the activity of identified radioisotopes. From the analysis of 9 soil samples, it was observed that all samples emitted gamma rays of specific energies from isotopes of the decay chains of Th-232 and U-238, but alpha spectroscopy would be needed to confirm the presence of the two isotopes.   

Point Cloud CycleGAN

We develop a graph convolutional CycleGAN model that translates between simulated and experimental event representations in the Active-Target Time Projection Chamber. The model simultaneously learns two taks: 1) modeling detector response and noise behavior and 2) removing noise and completing tracks for data cleaning. We modified an existing TreeGAN architecture to create a CycleGAN which can be used for point clouds. The point cloud CycleGAN can be used to convert simulated data to experimental data and vice versa. Through this transformation noise can easily be removed from experimental data, and simulations can be made more realistic.   

Testing neutron scattering on plastic scintillator observables to simulation

Plastic scintillators are widely used in nuclear physics experiments to detect neutrons. The MoNA collaboration uses them to measure neutrons from the decay of neutron-rich nuclei. These studies rely on simulations to interpret results; thus, it is essential to test the accuracy of simulating neutron scattering in plastic scintillators. Two Monte Carlo based simulation models were tested. The default package in GEANT-4 uses a cascade-based approach to simulate neutron scattering. Alternatively, a separate package called MENATE_R uses a cross section-based approach to simulate the neutron interaction based on measured inelastic reactions. An experiment was conducted at the Los Alamos Neutron Science Center with an array of plastic scintillators optimized to measure neutron scattering angles and energies. Neutrons were delivered with energies ranging from 20-400 MeV. At low energies, simulation agrees with data fairly well. At higher energies, agreement becomes worse. The shape of the kinetic energy distributions relies heavily on the energies of scattered protons from the scintillators. Discrepancies between the experimental and simulated data points to improvements needed in GEANT-4 and MENATE_R simulation packages in simulating neutron scattering from plastic scintillators.   

Cross Section Measurements of Natural Molybdenum and Iridium

Cross-section measurements are an important tool in nuclear physics in predicting reaction probabilities in applications such as energy production, weapons yield, and radioactive medical isotope production.  This project focused on measurements of reactions with both natural molybdenum and iridium.  In the case of molybdenum, we focused on determining the cross sections for deuteron-induced reactions.  This was accomplished using the stacked foil method at incident deuteron beam energies of 7 MeV and 10 MeV.  Due to energy losses in the foils, we were able to determine the cross sections for a range of energies between 1 and 10 MeV.  Nickel monitor foils were used to measure the deuteron beam flux.  For the iridium, we focused on neutron-induced cross sections at incident neutron energies of 12.5 and 13.5 MeV.  In these measurements, we used a single iridium foil sandwiched between two gold monitor foils, which provides a mechanism for normalizing to the incident neutron flux.

    

Study of Asymptotic Normalization Coefficients for alpha clusters

The asymptotic normalization coefficient (ANC) is an important characteristic of the asymptotic form of the wave function describing the relative motion of the nuclear core and a fragment, in a particular channel. Evaluation of ANCs is central for many useful methods in reaction physics and astrophysics. Unlike some alternatives, ANCs are well defined theoretically and are invariant under finite-range unitary transformations. Single-particle ANCs are well studied and somewhat well understood since they can be easily explored in particle plus potential models. However, ANCs related to clusters are less well understood. In this work we study how to determine ANCs for alpha clusters, we explore the role of Pauli blocking, and we discuss methods of evaluation of ANC's using Harmonic oscillator basis and configuration interaction techniques. 

This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under Awards No. DE-SC0009883.   

Fusion Reaction Measurements with the "Encore" Active Target Detector

"Encore" is an active target Multi-Sampling Ionization Chamber (MUSIC) detector developed at Florida State University. "Encore" consists of a segmented anode within a gas filled ionization chamber. The gas acts as the counting medium as well as provides the target material. This allows "Encore" to measure the loss of energy of a beam of particles as it passes through the detector and interacts with the gas in the chamber in an event-by-event basis and thus it is able to extract a large portion of a reaction excitation function with a single beam energy. "Encore" is a flexible, portable, efficient detector which has been used to measure several nuclear reactions. In particular, fusion reactions important for stellar processes and nuclear structure information have been measured using CH2 as counting gas.In this work, the nuclear fusion interaction between 15N beam and 12C in the CH2 gas target is studied. The data gathered by the experiment is further analyzed and the cross-sections pertaining to these fusion interactions along the detector are measured and compared to known experimental outcomes.   

Imaging Optics for the Single Atom Microscope (SAM) for Nuclear Astrophysics

We are developing the technique of optically detecting individual atoms embedded in thin films of cryogenically frozen solids in order to measure low yield nuclear reactions relevant to nuclear astrophysics. Noble gas solids such as frozen neon are an attractive medium because they are optically transparent and provide efficient, pure, stable, & chemically inert confinement for a wide variety of atomic and molecular species. The excitation and emission spectra of atoms embedded in solids can be separated by up to hundreds of nanometers making optical single atom detection feasible. We propose to couple a single atom microscope (SAM) detector to a recoil separator which would minimize the heat load on SAM while allowing for isotope discrimination. This technique has the potential to capture and detect every product atom with near unity efficiency. Because of the additional selectivity provided by resonantly exciting the atomic transitions of the captured product atom, SAM would have a negligible false positive rate which would help loosen the often demanding beam rejection requirements imposed on recoil separators. We will present our study of the dependence of the light collection efficiency of the optical imaging system on a variety of parameters including magnification.  

    

Measuring Drift Velocity in the Active Target Time Projection Chamber

The Active Target Time Projection Chamber (AT-TPC), constructed at the National Superconducting Cyclotron Laboratory (NSCL), serves as both a gas target and charged particle detector for nuclear reactions. As a charged particle traverses the detector, it ionizes the gas producing electron-ion pairs. The charged particle tracks are reconstructed from the collection of the electrons on the pad plane. An important factor in analyzing experiments is the drift velocity of electrons in the detector. It is required for accurate track reconstruction and also serves as an indicator of unwanted gas contaminants leaking into the detector. During a 2020 experiment at the NSCL, the detector was filled with helium gas. To determine the drift velocity, digitized signal of particles near the window and near the pad plane were isolated and fit. From this, the drift velocity throughout the week-long experiment was extracted. By doing this, we were able to assess the impact of changing environmental conditions (temperature, pressure, etc.) as well as the possibility of contaminants leaking into the detector.   

Study of Radon-induced Background Mitigation in an HPGe Counting System

The spectrum of gamma-rays emitted from a material can be used to measure or place limits on the presence of contamination with radioisotopes. High purity germanium detectors are a powerful tool for such spectroscopy due to their relatively high probability to absorb gamma rays and typically excellent energy resolution which aids separation and identification of gamma rays characteristic of the contamination. In the case of 238U, a long-lived radioisotope of importance in low-background rare event searches, sensitivity to the contamination is often impeded by the presence of 222Rn, a relatively long-lived noble gas daughter of 238U, emanating from materials in the counting lab and diffusing into the sample volume. In this poster, we report on the 222Rn background in a HPGe counting setup and efficacy of techniques such as nitrogen gas purging to mitigate this background.   

Simulating the Germanium Crystal Segments of the GRETINA Detector Array

The Gamma-Ray Energy Tracking In-beam Nuclear Array, GRETINA, is a γ-ray spectrometer used to study the structure of atomic nuclei. GRETINA reconstructs the energy and location of each γ-ray interaction point from the nucleus as it de-excites using thirty-six high-purity electrically segmented germanium crystals. The research is centered around improving the accuracy and realism of the simulation that mimics the germanium semiconductor detectors in the gamma-ray spectrometer GRETINA. The objective is to implement a realistic segment shape in simulation and compare it with data for one detector by studying the efficiency of the segments. Python programming was used to create a function that yields segment number values from the crystal (x,y,z) coordinates, which allows us to remap the segment numbers in simulation. This allows us to look at the germanium crystal segments with more accuracy and better reproduce their efficiency for measuring γ-rays. Under those circumstances, we are able to gather data at a greater level of precision, which increases our level of confidence when using simulation to understand and interpret experimental data.   

Search for states in 23Na above the proton threshold

Globular clusters are dense groups of stars that exist near the galactic plane. Understanding their history and evolution sheds light on the history and evolution of galaxies. The presently observed stars contain elements resulting from previously unknown polluting sites. Identifying those polluting sites requires improved knowledge of nuclear reaction rates. One important rate is the ²²Ne(p, ɣ) reaction.

There are several unmeasured resonances lying just above the proton threshold for this reaction, and although many studies have been already conducted, resonances at E_cm = 68 and 100 keV (8894 and 8862 keV excited states) have not yet been confirmed. These potential resonances, which are based on two tentatively observed states in the compound nucleus ²³Na, have never been observed. In fact, it is unclear if the underlying states giving rise to these resonances even exist. These resonances have a large influence on the reaction-rate uncertainty and predicted final abundances, depending on whether they are included in the final rate.

For this experiment, we performed a new high-resolution study where a magnetic spectrograph was used to search for states above the proton threshold in ²³Na via the ²³Na(p,p’)²³Na reaction, using this reaction due to its low selectivity to the structure of the excited states.

Investigation into the existence of these states in the existing data is being performed. Preliminary results will be shown that suggest the inexistence of the Ex = 8894 and 8862 keV states.   

Non Destructive Beam Monitor Prototype

In order to produce astatine-211, a promising new therapeutic for cancer, a large amount of accelerated helium ions are impinged on a bismuth target. Measuring relatively low-intensity particle beam current without interfering or modifying the beam is difficult. Development of such a device has been enabled by construction of a desktop prototype. The nondestructive prototype beam monitor simulates a method by which the current of a beam can be measured without destroying or obstructing the current. For offline development, a copper rod is centered in a desktop prototype of a beam pipe a section of the beam pipe contains the copper coil, in which an induced current is formed. This induced current, which is initially alternating is rectified and amplified using a circuit designed for this purpose. The current is then read using a picoammeter and compared to the current passed through the central copper rod. The output reading for the user is adjusted to match the current in the copper rod and displayed on a graphical user interface. Using this method, the current in the copper coil can be determined without directly measuring the current. This prototype can then be expanded to a beam pipe where the current of a beam can be measured using the induced current around it. This is especially useful when trying to monitor the beam's current without interfering with or modifying it in facilities that irradiate targets to produce medically relevant radioisotopes. Prototype improvements and performance will be shown.   

99Mo Radioisotope Production

The goal of the present work is to obtain the cross-section for the ⁹⁹Mo radioisotope production. The ⁹⁹Mo is used as a medical radioisotope very important in nuclear medicine for diagnostic imaging procedures. The production was performed by using inverse kinematics with a ¹⁰⁰Mo ion beam impinging on a ⁴He gas cell target. The experiment took place in the K500 Superconducting cyclotron facility at the Texas A&M University. The 12 MeV/u ¹⁰⁰Mo beam enters the gas cell target filled with ⁴He gas cooled to 77 K with three different pressures at 102 Torr, 213 Torr, and 1009 Torr. After passing the gas cell the beam stops at a thick Al foil. All the radioisotopes produced during the irradiation are also collected at the Al foil. An offline gamma analysis of the irradiated Al foils was performed and the respective activities at End of Bombardment were obtained. The beam energy loss for the two lower pressures irradiation is small enough in respect to the incident beam energy, DE/E = 0.03 and 0.07 respectively, to be treated as thin targets. On the other hand, the high pressure gas irradiation is considered to be a thick target. The cross section for the ⁹⁹Mo production was determined considering the contribution from the beam interaction with the gas, α(¹⁰⁰Mo, ⁹⁹Mo) ⁵He, and with the Al foil , ²⁷Al(¹⁰⁰Mo, ⁹⁹Mo) ²⁸Al.

 

    

Oxygen-14 Beam Production at 5 and 15 MeV/u with MARS Spectrometer

Oxygen-14 (¹⁴O) is a rare isotope beam of interest for many groups studying the structure of proton-rich nuclei. At the Cyclotron Institute of Texas A&M University, there were two groups interested in studies with ¹⁴O. The Center for Exotic Nuclear Studies at the Institute of Basic Science in South Korea requested an ¹⁴O beam at 5 MeV/u and a group from Washington University in St. Louis has requested an ¹⁴O beam at 15 MeV/u. The ¹⁴O beams were produced and separated with the Momentum Achromat Recoil Separator (MARS). The LISE++ spectrometer simulator, designed to predict the intensity and purity of rare isotope beams, provided useful projections of particle production through the MARS beam line with nitrogen-14 as the accelerated projectile and hydrogen-1 gas as the target (to cause ¹⁴O production). Using these predictions, production tests for ¹⁴O beams at the two energies requested have been conducted. In this presentation, the experimental results of these production tests will be compared with the predictions of the LISE++ simulations of the MARS beam line.    

Mapping a Dual-Axis Duo-Lateral Position Sensitive Silicon Detector

A Dual Axis Duo Lateral (DADL) position sensitive silicon detector, used in the Forward Array Using Silicon Technology (FAUST), was developed to record data on position and energy as high energy charged particles pass through. In the process, the particle encounters multiple materials that contribute to energy loss, including the varying thickness of the silicon and aluminum dead layers within the DADL. Mapping these two materials across the face of the DADL results in improved energy and position resolution. This process involved comparing energy loss data at different dead layer thicknesses and resultant particle energy throughout the face of the detector. Identifying these variables required us to be able to maximize our resolution to the manufacturer’s specification for the silicon detector. Furthermore, we have constructed, tested, and analyzed different biasing configurations for the DADL to see if an improvement to energy and position resolution could be made to the current configuration used in the FAUST array. The primary motivation for the improved resolution in this work is to enhance the mapping of the dead layer thicknesses. Current findings demonstrate a requirement for a 1.5 keV or less energy resolution to map these materials to a dead layer thickness variation of 100 Angstrom across the face of the silicon.

    

Constructing a Microwave Camera to Explore the Behavior of ECR Ion Sources

Electron Cyclotron Resonance (ECR) Ion Sources have many useful applications including advancing cancer treatment. Observations of the governing processes in the electron population from electron cyclotron emission will inform models for simulating new beams. This research focuses on developing computer control and data acquisition for a microwave camera to image the ECR plasma. Developing a user-controlled system, interfacing with devices, and manufacturing a Digital Delay Generator (DDG) were necessary steps taken to become able to observe dominant processes in the plasma. The user-controlled system allows one to access and update configuration files of devices used for the camera. The system also interfaces with a receiver and the DDG to sweep through spans of frequencies, then plotting the data and writing it to separate files. The information from the sweeps will be used to determine achievable frame rates to inform which dynamic processes can be observed through the camera.

    

Coalescence probabilities of polarized and unpolarized mesons

The recombination of two particles into angular momentum eigenstates in a 3D isotropic harmonic oscillator potential was explored. Recently, the probabilities for coalescence of two particles into a bound state with well-defined angular momentum quantum number l, and summed over the magnetic quantum number m, where the particles are represented by generic wave packets, was computed in “Angular momentum of the isotropic 3-D harmonic oscillator: Phase-Space-Distributions and coalescence probabilities” [Kordell II, Fries, and Ko, Ann. Phys. 443, 168960 (2022)]. We have added to this work by computing probabilities dependent on m, which allows us to consider the polarization of mesons coalescing from quarks. We have utilized Monte Carlo integration to compute the spectrum of mesons if the initial quarks are given by thermal distributions with various temperatures and collective motion. We have tested our Monte Carlo integration in limiting cases where analytic results are known. We have demonstrated that polarization of mesons can be produced directly from the orbital angular momentum of quarks.

    

Organic and Inorganic Scintillation Detector Calibration and Optimization for Neutral Atom Trap

At TRIUMF's Neutral Atom Trap, we investigate the time-reversal symmetry in beta decays of trapped atoms. We look for the correlation of three momenta from beta-neutrino-gamma coincidences when a gamma is emitted from the radioactive nuclei that could indicate a violation of time-reversal symmetry. The decay products are detected with organic and inorganic scintillators with Si photomultiplier (SiPM) readouts. We report the calibration and optimization studies for a 35 mm-thick plastic and two GAGG (Gadolinium Aluminium Gallium Garnet) scintillators. We studied the effect of the increasing overvoltage bias on the gain, the photon detection efficiency, and the dark current. Several reflectors used for wrapping the detectors were compared in terms of the change in the energy resolution. Overall, an overbias voltage of 5.5 V with PTFE and ESR wrappings was found to improve the energy resolution. The average resolutions for the GAGG detectors were determined as 8.9% and 6.9% at 662 and 1333 keV gamma-ray photopeaks, while the resolution for the plastic scintillator was measured as 10-11% for IC electrons around 1 MeV. The coincidence timing resolution for the gamma-ray coincidences between the GAGG detectors was also determined as 6.1 ± 0.5 ns.   

Utilization of UCGretina Simulations for analyzing the 30P(d,pγ)31P Reaction with GODDESS

The production of ³¹S by the ³⁰P(p,γ)³¹S reaction is a bottleneck reaction that determines the abundances of silicon, phosphorous, and sulfur in novae. The ³⁰P beam intensities available do not allow for the direct measurement of this (p,γ) reaction, so a neutron transfer reaction was used to determine resonance strengths indirectly. The GODDESS (GRETINA-ORRUBA: Dual Detectors for Experimental Structure Studies) detection system and a ³⁰P beam from RAISOR at 8 Mev/A at ATLAS were utilized to measure states populated via the ³⁰P(d,pγ)³¹P reaction. The results will be used to inform reaction rates of the ³⁰P(p,γ)³¹S reaction through the properties of mirror symmetry. An ionization chamber was used to cleanly select ³⁰P(d,pγ)³¹P reaction events and remove beam contaminants. The UCGretina package for Geant4 simulations was employed to determine the efficiency of Gretina under the specific triggering scheme and conditions of the experiment up to ~7 MeV. This will be compared to the measured efficiency at lower energies. A comparison between the experimental efficiency curve and the simulated efficiency curve, results from the ionization chamber, and reaction rate calculations will be shown.   

Simulations of the NEXT Detector for Reactions

    The University of Tennessee (UTK) high resolution Neutron dEtector with Xn Tracking (NEXT) [1] is used to measure the energies of neutrons coming from reactions and following beta decays, using the time of flight method. The ²⁰Ne(d,n)²¹Na reaction was performed at ReA6, at the NSCL, Michigan State University using a 10 MeV/A ²⁰Ne beam on a C₂D₄ target. This was an effort to measure the energies of neutrons emitted from the (d,n) proton-transfer reaction that is useful in nuclear structure and astrophysics research.  While NEXT has been used to measure beta decay previously, this was the first inverse-kinematics reaction measured by NEXT and more analysis is needed to find the best geometrical setup to achieve the best balance between efficiency and resolution for future experiments.

    Using Geant4, a  simulation has been developed for the (d,n) reaction to better understand the efficiency of NEXT with different geometrical setups.  The information gained from these simulations will help to improve the design of experiments using NEXT and better understand the data collected by NEXT. Since this is the first inverse-kinematics reaction measured by NEXT a known reaction was used in order to benchmark the technique and find the efficiency with different geometrical setups.   

Measuring Ions Per Bunch in the RFQ

The 6He-CRES collaboration centered at the University of Washington is focused on finding beyond-the-standard-model physics contributions to the electroweak interaction. Current understanding of ions traps suggest that our radio frequency quadrupole (RFQ) is limited to 104 ions per bunch, but from simulations it predicts yields of 106 ions per bunch. The next stage of the collaboration’s experimental program is to implement an ion trap to reduce systematics affecting their current setup. The motivation for getting 106 comes from the low statistics expected from smaller bunch sizes. The planned upgrade will allow for several experiments to be done with different sources in a reasonable timeframe. To experimentally find the space-charge limit of the RFQ, we will be sending potassium ions through an RFQ with low intensity and slowly increase the gain of the source until the RFQ becomes saturated with ions. By experimentally showing that it is possible to achieve 106 ions per bunch, we will show that an ion trap addition to the 6He-CRES experiment will not be at the trade-off of a great loss in count rate. We sought to measure the potential bunch size by changing several parameters to change the bunch size without greatly increasing our beam spread. The results that will be shown will contribute to the future direction of the collaboration. 

    

Designing a Detector for Superheavy Elements Produced from Multinucleon Transfer Using Monte Carlo Method

It has been proposed that superheavy elements (SHE) in the island of stability may be created through a process called multi-nucleon transfer (MNT). When two elements collide, MNT theorizes that one element will pick up nucleons from the other, thus forming a SHE. This work centers around a simulation of a blackbox detector created to benchmark the viability of detector parameters to identify alpha decay chains from superheavy elements using Monte Carlo simulations and statistical likelihood analysis. In the simulation, an argon filled detector is modeled. The MNT reaction occurs when a gold beam hits a gold target. Inside the target a SHE is produced, which then travels out of the target and into the detector where it is embedded and subsequently undergoes its decay chain. The energy loss both in the target and in the detector medium is calculated to determine where the SHE is stopped. Alpha particles detected from the decays are then paired with their decay chain based on their energy of the alpha particle and the time between each decay event. Once the work is completed, the confidence of detecting SHE produced from MNT using a detector will be discussed.   

First Results from Testing the Utility of Prototype Solid State Detectors With Particle Beams

Neutron and heavy-ion detection has traditionally been both expensive and bulky, making arrays of detectors both cost-prohibitive and difficult to transport. The prototype solid-state detectors tested in this experiment aim to solve both these issues. These detectors are both relatively cheap to produce and incredibly small (approximately 1 by 2 cm). The detectors take advantage of non-volatile charge storage SONOS (Silicon, Oxide, Nitride, Oxide, Silicon) chips. When a heavy-ion passses through a chip, it depletes the charge stored in the SONOS region it passes through. These bits can then be read out later and this voltage drop can be measured. These detectors were examined to determine their applicability as heavy-ion detectors and to help understand the base idea which could be applied to neutron detectors based on the same SONOS memory chip. These chips were placed into either a 10 AMeV 4He beam or a 15 AMeV 14N beam to test the reliability and sensitivity of these chips for different particle energies. In addition, the devices were tested for various amounts of time to determine if the chips respond to charged particle beams in a predictable way. The results from the first ever heavy-ion beams incident on these detectors will be shown.   

Search for an S-wave Resonance in 7Li just Above the Proton Decay Threshold

Near threshold resonances play an outsized role in nucleosynthesis and applied nuclear science. The study of nuclei removed from stability has greatly extended the list of resonances very close to decay thresholds. The No Core Shell Model with Continuum (NCSMC) recently predicted an S-wave resonance just above the proton decay threshold of ⁷Li at an excitation energy of 10 MeV [1]. The ⁶He(d,n)⁷Li reaction was employed at the Cyclotron Institute at Texas A&M to selectively populate this resonance where 4 ΔE-E [Si-Si] telescopes were used to detect and identify the ⁶He+p fragments. For this experiment, the detector design, constraints, and setup are examined as well as some early invariant-mass results. This case of a near-threshold resonance is unique because it is not important for an astrophysical reaction pathway. It is only dependent on the quantum mechanics of the ⁶He+p fragments extended into the continuum.

[1] M. Vorabbi, el al., Phys. Rev. C 100, 024304 (2019).   

17F(p, ɑ) Measurements with TriSol

Since its creation in the 1990’s, the University of Notre Dame has been at the forefront of Radioactive Isotope Beam (or RIBs) research as a result of the TwinSol system. This system has undergone an upgrade through the addition of a 15 degree bending magnet, a set of vertical and horizontal slits, and a third solenoid and thus has become the TriSol system. The capabilities of TriSol  include much improved beam focusing and a better beam purification. This allows for the acquisition of more precise experimental data. As part of a campaign of new measurements being done with this system, the 17F(p,ɑ) reaction has been studied to constrain the time-reverse 14O(α,p) reaction, which is a trigger reaction to the αp process in X-ray bursts. Preliminary data will be shown.    

Study of St. George Beam Position and Energy Diagnostics

The St. George Recoil Separator at the Nuclear Science Laboratory of the University of Notre Dame is a powerful tool for measuring (α, γ) reactions, which have high relevance in astrophysics. In order to achieve optimal performance, it is critical to have understandings of the properties of the beam, specifically 1) beam profile after the accelerator, 2) beam position within St. George, and 3) precise energy of the beam, to guarantee the reproducibility of experiments. We will present the signal processing software of the beam position system that we implemented to extract key position information, as well as the energy calibration of the accelerator analyzing magnet over a large p/q and mass range. Preliminary position sensitivity studies of the St. George detection system will also be discussed.   

Gas Catcher Development for the St. Benedict Project

The Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) project, currently under development at the University of Notre Dame Nuclear Science Laboratory (NSL), seeks to probe the limits of the Standard Model by measuring superallowed mixed decays to test the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Any deviation from unitarity, even by a small amount, could provide evidence for physics beyond the Standard Model. Several complex devices are required for this endeavor, including a large volume gas catcher. This device is used to thermalize the fast radioactive ion beam from the NSL TwinSOL facility and extract the beam at a low energy so that it can be bunched and transported to an ion trap where the measurement of the nuclear beta decays will take place. The gas catcher includes both DC and RF circuitry that provide voltages to electrode rings surrounding the interior of the gas cell in order to contain and transport ions through the chamber. These features, as well as the vacuum capabilities of the chamber, were tested and improvements were made to increase the efficiency of the RF and DC systems. The future work needed before commissioning the gas catcher for use in St. Benedict is discussed.   

Performance of The New fIREBall Si(Li) Detectors

Authors: Alina Bennett and John Read

In collaboration with: Kevin Lee, Joey Guerra, Wanpeng Tan, Shelly Lesher, Ani Aprahamian

The measurements of conversion electrons for gamma-rays depopulating an excited nucleus can reveal the multipolarity and the character of the gamma-ray shedding light on nuclear structure. The Internal Conversion Electron Ball  (ICEBall) is being upgraded to the fInternal conveRsion Electron Ball (fIREBall) by several ways starting with simulation to determine the best geometric configurations of the magnets to enable the highest possible collection of electrons. As well as the purchase of new detectors to replace the old Si(Li) detectors that are now over 25 years old with new detectors. The detectors were purchased from the Lawrence Berkeley National Laboratory (LBNL) but delivery of the detectors was significantly delayed by two years due to complications related to COVID. This year, we have received two of the detectors and we have assessed their performance. Before this project was started, it was observed that the LBNL detectors had an efficiency deficiency of 20% when compared to the older detectors from Canberra. A 207Bi conversion electron source and an alpha source of mixed radioisotopes of 148Gd and 241Am were used to determine the efficiencies of the new detectors in comparison with the old ones. We suspect that the production of these detectors suffer from a deadlayer which is not smooth and interrupts the performance of the detectors.  The deadlayer is not uniform due to the lithium drifting, and there are distinct and measurable edge effects on the new detectors. We expect this to negatively impact the increased efficiency we envisioned with the new fIREBall. We have made several measurements and the results are reported in this report.   

Analysis and characterization of bismuth incorporated graphene targets

One method of producing heavy exotic nuclei that lie far from the β-line of stability requires a reaction between a target and a beam. For heavy element reactions, the target is typically a thin film made from a heavy isotope, while the beam will be made using a lighter isotope. Bombarding thin films with ion beams leads to target damage and degradation so having them made of robust materials is very beneficial. For this reason, investigating targets made of bismuth nanoparticles suspended in a graphene matrix for the production of heavy elements is of interest. Graphene allows for good structural integrity and has a high melting point, increasing its ability to withstand high beam intensities used to produce heavy and unstable exotic nuclei in low cross-section reactions. Two of these graphene incorporate bismuth thin film targets have been analyzed using confocal scanning microscopy to check for surface morphology, uniformity, and anything abnormal. Interestingly, large bismuth particles can be found semi-regularly throughout the target, and these large pieces have been found to have enormous heights ranging from 25 μm to over 50 μm in width and 20 μm in height, well beyond the manufacturer's specified nanoparticle sizes.  Other characterization techniques used were X-ray diffraction to verify chemical composition and alpha particle energy loss to confirm target thickness. To test these targets in beam, we plan to run the fusion evaporation reaction ²⁰⁹Bi(⁴⁸Ca, 3n⁰)²⁵⁴Lr.   

Monte Carlo Simulation of Mass Measurements of Heavy Element Complexes

Relativistic effects are predicted to alter heavy and super heavy elements’ (SHEs) chemistry, potentially leading to the breakdown of periodic table trends at heavier masses. Understanding complex formation in SHEs could reveal impacts of relativistic effects. To date, this has only been studied in broad terms where the chemical behavior of a SHE is compared to its lighter homologues, and theory is used to estimate complexes formed. For the first time, we can perform chemistry on SHEs and measure the masses of resulting complexes using LBNL's FIONA spectrometer.

Recent FIONA experiments measured the masses of nobelium complexes formed from nobelium and several reactive gases. Complexes impact FIONA’s detector at distinct positions, according to their mass-to-charge ratio. Monte Carlo simulations were performed to precisely determine where masses impact FIONA’s detector, calculate the mass dispersion, and assign masses to data. The Monte Carlo simulations were optimized using astatine calibrations, then applied to nobelium experiments.   

Extracting Neutron Yield From High Mass Background

The Neutron Detection Efficiency (NDE) is an essential property of the CLAS12 Detector at Jefferson Laboratory. It is measured with the ratio of detected neutrons to expected neutrons from the e¹H → e' π⁺n reaction which provides tagged neutrons. Expected neutrons are found by swimming the neutron track, using only the e' π⁺ information, to see if it strikes CLAS12. Detected neutrons are ones observed in the region of the expected neutron. Missing mass (MM) spectra of the neutron are created through four-momentum conservation and can be used to determine the neutron yield. We fit the spectra to separate the neutron events from the higher MM background. The fitting is done asymmetrically using the Crystal Ball function in bins of missing momentum. The function is a combination of a gaussian fit around a central peak and a low - MM tail that is fit with a power law, MMⁿ, where n is a fit parameter. The overlap point of the two functions is determined by another fit parameter, α. The fit is done with the CLAS12 Common Tools written in Java. The Crystal Ball function produces better fits to the neutron peak ( <χ²/ν> ~ 1.3). The fit parameters vary smoothly with missing momentum of the neutron.

    

Investigating High Voltage Breakdowns for the nEDM Experiment at ORNL

Roshan Gautam (Valparaiso University) 

For the nEDM collaboration

The neutron electric dipole moment (nEDM)experiment at Oak Ridge National Laboratory’s (ORNL) Spallation Neutron Source (SNS) aims to measure the nEDM to the level of 3 x 10-28e.cm , an improvement of two orders of magnitude from the current limit. In order to reach this goal, it is necessary to produce an electric field of 75 kV/cm inside a measurement volume containing superfluid helium at 0.4 K. But to obtain such a high operating field and properly inform the design of the final high voltage (HV) system in the experiment, a better understanding of electrical breakdown in liquid helium is needed. Several cryogenic HV apparatuses, including the Half-Scale HV (HSHV) and Small-Scale HV (SSHV) systems, have been constructed at Los Alamos National Laboratory (LANL) to support this effort. In this talk, the purpose of these two systems will be explained.  In addition, details on the work to improve the performance of the HV transfer line in the HSHV system as well as testing of the modifications to the SSHV system will be presented.

    

Testing silicon detector characteristics and simulating charged particle activity for the Nab Experiment

Precise measurements of neutron beta decay can be used to expand upon the Standard Model. The Nab Experiment at the Spallation Neutron Source at ORNL will make precise measurements of beta decay by measuring the electron-antineutrino correlation coefficient, a, and the Fierz interference term, b. Variable a is useful for finding the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix up- to down-quark element Vud. The CKM matrix should be unitary; however, experimental measurements of the top row’s elements disagree with unitarity by over 2??. In the Standard Model, the Fierz interference term b equals zero. The Nab experiment uses a 7 meter-long spectrometer with a silicon detector at each end to measure the electron’s energy and the proton’s momentum. To ensure quality data, we quantified baseline noise for each pixel on each detector. We collected waveform data and processed them. We analyzed the data to determine which pixels are primed for data collection and which pixels have exceptionally high or low noise or are disconnected from their electronics chains. Additionally, we simulated charged particle activity in the detectors with Geant4. Understanding detector characteristics with these studies helps Nab achieve its overall precision goal of Δa/a = 0.001 and Δb = 0.003.

    

Design of Modular NaI(Tl) Detectors for Fundamental Symmetry Measurements with Neutrons

The NOPTREX and Nab collaborations seek to utilize the fundamental nature of the neutron to probe the weak interaction. These experiments exemplify the variety of demands for different detection parameters, such as the gain or timing/energy resolution. In an effort to efficiently meet these various requirements using one set of detectors, we have developed an array of modular NaI(Tl) detectors with novel electronics that allow for operation in both current or pulse mode to accommodate better energy and timing resolution, respectively. To process the data from the detectors, we also have two independent data acquisition systems tailored to the demands of each experiment consisting of the CAEN DT5751 digitizer for the Nab timing measurements and the CAEN DT5560SE digitizer for the NOPTREX P- and T-Odd measurements. The development of this system has involved conducting experiments to determine the optimal design for the detectors, characterizing the detector components, and testing the data acquisition systems. The adaptability of these detectors will allow for a wide range of uses in nuclear physics experiments.   

Design for a Next-Generation Neutron Detector

Having good detection techniques allows one to understand the physics and structure of neutron-rich nuclei beyond the neutron dripline. The Facility for Rare Isotope Beams (FRIB) will give access to more exotic nuclei where multi-neutron decay is expected. The next generation MoNA1 detector will need to measure multi-neutron events, and improved algorithms are needed to enhance the extraction of these events with a good signal to noise ratio (cross-talk). A complete Geant4 simulation was developed to study the possible configurations of this new array. Implemented models include a description of multi-neutron decays, including n-n signature correlations. Various combinations of geometrical parameters were simulated and analyzed. The resolution and efficiency of the detector were calculated for 1n through 4n decay for each case. 

    

Analysis of Neutron Scattering Interactions in Plastic Scintillators

The MoNA collaboration is a group of primarily undergraduate institutions that studies neutron-unbound nuclei at FRIB. To better understand neutron scattering in our plastic scintillator detectors and to test the prediction accuracy of our Geant4-based Monte Carlo simulation, our group conducted a neutron scattering experiment using a pulsed neutron beam at the LANSCE facility. Neutrons scatter in various ways from the H and C nuclei in the scintillator detectors, some of which produce sufficient light to be detected above detector threshold (n-p charge exchange, carbon excitation, ...). In particular, n-p charge exchange scattering produces high energy protons which can travel from our target bar to the back wall of our array. We measured the energy-dependent angular distribution of these charge-exchange protons relative to the beam axis. We removed the muon background by using a scaled version of data taken during beam-off cycles. We compared our neutron scattering measurements with simulation to determine simulation's accuracy to predict neutron kinematics inside our scintillator array. Our next experiment will use a diamond detector as an active target to measure several elastic and inelastic n-C interactions with minimal background contribution. Results will be presented.   

LANL II Neutron Dark Scattering Analysis

The MoNA Collaboration studies the properties of unstable neutron rich isotopes at the drip line. Using an array of highly efficient MoNA neutron detectors, we measure the energy and momentum of decay neutrons to determine the properties of the parent nucleus. Neutron scattering in our detectors is complex as it involves both H and C scattering. To interpret our results, we rely on Monte Carlo simulation. Our first neutron scattering experiment at the LANSCE facility revealed significant disagreements between data and simulation, especially at higher neutron energies. Our second LANSCE experiment was designed to focus on neutron "dark" scattering arising from elastic n-C scattering (which produces light below detector threshold). The three main sources of background for our dark scattering measurements are cosmic muons, "wrap around" neutrons, and scattered beam neutrons. The scattered beam neutrons are present whenever the neutron beam is on and unable to be isolated, causing them to be the major source of background and most challenging to remove. We used data from target-out runs to develop a method to subtract scattered beam contributions. Resulting angular distributions for dark scattered neutrons, and methods used to remove background contributions, will be presented.   

Machine learning algorithms for classifying multi-neutron decay measurements of neutron-unbound systems

The MoNA Collaboration studies neutron-unbound systems using a set of large-area high-efficiency neutron detectors, the Modular Neutron Array (MoNA) and the Large multi-Institutional Scintillator Array (LISA). These detectors enable invariant mass spectroscopy experiments to study neutron-unbound nuclei and provide information for benchmarking models of the atomic nucleus. A crucial step in the analysis of systems that decay by emitting multiple neutrons involves classifying events according to the number of neutrons detected. To address this, machine learning techniques are being tested as a means to improve the efficiency of the classification process. We will present preliminary results from training a neural network to classify simulated two-neutron events and discuss plans to test this network with labeled data.   

Impact of the Material Choice for the Solenoid Magnet of an EIC Central Detector on Muon Tracks

Two superconducting magnet technologies are currently being considered for the central solenoid of a second EIC detector: Al-stabilized and Co-stabilized Nb-Ti superconductors. The former utilizes minimum material and weight, which increase the magnet’s transparency for charged particles, but it comes with high monetary costs. The latter has lower transparency but has a lower cost and could lead to substantial cost savings. Since a muon detector would be placed outside of the solenoid, the effect of a Co-based solenoid on the muon identification needs to be studied. The goal of this research is to compare the effect of copper and aluminum magnet materials on muon tracks by using Geant-4 simulated data. Muons with momenta 0.5 – 4.0 GeV/c and pseudorapidity of -1 – 1 were generated and propagated through the Fun4All CORE detector simulation. The change in the components of the muon three-momentum vector through the magnet was studied for both materials. The widths of the event distributions over these variables are used to quantify the magnet material effect and are presented here as functions of muon momentum and pseudorapidity. Our estimates are critical for the choice of magnet material for the second EIC detector and for the design of a muon detection system there.   

Photogrammetry Modeling of Scintillating Fiber Detectors in Muon g-2 Experiment

The Muon g-2 Experiment at Fermilab will perform the most precise measurement of the muon's anomalous magnetic moment to date, which could provide evidence of physics outside the standard model. Within the experiment, scintillating "fiber harp" detectors are used to directly measure the motion of the muon beam. Data collected from these harps may be used to tune simulations that compute corrections to the final experiment result. Knowing the locations of the fiber harps more precisely within the vacuum chamber may improve the uncertainties of these corrections. A fixture holding a camera was built and inserted into the vacuum chamber to take hundreds of pictures of the scintillating fiber harps. With these pictures, photogrammetry software was used to construct three dimensional models of the fiber harps. A program was developed to locate the center positions and tilt angles of individual fibers in the 3-D models. The primary focal points of this presentation are the design of the fixture and the process of finding positions with the 3-D models.   

Measurements of Neutron-Induced Gamma Ray Background of 100Mo for CUPID

CUPID (CUORE with Upgraded Particle IDentification), an update to CUORE (Cryogenic Underground Observatory for Rare Events), is an experiment designed to search for neutrinoless double beta decay using the candidate isotope ¹⁰⁰Mo. To analyze the neutron-induced gamma ray background of ¹⁰⁰Mo, an experiment was conducted by TUNL (Triangle Universities Nuclear Laboratory) in which neutron beams ranging from 4-8 MeV were targeted at varying samples of ¹⁰⁰Mo, ⁵⁶Fe, and Cu. Germanium detectors were used to measure the resulting gammas. In order to determine the neutron-¹⁰⁰Mo cross sections, we are analyzing the TOF (Time of Flight) data for ¹⁰⁰Mo and ⁵⁶Fe. This is done by fitting the peaks in both ⁵⁶Fe and ¹⁰⁰Mo and using the well-known neutron-⁵⁶Fe cross sections to extrapolate the ¹⁰⁰Mo cross sections. We will be presenting the current results of this analysis.   

Development of an Adaptive Noise Canceling Algorithm for CUORE Data

The Cryogenic Observatory for Rare Events (CUORE) is an experiment searching for neutrinoless double beta decay (0νββ). In Italy, the search at the Gran Sasso National Laboratory (LNGS), bolometers are used to detect small heat signals in crystals cooled to 10mK. Seismic, acoustic, and electrical interference riddle the signal with noise affecting the bolometers' resolution. At CUORE we have installed microphones, accelerometers, and antennas to measure the acoustic background noise of the system. We have also implemented an algorithm that denoises a system using those auxiliary devices to measure the coherent noise in the sensors. We determine whether background noise is coherent by analyzing the transfer function between the auxiliary devices and the sensors. The acoustic noise from pulse tubes and turbo pumps that help cool the cryostat down tends to be relatively constant compared to seismic noise from earthquakes. In the frequency domain, the acoustic noise power has a stable bandwidth measured on both devices. My poster will give an overview of how the algorithm uses a snapshot to develop a denoising filter. I will also update the development of an active noise template that uses a transfer function to filter important data for calibration and background measurements.

    

Characterization of Silicon Photomultipliers for the UCN?? Experiment

The UCN?? experiment held at Los Alamos National Laboratory works to precisely measuring the lifetime of the neutron which has implications for other fields such as Cosmology, Nuclear Physics and Particle Physics. Because UCN??+, the upgrade for the existing experiment, will upscale the number of stored ultracold neutrons (UCN), an increase in detectors will be needed to properly catalogue individual events. A portion of the paper is contributed to the data analysis of silicon photomultipliers and other observed characteristics. We produce single photoelectron spectra for the candidate SiPMs and find good performance as required for the detector under development. This performance, along with a fast, high light output scintillator is needed to handle the high rates we expect to encounter in the improved UCN?? experiment. This paper will also describe the experiment of the data set used which mimicked a high neutron count environment with and without SiPM cooling to reduce dark counts.   

The Constituent Counting Rule in Meson-Baryon Photoproduction

In 1975, S.J. Brodsky and G.R. Farrar proposed the dimensional scaling laws as an approach to understand the energy dependence of high energy scattering processes at a fixed center-of-momentum angle. The Constituent Counting Rule (CCR), based on perturbative Quantum Chromodynamics (pQCD) framework, predicts the scaling behavior of the differential cross-sections of scattering processes at high energies: dσ/dt=f(cosθ)/s^N. Where s and t are Mandelstan variables, θ is the scattering angle and N=n-2, in which n is the number of constituents fields in the reaction. On meson-baryon photoproduction, N is expected to be 7. Nonetheless, various studies have shown that it does not hold true for all reactions at all kinematic regimes.

We introduce a systematic study of pseudoscalar mesons-π,η,η^'-photoproduction reactions in the 3-8 GeV² s-range. At the same time, we study the evolution of N with respect to the transverse momentum (P_⊥²) of the produced particles.

We investigate the energy dependence of pseudoscalar-meson photoproduction by analyzing previously published data from Jefferson Lab's CLAS experiment. We also investigate why some reactions do not have the expected N=7. A reason we have considered is the different production mechanism of the reactions and the energy range of the data. We are collaborating with theorists to better understand the photoproduction of the pseudoscalar-mesons.   

MCSTAS Simulation of the NSR apparatus

The NSR collaboration has designed a neutron spin polarimeter that can  measure deviations in the average spin rotation of a beam of neutrons down to the 10E-7 rad/m level. The collaboration is considering using this polarimeter at the Missouri University Research Reactor to carry out experiments to test a predicted class of short range spin dependent forces  that affect neutron polarization as they pass close to other dense masses of fermions. If these forces are demonstrated to exist this would extend the standard model of particle physics. Over the summer we developed a Monte Carlo simulation of the instrument in MCSTAS to estimate transmission rate for this instrument on a thermal rather than cold neutron beam and to begin the study of systematic errors. The simulation found that Helium polarization cells were more effective than supermirror polarizers tuned to cold neutrons. We find that about 0.2% of the neutrons that come out of the beam port at the MURR make it to the end of the beam and thus we could expect to measure a rotation angle at the level of 10^-7 radians in a couple months of beam time.

    

Measuring Proton Energy Loss through Gold Films

The NIST neutron-lifetime measurement counts protons resulting from neutron beta decay by accelerating the resulting protons to around 30keV and then detecting them in silicon charged particle detectors.  To account for proton losses in dead layers, backscattering, or energies below the detection threshold, a variety of energies and silicon detectors are used which have entrance windows consisting of silicon or various thicknesses of gold.  Our project aims to better understand proton energy loss in detector entrance windows and compare our measurements with known stopping powers and simulations of spectra using SRIM.  We create these thin (10s of nm) gold layers directly on the silicon surface of PIPS detectors, measure the thickness of the layer, and vary the proton beam’s energy to obtain the detected energy spectra for protons traveling through the gold-plus-silicon dead layer and through just the bare silicon dead layer as function of incident proton energy and gold thickness.  To deposit the gold, a thin wire is thermally evaporated under a vacuum.  We have used different techniques to determine the thickness, including UV-Vis spectroscopy and an Atomic Force Microscope.  We discuss our experimental techniques, challenges, results, and future improvements.

    

Study of Missing Mass Background in the CLAS12 Detector

At Jefferson Lab we use the CLAS12 detector to measure the neutron magnetic form factor. An accurate measurement of the CLAS12 neutron detection efficiency (NDE) is required. We use the nuclear reaction ep→e'π⁺n as a source of tagged neutrons and obtain the NDE from the ratio of expected neutrons to detected ones. We assume the final state consists of  e'π⁺n only, use the e'π⁺ information to predict the neutron's position(expected) and then search for that neutron(detected). We select neutrons with the missing mass (MM) technique. We use simulation to validate our methods. We simulated events with the Monte-Carlo code GEMC and included background events. Even with background, the resolution of the simulated data is too small, so we used an existing smearing function and increased the resolution of the magnitude of the momentum and the angles of the electron and pion by a Resolution Scale Factor (RSF) to make the neutron MM resolution more realistic. We compared the simulated results with the run data distributions for several quantities like MM, energy, angles, etc. We selected the RSF that produced the best match. We then studied the composition of the low-MM background to understand its source. 

    

Measuring Beam Spin Asymmetry of π- photoproduction off deuterium in the 8-10 GeV Range

Studying meson-photoproduction amplitudes is one of the powerful ways of learning about excited nucleon resonances. However, measurements on neutron targets, as well as on proton targets, are needed to fully disentangle isoscalar and isovector couplings, and no feasible neutron target has ever been built. One common technique is to study photoproduction from neutrons in deuterium in quasi-free kinematics. Such measurements have previously been performed with beam energies reaching up to a few GeV. Data from the Hall D Short-Range Correlations / Color-Transparency Experiment, conducted at Jefferson Lab in the fall of 2021, may extend our knowledge out to the 8-10 GeV range. Using the higher beam energy available at Hall D, combined with the capabilities of the GlueX spectrometer, the fully exclusive γ d -> π- p p reaction can be reconstructed. The experiment scattered a linearly polarized photon beam from deuterium, helium, and carbon targets, with a minimally selective trigger, using GlueX to reconstruct the produced charged particles. I have worked to identify events with a deuteron target which produced a single ??- meson. By comparing the azimuth of the meson and the polarization of the photon beam, a measurement of the ?? beam spin asymmetry of the photoproduction of ??- mesons from neutrons in deuterium can be made in the 8-10 GeV range. I will present the status of the analysis and projected uncertainties.   

Optimization problems in the development of a blimp to monitor radiation levels in the CERN FCC environment

To prevent unecessary human exposure to the extremely high levels of radiation present in the environment of the Future Circular Collider at CERN, robotic systems are a primary focus of research and development. Monitoring radiation levels, as well as other metrics, is a task well suited for flying robots which can access all unobstructed parts of a detector cavern. The blimp is the flying robot of choice for this task because of its relatively low likelihood of causing damage in the case of catastrophic failure of a motor. One challenge with developing a blimp for this purpose is the high magnetic field levels present in a detector cavern which interfere with the normal functioning of electromagnetic motors. Therefore, the design of a blimp requires not only a system to locate the blimp in space but also the capability to resist magnetic forces in any direction (and along any axis in the case of torques caused by magnetic forces). This work consisted of the determination of an optimal placement of cameras in a motion capture system used to locate the blimp in space as well as the determination of an optimal configuration of actuators on a blimp to allow it to counteract a desired set of disturbances.   

Determining the longitudinal double-spin asymmetry (ALL) for π0 production from STAR 2013 Endcap Calorimeter Data

The Solenoidal Tracker at RHIC (STAR) located at Brookhaven National Laboratory uses longitudinally polarized proton-proton collisions to study the gluon spin contribution to the known proton spin of ½ h-bar. The relative contributions of the quarks and gluons to the spin of the proton remain uncertain. Using data from the 2013 longitudinally polarized proton-proton collisions we study the asymmetry of proton spin-dependent production of neutral pions (π⁰s) from these collisions. π⁰s rapidly (8.5*10^-17 s) decay into 2 photons that are detected by the Endcap Electromagnetic Calorimeter. By comparing the number of π⁰s produced when protons collide with different helicities, the asymmetry of π⁰ production (A_LL), which can be related to the contribution of the gluon spin to the spin of the proton, can be measured. The two-photon invariant mass spectrum is reconstructed and then fit using a skewed Gaussian function to represent the π⁰ signal and a Chebyshev function to characterize the background. Various checks must be made to assure the quality of the data being analyzed. The status of this analysis will be presented.

    

A Novel Reaction Plane Detector for the ATLAS Experiment

The CERN LHC began Run 3 physics data taking in July 2022. During the three years of Long Shutdown 2 (LS2), LHC experiments had the opportunity to refurbish their existing apparatus, as well as expand their physics capabilities with the implementation of new sub-systems. 

In this period, the Nuclear Physics Laboratory at the University of Illinois at Urbana-Champaign (UIUC) has developed a novel reaction plane detector (RPD) to be installed in the LHC together with the ATLAS Zero Degree Calorimeter (ZDC) for heavy ion (HI) data taking. 

The detector consists of 256 fused silica fibers that are grouped in a total of 16 channels and read out by Photo-Multiplier Tubes (PMTs). In HI collisions, the correlated transverse deflection of spectator neutrons is directly related to the reaction plane (RP) characterizing the event. The RPD enables the RP measurement in HI collisions by mapping the transverse profile of the showers generated by the spectators in the ZDC. 

In this contribution, we present the design of the new ATLAS RPD built at UIUC for the Run 3 HI program. Details about detector design, radiation hardness and integration with ATLAS DAQ system and electronics will be discussed. The RPD was tested at the SPS in July and initial results from the test will be shown.   

Developing Beam Instrumentation at the Exotic Molecules and Atoms Lab

The group at the Exotic Molecules and Atoms Lab at MIT aims to study the structure of atoms and molecules composed of both stable and radioactive nuclei through measuring the electrons that are bound to them [Gar20, Ver22]. These measurements give us key insights about nuclear structure and will form the basis for study of symmetry violating nuclear properties. The lab has a particular focus on improving the precision of current ultra-sensitive techniques, and can be employed at world leading radioactive ion beam facilities such as ISOLDE CERN and the Facility for Rare Isotope Beams (FRIB).

This contribution presents the development of laboratory instrumentation such as the reading and monitoring of ion beam currents and vacuum pressure along our setup. This infrastructure plays a crucial role in all experiments performed at the lab.

[Gar20] Garcia Ruiz, R. F., et al. Nature 581, 396–400 (2020).

[Ver22] Vernon, A.R. et al. Nature 607, 260–265 (2022).

    

Aging and Calibration Studies of sPHENIX Hadronic Calorimeter Scintillating Tiles

sPHENIX will soon probe the hot, dense state of nuclear matter known as Quark-Gluon Plasma at the Relativistic Heavy Ion Collider. The sPHENIX Hadronic Calorimeter (HCal) measures the energies of incoming particles from the collisions. The HCal achieves this with scintillating tiles that produce light when struck by a particle. The light is then routed to an SiPM, and digitized. To calibrate the detector, the tiles were tested using cosmic rays to determine the performance characteristics. We are continuing to test a small selection of these scintillating tiles to determine the aging characteristics of their performance. Calibrations will also be monitored and adjusted while sPHENIX is collecting data, as it is expected that the SiPMs in the detector will suffer from radiation damage. There are currently two methods being considered; one is to continue to take cosmic ray data, and the other is to shine an LED on the tiles to see any change in performance. Comparisons of those two methods are currently underway. This poster will present the results of these studies and the results of the aging tests.   

Application of Machine Learning with the Minimum Bias Detector (MBD) in sPHENIX

The PHENIX detector is one of two main detectors used to track high-energy collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Designed to collect nuclear data for analysis, these detectors have expanded our collective knowledge of quark-gluon plasma (QGP). An upgrade to PHENIX, called sPHENIX, will enable far better measurements of upsilon production and heavy flavored jets. The minimum bias detector (MBD) is a subsystem of sPHENIX that acts as the primary trigger for collisions and uses the original beam-beam counter (BBC) from PHENIX. Instead of using standard digital signal processing techniques to extract the time of arrival and charge in the MBD, I used machine learning techniques such as boosted-decision trees, convolutional neural networks, and linear regression models to obtain these values. I have built various models utilizing these techniques to compare the accuracies and mean-average errors (MAE), as well as the speed of execution. At the beginning of sPHENIX data-taking this program will be used in the reconstruction of the MBD data.   

Physics with the sPHENIX Event Plane Detector

The new sPHENIX Event Plane Detector (sEPD) will enable measurements of both the centrality and event plane outside the mid-rapidity region of collisions at the Relativistic Heavy Ion Collider (RHIC). Centrality is an experimental measurement used to estimate impact parameter, a vector that represents the distance between the center of two colliding nuclei. The Event Plane is the experimental measurement used to estimate the reaction plane of a collision. With a pseudorapidity acceptance in the range 2.1 < │η│ < 4.9, the event plane and centrality determination will avoid auto-correlations with the jet, heavy flavor and other observables measured by sPHENIX. This poster will explore the benefits of using the sEPD to determine these key parameters in our studies. This material is based upon work supported the National Science Foundation under Grant No. 2117773.   

Comparing STAR and sPHENIX Background Subtraction Routines in Particle Jet Analysis

Quark-gluon plasma (QGP) is formed by colliding heavy ions at relativistic speeds. When these collisions occur, the ions' constituent quarks and gluons can hard-scatter off of each other and fragment into particle jets, which lose energy as they travel through the QGP. Several algorithms have been created to pick out particle jets in collision data, and several methods of subtracting the heavy ion background off of this jet data have been proposed and implemented across different experiments. In this research, two such background subtraction routines are applied to a simulated collision dataset, and their results are analyzed and compared by looking at the effect on the scale and resolution of the output jets. Specifically, the two methods employed in the Relativistic Heavy Ion Collider's STAR experiment and its upcoming sPHENIX experiment are used for comparison.   

Testing and Characterization of Analog Electronics for the sPHENIX Experiment

The sPHENIX experiment is designed to measure jets with over 25,000 calorimeter detectors. These detectors are read out by more than 400 analog-to-digital converter (ADC) custom electronics. These electronics are critical to ensure highly precise and accurate measurements of jet energies. My research involved the visual inspection and testing of the ADC electronics. An injector module is used to input known charge to calibrate each channel's pedestal, gain, and overall linearity of response. Modules are also tested for a token-passing, high speed data transfer over the backplane to a transmitter module (XMIT). Results on the testing will be presented along with implications for the sPHENIX jet program.   

sPHENIX Electromagnetic Calorimeter Block Evaluation

sPHENIX is a detector under construction at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, and will begin collecting data in February of 2023. By the collision of heavy nuclei, RHIC is capable of creating a quark-gluon plasma (QGP), a hot, dense state of unconfined quarks and gluons. Jets, collimated sprays of energetic particles, serve as important probes of the plasma, as they have been modified relative to jets in baseline proton-proton collisions because their parent partons have lost energy to the QGP. In order to provide precision measurements of jets and jet energy loss, sPHENIX has both electromagnetic and hadronic calorimetry at midrapidity. The electromagnetic calorimeter (EMCal) is the innermost calorimeter system and is composed of blocks made of tungsten powder and scintillating fibers. Particles will embed energy into the calorimeter blocks, and the fibers collect that energy in the form of light, which is then read out by a silicon photomultiplier (SiPM). We report a study of the EMCal's energy response to single photons measured in an sPHENIX-based GEANT4 simulation. We have evaluated the average response, as well as how the response varies as a function of where a photon lands in the EMCal. Inefficiencies in light collection near the edges of the towers are seen and corrected for, using a procedure developed during beam tests of EMCal prototypes. This poster presents the results of these studies.   

Studying the Cone-Size Dependence of Jet Suppression in Heavy-ion Collisions with PYTHIA

At sufficiently high temperatures, quantum chromodynamics (QCD) matter becomes a hot dense medium of deconfined quarks and gluons called the Quark-Gluon Plasma (QGP). The QGP can be experimentally reproduced through relativistic heavy-ion collisions. Jets, which are sprays of particles in a cone shape, are expected to lose energy in the QGP and can be used to probe its qualities. Specifically, the ratio of the jet yield in heavy-ion collisions to the expected unmodified yield in proton-proton collisions, the nuclear modification factor (R_AA), is a useful parameter that gives access to energy loss information. This information, in turn, gives insight into the QGP medium. Particularly interesting is the cone-size (R) dependence of the R_AA, as it can help separate out the different energy-loss mechanisms, such as out-of-cone radiation and the medium response. One open question is how the various energy loss mechanisms would contribute to the R-dependence of the R_AA separately. To answer this question, I will show the R_AA calculated from modified PYTHIA simulations at 5.02 TeV in comparison to existing experimental results in order to investigate the relative contributions of different energy loss mechanisms at different cone-sizes.   

Leveraging Machine Learning for Jet Energy Reconstruction in Heavy Ion Collisions

In understanding the effects of quark-gluon plasma on jet spectra in heavy ion collisions, it is essential to have accurate values of jet energy. Machine learning is increasingly prevalent in high energy physics, but is it a reliable tool for jet physics, and what are the best applications for it? We have reproduced the results from [Phys.Rev.C 99 (2019) 6, 064904, Machine-learning-based jet momentum reconstruction in heavy-ion collisions], and extend them to include kinematics relevant for sPHENIX collision energies at RHIC. We also evaluate potential biases in the algorithm and how to mitigate them. Our study aims to contribute to the broader trend of embracing machine learning, and to delineate appropriate domains for its use.