Session DB03: CEU Poster Session & Physical Review Reception (2:00 P.M. - 4:00 P.M. HST)

Neutron and gamma-ray discrimination based on pulse shape information and study of (p, n) reactions for isobaric analog states

 Our group has been developing the PANDORA neutron detector. It is a one-dimensional position-sensitive neutron detector and can discriminate between neutrons and gamma rays using the difference in the decay time of their scintillation light. In order to demonstrate this discrimination and the ability to obtain clear neutron spectra, we measured isobaric analog states (IAS) via (p, n) reactions at 230 MeV for ²⁷Al, ⁹⁰Zr, ⁹³Nb, and ²⁰⁸Pb at RCNP. Neutron and gamma-ray events have been successfully separated using their decay-time difference, and clear IAS peaks have been observed. The reaction Q-values for the IAS transitions are expected to be inversely proportional to the target charge radii. Thus, the systematic study for targets with different mass numbers A has enabled us to experimentally confirm the proportionality between the nuclear radius and A^1/3. The present discrimination method uses the charge information corresponding to different decay-time components. We have been developing new Constant Fraction Time-Over-Threshold (CF-TOT) method using the timing information only. In the additional measurement using a neutron source, the data were collected by the SPADI data acquisition system (AMANEQ) and we have been trying to distinguish the different decay-time components by using the correlation between TOT and CF-TOT information. The current status of this development will be presented.   

Study of spin-dipole transitions from 16O via the (p,n) reaction and improvement of position resolution of two-dimensional neutron detector NPOL2

The ¹⁶O(ν,e^-)¹⁶F reaction is caused by weak interaction and the quantitative understanding of the transition strength is essential for the neutrino detection efficiencies of water Cherenkov detectors such as the Super-Kamiokande. In order to evaluate this transition strength, the ¹⁶O(p,n)¹⁶F reaction is useful since the relevant ¹⁶F states are strongly excited, and thus we can obtain the information based on the data with reasonable statistical accuracy. Since ¹⁶O is a doubly magic nucleus, spin-dipole (SD) states are strongly excited at small momentum transfers whereas Gamow-Teller ones are weakly excited. The SiO2 and Si targets were each bombarded with protons at 230 MeV and 8 degrees where the SD states are most prominently excited. The ¹⁶O(p,n) spectrum has been successfully obtained by subtracting Si contribution from the spectrum for SiO₂. The data were compared with the distorted wave impulse approximation plus random phase approximation calculation to assess the SD strength.

Our group plans to measure the polarization observable for the same reaction to separate the observed SD states into each spin-parity state. Our neutron detector NPOL2 has the two-dimensional position sensitivity and its resolution affects the efficiency of the polarization measurement. Therefore I have been trying to improve the position resolution using the correlation of timing information of NPOL2. The current status of this development will be presented.   

Performance evaluation of Mini TPC in CAT-M

Systematic measurements of the incompressibility of the stable isotopes and radioisotopes are necessary to clarify the equation of state of nuclei. To measure the incompressibility of the unstable nuclei, inverse kinematics measurement of isoscalar giant monopole resonance is conducted.

A gaseous active target CAT-M is a TPC developed to realize such measurements by irradiating heavy-ion beams at an intensity up to 1 Mcps. Nuclei of interest enter and react with deuteron which is the nucleus of detector gas. The four momenta of recoil particles are simultaneously measured by CAT-M for missing mass spectroscopy. Our measurements have been done for Kr, Xe, and Sn isotopes at an incident energy of 100 MeV/u.

Such a heavy-ion injection produces a number of delta-rays which causes many noises in an active target. A static magnetic field is formed around the beam axis to remove such noises, so the beam trajectory can’t be detected directly. In addition, the beam itself is also deflected, so it’s necessary to estimate the beam trajectory near the reaction point with a resolution less than 1 mm.

For that purpose, the development of a small TPC called Mini TPC to be placed near the entrance and exit of the field cage is ongoing. Two layers of thick GEMs with a hole diameter of 200 μm and a hole pitch of 500 μm are used as the amplification part of Mini TPC.

In this talk, the structure of Mini TPC and its basic performance such as a bias dependence of gain and charge resolution will be presented.   

Test measurement of the 12,13C (p, p alpha) Reactions for the PANDORA Project

The PANDORA project plans to investigate photo-nuclear reactions in the mass region below A ∼ 56. The main motivation of this project is to understand the energy loss process of nuclei consisting of ultra-high-energy cosmic rays (UHECRs) in inter-galactic propagation. The origin, acceleration mechanism, and composition of UHECRs are still unknown. However, UHECRs with energies above 10²⁰ eV are observed by large cosmic-ray air-shower observatories such as Pierre Auger and Telescope Array. Analyses of air-shower depth distributions revealed a trend to be heavier in the mass composition between protons and iron at the highest energies.

UHECR nuclei are predicted to primarily lose their energy by emitting particles after photo-nuclear excitation by absorbing a cosmic microwave background (CMB) photon. Therefore, photonuclear reaction cross-sections and decay branching ratios are crucial elements for understanding the energy and mass evolution of UHECRs during inter-galactic propagation.

In the experiment, virtual photon exchange by proton scattering will be used to excite target nuclei and determine the photo-absorption cross-sections covering the giant dipole resonance. The detection of decay particles will extract branching ratios.

Data for the ^12,13C (p, p alpha) reactions at 392 MeV were measured in a test experiment in Dec. 2022 and some improvement points were identified.

I will report the status of the experimental setup for a beam time in Oct. 2023.   

Performance Evaluation of Time-Measurement System Using Ultra-fast Plastic Scintillation Detectors in BigRIPS (2)

The Bρ-TOF-ΔE method is often used to identify nuclides of produced secondary beams at the inflight RI beam facilities. To improve the resolution of the mass-to-charge ratio A/Q, it is essential to improve those of the magnetic rigidity Bρ and time-of-flight (TOF). To achieve this requirement on the time resolution of the TOF, the performance-evaluation experiment was performed using the BigRIPS at the RIBF. A secondary beam containing unstable nuclei around 300-MeV/nucleon ¹³⁰Sn, which was produced by irradiating a Be target with a ²³⁸U primary beam, was used for the TOF measurement.

Two TOF detectors were installed at the two focal planes, F3 and F7, respectively (Four in total). A new TOF detector consists of a Elijen EJ-232 plastic scintillator and two HAMAMATSU R13089 PMTs. The EJ-232 has an ultra-fast response with a faster rise time than an EJ-230, which is usually employed at the BigRIPS, instead of reducing the light intensity. The R13089 PMT has a small transit time spread. For the data acquisition, a TAC-ADC system was used in parallel with the existing TDC to evaluate the effect on the intrinsic time resolution from the signal transport and timing jitter of electronic circuit. The time resolution of each TOF detector was extracted from the corresponding TOF and compared. In addition, the resolution of the A/Q was derived from the TOF measured with the newly developed detectors. The achieved TOF resolution and relative A/Q resolution were 50 ps(σ) and 0.034%(σ), respectively.    

New detector system for a (p, pN) reaction in inverse kinematics

 Anomalous phenomena have been observed in neutron-rich nuclei. In order to understand the phenomena, the weakly bound states have been extensively studied. On the other hand, the deeply bound states have not been investigated. Therefore, we plan to systematically measure the physical quantities of the deeply bound states by means of a (p, pN) reaction. The experiment will be performed, using the SAMURAI spectrometer, at RIKEN-RIBF.

 In this project, we first performed a simulation using GEANT4 and optimized the experimental conditions. Then, based on the results, we developed following equipment necessary for the experiment. The first is a uniform 5-mm-thick solid hydrogen target. We constructed a cryostat and made a solid hydrogen target. The second is two large NaI (Tl) calorimeters which are used to measure total energy of recoil protons. We evaluated performance of the manufactured detector. The third is 64 plastic scintillator bars to measure time of flight of knockout nucleons. We studied stability of the PMT gain under the leakage magnetic field from the SAMURAI magnet.

 In this talk, I will describe the outline of the experimental setup and the details of the development.   

Can spatial distributions of deeply bound nucleons in unstable nuclei be determined by a (p,pN) reaction?

 Unique phenomena such as neutron halos, which are not found in stable nuclei, have been discovered in nuclei far from stability, especially neutron excess. Weakly bound states, which are the cause of these phenomena, have been studied in various ways, but deeply bound states remain unexplored. Therefore, in order to obtain systematic information on proton single-particle orbitals of carbon isotopes, especially deeply bound 1s_1/2 orbitals, experiments of ^9-16C(p,2p) knockout reactions were performed at HIMAC, National Institute of Radiological Sciences. In the previous study, the 1s_1/2 orbitals were selected by identifying residual nuclei. The radius of the 1s_1/2 orbit was then obtained by Fourier transform of the momentum distribution.

 In this study, we discuss methods for extracting the size of the 1s_1/2 orbital from the measured momentum distribution. For example, in case of stable nuclei, the multipole decomposition is used to discriminate orbits. We verify whether the technique can be applied to the momentum distribution, and discuss the difference between the obtained radius and the values in the previous study. In this presentation, the results will be discussed.   

Evaluation for $¥gamma$-ray detection efficiency with an activated Tantalum for the half-life measurement of $¥mathrm{^{180m}}$Ta decay

An nuclear isomer, $¥mathrm{^{180m}}$Ta is the rarest isotopes, and the finite half-life has not been measured. The latest result gives a lower limit of $1.5 ¥times 10^{19}$ years.

We measured the half-life of $¥beta^{-}$ decay and electron capture of $¥mathrm{^{180m}}$Ta by analyzing the $¥gamma$-ray energy spectra observed with a ultra-low background(BG) HPGe detector installed in the Kamioka Underground Laboratory.To estimate the half-life of $¥mathrm{^{180m}}$Ta decay from the number of $¥gamma$-ray events, we estimated the $¥gamma$-ray detection efficiency of Ge detector. 

We measured the $¥gamma$-ray energy (93 keV - 351 keV) from the daughter nuclear.We evaluated the detection efficiency at low energies by covering the entire Ge detector with an activated sample of Ta.We used $^{252}$Cf neutron source to activate the Ta sample. Fast neutrons emitted from $¥mathrm{^{252}}$Cf was thermalized with polyethylene moderator and captured by $^{181}$Ta (99.998¥% in natural Ta). By using activated Ta, a uniformly $¥mathrm{^{182}}$Ta which is identical to decaying $¥mathrm{^{180m}}$Ta in natural Ta sample can be produced. The detection efficiency is evaluated by focusing on $¥gamma$-rays with energies of 100.1 keV, 152.4 keV, 222.1 keV, etc. emitted by $^{¥mathrm{182}}$Ta. We will present he results of the evaluation of the detection efficiency.   

Gamma-rays detection efficiency evaluation of low background HPGe detector for the half-life measurement of $^{180m}$Ta

The nuclide $^{180m}$Ta is considered to be the longest lived nuclear isomer. It undergoes decay processes such as beta decay, electron capture, and deexcitation, but its half-life has not yet been measured. The latest lower limit of the half-life is $ imes$ 10$^{19}$ years. Using an ultra-low background HPGe detector installed in the Kamioka Underground Laboratory, $gamma$-ray emitted from $^{180m}$Ta decay was measured by placing natural Tantalum sample(850 g) for about 500 days. In this research, we evaluated the $gamma$-ray detection efficiency of the HPGe detector to determine the half-life from the $gamma$-ray counts, and reproduced the detection efficiency by Monte Carlo simulation (MC).

It is particularly important to evaluate the detection efficiency in the energy range of 93 keV to 351 keV, where the $gamma$-ray energy from $^{180m}$Ta decay is observed. Detection efficiencies are measured for 81 keV-- 356 keV using $^{133}$Ba calibration source. The Ta sample was placed to cover the entire HPGe detector. Since the detection efficiency of such low energy $gamma$-ray has position dependence, measurements were taken at the head and sides of the HPGe detector irradiating a collimated $gamma$-ray source of ¹³³Ba in 2mm steps. The obtained results of the position dependence of $gamma$-ray detection efficiency and the reproduction by MC will be presented.   

Production of Activated $^{182}$Ta for the Half-life Measurement of $^{180m}$Ta Decay

Among various nuclear isomers, $^{180m}$Ta is considered to have a

long half-life but it half-life has not been measured. The current

lower limit of the half-life is 1.5 $¥times$ 10$^{19}$ years. Using an ultra-low

background HPGe detector installed in the Kamioka Underground Laboratory,

we measured a natural Tantalum sample (850g) for about 500 days.

The $¥gamma$-rays energy spectrum was analyzed to measure the half-lives of $¥beta$-decay

and electron capture of $^{180m}$Ta. In order to obtain reliable half-life from

the number of observed events, it is necessary to precisely evaluate

the detection efficiency for each $¥gamma$-ray energy. In this study, we experimentally

evaluated the detection efficiency using $¥gamma$-rays emitted from the

$¥beta$-decay of $^{182}$Ta.

A natural Ta sample, which is an identical sample with that of half-life measurement,

was activated by

thermal neutron capture reaction (182Ta sample).

To increase the activity of the 182Ta calibration sample, the neutron emitted

from $^{252}$Cf source was efficiently thermalized in the 10cm thick polyethylene,

and reflected with 20cm thick graphite.

To obtain the accurate efficiency, the uniform activity of 182Ta

sample was required. The specimens were also placed with the 182Ta

sample to investigate the uniformity of activation.

The obtained activity and uniformity of 182Ta sample will be presented.

The accuracy of the $¥gamma$-ray efficiency obtained using the 182Ta sample will be also discussed.   

Half-life measurement of $^{180m}$Ta decay with ulta-low background HPGe detector at Kamioka Underground Laboratory

 Among various nuclear isomers, $^{180m}$Ta is a nuclide with a long lifetime that its decay has not been detected. The main decay processes are considered to be $eta^{-}$ decay and the electron capture (EC). The most stringent half-life limit for $^{180m}$Ta decays is $1.5 imes 10^{19}$ years. In this research, we analyzed the data measured for about 500 days using an ultra-low background(BG) HPGe semiconductor detector installed in the Kamioka Underground Laboratory, with a natural Ta sample placed. The half-life of $^{180m}$Ta was evaluated by identifying $gamma$-rays emitted from the excited states of $^{180}$W ($eta^{-}$ decay) and $^{180}$Hf (EC).

 The search for rare decay events[s6]  of $^{180m}$Ta requires a long-term measurement, for which the detector gain often changes. The gain changes deteriorate the detector energy resolution. To overcome this problem, a constant pulse height artificial signal with 1Hz was fed into the pre-amplifier of the HPGe detector during the measurement to make correction of the gain variation.

 We also tried to separate environmental BG $gamma$-rays from $gamma$-rays emitted by $^{180m}$ Ta decays by analyzing the waveform.

 The obtained energy spectrum and the sensitivity of the $^{180m}$Ta half-life measurement will be presented.   

Measurement of alpha elastic scattering on 104,106,108Pd at Eα=386 MeV

We conducted measurements of elastic and inelastic scattering of 386 MeV alpha particles off the ^104,106,108Pd isotopes to investigate the isoscalar giant monopole resonance. The experiment was carried out at the Research Center for Nuclear Physics, Osaka University. The alpha particles were accelerated to 386 MeV using the AVF cyclotron and the ring cyclotron and bombarded on the target in the scattering chamber. The scattered alpha particles were analyzed using the high-resolution magnetic spectrometer Grand Raiden, and subsequently detected by multi-wire drift chambers and two plastic scintillators.

We plan to analyze the obtained differential scattering cross-sections using the distorted-wave Born approximation calculations to examine the giant resonances in palladium isotopes. For this analysis, we need the optical-model potential for the elastic scattering between the incident alpha particle and target nuclei. To obtain this optical-model potential, we used the single-folding model where the effective interaction between the alpha particle and nucleons in palladium nuclei was convoluted with the nucleon density distribution calculated by the relativistic mean-field theory. We optimized the parameters of the effective interaction to reproduce the measured cross section for the elastic alpha scattering from each palladium isotope. The resulting effective interactions were then compared among the palladium isotopes.   

Test of quantum effect on elastic-scattering cross section of identical particles

In quantum mechanics, wave functions for identical bosons or fermions must be symmetrized or anti-symmetrized, respectively. This fundamental principle causes deviations in the cross sections of scatterings between identical particles from those of the Rutherford scattering. These deviations occur due to the interference between the direct and exchange terms in their scattering amplitudes. In order to confirm this quantum effect on identical particles, we measured scattering cross sections in different configurations: between identical particles or between different particles.

The measurement was conducted at the tandem accelerator facility in Kobe University. ¹²C and ¹³C beams accelerated up to 4.8 MeV or 6.0 MeV were injected to a ¹²C target. A proton beam at 2.8 MeV was also injected to an aramid film as a proton target. The scattered particles were detected by a Si detector at θ=16—60°, and the beam current was monitored by a hand-made Faraday cup. 

Whereas the angular distribution of the cross section for the ¹²C-¹³C scattering agreed with that of the Rutherford scattering, that of the ¹²C-¹²C scattering exhibited a prominent oscillation pattern due to the quantum effect on identical particles. However, the similar oscillation pattern was not observed in the proton-proton scattering due to its small Sommerfeld parameter despite being a scattering process between identical particles.   

It's Wrong But How Wrong? Studying The Effects of Assumptions About Cross Sections in Experiments and Theory.

To understand stellar nuclear reactions, we need to know the likelihood of interaction for different colliding systems at different energies in MeV. Experiments are conducted to recreate these reactions and for many important reactions, one of the reactants is unstable and the beam intensity which can be provided for these cases is often too low to measure the cross sections of interest. One approach often used is to measure at higher energies where the cross section is higher and to use statistical models to extrapolate the important energies. However, these statistical models make a number of approximations, most importantly they often do not include resonance behavior which are observed in many experiments and many modern experiments using gas targets have poor energy resolution and do not observe the strong resonance structures which can exist. The purpose of this project is to investigate what systematic uncertainties result from these experimental and theoretical assumptions. To do this, a program is being built using C++ and Python to simulate these reactions numerically with and without the model assumptions, allowing us to make the comparisons necessary to estimate the extent of the systematic uncertainty.   

Radioactive Stacked Foil Analysis for Nuclear Cross-sections

A very innovative method for cancer treatment is emerging, known as targeted alpha therapy (TAT). The goal is to target alpha-emitting radionuclides to cancerous tumors without injuring healthy tissue, using targeting vectors. One potential isotope to target carcinogen tumors is terbium-149. This isotope is of particular interest due to its unique property of having both beta (83.3%) and alpha decay (16.7%).

This project aims to discover what other isotopes were created during the production of terbium-149 which consisted of a beam of lithium-6 on a natural samarium target at different energies. Some predictions can be made by looking at the chart of nuclides and focusing on the isotopes’ half-lives, stabilities, and properties. After a single night of beam, the foils were counted a day after irradiation, using three high-purity germanium (HPGe) detectors. Background, natural samarium foils (with thicknesses of 100 and 250 micrometers), europium-152 source, and gold foils (with a thickness of 5 micrometers) data was collected on the HPGes. To analyze these spectra, the python toolkit called Curie was used to simplify the identification and fitting of the peaks. After calibrating the spectra using the europium-152 source in Curie, the resulting isotopes can be identified. With this data we can conclude that the isotope production of terbium-149 via this method may be possible, but more measurements will need to be performed to confirm the optimal production pathway.

The project focus on one single night of data collected. Three detectors were used. The data was gathered a day after the reaction occurred. Each detector holds data files of background (when no beam or target are involved), natural Samarium with a thickness of 100 and 250 micrometers (Which may include different stable isotopes), Europium-152 (Used as calibration energy source), and Gold with a thickness of 5 micrometers (used as target). Giving us an approximate total of 700 runs.   

Developing and Investigating the Response of an SRAM Dosimeter for Use in Radiation Effects Facilities

The Texas A&M University Cyclotron Institute’s Radiation Effects Facility (REF) provides researchers with heavy ion beams to test their electronics for use in terrestrial and aerospace applications. Reliable dosimetry is currently provided at the REF through the use of scintillator detectors, but a more mobile option would be beneficial to users at the REF and other facilities to verify their beams. A mobile dosimeter system using the response of an SRAM chip demonstrates total error cross section and multiplicity dependencies on linear energy transfer (LET), allowing for two distinct ways of characterizing the incident beam. In this project, improvements to the original dosimeter printed circuit board (PCB) were implemented, including a new mounting solution for quicker set-up, a reduction of electronic signal noise, and the ability to easily switch out the SRAM under test. The response of the redesigned dosimeter was tested using undegraded 40 MeV/u ⁷⁸Kr ions, which were also degraded to lower energies to obtain a series of LETs, to confirm its LET-dependent response. Part-to-part variation was also investigated by exposing multiple SRAM chips to the beam.   

Measurement of Beam Intensity for Cross Section Measurement Normalization

Determination of beam intensity plays a major role in the normalization of cross section measurements, which are vital in nuclear structure and nuclear astrophysics. By developing a technique to measure beam intensity in cases where Faraday cups cannot be used, this work will improve cross section measurements with MARS (Momentum Achromat Recoil Separator), where most measurements are made close to 0°. In addition to beam intensity determination, this setup will also be used in future experiments with reaccelerated beams at the Texas A&M Cyclotron Institute. In this work, the elastic scattering resulting from the collision of a ⁴⁰Ar beam of 15 MeV/nucleon onto a ¹⁹⁷Au target of thickness 0.1 mg/cm² was measured. This was done by setting up a detector mount with specified angles inside the target chamber of the MARS. Silicon and diamond detectors were positioned at various angles to measure particles’ elastic scattering, while utilizing a Faraday cup positioned at 0° to normalize the measurements made by the detectors. By measuring the ⁴⁰Ar at fixed angles, a comparison of the yield measured to charge collected on the FC can be made, providing a needed normalization for cross section measurements. The analysis was done using ROOT, and the experimental cross section is compared to the Rutherford scattering model. The measured differential cross section showed some enhancement versus the Rutherford differential cross section.

 

Key words: beam intensity, cross section, diamond detector, Faraday cup, silicon detector.   

Indirect study of the 7Be(α,γ)11C reaction

The chemical evolution of Carbon-12 in nature is of great interest due to the importance of this element in the formation of organic compounds. The production of carbon-12 occurs naturally in low metallicity stars through the so-called Hot P-P chain. This process is described by the chain ⁷Be(α, γ)¹¹C(p, γ)¹²N(β,v)¹²C. However, the reaction rates for this process remain uncertain. In particular, the first reaction of the chain has significant uncertainties at the lowest energies due to the presence of the subthreshold resonance in ¹¹C (3/2⁺ state at 7.5 MeV) which dominates the α-capture at energies below a few hundred keV. One way to constrain this reaction rate is to apply an indirect method and populate the subthreshold state in ¹¹C using the ⁷Be(⁶Li, d)¹¹C α-transfer reaction. We developed a new high-efficiency experimental setup that allows low-energy measurements of the α-transfer reactions to sub-threshold states. This is done using an efficient γ array and a silicon detector placed at zero degrees on the beam axis after the ⁶Li which is thick enough to absorb the ⁷Be beam, but still thin enough to allow for transmission of deuteron recoils. Deuterons are measured in coincidence with the γ-rays (7.5 MeV in this case). The cross-section for the α-transfer reaction measured this way will then be used to determine the α-asymptotic normalization coefficient of the 3/2⁺ state at 7.5 MeV in ¹¹C, constraining the ⁷Be(⁶Li, d)¹¹C reaction cross section at the lowest energies. The presented project discusses the Monte Carlo simulations being developed to study the feasibility of the proposed technique.   

Investigating new analysis methods for neutron multiplicity identification

Neutron detectors are important to accurately determine the number of free neutrons emitted from nuclear collisions. The Texas A&M 4π neutron ball can observe and detect neutrons from in-beam experiments in a large geometric range of neutrons. Several examples of the importance of this capability are characterizing the violence of a collision or tracking the NZ equilibration during a collision. For much of its 30-year history, the neutron ball utilized analog electronics which limited the detection capabilities because of the inherently simple assumptions for determining neutron multiplicities that were implicit as a result. Recently, the neutron ball scintillator fluid was replaced, and the electronics were upgraded to employ waveform digitizers to read the photomultiplier tubes. Studying the waveforms presents an opportunity to better understand the performance of the neutron ball and potentially identify neutrons that were previously unaccounted for. The resulting capture time and probability distributions from the study of these waveforms will be shown.   

Probing Neutrinoless Double Beta Decay: A Search For Correlations With Sub-Barrier Multi-Nucleon Transfer

This work analyzes sub-barrier nucleon transfer during heavy ion elastic scattering events and compares them to ββ^+/- decays. It

is postulated that correlations can be found between the transforming nucleon and nucleon transfer using a classical form of the

Hartree Fock method (neck model). Data taken from the Nuclear Data Services (NDS) is used to derive information from β^+/- to

calculate the nuclear matrix element for each decay. By calculating the Q of the decay by means of the Weizsacker Formulation and

comparing to the nuclear matrix element determination of ββ^+/- will be revealed and cross sections for each are calculated. Using

the neck model the cross sections for heavy ion elastic scattering events are calculated, and correlations within the cross sections

between the two may be found.   

Exploring the Maximum Ion Rate Through TAMUTRAP’s RFQ

Radio-frequency quadrupoles (RFQs) are crucial in cooling, bunching, and focusing continuous beams of charged particles by utilizing alternating radio-frequency (RF) electric fields. The larger objective of this research is to develop an RFQ that produces bunches of 10^6 ions for the He6CRES (Cyclotron Radiation Emission Spectroscopy) experiment at the University of Washington. With their focus on accurately measuring beta-decay spectra, the higher ion bunching rate aims to significantly reduce the runtime required for sufficient data collection, which calculations previously expected to take over a year of continuous operation. A successful upgrade of the RFQ will enable the incorporation of a Penning trap in the CRES experiment, which would address dominant sources of systematic uncertainty in the measurement, greatly improving the sensitivity to physics beyond the standard model. 

In this specific project, my primary focus was to measure and optimize the efficiency of the RFQ as we increased the source intensity. To achieve this, we manipulated electrode values within the beamline to determine the maximum ion intensity before space-charge effects overload the system. For our analysis, we installed Micro-Channel Plates (MCPs) before and after the RFQ utilizing high-resolution imaging and timing techniques to assess efficiency. However, we encountered some challenges with the RFQ that prevented us from directly measuring its efficiency. As a result, this poster will detail how we characterized the initial beam from an offline ion source. Specifically, we focused on identifying the optimal settings for a stable source and compared the obtained beam size with Simion calculations using the MCP before the RFQ. Moving forward, the subsequent steps of this research focus on studying the effects of bunching and examining the relationship between efficiency and intensity.   

A T-Matrix Approach to Charmonium Bound and Scattering States

This poster will give an overview of the temperature evolution of the charmonium particle in the Quark-Gluon Plasma (QGP). This evaluation was done through the use of a Transition (T-) Matrix in the S wave channel incorporating a two particle propagator and a momentum dependent interacting potential. The temperature dependence manifests itself in the potential coupling constant, single particle effective mass, and the single particle self-energy. The T-Matrix aptly demonstrates the in medium effects on the bound state, namely where it occurs and the dissolution into the continuum at high temperatures. The T-Matrix is then further applied to calculate the charmonium Spectral Function and Euclidean Time Correlator with a zero energy mode contribution. By normalizing the Euclidean Time Correlator with a reference function, the sensitivity of the bound and scattering states to temperature is demonstrated. Finally, the effects of the zero energy mode contribution to the charmonium particle is explored.   

Design of output electronics for a Multi-Wire Proportional Counter (MWPC) detector system

The TRIUMF Neutral Atom Trap for Beta Decay (TRINAT) facility seeks to measure properties of nuclear beta decays in order to test the predictions of the Standard Model at low energies. One type of detector which may be used in the TRINAT facility is the Multi-Wire Proportional Chamber (MWPC). To obtain particle position information from the wires of the MWPC detectors, a system of passive delay lines is used in our design, allowing the time-based differentiation of signals from many detector wires using only two output channels. Examining the pre-amplifier PCBs previously obtained for this application, a feedback loop was observed in the circuit. To replace the PCB pre-amplifiers, a bipolar transistor pre-amplifier design employing a cascode topology for the input/gain stage with capacitive feedback from a DC-coupled voltage buffer output stage was designed and built. Results of our pre-amplifier design are listed.   

Gap Uniformity Characterization of MicroMegas Detector

A Micromegas (Micro-MEsh GAseous Structures) is a novel, highly segmented gas-gain detector often used in Time Projection Chambers (TPCs). At the Cyclotron Institute, Texas A&M University, Micromegas are utilized in active target detectors TexAT and TeBAT, which are used for experiments with rare isotope beams to study the structure of exotic nuclei and nuclear astrophysics measurements. A facility is being developed to perform automated tests of Micromegas detectors to produce a gain map across the large area of the detector to improve energy resolution, which is essential for particle identification. Both the data taking and the analysis are completely automated using and controlled by the Python scripts and C++ ROOT6 Code. This allows for an efficient, accurate, and highly reproducible gain map to be constructed. Note that the map is unique for each realization of the Micromegas, even if they are built using identical blueprints. These maps will be applied to the future experimental data obtained with TexAT and TeBAT active target detectors.   

Second Round Results from Testing the Importance of Radiation Detectors

Recently, it has been proposed that SONOS (Silicon Oxide Nitrogen Oxide Silicon) chips, which are generally commercially available, might have the potential to be used for radiation detection. If true, these devices may have relevance to various applications, including dosimeters, satellites, and military checkpoints, where such detection systems are necessary. When a heavy ion passes through one of these chips, the voltage across certain sites within that chip changes and can be measured. By systematically investigating this voltage change an enhanced understanding of the behavior of these chips can be achieved. An experiment was run where a ⁷⁸Kr beam of energies 40 and 36 MeV/u was directly applied to the chips and the voltage before and after exposure were compared. These results will be shown in comparison with previously acquired data using ⁴He and ¹⁴N beams. Other systematic behaviors of these chips will also be demonstrated.   

β decay strength function for 53, 55Ni and 52, 54Co

Proton-rich nuclei in the universe are created by rp-process and the νp-process. This work deals with four nuclei relevant to the nucleosynthesis of the p-nuclei: ^52,54Co and ^53,55Ni.  β+ decays for each isotope were recorded with the Summing NaI(Tl) detector¹ at the National Superconducting Cyclotron Laboratory.  A preliminary β+ decay intensity function, Iβ+, was found for each isotope by utilizing Total Absorption Spectroscopy (TAS). A variety of experimental spectra (e.g TAS, Sum of Segments, Multiplicity, and pixelated surface barrier detector) were compared to GEANT4 simulations of the full detector setup based on information from the National Nuclear Data Center. An important feature in the measurement of ⁵³Ni is that protons from a β delayed proton decay were detected in the pixelated surface barrier detector and gave information on the strength to proton-unbound states. The measured spectra, when fitted with the simulated spectra, give the probability that a particular child level is populated during decay. Results, when compared to shell-model theory, will provide insight and help to improve the understanding of the formation of p-process elements.

1. Simon et. al Nucl. Instr. and Meth. A703, 16 (2013)   

Characterization and Testing of SiPMs for a Next-Generation Neutron Detector

MoNA-LISA is a position-sensitive neutron detector at the Facility for Rare Isotope Beams (FRIB) used to probe neutron-unbound states through invariant-mass spectroscopy. Position resolution of the neutron detector is a key factor in invariant-mass measurements. A better neutron position would significantly improve the overall reconstructed decay energy resolution and would therefore lead to a better understanding of nuclei near and beyond the dripline. The MoNA collaboration is designing a next-generation neutron detector to improve the current MoNA-LISA resolution (~5cm). The new design will replace the PMTs for SiPM arrays as readout technology. The use of SiPMs (more compact) for neutron detection is being tested within the Collaboration and its performance characterized with a simple detector made up of a circuit board with SiPM sensors coupled to a plastic scintillator. The response of each SiPM has been studied (breakdown voltage and dark current count rate). As position sensitivity is a main requirement for the planned next-generation neutron detector, a multitude of tests with cosmic rays and collimated gamma sources, such as 60Co and 65Zn, have been performed as well to evaluate the new design's position resolution. Along with these tests, algorithms have been developed to reconstruct the interaction point based on the light collected by the SiPMs. Preliminary results of these ongoing tests will be presented.   

11B states above the α-decay threshold via 10B(d,p)11B

Interest in the resonance region surrounding ¹¹B has increased due to discrepancies in branching ratio calculations of β-  delayed proton emission, a rare type of decay mode. Theoretical calculations predicted a significantly smaller ratio than observed in a recent experiment. However, the discovery of an 11.4 MeV state just above the proton threshold in ¹¹B through two recent experiments may explain the disagreement between theory and experiment. 

To further study this region of interest, a neutron transfer reaction was performed using Florida State’s tandem Van de Graaff accelerator and Super Enge Split-pole Spectrometer. At least 6 states above the alpha-decay threshold of ¹¹B were observed. A strongly populated state at 11.25(1) MeV with a width of 108(12) keV was observed, and angular distributions were measured for the first time. DWBA calculations were performed to extract the spectroscopic factors for four of these states. The previously observed 11.4 MeV state was not observed. However, this is consistent with the fact that this state has a strong proton component, so we are unlikely to observe it in a neutron transfer reaction.     

Identifying excited states in 35S via 34S(d,pγ)

An experiment was conducted at FSU’s John D. Fox Accelerator Laboratory to improve the systematics of the sparsely researched ³⁵S. The goal is to contribute to understanding the systematics of the l = 1 and l = 3 splittings for N = 19 isotones, and help explain the sudden changes to the nuclei such as ³⁴Si claimed to have a proton bubble. A 16 MeV deuteron beam was directed toward a ³⁴S target using a tandem accelerator. This neutron transfer reaction was performed using the Super-Enge Split-Pole Spectrograph with an interior focal plane detector located at 37 degrees. Seven CeBr₃ PMT detectors surrounded the reaction target. Using the positions of the protons observed by the focal plane detector, we determined energies of excited states. ³⁵S states (1.99, 2.34, 4.903, and 4.963 keV) were identified and confirmed by gamma ray coincidences. Furthermore, we determined the lifetime of the 1.99 MeV state in ³⁵S using the time-difference between CeBr₃ gamma ray detectors and protons detected in the Super-Enge Split-Pole Spectrograph. Preliminary results will be presented.   

Point cloud-based regression models for the Active-Target Time Projection Chamber

The Active-Target Time Projection Chamber (AT-TPC) is a detector system that produces high resolution, 3D “images” of low energy nuclear reactions. In traditional analyses of data produced in the AT-TPC, extracting kinematic information from this data is time consuming. We propose the use of a point-cloud based deep learning architecture, PointNet, to accomplish this task quickly with equivalent accuracy to the traditional methods. For this work, we focused on predicting the energy loss of reaction products of a simulated ²²Mg + α experiment at the Facility for Rare Isotope Beams. 

The AT-TPC records the trajectories of charged particles as they travel through the gas, losing energy in this process. We train a PointNet model to predict this energy loss for each point in each track. The architecture's shared multi-layer perceptron layers process individual points in a permutation invariant manner, while global feature aggregation captures broader characteristics of the events. The PointNet model is trained as a point-wise regression task, with the inputs being the spatial coordinates and charge amplitude recorded in the detector electronics. Performance metrics such as mean absolute error will be presented on a subset of data that was not used in training.   

Angular Distributions of High Energy Neutrons Scattered off a Plastic Scintillator

The Modular Neutron Array Collaboration ran an experiment at the Los Alamos Neutron Science Center to test the performance of neutron detectors and simulations used in experiments studying neutron-rich nuclei. The experiment consisted of a beam of 20-800 MeV neutrons colliding with a plastic scintillator target. An array of detectors was set downstream in a staircase pattern. The angles of the scattered neutrons were measured, with particular interest in neutrons that were not detected by the target detector but seen in the array. These neutrons were not detected by the target because the interaction of a neutron with a carbon nucleus in the scintillator did not produce enough light to be detected, but the products of the collision scattered into the array. Interaction with carbon is more likely than hydrogen in the scintillator, so a large amount of counts are from this interaction, but difficult to record. This is problematic in studying the decays by neutron emission as it records the wrong initial position vector for the neutron. To measure "dark scattering," scattering angles were composed from runs with the target in and out. These scattering angles were then compared with simulations using two different neutron interaction packages. Preliminary results will be presented.   

Sparse Tensor Computation for Active-Target Time Projection Chamber Data

The Active-Target Time Projection Chamber (AT-TPC) is used for imaging reactions of rare isotopes. In this project, we use data from the ¹⁶O + α experiment conducted in the AT-TPC at the Facility for Rare Isotope Beams (FRIB). The reactions in the experiment produced events with varying numbers of tracks, or reaction products. Four- and five-track events are of interest for understanding the production of carbon in stars. This project utilizes supervised deep learning to identify and select these types of events. A PointNet model implemented using the Minkowski Engine (ME) library was trained to determine multiplicity in AT-TPC events, with a focus on selecting four- and five-track events. The ME provides significant computational advantages for sparse tensor computation, omitting trivial calculations that typical networks evaluate. The ME PointNet architecture is used to train a classification model for track-counting in the ¹⁶O + α experiment. We achieved a 0.93 average F1-score for selecting events with 4 and 5 reaction products in the AT-TPC and an accuracy of 0.85 across all multiplicities.   

Rutherford scattering based detector for the MoNA Collaboration

The MoNA Collaboration has been studying neutron rich nuclei along the neutron dripline for two-decades using the MoNA-LISA-Sweeper setup at the then National Superconducting Cyclotron Laboratory and will continue to do so at the Facility for Rare Isotope Beams which started operation in the Spring 2022. A detector based on the Rutherford scattering process is being developed by the MoNA Collaboration to calibrate experiments against each other. A Geant4 Monte Carlo simulation was also built to benchmark the physics list using a recently acquired kit from Leybold and optimize the detector geometry and performances. Data from the kit were acquired during the 2023 Physicists Inspiring the Next Generation: Exploring the Nuclear Matter summer program. The preliminary results obtained with two targets (gold and aluminum) along with the design of such detector will be presented and discussed.   

Assessment of Neutron-Gamma Reactions on Barium Isotopes in Neutron-Rich Stellar Environments: A TALYS Theoretical Calculation and EXFOR Experimental Data Comparative Analysis

Nucleosynthesis in neutron-rich stellar environments is where most of the elements above iron are created. One of the processes in these environments is the intermediate neutron capture process, or i-process. Of particular interest for the i-process are neutron capture reactions on barium isotopes; some of these neutron capture rates have been experimentally measured. Here I employ the TALYS nuclear reaction code to theoretically calculate these reaction rates, allowing for a comparison with the experimental data obtained.

Here I perform a comparative analysis of experimental data from the EXFOR database, a comprehensive repository of experimental nuclear reaction data, with theoretical calculations done in TALYS. By comparing our theoretical TALYS calculations with this extensive dataset, we validate and expand our understanding of neutron-gamma reactions involving stable barium isotopes.

By comparing different theoretical models in our TALYS calculations to experimental data, we hope to illuminate which theoretical models are most accurate and which will be best to use in the calculation of reaction rates that have not yet been measured. This study provides valuable insights into the fundamental processes occurring in stellar environments as well as trends in the nuclear theory used to model these stellar environments.   

The Optimal Intrinsic Parameters for Low Light Detection in silicon photomultipliers(SiPM

Over the past century, photon detectors have played an increasingly important role in radiation detection in medical diagnostics and nuclear physics research. Since the 1930s, we have used photomultiplier tubes (PMT) that have been pivotal in obtaining scientific knowledge. However, the PMT, with its bulky design, sensitivity to magnetic fields, and high operating bias voltage of 1-2 kV limits their viability when quantifying and or time stamping light signals are important (high energy physics,biophotonics,and LiDAR). The silicon photomultiplier (SiPM) has recently become a valid alternative for many applications requiring photodetection. SiPMs are less expensive and require a much lower bias voltage than PMTs. When detecting scintillation light (photons emitted when a scintillator absorbs energetic radiation, for our purposes from scattered neutrons), SiPMs allow for more freedom to arrange the sensors in optimal locations to maximize the detection of light around the scintillator. The added flexibility that SiPMs bring to designing neutron detectors will allow us to make higher resolution measurements of nuclear decays that will allow us to further study the nuclear structure of unstable isotopes that exist in neutron stars. With the use of a multichannel analyzer (MCA) and an analog to digital converter (ADC) the breakdown voltage and dark count rate will be found for a wide variety of SiPM types.   

Searching for an Octupole Rotational Band in 71Ga

Recently, a rotational band with static octupole deformation (pearlike shapes) was observed in ⁷¹Ge, the first odd-mass isotope in the mass A ≈ 70 region to show evidence of this behavior. Systematic experimental and theoretical studies of nuclei in this region indicate that octupole deformation might be enhanced for isotopes with N = 40. The goal of this work was thus to search for an octupole rotational band in the N = 40 isotope of gallium (⁷¹Ga) while enhancing the existing level scheme. A ⁶²Ni (¹⁴C, αp) reaction at 50 MeV was performed at Florida State University to populate high-spin states in ⁷¹Ga, and their decays were measured in coincidence using a Compton suppressed array of Ge detectors, including 3 Clover detectors and 7 single-crystal detectors. Using gating to filter out isotopes more strongly produced in this reaction, recently observed transitions and their placement within the level scheme were confirmed, and their intensities were measured. No conclusive evidence was found for a possible octupole rotational band, however. Cranked shell model calculations were performed to make a systematic comparison of the kinematic moments of inertia in the lowest positive- and negative-parity bands across a range of odd-A Ga isotopes, which all show very similar behavior for A > 67.  The aligned angular momentum for these isotopes behave similarly as well. Total Routhian surface (TRS) calculations show a competition between single-particle and collective behavior as angular frequency increases.   

Quenching of the Octupole Rotational Band in 71Ge

Static octupole deformation, having pearlike shapes, has been observed in several even-even nuclei in the mass A ≈ 70 region (⁷⁴Se, ⁷⁶Kr, ⁷⁸Kr, and ⁸²Sr).  Recently, experimental evidence for an octupole rotational band was observed for the first time in an odd-A isotope (⁷¹Ge). However, only very limited experimental information about this band is currently available. The goal of this study was to enhance the knowledge of the properties of this band and to investigate whether the band persists to even higher spin. An experiment at Florida State University using the ⁶²Ni (¹⁴C, αn) reaction at 50 MeV was used to produce ⁷¹Ge at high spin. An array of 10 Compton-suppressed Ge detectors, consisting of 3 Clover detectors and 7 single-crystal detectors, was used to measure the gamma decays in coincidence. An analysis of the resulting coincidence spectra resulted in the placement of six additional transitions in the ⁷¹Ge level scheme, one of which (1092 keV) extends the octupole band to a (35/2^-) state at 8208 keV. Calculations of the kinematic moment of inertia and aligned angular momentum for the octupole band show that the 1092-keV transition disrupts the smooth rotational pattern and may point to a band crossing, potentially quenching the octupole deformation. Comparisons between the octupole band in ⁷¹Ge and those of other neighboring even-even nuclei show similar behaviors.      

Preliminary Results in the Development of 14C AMS at the University of Notre Dame's Nuclear Science Laboratory

Accelerator Mass Spectrometry (AMS) has proven the most sensitive method of measuring the amount of 14C present in a material for the purpose of radiocarbon dating. The AMS group at the University of Notre Dame’s Nuclear Science Laboratory has graphitized and dated both a sample believed to be sourced from the shipwreck of Le Griffon and an insect living in the depletion zone of the Alaskan glaciers provided by collaboration with the University of Notre Dame Department of Biology. Preliminary results of the former show a radiocarbon age of 1105±641 years, while preliminary results from the latter show a radiocarbon age of 6738±1290 years. Since Le Griffon sank in 1679, further study is required to determine the sample's source.

To achieve these results, each sample was measured in sets of four consecutive fifteen-minute trials along with 14C standards and blanks to calibrate the resultant counts. OxCal software was used to determine the age range of the sample from the calculated 14C/12C ratio.

The wide error margins are due to inconsistent count rates of 14C between trials. For a discussion of developments in measurement precision and capability, see Griffin Mulcahy’s CEU abstract, Carbon Dating for Interdisciplinary Research and Teaching: Developing 14C AMS at Notre Dame. The first results of these experiments will be presented at the CEU poster session and will include recent developments.   

Proton-Emission Resonance Levels in 11B

A narrow near-threshold proton resonance in 11B was proposed near E_x=11.44 MeV to explain the branching ratio discrepancy of 11Be→10Be. The proton resonance was thought to enhance the beta-delayed proton emission in 11Be and leads to a larger than expected decay branch to 10Be. The reaction 7Li(alpha,p)10Be was performed using the FN accelerator at ISNAP in the University of Notre Dame to search for the resonance. A range of energies were tested with a focus on the hypothetical excitation value. After the conclusion of the experiment and analysis of the data, there seems to be no resonance level at the indicated value nor any other unknown resonance in the aforementioned energy range though there were unreported triton decays found at higher energies. A more thorough study of the alpha angular distribution or an approach that would detect a proton resonance width only would be of benefit to this decay. Otherwise, the 11Be→10Be decay would require some form of exotic decay to explain it and with it comes the potential for new physics.   

Complete Analysis of 19F Energy Levels in 2021 Experiment of 15N(α, γ)19F Reaction

Following on to a preliminary analysis of 15N(α, γ)19F performed in 2021, a more complete analysis was required. Studying fluorine-19 provides deeper understanding to its mirror nucleus, neon-19, and gives understanding to novae nucleosytnesis as a result. The analysis of the experiment to confirm the initial conclusions made about fluorine-19 from 2021 was completed. This analysis looked at the previously completed experiment in detail to prove the accuracy in the 2021 early conclusions. We found positive correlations between the gamma rays in the experiment and where we expected to see them, thus confirming the work from O'Donnell. The further completeness of the energy levels in fluorine-19 will allow for future conclusions to be made about its mirror nucleus neon-19 which impact estimates of 18F synthesis in novae.   

Resolution Testing of the Notre Dame Enge Split-Pole Spectrograph Focal Plane Detector

Study of nuclear structure for astrophysics demands high precision to indirectly determine certain nuclear reaction rates, because uncertain measurements cause imprecise calculations of these reaction rates. Notre Dame has acquired an Enge split-pole spectrograph which can be used to precisely measure nuclear level energies by magnetically separating and focusing particles onto the focal plane detector based on their momentum. This high-precision spectrometer provides a means to ascertain astrophysical reaction rates, providing a deeper understanding of nuclear processes in astrophysical environments. To full harness this machine's capabilities, the current commissioning phase is focused on ensuring precise position measurements from the focal plane detector which requires determining inherent resolution of the electronics by analyzing histograms of pulser data. Future tests include using a collimated alpha source to provide a more realistic determination of the detector's resolution. Presently, the analysis of the Notre Dame spectrograph's test results is in progress. Analysis of the pulser data and future plans will be presented.   

Carbon Dating for Interdisciplinary Research and Teaching: Developing 14C AMS at Notre Dame

The purpose of developing 14C Accelerator Mass Spectrometry (AMS) at Notre Dame is to provide carbon dating capabilities to researchers internally and to develop a program to introduce AMS techniques to graduate and undergraduate students.

The AMS Group at Notre Dame's Nuclear Science Laboratory uses an NEC MC-SNICS ion source (SNICS), FN Tandem Accelerator, and various detector systems to determine the concentration of isotopes of interest in samples. A retractable compact-IC and offset FCs were used to measure 14C counts and 12C & 13C beam currents in tandem.

Thus far, the maximum 12C current reached on the post-SNICS FC  is ~4.3 microamps, the maximum transmission of 12C through the system is ~3.16%, and the average background ratio of 14C/12C is ~2.4x10^-14. Short-term objectives of the 14C project include achieving: 8 microamps of 12C beam current on the post-SNICS FC, a consistent transmission rate of 5%, and a reduction of 14C/12C background to ~5x1o^-15.

For a discussion of preliminary results from these experiments see William Peeler’s CEU abstract, Preliminary Results in the Development of 14C AMS at the University of Notre Dame's Nuclear Science Laboratory. The first results of these experiments and any more recent developments will be presented at the CEU poster session.

This work is supported by the National Science Foundation grant award number NSF PHY-2011890   

Improving St. George Through Pressure Regulation of the HIPPO Gas Jet Target

The St. George recoil separator at the University of Notre Dame’s Nuclear Science laboratory is employed with the study of reactions of astrophysical interest, specifically radiative capture reactions. St. George’s High Pressure Point like gas jet target (HIPPO) is used to provide a constant diameter point-like target to the system. The thickness of the target observed by the beam depends on the injection pressure applied to the nozzle of HIPPO. Improvement to the pressure regulation of HIPPO has been studied and conclusions regarding the possible significant improvement of thickness stability of the gas target have been reached. Furthermore, recommendations regarding the permanent implementation of a more robust mass flow system and the possible benefits of implementing such a system are discussed.   

Improved characterization of the structure of 16O above the proton separation energy

The level structure of the ¹⁶O compound system is of particular interest for reactions that determine energy production and nucleosynthesis during the early burning stages in massive stars. During hydrogen burning, the system is populated by both the¹⁵N(p,γ)¹⁶O and ¹⁵N(p,α)¹²C reactions, whose relative cross sections determine one of the branch points in the carbon-nitrogen-oxygen cycle that is the main source of energy production. During the next stage, helium burning, the ¹²C(α,γ)¹⁶O reaction populates this same system. Uncertainty contributions for both of these reactions stem from unknown population strengths of higher energy levels, which remain relatively poorly characterized. We have therefore made a new high precision, thin-target, relative cross section study of ¹²C+α induced reactions over the laboratory α-particle energy range from 7.5 to 11.5 MeV, which extend the range of previous studies. Measurements were preformed using the 2 m scattering chamber at the University of Notre Dame Nuclear Science Laboratory at 28 unique angles between 30 and 170 degrees. Excitation functions for the α₀, α₁, and p₀ channels and preliminary R-matrix calculations will be presented.   

Calculations of charge state distributions of ions passing through the HIPPO gas jet target

We will present calculated charge state distributions of ions passing through the HIPPO helium gas jet target of St. George, a recoil separator at Notre Dame’s Nuclear Science Laboratory. The operation of St. George involves directing a heavy ion beam through HIPPO and using a series of magnets to allow alpha-capture reaction products of a selected charge state to reach the detection system and reject the much more abundant unreacted beam. Charge state efficiency, i.e. the fraction of reaction products that are in the selected charge state, plays a crucial role in the overall efficiency of St. George. To evaluate this efficiency, we use the BREIT code[1] to calculate the charge state distribution of reaction products after passing through the appropriate thickness of helium. This program uses user-supplied cross sections for electron capture and electron loss. Through a comparison between calculated and experimental charge state distributions for different thicknesses of helium gas, we are gaining insight into the accuracy of the BREIT code in predicting charge state distributions.

[1] N. Winckler et al., Nucl. Inst. & Meth. Phys. Res. B 392, 67 (2003).   

Cross Sections for Electron Loss and Capture for Ions Passing through a Helium Gas Jet Target

The St. George recoil mass separator at the University of Notre Dame uses inverse kinematics to study alpha capture reactions induced by ions passing through a helium gas jet target. It uses a series of dipole and quadrupole magnets and a Wien filter to allow ions with a selected charge state and a specific momentum to pass through to the detector. The charge state of the ion changes as it passes through the target because of electron exchanges with the target gas, and it is important to know what fraction of the ions emerging from the target are in the selected charge state. The distribution of charge states can be calculated if the cross sections for electron loss and electron capture from and by the ion are known. A number of methods for calculating these cross sections, as well as some measured electron-loss and electron-capture cross sections, are available in the literature, and we are evaluating the ability of these calculational methods to accurately predict the measured charge state distributions.   

Challenges in identifying very low-energy ions with the St. George detection system

The University of Notre Dame’s St. George recoil mass separator is used to study the process of nucleosynthesis during stellar helium burning by measuring the cross sections of alpha capture reactions.  Beams of heavy ions are directed onto a helium gas jet target, and reaction products are separated from unreacted beam particles by a series of dipole magnets and a Wien filter. The rejection of unreacted beam is not perfect, however, so it is necessary to distinguish between reaction products and unreacted beam at the end of the separator.  The St. George detection system does this by measuring the speed of detected ions with a pair of timing detectors utilizing microchannel plates and a silicon strip detector for measuring the particle’s kinetic energy.  Ions of different mass appear on different bands on a two-dimensional plot of time-of-flight (TOF) vs. Energy.  However, there are some challenges in identifying very low energy ions, where the mass bands are less well separated. This presentation will present possible explanations for an apparent discontinuity in the mass band of unreacted beam ions at very low energy, around 100 keV/nucleon. Another challenge arises when dealing with energy resolutions, this is due to the limitations of the precision with which low-energy ions can be identified. Lastly Calibrating the detection system for very low-energy ions can be challenging since there are limited well-known standards at such energies, potentially impacting the accuracy of energy measurements and the identification of specific ion species.    

Isospin Symmetry Breaking in the IMSRG and CKM Unitarity Tests

Unitarity of the quark mixing Cabibbo-Kobayashi-Maskawa (CKM) matrix provides one of the stringest tests of the Standard Model of particle physics, with violations of unitarity signaling physics beyond the Standard Model. One way to test CKM unitarity is through nuclear beta decay with so-called superallowed $0^+ o 0^+$ Fermi beta decays. Measurements of these transitions have become precise enough that the main source of uncertainty in calculations of elements of the CKM matrix, such as $V_{ud}$, stems from theoretical corrections. One such contributing correction is encoded in the term $delta_c$ which denotes corrections due to isospin symmetry breaking which are dependent on nuclear structure. Quantifying $delta_c$ can be done using nuclear structure calculations and ab initio nuclear many-body methods such as the In-Medium Renormalisation Group (IMSRG) method. We investigate and report on possible sources of error and uncertainty induced by basis truncation involving IMSRG methods and the nuclear shell model.   

Implementation of Skewed Gaussian Fitting for Phase-Imaging Ion-Cyclotron-Resonance Calculations

Atomic masses are one of the fundamental properties of atomic nuclei, and their measurement provides access to information on nuclear binding energies, nuclear states, and nuclear reaction Q-values. This has applications as varied as neutrino physics, inputs to nuclear astrophysics models, and the search for beyond-the-Standard Model physics, all of which need precise and accurate mass measurements. Hence, the Canadian Penning Trap (CPT) at Argonne National Laboratory has measured the masses of over 300 isotopes produced by the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) ²⁵²Cf spontaneous fission source using the Phase-Imaging Ion-Cyclotron- Resonance (PI-ICR) technique. However, PI-ICR data can sometimes have a tail behind the cluster of ions that can arise from many different sources such as ion-ion interactions, incomplete excitations, poorly-tuned beams, or temporal drifts in the system during the measurements. I will present results of the analysis of measurements of masses of Sn, Sb, Te, and I isotopes and isomers around A≈130, alongside my implementation of a skewed Gaussian fitting model in an attempt to improve the precision of the analysis by accounting for the tail.   

Uncovering the Mystery of Proton Mass: Muon Channel Analysis for the J/Ψ-007 Experiment

The proton is an essential building block of our existence–found in every atom in the universe–but the origins of the proton's mass are not well understood. Although the proton is composed of quarks and gluons, the masses of those particles sum to only a small fraction of the proton's total mass. The majority of the proton's mass, then, must derive from something else: the energy contained in the strong force itself. The strong force, mediated by the gluons, binds quarks and gluons together into protons. However, little is known about the behavior of these gluons and their distribution within the proton. This experiment aimed to probe the gluonic structure of the proton by measuring the near-threshold photoproduction of the J/ψ particle, which can be used to determine the gluonic gravitational form factors of the proton. J/ψ particles have about equal probability to decay into an electron or a muon pair. We analyzed the muon channel of J/ψ for the first time, complementing the electron-channel results that were recently published in Nature. By measuring the differential cross-section of J/ψ that decay into muons, we doubled the available statistics to study the proton mass structure, compared to the published results. We determined the gravitational form factors of the proton, and we concluded that the proton's mass radius is significantly smaller than its electric charge radius.   

Characterizing and controlling temperature-dependent gains of GODDESS preamplifiers via active cooling

The GODDESS detector system detects charged particles in coincidence with gamma rays emitted in beam experiments at DOE User Facilities, such as ATLAS and FRIB. These typically run over multiple weeks or months to inform on nuclear structure and to constrain nuclear reaction rates important for astrophysical processes. Therefore, gain-stability over long periods is important. A critical component in the electronics are charge-sensitive preamplifiers, which amplify the small signals from the silicon detectors. These preamplifiers generate heat, and because they have limited passive ventilation, they have previously been force-air cooled by constant fans. Because they exhibit temperature-dependent gains, and room temperature is not stable over long periods, in-situ gain drifts have been observed that degrade total resolution. To combat this, an active approach to cooling has been investigated and prototyped. This approach uses temperature sensors, microcontrollers, and motor drivers, to measure the preamplifier temperature and modulate airflow in order to compensate for external changes. Analysis of the temperature dependency of the preamplifier gain, and details of the prototype temperature readout and active-control cooling system and its performance will be presented.

Work supported in part by U.S. Department of Energy.    

Implementation of an Autoencoder Neural Network to Nuclear Reaction Kinetics

Supernovae are the most colossal and awe-inspiring events that mark the end of some stars' lives, playing a crucial role in the evolution of galaxies and the synthesis of elements essential for life as we know it. During the collapse of massive stars, the extreme conditions can induce fusion reactions, creating new atomic nuclei in a process called nucleosynthesis. The creation of heavier elements is thought to be predominantly produced by supernovae. The work here holds significance for studying both core-collapse and thermonuclear supernovae. Astrophysicists seek to unravel the complexities of supernovae nucleosynthesis through simulations that use nuclear reaction kinetics. Simulating NRK for supernovae nucleosynthesis becomes increasingly impractical as the network size grows. The primary challenge lies in accelerating these simulations to handle the expanding network size effectively. One approach to address this is the use of machine learning to reduce the time and computational demand of these simulations for real-world applications. Specifically for this work, we implement an Auto-Encoder (AE) for a reaction network in nuclear reaction kinetics using the code XNet. The AE is first trained to find a lower-dimensional representation of the data, and then it reconstructs the data using this lower-dimensional representation. The data set used to train the AE is comprised of molar abundances from a 14-species nuclear network evolved using XNet. In this work, we explore the application of AEs as a means to achieve a lower-dimensional representation of nuclear composition data within XNet, offering promising advancements in both accuracy and computational efficiency.   

Physically-Motivated Uncertainty Analysis and Simulation of Nuclear Reactions in X-ray Bursts: Insights from TALYS and CINA

X-ray bursts occur when material from a main sequence star is pulled by gravity onto the surface of a neutron star and causes a thermonuclear explosion. It is critical to understand the nuclear reactions that power these events. Theoretical predictions of nuclear reactions important in X-ray bursts and other astrophysical scenarios are critical to guide measurements but have many challenges. Identifying a range of reaction cross section uncertainties based on uncertainties of the structure of these nuclei would help focus simulations and experiments using these predictions, and are preferred over assigning arbitrary uncertainties such as a factor of 10 or 100.

We used the TALYS reaction code to predict total and partial cross sections using eight different nuclear inputs in the form of alpha-nucleus optical models. These cross section predictions were entered into the Computational Infrastructure for Nuclear Astrophysics (CINA) to simulate the nucleosynthesis occurring in an X-ray burst. In this study, we focused on the reactions ³⁴Ar(α,p)³⁷K , ²²Mg(α,p)²⁵Al, ¹⁸Ne(α,p)²¹Na, ³⁰S(α,p)³³Cl, and ²⁶Si(α,p)²⁹P. Our approach generates more realistic uncertainties in TALYS cross section predictions. Predictions that are used in CINA to estimate uncertainties in the nuclear energy generation rate in X-ray bursts and then compared to the light curves in the Multi-INstrument Burst ARchive (MINBAR). We also use the partial cross sections at multiple energies to identify trends within each predictive optical model.   

Study of the Beta decay strength of 28Ne

The modern nuclear shell model, so called configuration interaction model, describes nuclear states using a basis of simple wavefunctions in an external potential and a residual interaction between nucleons. To solve the shell-model Hamiltonian, we use a modern diagonalization code called Kshell. With it we calculate the energies of excited states and nuclear transformations such as beta-decay. This allows us to compare them to experimental data and validate the accuracy of the nuclear interaction used. This is vital to improving the interactions needed to encompass the totality of the table of nuclides. Using Kshell and the SDPF-M interaction, we calculated the beta decay strength of Ne28 to Na28. The data was then filtered to isolate the excitation energy and beta decay energy of the transition from Ne28 to Na28. The experimental spectrographs of the gamma-ray events following the beta decay of Ne28 to Na28 were investigated, noting peaks in the spectrograph corresponding to the count of gamma-ray events of a particular energy. These peaks were compared to the gamma-ray events of Ne28 to Na28 published in "β-delayed γ spectroscopy of neutron rich 27,28,29Na" by Tripathi et al, 2006. Of the 16 reported gamma-ray events, 12 were observed in the experimental data investigated.   

Validating Rivet Analyses Using MC Event Generators

Rivet (Robust Independent Validation of Experiment and Theory) is a software framework that allows for direct comparisons between experimental data and Monte Carlo event generators, like PYTHIA and Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE), in relativistic heavy ion collisions. Variations between Rivet analyses of real-world data and models can be used to determine which aspects of heavy ion collisions are described well by models and where our models need improvement. PYTHIA is a Monte Carlo event generator based on the Lund String Model, which was originally developed to describe e⁺e^- and pp collisions. It was extended to include heavy ion collisions, like AuAu and PbPb, with PYTHIA Angantyr. JETSCAPE models partonic energy loss in a hydrodynamical medium. We will show comparisons between data and these models using Rivet.   

Using Machine Learning to Improve Equations of State for Core-Collapse Supernovae and Neutron Star Mergers.

The equation of state for matter under extreme densities and temperatures is important for understanding the behavior of core-collapse supernovae and neutron star mergers. The equation of state is typically computed in tabular form for simulations. However, due to the large number of nuclear species involved, the numerical evaluation can be unstable, leading to acausal speeds of sound. We fix these tables with a machine learning algorithm called Gaussian process regression (GPR). GPR is used to correct the acausal points by interpolating over the Helmholtz free energy of nearby points that have causal speeds of sound. The rest of the entries in the EOS table can be derived from this interpolated free energy. We will demonstrate fixing a region of acausal points in the EOS table using GPR.   

Analyzing Decay Patterns of Xenon-134

The primary objective of this experiment was to measure neutron-induced backgrounds on isotopes of interest to neutrinoless double-beta (0νββ) decay observations. At Triangle Universities Nuclear Laboratory (TUNL) we can study neutron-induced backgrounds with our enriched sample of 134Xe. In this study, we focused on the 134Xe(n, 2n)133Xe interaction. We utilized germanium detectors to detect gamma rays emitted during the subsequent decay of 133Xe. The acquired data was analyzed to understand the decay patterns of 133Xe and evaluate the probability of external neutrons influencing future 0νββ-decay experiments, which involve mixtures of Xenon isotopes. Two potential decay paths were identified for the resultant 133Xe: isomeric transition with a half-life of 2.918 days and typical beta-decay to 133Cs with a half-life of 5.2475 days. By measuring specific gamma-ray counts at 233.221 keV (for isomeric transition) and 81 keV (for typical beta-decay) over time, the study aimed to establish an exponential relation between the counts and decay time, which has been observed. These known half-lives and expected gamma-ray values were employed to identify false counts and determine the cross-section of the 134Xe(n,2n)133Xe interaction for incoming neutron energies of 10.0 and 12.0 MeV.   

Measurements of the 134Xe Neutron Capture Cross-Section Between 0.43 and 5.5 MeV

In the study of rare event physics, such as neutrinoless double beta decay, it is important to understand potential background events. Neutron-induced events can take place even deep underground. Experiments that study the neutrinoless double beta decay of 136Xe use material enriched in 136Xe, but the material still contains a significant fraction of 134Xe. One neutron-induced event is neutron capture on 134Xe, which can emit gamma rays that have the potential to Compton scatter into the Q-value region of interest for 136Xe double beta decay. In this study, we investigate neutron capture on 134Xe by looking for gamma rays emitted from de-excitation from long-lived excited states of 135Xe and the subsequent decay to 135Cs. The xenon gas used was irradiated in the neutron beam at Triangle Universities Nuclear Laboratory, and the decays were counted in the low-background counting facility located in the Duke Physics building. We will report our results of the neutron capture cross section for incident neutron energies at 0.43, 0.8, 1.5, 2.0, 4.2, and 5.5 MeV.   

Simulating Self Absoption in 134 Xenon for Neutrinoless Double Beta Decay Research

An important aspect of rare event nuclear physics research such as neutrinoless double beta (0νββ) decay is filtering out background events that can lower data resolution. The search for 0νββ decay of 136Xe utilizes enriched 136Xe but still contains significant amounts of 134Xe. This poses a problem because, despite many experiments taking place in underground facilities, neutron-induced reactions can still occur in the sample and interfere with the data collected. Two background processes of interest are neutron inelastic scattering and neutron capture in 134Xe. The resultant de-excitation gamma rays from neutron inelastic scattering of 134Xe can scatter into the region of interest for 136Xe neutrinoless double beta decay. At Triangle Universities Nuclear Laboratory, we have measured neutron inelastic scattering and neutron capture on 134Xe. To fully understand the results of this experiment, we need to know the self absorption (a measure of the percentage of gamma rays that deposit energy in a sample) of the 134Xe sample. We simulated the absorption in a sample of 134Xe using Gears and Geant 4 along with the Root data analysis package to directly get the absorption number for use in data analysis. We will report this absorption number for various gamma ray energies of interest.   

Studying 32S(6Li,t)35Ar Reactions: Mimicking Nuclear Reactions in Classical Novae

Thermonuclear reactions drive stellar explosions including classical novae. Ashes from these reactions are found in presolar grains that are encapsulated in meteorites and then found on Earth. One reaction that affects the composition of these ashes from classical novae is the ³⁴Cl(p, γ)³⁵Ar reaction.  However, studying this reaction is very difficult because of the low cross section of ³⁴Cl(p, γ)³⁵Ar and the lack of intense ³⁴Cl beams. Instead, we measured the ³²S(⁶Li,t)³⁵Ar*(p)³⁴Cl reaction in order to mimic the ³⁴Cl(p, γ)³⁵Ar reaction. In collaboration with Florida State University, we studied the ³²S(⁶Li,t)³⁵Ar reaction using the Super Enge Split-Pole Spectrograph (SE-SPS), which detects the reaction tritons with a focal plane detector.  Proton-decays of excited states in ³⁵Ar populated via this transfer reaction were measured with the Silicon Array for Branching Ratio Experiments (SABRE).  SABRE measured the proton decays in coincidence with the tritons from the ³²S(⁶Li,t)³⁵Ar reaction in order to determine nuclear information on states in ³⁵Ar above the proton threshold, such as proton branching ratios. Analysis of these data and preliminary results will be presented. 

    

Measuring the 86Sr(α, α) Cross Section to Constrain the Optical Model

The alpha optical model potential (α-OMP) is a phenomenological approach used to describe elastic scattering. It is a necessary input for the calculation of thermonuclear reaction rates in explosive stellar environments. Uncertainties within the α-OMP lead to imprecise predictions that cannot be easily compared to observations. In order to improve the precision of the α-OMP, additional nuclear physics data is required. For our experiment, the ⁸⁶Sr(α, α) elastic scattering cross sections was measured to determine a local optical potential to predict ⁸⁶Sr(a, n) and ⁸⁶Sr(a, γ) cross sections. Natural and enriched strontium targets were placed inside of a scattering chamber at the Triangle Universities Nuclear Laboratory 10 MV tandem accelerator. Collimated silicon surface barrier detectors on two rotating tables were used to detect the α particles . Angular distributions were measured at E_α;Lab = 12,18, and 21 MeV. Results of the experiment and our efforts to constrain the α-OMP parameters will be discussed.   

Cooling Methods and Materials Studies on a MAPS Based Silicon Vertex Tracker

The silicon vertex tracker (SVT) is a significant component to the ePIC detector for the Electron Ion Collider (EIC) and is currently underway at Lawrence Berkeley National Laboratory. The purpose of this experiment is to explore the mechanical options for the silicon detector responsible for charged particle tracking and collision vertex determination. Additionally, a compact material budget is necessitated in this experiment to prevent particle scattering, which leads to incompetent tracking performance and resolution. Two carbon samples with differing material properties such as specific heat value, thickness, and porosity texture are tested within a reasonable cooling capacity target to determine efficient material candidacy for the SVT. It is important to understand this capacity and avoid exceeding its bounds to ensure that the tracker will not overheat. Thermal measurement can be strongly improved with the development of a new temperature reader built with an Arduino Uno ECB, RTD sensor and coplanar amplifier. Additionally, the glue used to attach the silicon sensor to the mechanical support must be carefully considered and tested to determine its optimal thermal properties. This poster will cover the various approaches to testing these materials with air cooling methods utilizing various airflow values and power densities.   

GRETA Filter Parameter Optimization and Calibration

The Gamma-Ray Energy Tracking Array (GRETA) will be a world-leading gamma-ray spectrometer, used at FRIB and ATLAS to explore the properties of exotic nuclei by reconstructing gamma-rays emitted from excited nuclear states with better resolution and peak-to-total than previous generation arrays. While its predecessors were predominantly calibrated and optimized by human scientists, it is planned for GRETA to automate those tasks by utilizing Bayesian optimization and other machine learning techniques. I will present on work to optimize energy resolution by  optimizing specific shaping parameters and exploring various criteria for energy resolution in the reconstructions. In creating an optimization-calibration loop that will feed the best filter parameters to the system and calibrate the output to accurate energy values, the human workload to set up GRETA will be greatly reduced and much more efficient. Additionally it will help scientists better understand how GRETA is functioning and the status of each of the detectors throughout its use.   

Chemical Interaction with Radioactive Polonium and Water

One of the branches of chemistry is the investigation of chemical properties to study the ways they interact, combine, and change to see what new substances can be formed. Unfortunately, the investigation of the chemistry of certain elements is complicated as there is no stable, naturally occurring isotope. At Lawrence Berkeley National Laboratory, the Heavy Element Group we are working towards new methods of studying the chemistry of the shortest elements. First, these elements are produced a single atom-at-a-time at the 88-Inch Cyclotron Facility. Then, using a combination of the Berkeley Gas-filled Separator and the FIONA mass analyzer, the short-lived elements can be separated from other reaction products, trapped, and allowed to react with reactive gasses. Then the reaction products are separated by their mass-to-charge ratio. Recently, FIONA has been used to investigate reactions between polonium and gasses such as water, chloromethane, oxygen, and more. Here we will show the results of recent experiments investigating how the amount of water in the trap impacts the different complexes that Po forms with water.   

Characterizing the Performance of Graphene Field Effect Transistors

Graphene field-effect transistors (GFETs) hold significant promise in electronics due to graphene's extraordinary, intrinsic properties. With a high carrier mobility and the potential operation beyond the THz regime, GFETs offer exciting possibilities for high-frequency applications. A thorough characterization of the GFET is of particular interest for assessing its utility for particle and radiation detection for LEGEND-1000 and other applications. To this end, the output and transfer characteristics were investigated for several GFETs of varying channel dimensions via several DC sweeps across different gate configurations. The study and its results on the GFET performance are presented.   

High Energy Neutron Production for Nuclear Data Needs

High energy neutron-induced reaction data is in increasing demand for the design of shielding for space exploration and materials damage for fusion energy systems. We have developed a Chi-Squared analysis tool that facilitates comparisons between experimental and evaluated cross section data sets. This method displays shortcomings due to a lack of data that creates inaccuracies in all predictive simulations, driving the need for new measurements.

However, many neutron sources do not have the correct characteristics to perform the experiments needed to address these data needs. Ion-source based “DT” and “DD” neutron generators produce quasi-monoenergetic energy neutrons with low intensity, and multi-100 MeV spallation sources yield high intensity, but over a very wide range of energies. 

This project focuses on the design and testing of a multi-layer beryllium breakup target. Using existing models of thick target beryllium breakup and SRIM modeling in beryllium and water, the target was designed to produce 10-20 MeV neutrons when bombarded with a 40 MeV deuteron beam. A separate test of the critical heat flux (CHF) for beryllium-water interface is required before running. A single channel steel target bombarded with alphas to mimic the conditions of the multi-layer target will be used to test the CHF.

Note: Will be Co-Presented with Elan Park-Bernstein   

The design and use of a Peltier-powered cloud chamber for outreach and classroom laboratory measurements

One challenge facing the scientist who studies anything at the nuclear level is convincing both the general public and students that what they are studying is real. Astronomers are able to show beautiful images of stars and galaxies, geologists let you hold a 3 billion year-old rock in your hand, but the nuclear physicist must come up with other methods to demonstrate the equally fascinating science that they engage with. At Siena College, we have worked for almost 10 years to improve upon a design for a Peltier-powered cloud chamber that does not require dry ice and is very portable. The design has been driven primarily by students in our Applied Physics program who have used their general design skills and 3D printing acumen to make the device easier to build and transport. This makes it ideal for both outreach activities and in-classroom demonstrations, usually in a Modern Physics class. In addition, Siena students have worked hard to document the construction process on the popular website, Instructables, so that others can build their own. Recently, we have developed a lab in which students use the device to extract scientific data. This involves a video analysis of a radioactive sample placed in the cloud chamber and the lengths of tracks are measured from a video analysis program. These lengths are used as an analog of the energy of the emitted particles and a spectrum is produced and compared to literature. A similar study can be done with cosmic rays where the lengths of the tracks map onto the angle of entry. The current status of both the cloud chamber design and the efforts to turn this into a classroom lab will be presented.    

Determination of the Timing Resolution of the SuperBigBite Spectrometer Hadron Calorimeter using Flash Analog to Digital Converters (FADCs)

This research conducted at the Department of Energy's Thomas Jefferson National Accelerator Facility (JLab) successfully enhanced the timing resolution of the SuperBigBite Spectrometer Hadron Calorimeter (HCal), a device critical for measuring the characteristics of subatomic particles known as hadrons. Under the scope of JLab's mission to advance nuclear physics research, the project aimed to increase the precision of experimental outcomes by fine- tuning the HCal's timing resolution. The project employed a range of strategies including rigorous data selection and data correction algorithms. The researchers succeeded in significantly improving the timing resolution from an initial 6.7 nanoseconds (ns) to a more precise baseline of 1.2 ns. This was achieved through strategic data cuts, time-shift corrections due to signal amplitude variations, and an innovative pulse edge fitting algorithm. Despite the inherent challenges posed by the setup of the FADCs, most notably the length of the cable connecting the HCal to the FADCs, the study confirmed the competitiveness of the FADC method when paired with the right strategies. Future improvements could potentially be achieved by examining data in more detail, applying additional corrections, optimizing infrastructure, and eliminating electronic crosstalk. The professional development gained from this opportunity was vast, encompassing hands-on experience with high-energy physics experiments, the opportunity to devise and implement innovative solutions, and develop a deeper understanding of how improving the timing resolution of the HCal could enhance overall experimental precision in the field of nuclear physics. Furthermore, the project demonstrates the smallest steps that must be taken in order to achieve the best results. The project's success reinforces the relevance of JLab's mission and offers valuable insights for future work at the facility.   

Ion Beam Analysis of Zircon with Applications to Earth Science

Diffusion is vital for interpreting geochronometric data, however, there are still gaps in our knowledge about this process for key minerals such as zircon. Zircon crystals are some of the oldest mineral grains on Earth and have strong chemical retention properties. Thus, zircons act as a window into the environment of the early Earth. Using nuclear analysis techniques on zircon crystals to measure the diffusion properties of tracer elements and those relevant to radioactive decay can improve estimations of mineral ages and provenance, thus aiding in a greater understanding of Earth and the early Solar System. Rutherford backscattering analysis (RBS) can be used to measure the diffusion of helpful geochemical indicators such as lead, tantalum, phosphorus, and xenon in synthesized zircon (ZrSiO4). RBS analysis supplies crucial data from which concentration profiles can be extracted. These profiles yield element concentration at various crystal depths on the nanometer scale. From these concentration profiles, a diffusion constant and closure temperature of an isotopic environment can be determined. The Ion Beam Lab at the University at Albany has been used to perform RBS analysis. Preliminary data has been collected for the diffusion of tantalum in zircon and will be presented.   

Incompatible Gamma Emission between GEANT4 Thermal Neutron Capture Simulations and ENDF Data

GEANT4 is a software toolkit that uses Monte Carlo methods to simulate how particles travel through matter. One of its applications is to model neutron capture reactions and subsequent gamma-rays. These gamma ray emissions create a unique spectrum for every isotope that can be used to identify material composition and are important for space exploration, oil well logging, nuclear forensics, and non-proliferation. GEANT4 uses data from the Evaluated Nuclear Data File (ENDF/B), and we performed thermal neutron capture simulations for various isotopes in order to compare their spectra. This work, performed at the National Nuclear Data Center (NNDC), demonstrates discrepancies between gammas produced by GEANT4 and those of ENDF. We have also explored different combinations of input flags, which modify how GEANT4 models capture gamma-ray emissions, and their effect on the spectra of several target isotopes was investigated. With these assessments of GEANT4's quality, we point to alternatives that would better determine gamma ray emissions from a given cascade based on emission probabilities per energy level. If implemented, these alternatives would allow for a more accurate simulation of neutron capture reactions in a variety of experiments.   

Implementation of machine learning models for prediction of primary gamma-ray emissions from thermal neutron capture reactions.

The National Nuclear Data Center (NNDC) at Brookhaven National Laboratory maintains a dedicated effort towards providing easy access of reliable and evaluated nuclear data. Nuclear data includes features describing the lifetime, mass, types of decays, and energies related to a nuclide. Optimizing fuel, space exploration, and nuclear nonproliferation depend upon a precise capture gamma-ray evaluated library. Using the Evaluated Gamma-ray Activation File (EGAF) and NuDat, the goal of this project is to employ machine learning methods to predict primary gamma ray emissions from isotopes which have undergone neutron capture at thermal incident energies. A neutron capture reaction is identified by the formation of a residual nucleus composed by the projectile neutron and the target isotope. This new system is presumed to be formed at an excited state of the compound nucleus and undergoes a sequence of gamma ray emissions as a mean of de-excitation, until eventually reaching its ground state. To comprehend the cascade of emissions, it is most significant to understand the first steps in the decay­: the primary emissions. Multiple characteristics of an isotope, relevant to its susceptibility to neutron capture or lack thereof, can greatly enhance our comprehension of nuclei and their inherent properties. Instead of using standard theoretical nuclear models, training classification and regression models using machine learning algorithms –such as Random Forest and K-Nearest Neighbors– with experimental data can allow for the machine to predict primary gamma ray emission probabilities missing in data sets with greater accuracy. Upon successful project completion the NNDC will be able to provide more precise capture gamma-ray spectra in evaluated libraries. Throughout this project, I became skilled in data analysis, mining, and visualization in addition to implementing and optimizing different machine learning models in Python.   

Astrophysical benchmarks of the Evaluated Nuclear Data File library

The Cross Section Evaluation Working Group at Brookhaven National Laboratory is currently developing the next release of the Evaluated Nuclear Data File (ENDF), known as ENDF/B-VIII.1, with a scheduled release in February 2024. The ENDF libraries are the primary and widely-recognized source of nuclear reaction data for various earthbound nuclear applications, including reactors and detector systems. They play a critical role in providing essential nuclear data, such as cross sections and decay data, crucial for designing and analyzing nuclear reactors. The main objective of this project is to evaluate and compare the performance of the beta release of ENDF/B-VIII.1 against several other evaluated data libraries and experimental results, using various integral metrics. Among these metrics is the Maxwellian Average Cross Section at 30 keV (MACS(30 keV)), representing the average cross section of neutrons in a thermal bath at 30 keV. This metric holds significant importance as a key input in simulations of nucleosynthesis processes. The next phase of the project involves utilizing the information stored in the ENDF library to predict isotopic abundances resulting from nucleosynthesis. To facilitate the collation process and enhance the project, I utilized Python to introduce several new classes. This allowed for seamless incorporation of the latest nuclear data libraries, aiding in the comprehensive evaluation and comparison of different data sources.   

Iterative Spin Reclassification of Neutron Resonances

The performance of nuclear reactors and other nuclear systems depends on a precise understanding of the neutron interaction cross sections, the probability for certain neutron interactions, for materials used in these systems. These cross sections exhibit resonant structure whose shape is determined in part by the angular-momentum quantum numbers of the resonances. In this project, conducted at the National Nuclear Data Center at Brookhaven National Laboratory, we apply machine learning to automate the quantum number assignments using only the resonances' energies and widths and not relying on detailed transmission or capture measurements. Current work is moving towards an iterative method of reclassifying the quantum numbers for flagged resonances.   

Resonance Capture Widths for the Bayesian Resonance Reclassifier

An accurate description of the neutron interaction cross sections for the most abundant isotopes of lead are essential for application in practical nuclear systems. These nuclear reaction cross sections demonstrate resonance phenomena in the presence of low-energy or thermal neutrons. The cross section shape is obtained by classifying the associated angular-momentum quantum numbers for each resonance. These classifications, however, are often subjective and not fully reproducible. This leads to incorrect assignments. In this project, we attempt to rectify assignments for ²⁰⁶Pb by using a machine learning (ML) approach. ML is a process that attempts to learn patterns and make predictions based on the given training data and set of features. Quality ML training requires abundant and diverse training data. The real data is often incomplete and contains errors, so instead, we build synthetic data that mimics the statistical properties of real resonances. For neutron capture reactions, we have found that a realistic distribution of resonance decay widths contributes substantially to the success of the ML algorithm. To accomplish this, we provide our synthetic data with capture widths sampled from a Porter-Thomas distribution, where the degrees of freedom ν is fit from the real data.   

Sensitivity of nEXO VUV Silicon Photomultipliers at 410-2400 nm

nEXO is a 5-ton liquid Xenon time projection chamber (TPC) operating at cryogenic temperatures and is one of the most sensitive detectors being proposed to search for neutrinoless double beta-decay, which if discovered would fundamentally change our understanding of the nature of neutrinos. Brookhaven National Laboratory is developing the readout electronics and photon detectors in nEXO, which will detect the scintillation flash at 175 nm produced when a double beta decay event occurs. nEXO scientists are concerned that there is the possibility of a background to the VUV photon measurement due to potential crosstalk from Infrared (IR) photon emissions caused by the electron avalanche in the Silicon PhotoMultipliers (SiPMs). We measured the Photon Detection Efficiency (PDE) of the SiPMs at high wavelengths to help understand this effect. To achieve this, an OPOTEK 355 LD tunable laser was set up and calibrated, then used to determine the PDE of the SiPMs from 410-2400 nm. These measurements, when combined with future measurements of the IR emission from SiPM avalanches, will allow nEXO to estimate the effect of this possible crosstalk on the energy resolution.   

Verifying the improved systematic predictions of β-delayed neutron emission and β+-delayed proton emission probabilities

The probability P_n for emitting a neutron following β decay is important for improving how we use nuclear reactors and for our understanding of astrophysics, and nuclear structure. However, many of these values are unknown and since they are crucial in many nuclear physics applications, systematics and phenomenological formulas, like the Kratz-Herrmann formula (KHF), have been used to calculate P_n. By incorporating the half-life for a given nuclide we can improve on the KHF. To explore this improvement, I developed a modular set of Python codes that use newly evaluated half-life, T_1/2 and P_n data for the entire chart of nuclides. After parsing and cleaning the data, I graphed correlation plots to improve the systematic prediction of the delayed neutron probabilities for various regions of the chart. I will be presenting the results of the systematics, as well as, the extended investigation for β-delayed proton emitters, and how the evaluations made for β decay to find more accurate P_n values can be implemented similarly for β-delayed proton emitters.   

Sensitivity of galactic chemical evolution to reduced 22Ne(α,n)25Mg cross section

The ²²Ne(α,n)²⁵Mg reaction is one of the most important neutron sources for s-process nucleosynthesis, which is responsible for the production of ~50% of the elements heavier than Fe in the Solar System. A recent experimental study (S. Ota et al. 2020) indicated that the cross section at stellar temperatures might be smaller than the conventional ones, leading to ~4 times lower stellar reaction rates. We probed the impact of the new ²²Ne(α,n)²⁵Mg reaction rates on the chemical abundances in massive stars and core-collapse supernovae. We simulated the nucleosynthesis of stars with different initial masses (12 - 25 M☉) and metallicities (0.0001-0.02) using the conventional and new rates with NuGrid’s multi-zone post-processing nucleosynthesis code, MPPNP. The stellar yields from MPPNP are fed into the galactic chemical evolution (GCE) code OMEGA+. The galactic abundances of s-process isotopes are reduced by up to 65% when comparing the new and conventional rates. The ratio of ⁶⁰Fe to ²⁶Al , s-process radioactive isotopes, using the new cross section reproduces the observed ratio by the INTEGRAL satellite within the uncertainties. Overall, accurate ²²Ne(α,n)²⁵Mg cross sections can have a significant impact on GCE to reproduce the astronomical observational data.    

Improving the Geometric Description of the sPHENIX Hadronic Calorimeter in GEANT4 for Accurate Jet Energy Measurements

The sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC) includes tracking detectors, an electromagnetic calorimeter (EMCal), an inner hadronic calorimeter (HCal), and a solenoid magnet surrounded by an outer HCal. GEANT4 is used to study the hadronic energy deposited in the HCal by jets formed during 200 GeV p+p and Au+Au collisions. The outer HCAL geometry is quite complex, for example, the cryogenic services required to cool the super-conducting magnet requires a cut-out in a section of the outer HCal. The level of detail included in the simulation of the detector, specifically in the description of the chimney cutout, can affect the accuracy of the simulation of jets produced at sPHENIX. The description of the HCal geometry uses a geometry description markup language (GDML) implementation of the as-built CAD drawings of the detector which provides a highly realistic description of the detector geometry at the expense of increased computational time. This poster will present a comparison of a detailed description of the geometry from a GDML implementation of the CAD drawings to using simple GEANT4 shapes to approximate the geometry. The necessary detail in GEANT4 will be evaluated by comparing results of jet performance plots between the detailed geometry and a simplified model, to gauge if there are deviations and changes in the jet performance.   

Characterization of a Candidate Electron Detector for the KATRIN Neutrino Experiment

Observed neutrino oscillations contradict the Standard Model idea of a massless neutrino, but the mass of the neutrino remains a mystery. The KArlsruhe TRItium Neutrino (KATRIN) experiment performs sub-eV sensitivity, theory-independent measurements of the mass of the electron antineutrino produced from the beta decay of tritium. Through direct measurement of the decay electrons, KATRIN has placed an upper limit of 0.8 eV at 90% Confidence Level. The KATRIN experiment detects beta decay electrons, using a silicon semiconductor PIN-diode array. Previous analysis of the KATRIN data results and Monte Carlo simulation suggests a dead layer thickness of 155.4 ± -0.5 ± - 0.2 nm, which presents an opportunity for improvement in energy resolution. The LBNL detector group has developed a PIN-diode, using novel manufacturing practices. I am characterizing this new detector's dead layer thickness as well as the influence of temperature and applied bias voltage on its energy resolution and leakage current. My characterization of this detector will contribute to future detector development and determine this detector candidate's suitability for neutrino mass measurements.   

Performance tests of LYSO crystals for the new PIONEER experiment

PIONEER is a new and approved rare-pion decay experiment which will be mounted at the Paul Scherrer Institute (PSI) in Switzerland. The first goal of PIONEER will be to measure the branching ratio π→e/π→μ to the precision of 10^-4 which would represent the world’s most sensitive test of Lepton Flavor Universality. Such a measurement requires a calorimeter with more than 20 radiation lengths, fast response time and an energy resolution approaching 2-3% at 70 MeV. These specifications may be achieved using a large array of LYSO crystals. LYSO is a fast, dense, high light-yield scintillator whose intrinsic properties suggest it would be a natural candidate for the experiment. Despite its advantages, a large, LYSO-based calorimeter has never been developed. Ongoing bench tests have demonstrated impressive single crystal resolution and uniformity at low energies when crystals are wrapped in a well-fitted specular reflector. We present the results of these tests using radioactive sources at the 0.51-4.14 MeV energy scale. A beam test of a 2x2 array of LYSO crystals using 17.6 MeV gamma rays is planned in the late summer and a beam test at PSI using a 100 MeV positron beam incident on a 3x3 array in November.   

Analysis of Monte Carlo Simulations for the J-PARC E50 Mu-ID Detector Extension

The inner dynamics of a proton remain a mystery of modern science. Understanding quark-gluon interactions in protons through analysis of collisions is essential to solving this puzzle, and this can be done by looking at the exclusive meson-induced Drell-Yan process. To study this process, an extension is proposed to the J-PARC E50 Charmed Baryon Spectroscopy experiment. Analysis of ROOT files (produced by GEANT4 simulations of the extension's hadron absorber) was done with C++ macros that matched up dimuon pairs, smeared the simulated data to match experimental uncertainties, and used gaussian fitting techniques to identify a relevant missing mass window around the nucleon mass. These steps ensured that the signal data was only Drell-Yan dimuons, and were repeated for background simulations as well. Counts of events were recorded, and the signal to background (S/B) ratio was studied for hadron absorber length dependence. Fewer background events were simulated than required by the process cross sections, so weighted distributions were used to ensure the S/B ratio was compatible with expectations. This ratio was optimized at a length of 13 centimeters. While limitations of time and computational power suggest this number is not fully accurate, the analysis framework developed can be applied to new simulations to obtain a better result. This research was conducted as a part of NSF-funded PIRE-GEMADARC, at the Academia Sinica Institute of Physics in Taipei.   

Analysis of the UCNtau Neutron Lifetime over the 2019-2022 datasets

There is a large discrepancy between the neutron lifetimes measured using the bottle method and the beam method; the discrepancy is ~10 seconds with an unresolved puzzle of why the lifetime of neutrons are longer in the beam method compared to the bottle method. The UCNtau experiment uses the bottle method to measure the neutrons in a magneto-gravitational trap. The yield and lifetime of the trapped neutrons are measured by observing that the neutron population decreases with time following the general exponential equation: Yeilds = et1-t2tau(1). The goal here is to extract a consistent neutron lifetime from runs with varying source output and detector geometries from the UCNtau experiment from 2019-2022. Counts from various neutron monitors are crucial to lifetime analysis, including the old gatevalve monitor and roundhouse monitor, which monitors how many initial neutrons are entering our system, and the dagger coincidence count which measure how many neutrons have entered our system after a prescribed holding time. We analyze the lifetimes by comparing a global analysis function to a pair analysis function. The global analysis analyzes all of the neutron coincidence counts and fits to a single lifetime function that will generate a single neutron lifetime. The other method of pair analysis uses a pair of adjacent runs of two different hold times, by using the exponential decay function, to extract many lifetime values from repeated measurements. Time-varying background also needs to be tracked and removed.   

Monte-Carlo study of High-Purity Germanium Detectors for the BL3 Experiment

The Beam-Lifetime 3 (BL3) experiment is a next-generation neutron lifetime experiment designed to measure the neutron lifetime by observing the decay of cold neutrons using a beam in the NIST reactor. To support BL3, a simulation is being developed to study the Alpha-Gamma device designed to calibrate the efficiency of the neutron fluence monitor. This device consists of three High-Purity Germanium (HPGe) detectors and six silicon detectors, which are used to count the alpha and gamma particle decay products of the neutron capture reaction at a centrally located target consisting of Boron-10. We use the framework of Geant4, a Monte-Carlo based simulation tool, to track the particles and their interactions with various geometries. To validate the detector performance, we start with simulations of energy depositions in the HPGe detectors using calibration sources, like Cobalt-60 and Cesium-137. Features on these energy spectra give insight to various signal and background physics processes. By comparing the energy spectra from detectors of varying dimensions, we choose a detector geometry that optimizes the signal efficiency while minimizing the sensitivity to background interactions. We study this background by simulating common sources of gamma emitters in the reactor environment. The plan is to develop a background model and use this simulation tool to design a shielding package, using lead or other high-Z elements, necessary to reduce and control the background. The data from these two simulations will be used to optimize the placement, dimensions, and shielding of the HPGe detectors in the Alpha-Gamma device for the BL3 experiment.   

Neutron Lifetime Measurements: Machine Learning Methods in Performing Ultracold Neutron Coincidence Analysis

As part of the UCNtau project, which is dedicated to the ongoing investigation of neutron lifetime, our work focuses on refining these measurements. The precision of neutron properties plays a pivotal role in our understanding of the Standard Model, in building more advanced physics structures, and in exploring the early universe. We devised a setup to detect ultracold neutrons (UCNs) through their scintillation effects and the resultant light pulses, which were captured by detectors. The subsequent analysis was conducted by implementing a time window with specific algorithms acting as thresholds. These algorithms are based on pulse detection by two photomultipliers operating in tandem, a process we refer to as coincidence analysis. This analytical method treats each neutron within a given time interval as a distinct unit for measuring lifetime, effectively eliminating background noise. This approach necessitates the identification of each UCN during the interval. We have obtained unadulterated data that preclude pileup effects and have generated a Monte-Carlo simulation based on these datasets. The simulation can output labeled pulse patterns and neutron counts. We utilized machine learning methods to train these patterns in various classification models and ascertain the accuracy of the counts corresponding to the patterns. Moreover, we attempted to develop several regression models to calculate the number of photons and the time difference that gave rise to these UCN patterns.   

Searching for a QCD critical point at finite strangeness densities using a Bayesian analysis in a holographic model

Currently searches are underway for the Quantum Chromodynamics (QCD) critical point, but they are hampered by the range of densities possible from existing lattice QCD calculations. To circumvent this issue, we use a holographic model of a 5-dimentional black hole to describe the QCD phase diagram, which includes hadrons in a gas and deconfined quarks and gluons known as quark gluon plasma (QGP). The QCD phase diagram has four thermodynamic dimensions: temperature, baryon number, electric charge and strangeness chemical potential. This model is constrained to replicate lattice QCD results for the thermodynamics at zero density, but including the susceptibility to a strangeness chemical potential, such that a critical point is predicted along the strangeness axis. In this work, we use a Bayesian analysis to improve the fits of the thermodynamic variables to find the location of this critical end point in the phase diagram at finite strangeness chemical potential.   

An LED-Based Calibration System for the ATLAS and CMS ZDC in the HL-LHC Era

The high radiation environment of the CERN high-luminosity (HL) LHC will present new challenges for its detectors. Among these challenges is the damage that this radiation may

cause to the photo-multiplier tubes (PMTs) of the new HL-Zero Degree Calorimeter (HL-ZDC) of the ATLAS and CMS experiments. To address this, an LED-based calibration system was included in the detector design to monitor the PMT performance and calibrate accordingly. This calibration is critical for distinguishing radiation damage from the physics signal in the detector, ensuring the quality of the recorded by the HL-ZDCs during Run 4 and beyond.

The University of Illinois Urbana-Champaign is collaborating with Kansas University to develop a new LED pulser board to use in this calibration system. In between events, the board will be triggered to drive multiple colors of LEDs to pulse the PMTs of the HL-ZDC and monitor the PMT performance in response to different wavelengths. In this contribution, we present results for extensive tests of the board, as well as different light distribution systems designed for it.   

Light Guides for the High Luminosity Zero Degree Calorimeter

The transition to High Luminosity (HL) operations of the CERN LHC requires the upgrade of several detector systems, including the Zero Degree Calorimeters (ZDCs) in ATLAS and CMS. The joint upgrade of these detector systems is led by the University of Illinois at Urbana-Champaign.

The importance of the ZDC lies in its responsibility for triggering and event geometry characterization in Heavy Ion (HI) collisions. The ZDC is a sampling calorimeter using tungsten absorbers, radiation hard fused-silica Cherenkov radiators, and photomultiplier tubes (PMTs) for light conversion into analog electric signals. The detector uses reflective air Light Guides (LGs) to transport Cherenkov light from the fused silica radiators to the PMT windows. Optimizing the efficiency and acceptance uniformity for the light transport is an important goal for the final HL-ZDC design’s performance.

In this contribution we validate our Monte Carlo simulation and report the performance of different LG geometries (nominally Winston cone and trapezoidal light guides) in the Electromagnetic and Hadronic sections of the HL-ZDC. With these simulation results, alongside data from in-lab experiments and on-site CERN electron beam tests, we determine what the HL-ZDC LG designs will be and develop a full mapping of their characteristics.   

Refining Precision Møller Polarimetry for the MOLLER Experiment Using the Magneto-Optical Kerr Effect

Møller polarimetry is an ideal method for measuring the polarization of high-energy electron beams [1]. The upcoming MOLLER experiment at Jefferson Lab aims to make improved high-precision measurements of the electron weak charge from parity-violating Møller scattering and requires ±0.4% precision on beam polarization. This will be dominated by systematic uncertainty, the largest of which arises from the use of a polarized iron foil as our target [2]. Using the Magneto-Optical Kerr Effect, the magnetization saturation curve of the foil can be determined, minimizing this source of uncertainty. Discussion here will focus on the challenges and progress from our apparatus and future plans.   

Numerical simulations for the exploration of pion structure beyond the leading twist

The non-perturbative component of the cross-section of high-energy processes may be expanded in terms of the process's large energy scale. This classifies parton distribution functions (PDFs) and their generalizations by their twist (mass dimension minus spin). The leading twist (twist-2) contributions have been at the center of experimental measurements, theoretical investigations, and lattice QCD calculations. It has been recognized that twist-3 contributions to distribution functions can be sizable. However, it is challenging to disentangle them experimentally from their leading counterparts, posing limitations on the structure of hadrons, such as the pion and the proton. Here, we will present preliminary results on the x-dependence of the pion twist-3 PDFs. The lattice QCD calculations have been performed using the LaMET method, which relates lattice matrix elements to light-cone PDFs. We implement one ensemble of two degenerate light, a strange and a charm quark (Nf=2+1+1) of maximally twisted mass fermions, reproducing a pion mass of 260 MeV.   

Exploring Dark Sector Physics in MicroBooNE using Graph Neutral Networks

The MiniBooNE experiment, designed to study neutrino oscillations, detected what has become a longstanding anomaly – an excess of low energy electron-like events from accelerator neutrino interactions. A possible explanation of the anomaly comes from neutrino interactions with nuclei that create heavier, sterile neutrinos. Specifically, we are focusing on sterile neutrino interactions that produce electron-positron pairs. Complementing this is the MicroBooNE experiment, a liquid argon time projection chamber, that can reconstruct events in both two and three dimensions. This reconstruction ability enables us to select dark sector neutrino interactions from all other possible interactions using machine learning techniques such as graph neural networks (GNNs). In this poster, I will present a simulation-based study which will be used to assess the signal to background discrimination power of our GNN in electron-positron pair events.   

MARS Neutron Measurements for COHERENT

The COHERENT collaboration studies the coherent elastic neutrino-nucleus scattering (CEvNS) through detectors stationed throughout a corridor labeled “Neutrino Alley” at Oak Ridge National Laboratory. Neutrinos are produced by the Spallation Neutron Source (SNS) through pion decay at rest, along with neutrons that form a background in COHERENT detectors due to their similarities in small nuclear recoils to CEvNS. The Multiplicity and Recoil Spectrometer (MARS), a mobile neutron monitoring system, serves to study and characterize these neutron signatures in order to better understand detector backgrounds. MARS exploits the use of gadolinium in order to map the neutron flux throughout the corridor of COHERENT detectors. I will present the current analysis of calibration data and work toward examining the neutron energy spectrum from recent MARS measurements.    

PMT Performance Studies for Neutrino Interactions for COHERENT

A coherent elastic neutrino-nucleus scattering (CEvNS) event occurs when momentum transfer is small compared to the inverse size of a nucleus, scattering coherently from the constituent nucleons. The COHERENT collaboration has observed this interaction, and continues to perform precise measurements in several detectors at the Oak Ridge Spallation Neutron Source. Understanding CEvNS events will help us learn more about supernovae, weak nuclear form factors and dark matter. We’re currently constructing COH-Ar-750, a 750 kg liquid argon scintillator detector. The detector will feature 122 R14374 3” PMTs. PMTs are essential to measure the signal from CEvNS events. We tested the gain, dark rate, and peak to valley ratio at room and liquid nitrogen temperatures to assure quality performance of the PMT in liquid argon over a wide dynamic range. Linearity was tested at different light levels with neutral density filters. This work exhibits that the PMT and amplifier chain resolves single photoelectrons, and we’re continuing linearity tests to verify performance for high light-output events. This will pave the way for the next generation of CEvNS studies with COH-Ar-750.    

Analyzing Nickel Cross-Sections for Applications in DT Fusion Research​

Background: The fusion of deuterium and tritium is a promising sustainable energy source. Despite recent

breakthroughs at NIF, progress is still needed. One possible diagnostic tool is to use activation foils to search

for any net center-of-mass velocity of the plasma. Since neutrons produced by DT fusion have E_n = 14.1 MeV,

reactions with a strong energy dependence in this range, such as ⁵⁸Ni(n,2n)⁵⁷Ni and ⁵⁸Ni(n,p)⁵⁸Co, can measure

small alterations of the neutron energy.

Purpose: Measuring the production cross-sections of the aforementioned reactions, ⁵⁸Co/⁵⁷Ni, can be used to

reveal insights about the mean neutron energy and velocity of the DT fusion plasma.

Methods: A deuteron beam was created at the TUNL tandem accelerator, which then hit a tritiated target.

Activation foils were placed at varying degrees from incoming deuteron beam. Neutron activation occurred for

10 hours. A HPGe detector was then used to identify the decays of ⁵⁷Ni and ⁵⁸Co. The cross-sections were

calculated.

Results: The cross-sections of the two reactions agree with the evaluations within uncertainty. In addition, the

ratio of cross-sections is reported with reduced uncertainty.

Conclusions: The production cross-sections for ⁵⁷Ni and ⁵⁸Co were measured at four incident neutron energies

around 14.1 MeV. This nuclear data may be used as a possible diagnostic tool for measuring small alterations in

the mean center-of-mass velocity DT plasmas.

This work was supported in part by the U.S. Department of Energy under grant DE-SC0022545.   

Experimental Measurements of Prompt Fission Gamma Ray Spectra

Prompt fission Gamma Ray Spectra (PFGS) play an important role in understanding the de-excitation process of newly formed nuclei produced from fission.  This study focuses on PFGS produced from photofission, as previous research primarily utilized neutron-induced or spontaneous fission. Fission was induced in Uranium-238 targets at the High Intenity gamma-ray Source (HIgS) and the resulting gamma rays were measured using LaBr and CeBr detectors. The PFGS are convoluted within the detector response, so the experimental spectra must be deconvoluted to report the true PFGS from photofission. Additionally, multiple offline analysis techniques were investigated to determine the best method of producing the gamma-ray spectra from the dataset. This includes a pulse-height analysis, a moving average waveform analysis, a pulse integration analysis, and the rejection of pulse pile up events. This work concluded that the pulse integration method provided the lowest resolution within the spectra. Pile up events were found at rates of 2-3% for the calibration data, and 6-8% percent for the fission data. Results for PFGS are preliminary and further work is being carried out to deconvolute the experimental fission gamma-ray spectra. This includes using a detector response matrix to reconstruct the experimental spectra, reporting the true PFGS in the process. This measurement of PFGS produced from photofission and can be used to better model the fission process.   

Machine Learning Applications for Radioisotope Neutron and Gamma Pulse Shape Categorization

When determining neutron and gamma signatures from radioisotope measurements, discrimination between the two events at low pulse height (PH) spectrums becomes ambiguous. This research overviews the applications of using AI in the form of unsupervised machine learning (UML) to create an algorithm to distinguish between neutron and gamma signatures. The UML model is trained on over 200 radioisotope measurements taken at Duke Free Electron Laser Laboratory (FEL) within the soccer ball arrangement. In addition to creating the UML algorithm, the mechanical process of encasing a fissionable 252-Californium (252Cf) sample was completed using CAD software, light reflective simulations, and workshop techniques for coating and assembly. The data was then compared to previous iterations of the sample encasing structure to determine reflective material efficiency and structure. After creating the UML algorithm and processing the collected data from the 252CF encasement , the source is further analyzed using graphical analysis.   

Development of Backscatter and Pile-up Identification for UCNA+

The UCNA Experiment at the Los Alamos Neutron Science Center (LANSCE) uses an electron spectrometer to observe angular correlations between the neutron spin and the momenta of beta particles emitted during the process of beta decay. Combined with neutron lifetime measurements, these observations probe physics beyond the standard model. In recent years there has been an effort to modernize the equipment to reduce the physical limitations of the experiment. The new prototype helps to reduce error via use of silicon photo-multipliers (SiPMs) and the SiPMs also have a greater quantum efficiency than the photomultiplier tubes (PMTs). However, there is still potential for error due to back-scatter, where an electron hits the scintillator and bounces off, but gets sent back into the scintillator by the magnetic field. Also when the SiPMs are activated they have a spike in voltage which exponentially decays. If 2 electrons hit within approximately 20 nanoseconds, there will be no new spike in voltage which results in a pileup in the data. My work has focused on how to recognize when pileup and or back-scatter occurs, and how to further reduce the error in this process.   

An In-situ Timing Apparatus for the Nab Experiment

The Nab experiment seeks to probe the weak interaction through the fundamental nature of neutron beta decay in order to discover potential new physics beyond the standard model. Nab will carry out high precision measurements of the electron-neutrino correlation parameter, a, and the Fierz interference term, b, by measuring the electron energy and proton time-of-flight which allows for estimation of the proton momentum. To make measurements of the precision required, Nab demands the average proton time-of-flight to be known with an uncertainty of less than 1 ns. The timing of the Nab Si detectors will be characterized through multiple methods, but we will be focusing on an in-situ timing study using a gamma detector (BaF2 or CeBr3) as an electron/gamma coincidence tag from radioactive sources for the Si detectors. We will present coincidence timing studies from BaF2 and CeBr3 and simulations of electron and gamma transportation in the spectrometer.   

Low-energy Proton Tracking with geant4 for the BL3 Experiment

The value of the neutron lifetime is very important, as it provides inputs in the quark mixing matrix constants in the Standard Model and in the primordial abundance of Helium-4 in Big Bang Nucleosynthesis. The goal of the BL3 experiment is to investigate the 4-sigma discrepancy between beam and bottle methods for neutron lifetime measurements. In order for BL3 to make a precise measurement of the neutron lifetime, the absolute neutron flux and proton rate will be measured. Thus, the BL3 experiment must have very efficient proton detection. We not only must understand the distribution of proton hits on the detector, we must also understand the interaction of the protons with silicon—namely, how the protons backscatter. We will discuss our systematic testing of detector position and implementation of a model for studying backscattering protons.   

Evaluating Radiative Corrections in Super Rosenbluth Experiments

Electron-proton elastic scattering experiments have mapped out the proton's electromagnetic form factors, i.e., how the proton's electric charge and current are distributed within its volume. Nevertheless, there are some inconsistencies in our determinations of these form factors, especially at high-momentum transfer. In this project, we are trying to determine the impact of radiation emitted by charged particles in collisions, a topic known as "Radiative Corrections," in a class of experiments called Super Rosenbluth experiments. We ran Monte Carlo simulations to conduct a Super Rosenbluth pseudo-experiment using several commonly used radiative corrections approximations in order to evaluate their suitability. We find that when using the Peaking Approximation, the radiative corrections in Super Rosenbluth experiments are smaller and less kinematics-dependent than in equivalent Rosenbluth experiments. However, this is not necessarily true when using more sophisticated models, calling into question the assumed advantages of the Super Rosenbluth technique.   

Testing Automatic Cut Finding Tool Performance for HADES Event Selection Optimization

As part of the international collaboration at the FAIR - GSI accelerator facility in Germany, a testing process has been conducted on the performance of an automatic cut finding tool for optimizing event selection as compared to the manual cutting process. Manually making cuts is a standard practice in hadron physics analysis but is known to take a considerable amount of time, and the analysis process is significantly streamlined by the introduction of an automatic tool. The cut finder accepts ROOT files containing data taken for measured collision variables, and chooses the most optimal subgroup of these variables on which to make cuts that lead to the best signal extraction and background suppression. For the first time, the tool was tested with experimental data from the HADES (High Acceptance Di-Electron Spectrometer) experiment, specifically events containing long-lived hyperons. This was done by first running the tool with simulated toy Monte Carlo signal and background data, followed by experimental data taken from beamtime in February of 2022. It was found that in both simulations and the lab setting, the automatic cut finder consistently chose the particle momentum components, decay vertices, and the polar angle to be the most optimal for cutting on in cases containing long-lived hyperon events. In this poster session I will be presenting the results of my work at GSI and my ideas for future applications.   

Protons in Quasielastic Neutrino Events

The NOvA experiment at Fermilab utilizes beams of neutrinos and antineutrinos to observe neutrino oscillation and probe questions that remain unanswered by standard model physics regarding neutrinos. Important to the measurement of oscillations in NOvA is the correct reconstruction of the incident neutrino interaction. Final state protons are often an important component of this energy reconstruction. Quasielastic neutrino events produce two final state particles, a muon and an proton. In these events, kinematic constraints enable a prediction of the proton momentum from the reconstructed muon momentum. These tagged protons in the neutrino data sample can provide a valuable test bed for studying the detector response. From information recorded by the detectors in the NOvA experiment, the quasielastic energy of the neutrino can be calculated. Using this neutrino energy, reconstructed muon momentum, and the known neutrino beam direction the momentum of the proton can be calculated. I will present my analysis which sought to identify a pure sample of quasielastic events and compare the detector response in data and simulation for the protons in these events.   

Program to Identify Secondary Background Sources in the MOLLER Experiment

The MOLLER project is a proposed experiment at Jefferson Lab aiming to measure the parity-violating asymmetry in electron-electron scattering. Electrons accelerated to 11 GeV are incident on a liquid hydrogen target. Those which scatter off of atomic electrons (electrons of interest) are directed by a magnetic spectrometer to a background-free region. However, the incident beam causes other high energy particles to scatter from this target in various directions. These particles could collide with other surfaces within the experimental chamber, consequently creating an additional, undesired source of secondary particles (so-called one-bounce backgrounds). The spectrometer collimation system has been carefully designed, aided by a program called "two-bounce" which checks to see if any of these one-bounce background sources are visible to the detector. We have developed "Two-bounce 3D" to model these sources in three dimensions to explore new potential pathways that may not be covered by analyzing the apparatus in two dimensions (r, z). Borrowing techniques from computer graphics, it employs a bounding-box R-tree to efficiently organize the geometry, allowing for significantly faster intersection computations. Additionally, it utilizes parallel computing to better optimize the usage of computational resources and increase the output resolution. This work will help optimize the experimental design and minimize the risk of unknown new sources of background in the final measurement.   

Development of a GEM based cosmic muon tracking system for characterizing Cherenkov detectors

The MOLLER Experiment at the Thomas Jefferson National Accelerator Facility (JLab) aims to measure the parity violating asymmetry (A_pv) in electron-electron (Møller) scattering with unprecedented precision. The flux of Møller-scattered electrons from the liquid hydrogen target is measured by Cherenkov detectors and the longitudinal polarization of the incoming electron beam is rapidly flipped to extract the right-left fractional flux difference and calculate A_pv. At the University of Massachusetts, Amherst, prototype detectors were designed, fabricated, and installed in an apparatus to characterize the Cherenkov detectors using cosmic muons. To investigate the performance of the Cherenkov detectors with different incident angles of muons, tracking detectors for the cosmic muons need to be employed. This study investigates Gas Electron Multiplier (GEM) detectors to implement the cosmic muon tracking system. The study includes a uniformity measurement in gain, energy resolution, and count rate using a Fe-55 source for the single mask triple GEM prototypes. The efficiency of the chambers is also measured using cosmic muons. The chambers are operated with Ar/CO₂ gas mixture in a continuous flow mode. The details of the experimental setup, methodology, and results are presented.   

Trigger Online Monitoring for the SpinQuest Experiment

The SpinQuest experiment at Fermilab aims to perform the first Sivers function measurement on sea quarks using the Drell-Yan process to find evidence for non-zero orbital angular momentum of light antiquarks in the nucleon. The SpinQuest spectrometer is designed to detect pairs of positive and negative muons produced in Drell-Yan process from colliding a 120 GeV proton beam with polarized NH3 and ND3 targets. The online monitoring system plays a crucial role in monitoring the performance and stability of the SpinQuest apparatus during data taking. Over the past year, the FPGA trigger online monitoring system was significantly improved to fulfill experimental requirements. In this poster presentation, an overview of the improved online monitoring system for the FPGA trigger as well as the motivation for this upgrade will be presented and discussed.   

Improving CUORE Energy Reconstruction Using Principal Component Analysis

CUORE (Cryogenic Underground Observatory for Rare Events), located in the Laboratori Nazionali del Gran Sasso in Italy, is an experiment designed to search for neutrinoless double beta decay (0νββ) in 130Te. Neutrinoless double beta decay is a theoretically predicted radioactive decay process that, if observed, would determine the Majorana nature of the neutrino. This would indicate that lepton number is not conserved and could help explain the matter antimatter asymmetry in the known universe. I present an analysis on the applications of PCA (Principal Component Analysis) on improving energy reconstruction for CUORE. Energy resolution is of great importance for CUORE as it would help better distinguish 0νββ signals from background events. Currently, CUORE uses a software trigger algorithm called an Optimum Filter (OF) trigger for energy reconstruction. However, OF assumes that signal shape is independent of energy which isn't true in CUORE. A PCA-aided reconstruction could mitigate the energy dependence of pulse shapes and improve the overall energy resolution of the CUORE detector. I will present the current results of this analysis.   

Effects of Carbon-12 Intranuclear α−Clustering on the Glauber Model

Measurements of light nuclei fragments produced in nuclear collisions are important in quantifying the damage that space radiation has on astronauts, electronics, and spacecraft. The Solenoidal Tracker at RHIC (STAR) has the capability to measure such events using their fixed target (FXT) program. The beams will model damage from galactic cosmic rays, currently planned at energies of √s = 5, 20, and 50 GeV, with species C, Al, and Ni. This study will focus on the nucleus-nucleus inelastic cross section in these collisions, because of its use as an indicator of the total nucleus-nucleus cross section and how frequently light nuclei fragments are produced. The goal of this study is to investigate a potential weakness with the Glauber model in accurately determining the inelastic cross section for carbon-carbon collisions. Carbon nuclei have the possibility of consisting of three intranuclear α−clusters, as opposed to consisting of a more typical continuous nucleon distribution. Multiple nuclear α−clustering distributions are considered, and the significance that this different nuclear density profile has on the inelastic cross section is investigated.    

Testing and characterizing the performance of the CRYO ASIC for the nEXO experiment

The next Enriched Xenon Observatory (nEXO) experiment uses a noble liquid time projection chamber detector to search for the neutrinoless double beta decay of Xenon-136. Interactions between double beta decay electrons and liquid xenon within the chamber produce ionization electrons and scintillation photons. The drift of the electrons generate charge signals that need to be amplified, digitized, and recorded. The CRYO ASIC is a system-on-chip waveform digitizer and serializer that is designed to operate at cryogenic temperatures for both the DUNE far detector and nEXO. The pre-amplification stage of the CRYO ASIC has been optimized for the input capacitances of DUNE and nEXO, which are 150 pF and 40 pF respectively. To test the nEXO variant of the CRYO ASIC, we use built-in charge calibrators that create a pulse to mimic a step signal input. The ASIC is tested under different environmental and thermal conditions to achieve a thorough characterization. Test results will be used to assess the functionality and performance of the ASIC and guide the design of future prototypes of the chip.   

Effects of evolution at high-x in the pion valence parton distribution

In its simplest picture, the pion is represented by a pair of up and anti-down valence quarks. Hard scattering processes which probe the pion’s structure have revealed an increasing number of quarks, antiquarks, and gluons with increasing momentum transfer Q². Parton distribution functions (PDFs) describe the momentum distributions of the pion’s constituent partons in terms of x, the fraction of the pion’s momentum carried by each parton. We expect the behavior of the valence PDFs to be represented by (1-x)^β as x→1. Brodsky-Farrar quark counting rules predict limiting values of β(x, Q²), but theoretical models disagree on their predictions of β(x, Q²). We have carried out leading order perturbative evolution of the valence PDFs of two models, based on light front holographic QCD and Dyson-Schwinger methods respectively, from their starting scales. We calculated moments of the distributions, and compared our results to experiment, lattice calculations, and global PDF fits. We determined asymptotic values of β(x, Q²)  for the models in the high-x and high-Q² limit. The models disagree at all Q², so the tension between models remains and more experimental data is needed. Forthcoming experimental data from Jefferson Lab and from the Electron-Ion Collider will provide a crucial test of the models and of the QCD counting rules.    

Quantitative Analysis of Proton Content in Deuterated Poly(methyl methacrylate) for Thin Neutron Window Material Selection in Ultra-cold Neutron Experiments

A suitable material selection for a dPMMA window used in the nEDM@SNS experiment, which aims to make the world's best measurement of the neutron's electric dipole moment, is essential. nEDM@SNS will significantly improve our understanding of how matter was formed during the Big Bang. To achieve this, nEDM@SNS requires maximum delivery of cold neutrons to the inside of a cell containing superfluid helium-4, cooled to 0.5 K, to produce the ultra-cold neutrons (UCNs) needed for the experiment.The ratio of the Hydrogen/Deuteron cross-section of ~12 highlights that materials containing hydrogen are much more likely to scatter, absorb, or deflect neutrons. This could potentially reduce the number of UCNs needed and produce unwanted background signals. To investigate the proton content of the deuterated poly(methyl methacrylate) (d-PMMA) sample, a Nuclear Magnetic Resonance (NMR) technique is used. TMS (tetra-methyl silane) and a separate fully-protonated PMMA sample are used for calibration. By employing a standardized sample preparation protocol and a MATLAB algorithm to calculate the signal strength attributed to the NMR peaks, the amount of protons in the polymer can be identified.   

Developing Molecular Plating Capabilities at SJSU

For heavy element reactions, lanthanide and actinide targets are key components. In order to produce these targets, it is essential to utilize target production techniques capable of high efficiency. This reduces potential waste of radioactive or rare enriched isotopes. To build our group's process knowledge, we aim to develop molecular plating capabilities starting with neodymium targets. As a lanthanide, neodymium serves as a surrogate for our ultimate goal, radioactive actinide targets. Molecular plating is an electrochemical technique where a target species in its molecular form is dissolved in an organic solvent and deposited on an anode. To date, we successfully built and operated a molecular plating cell for neodymium nitrate. Initial tests yielded consistent depositions on titanium foil, demonstrating our plating cell's functionality. Here, we report on the ongoing target characterization efforts and our future plans.   

Testing Radiopure Cables for nEXO

The subject of neutrinos has been a tricky one for physicists for decades. The discovery that they contain mass and can alter between different states leads to potential physics phenomena beyond the well established Standard Model. One possibility that can explain this behavior would be that neutrinos are Majorana particles, which means they can act as their own antiparticles and perform interactions that violate lepton number conservation. An effective way to ascertain whether they are Majorana particles would be searching for a process called neutrinoless double beta decay (0νββ). This decay mode includes two simultaneous beta decays in a nucleus. If neutrinos are Majorana particles, they can mutually annihilate resulting in the absence of any escaping neutrinos. nEXO is a 5 ton liquid xenon (LXe) Time Projection Chamber (TPC) that operates at cryogenic temperatures, proposed to search for 0νββ. Brookhaven National Laboratory is responsible for the photon readout electronics.  The detector is highly sensitive and measurement of 0νββ is on the order of keV. Consequently, the signal would be overwhelmed by any residual radioactive decay within the system. As a result, the  hardware is required to be as radiopure as possible. Hence, testing the performance of radiopure cables that will be part of the nEXO TPC is a high priority.  Furthermore, it will be important to test interconnections from the radiopure cables to prototype nEXO photon readout boards.    

SiPM and Plastic Scintillator Tile Test Bench for the ePIC LFHCAL: Experimental Setup and Python Simulations

The LFHcal (Longitudinally-Segmented -Forward-Hadronic-Calorimeter) for the ePIC(Electron-Proton/Ion Collider) detector at the future EIC(Electron-Ion Collider) facility is a hadron calorimeter based on plastic scintillator tiles, which are read out by SIPMs (Silicon Photomultiplier) in a SiPM-on-tile configuration. 

The goal of this research is to build and exercise a SiPM+tile bench test setup for the LFHcal. We built a light-tight container for SiPM and scintillator tile characterization studies. I-V curves for various SiPM models were acquired and analyzed to extract their breakdown voltage. SiPMs were illuminated by short flashes of light to obtain single-photon spectra for gain characterization. Scintillator tiles made from various materials with different machining techniques were mounted onto these SiPMs. The light yield of these SiPM-tile assemblies could then be tested from their response to cosmic radiation.

A Monte Carlo, Python code was developed to simulate cosmic rays with a cosine square angular distribution. The goal of this simulation is to find the geometric efficiency and mean path length of the cosmic rays depending on the scintillator geometry.

This poster will present the work carried out as part of the CANDID summer student program at ORNL in summer 2023.