Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session LL02: V: Nuclear Physics and Applications |
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Sponsoring Units: DNP Chair: Ramona Vogt, LLNL/UC Davis Room: Virtual Room 2 |
Tuesday, April 25, 2023 8:00AM - 8:12AM |
LL02.00001: Constraining Nuclear Models and Equation of State with Parity-violating Asymmetry of $^{208}$Pb and $^{48}$Ca Tianqi Zhao, Zidu Lin, Madappa Prakash, Andrew W Steiner, Bharat Kumar Neutron skin of $^{48}$Ca and $^{208}$Pb have been known to provide important information about the symmetry energy of nuclear matter. Previous skin measurements involving strong integration probes might be subject to various systematic errors. Purely electro-weak probes such as parity-violating asymmetry of $^{48}$Ca (CREX) and $^{208}$Pb (PREX) in elastic electron scattering are particularly valuable. We generate a few hundred thousand energy density functional and calculate finite nuclear properties, infinite nuclear matter properties as well as neutron star properties. Our joint analysis of PREX and CREX data flavor energy density functional with a large bulk symmetry energy $S_v$ and a small slope $L$, which is in 2-$sigma$ (95\%) tension with nuclei masses and charge radii. This tension leads to a strong constraint on symmetry energy slope $L=42^{+15}_{-17}$ MeV. The posterior distribution is dominated by CREX data since CREX ruled out large $L$ while PREX likelihood has a big tail which is compatible with small $L$. Joint analyses with astronomical constraints including maximum mass, tidal deformability, and radius observation slightly tighten the lower bound $L=43^{+15}_{-11}$ MeV. Furthermore, we found the result agree nicely with previous neutron skin experiment, dipole probabilities as well as ab-initial calculation. \ |
Tuesday, April 25, 2023 8:12AM - 8:24AM |
LL02.00002: Measurement of Neutron Polarization and Transmission for the nEDM@SNS Experiment. Kavish Imam The neutron electric dipole moment experiment at the Spallation Neutron Source (nEDM@SNS) will implement a novel method, which utilizes polarized ultra-cold neutrons (UCN) and polarized 3He in a bath of superfluid 4He, to place a new limit on the nEDM down to 2-3×10−28 e·cm. The experiment will employ a cryogenic magnet and magnetic shielding package to provide the required magnetic field environment to achieve the proposed sensitivity. This talk will describe the design and implementation of a 3He polarimetry setup at the SNS to measure the monochromatic neutron polarization and transmission losses resulting from passage through the magnetic shielding and cryogenic windows. |
Tuesday, April 25, 2023 8:24AM - 8:36AM |
LL02.00003: Background characterization and calibrations of SiPM detectors for UCNA+ Robert W Pattie The UCNA experiment at the ultracold neutron facility at Los Alamos National Lab measured the beta-asymmetry parameter A0 to a precision of 0.6 %. This parameter is used in determinations of the ratio of the axial and vector weak coupling constants and combined with measurements of the neutron lifetime is used to test the unitarity of the CKM quark mixing matrix and beyond the standard model physics searches. Upgrades of several key subsystems of UCNA are being investigated with the goal of reaching a precision of 0.2 % on A0. A prototype of the electron detector is in development which would eliminate the MWPC gas counter and traditional PMT's in favor of an array of edge-coupled SiPM's. The SiPM array will provide energy, position, and timing data with resolution that is equal to or better than the original detector and minimizing scattering on inactive material. A completed prototype was installed in the spectrometer at LANL in December to measure and characterized ambient and accelerator generated backgrounds in Area B. We will report on the tests of the data acquisition system, trigger logic, background rejection, and calibration of the prototype detectors. |
Tuesday, April 25, 2023 8:36AM - 8:48AM |
LL02.00004: The total kinetic energy release and fragment mass distributions in the fast neutron induced fission of actinide nuclei Walter D Loveland, Jonathan King, J. S Barrett, Ashley Pica, Alexander Chemey, Liangyu Yao The total kinetic energy release and fission mass distributions for the fast neutron (En=3-100 MeV) induced fission of 232Th, 233U, 235U, 237Np, 239Pu, 240Pu, 242Pu and 241Am have been measured using the LANSCE facility. The fission fragments were detected using Si PIN diode detectors. The actinide targets were made by vapor deposition leading to high quality targets. The TKE distributions were Gaussian in shape. In the case of 233U and 235U, our measurements agree with prior work. Our measurements for 232Th are unique. Our data agree with Viola scaling. The variances of the TKE distributions are larger than predicted by conventional models of scission. The heavy mass peak remains constant in position due to the influence of the N=88 and Z=50 shells. The GEF model predictions agree with the data in general as do the CGMF model predictions. |
Tuesday, April 25, 2023 8:48AM - 9:00AM |
LL02.00005: Gantryless Associated-Particle Imaging: A New Paradigm Matthew R Heath, Jason Newby, Jacob Daughhetee, Paul Hausladen, James Matta This work reports on the development of new techniques to enable in-field fast-neutron radiography measurements using associated-particle imaging (API). These methods utilize transmission neutron data to perform a data-driven detector localization of a pixelated fast-neutron panel with respect to the neutron source. This data-driven localization allows for in-field neutron radiography, even for cases in which the source-detector geometry does not allow for a normalization measurement and is not well known a priori. It also enables accurate image stitching, even for low resolution detector panels and for cases in which there is a small amount of overlap between individual images. These techniques are needed to enable field deployable API imaging systems where the source and detector are positioned by hand rather than held with respect to each other by a gantry. This presentation will discuss the system calibrations needed for subsequent analysis, the data-driven detector localization method, the process of calculating a normalization for a given source-detector geometry, and the method used to stitch images together. |
Tuesday, April 25, 2023 9:00AM - 9:12AM |
LL02.00006: 4D Trackers Based on AC-LGAD with Long Strip Readout Electrodes Shirsendu Nanda, Zhenyu Ye, Christopher Madrid, Ryan Heller, Claudio San Martín, Artur Apresyan, William K Brooks, Wei Chen, Gabriele Giacomini, Ohannes Kamer Koseyan, Sergey Los, Cristián Peña, René Rios, Alessandro Tricoli, Si Xie, Irene Dutta, Aram Hayrapetyan Silicon-based sensors that can deliver a timing resolution of a few tens of ps along with a significantly better spatial resolution (O(few µm)) have been studied extensively in recent years. In AC-coupled Low-Gain Avalanche Diode (LGAD), a highly-doped p+ gain layer is implanted between a continuous n+ layer and p-type bulk to form a high-field multiplication region. Electrical signals in the n+ layer are AC-coupled to metal electrodes that are separated from the n+ layer by a thin insulator layer. Signal sharing among the adjacent electrodes in AC-LGAD sensors enables a significantly better spatial resolution while maintaining the excellent fast-timing resolution offered by the conventional LGAD sensors. The AC-LGAD technology has been suggested to use for particle identification (PID), tracking, and far-forward detectors at Electron-Ion Collider (EIC). Precision timing detectors in EIC will provide PID capabilities below the threshold of Cherenkov PID detectors. We demonstrated for the first time the performance of large-area AC-LGAD sensors produced by Brookhaven National Laboratory (BNL) [1], which achieved an excellent spatial resolution of around 10 - 80 µm, and timing resolution of around 30 - 50 ps depending on the length of the strip. Despite the excellent performance of AC-LGADs in this prototyping run, we observed a significant non-uniformity of the gain layer [1]. A follow-up production was performed at BNL in order to improve the gain layer uniformity. In this presentation, we will present the signal characteristics and charge sharing of AC-LGADs from the latest production batch with laser and test beam measurements. |
Tuesday, April 25, 2023 9:12AM - 9:24AM |
LL02.00007: ETROC Project: First full-size and full-function ASIC for the CMS MTD Endcap Timing Layer (ETL) upgrade Jongho Lee The Endcap Timing ReadOut Chip (ETROC) is designed to process MIP-sensitive silicon low-gain avalanche diode (LGAD) signals with time resolution down to about 50 ps per hit to achieve 35 ps per track with two detector layers. Testing of the full-chain ASIC (ETROC1, size 4x4) during the last two years was successfully conducted on a beam telescope with three layers of bump-bonded ETROC1/sensors, resulting in a timing resolution of 42-45 ps per hit. The first full-size (16x16) and full-function prototype ASIC (ETROC2) has been developed on the basis of the pixel analog front-end design of ETROC1, and a switch-cell based network approach is introduced for the pixel readout and global readout design in ETROC2. The time-to-digital-converter (TDC) using uncontrolled delay which has been used for ETROC1 is also implemented on ETROC2. The ETROC2 includes new features such as the on-chip auto discriminator threshold calibration, built-in self-testing capability with digital pattern generation, and the capability to provide a coarse map of delayed hits continuously for every bunch crossing for monitoring or Level 1 triggering purposes. For design verification and testing purposes, the new pixel and global readout have been emulated in FPGA. The status of the initial testing results of ETROC2 is presented. |
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