Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H21: Instrumentation: Targets and PolarimetryLive
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Sponsoring Units: DNP Chair: Karl Slifer, UNH |
Sunday, April 18, 2021 10:45AM - 10:57AM Live |
H21.00001: Upgraded Polarized Helium-3 Target and Its Performance in Experiments at Jefferson Lab Junhao Chen Polarized Helium-3 target in Jefferson Lab has been upgraded to significantly increase the performance, including doubled luminosity and better polarimetry performance. This upgraded polarized Helium-3 target system was successfully used in \(A_1^n\) (E12-06-110) and \(d_2^n\) (E12-06-121) experiments at Jefferson Lab in Hall C with the 12 GeV upgrade, from December 2019 to September 2020. I will present the target performance in these recent experiments. [Preview Abstract] |
Sunday, April 18, 2021 10:57AM - 11:09AM Live |
H21.00002: The Liquid Hydrogen Target for TPEX Ievgen Lavrukhin, Wolfgang Lorenzon, Richard Raymond Significant efforts (both theoretical and experimental) have been made over the past decade to study two-photon exchange (TPE) contributions in elastic lepton-proton scattering. The three recent experiments (VEPP-3, CLAS and OLYMPUS), which have reported on direct measurements of TPE, show little evidence for large contributions of hard two-photon exchange up to Q$^2$ = 2.5 (GeV/c)$^2$. The Two-Photon Exchange eXperiment (TPEX) proposes to determine the hard two-photon contributions by measuring the ratio of positron-proton to electron-proton elastic scattering at beam energies of 2 and 3 GeV. This will extend the momentum transfer range up to Q$^2$ = 4.7 (GeV/c)$^2$, where the TPE effect is expected to be more substantial, while still overlapping with existent OLYMPUS data. For this new experiment, we propose to build a liquid hydrogen target that will yield a luminosity about a factor of 200 times higher than that of the OLYMPUS experiment. This higher luminosity will greatly shorten the run time needed at 2 GeV and help to make up for the lower cross section at 3 GeV beam energies. In this presentation, we will discuss the latest updates on the requirements, technical design and implementation of the liquid hydrogen target for TPEX. [Preview Abstract] |
Sunday, April 18, 2021 11:09AM - 11:21AM Live |
H21.00003: The Liquid Hydrogen Target for MUSE Haley Reid The Muon Scattering Experiment (MUSE) at the Paul Scherrer Institute aims to measure the elastic scattering of muons and electrons from a liquid hydrogen target in order to work towards resolving the proton radius puzzle. MUSE will perform the scattering of both lepton families simultaneously, and both charge variants sequentially, determining the scattering cross section in each case with high precision. To accomplish this goal, MUSE employs a vertically movable target with five different target positions respective to the proton beam. The main target is a cylindrical Kapton cell with copper end caps that holds 280 mL of liquid hydrogen. In this presentation, we discuss the technical design, implementation, and performance of the target system and its support infrastructure, presenting data to demonstrate the successful operation of the LH$_{\mathrm{2}}$ target. Additionally, we remark on the recent improvement efforts for the target system. [Preview Abstract] |
Sunday, April 18, 2021 11:21AM - 11:33AM Live |
H21.00004: Polarized $^3$He Target in High Magnetic Field at CLAS12 Dien Nguyen, Xiaqing Li, James Maxwell A nuclear spin polarized $^3$He target provides a unique advantage as an effective polarized neutron target in spin-dependent measurements of electron scattering from the neutron. Although optical pumping techniques for polarization of $^3$He in low-magnetic-field environments have produced successful scattering targets, increased wall relaxation has limited the effectiveness of these targets at high magnetic fields. Recent developments in high-magnetic-field optical pumping, including a polarized $^3$He ion source at RHIC for the EIC, have opened the possibility of a polarized $^3$He target within high-magnetic-field experimental facilities such as the CLAS12 spectrometer in Hall B at Jefferson Lab. A double-cell cryogenic target using the metastability exchange optical pumping method\footnote{J.~Maxwell and R.~Milner, arXiv:1911.06650} has been designed for a proposed experiment of spin-dependent electron scattering from a polarized $^3$He target at CLAS12\footnote{JLab Conditionally Approved Proposal PR12-20-002: {\it A Program of Spin-Dependent Electron Scattering from a Polarized $^3$He Target in CLAS12}, Co-Spokespeople: H.~Avakian, J.~Maxwell, R.~Milner, D.~Nguyen}. In this talk, the conceptual design, recent development, and future work of such a target will be presented. [Preview Abstract] |
Sunday, April 18, 2021 11:33AM - 11:45AM Live |
H21.00005: Development of thin film UO$_{\mathrm{2}}$ targets using spin coating and combustion synthesis methods. Ashabari Majumdar, Khachatur Manukyan, Stefania Dede, Jordan Roach, Daniel Robertson, Peter Burns, Ani Aprahamian Stable, uniform and cost-effective targets are essential in measuring the nuclear properties of actinides for nuclear astrophysics experiments. Existing methods of target production fall short in providing reliable and cost-efficient targets. The present work shows a novel technique for the production of actinide targets through a combination of solution combustion synthesis and spin coating methods. Depleted UO$_{\mathrm{2}}$ targets were produced with control of film thicknesses ranging from 30 -- 260 nm. Uniformity of the targets were measured using X-ray fluorescence (XRF) with variations found to be less than 5{\%}.~ Alpha spectroscopy confirmed a linear increase in uranium content with increases in film thickness. Target stability was tested using ion beam bombardment with Ar$^{\mathrm{2+\thinspace }}$ions at 1.7 MeV. XRF and alpha spectroscopy of irradiated samples showed no sign of sputtering degradation up to a fluence of 10$^{\mathrm{17}}$ ions/cm$^{\mathrm{2}}$.~ Phase transitions (amorphization and recrystallization) occurred in the targets after irradiation but the chemical composition remained unchanged. This talk will discuss the details of the production method and the properties of the newly developed UO$_{\mathrm{2}}$ targets. [Preview Abstract] |
Sunday, April 18, 2021 11:45AM - 11:57AM Live |
H21.00006: Diffusion Constant Measurement of Dilute $^3$He in Superfluid $^4$He for UCN Experiments Cameron Blake Erickson Ultra cold neutrons (UCNs) are commonly employed in precise measurements of fundamental neutron properties such as in the neutron electric dipole moment experiment at ORNL. High densities of UCN’s can be attained by down-scattering cold neutrons in superfluid $^4$He, but $^3$He impurities in the superfluid absorb neutrons, making it desirable to control the relative fraction of $^3$He to $^4$He in these experiments. The $^3$He diffusion constant at concentrations at or below that of natural $^4$He, around 1 ppm, is important for this control and determined by microscopic scatterings between $^3$He and phonon excitations in the superfluid. This talk discusses a planned measurement of the $^3$He spin diffusion constant using free induction decay for concentrations around 1 ppm and temperatures between 150 to 550 mK. This phase space covers both $^3$He-phonon and $^3$He-$^3$He dominated diffusion, providing a check against theory and a complement to previous measurements. [Preview Abstract] |
Sunday, April 18, 2021 11:57AM - 12:09PM Live |
H21.00007: Results and Insights for Moller Polarimetry during PREX-2 and CREX Donald Jones Jefferson Lab’s precision parity-violating electron scattering program has increasingly stringent requirements on the accuracy of beam polarimetry. The M\o ller polarimeter in Hall A was commissioned at low energy and successfully used during the recently completed PREX-2 and CREX experiments to meet the required precision. Along the way the polarimetry teaming gained experience and key insights necessary for the upcoming high-precision program. This talk will focus on the results of M\o ller polarimetry and understanding gained during these past two experiments. [Preview Abstract] |
Sunday, April 18, 2021 12:09PM - 12:21PM Live |
H21.00008: The Path to $\pm$0.4\% Moller Polarimetry in Hall A at Jefferson Lab Eric King The proposed uncertainty on beam polarimetry for the future MOLLER and SoLID experimental programs at Jefferson Lab is $\pm$0.4\%. The polarimetry team aims to reach this level of precision individually with both the M\o ller and Compton polarimeters in Hall A. This discussion will focus on the the M\o ller polarimeter and why and how we believe we can reach this goal given recent insights and experience from the PREX-2 and CREX experiments. [Preview Abstract] |
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