Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session JF: Mini-Symposium: Advances and Opportunities in Polarized Targets and Beams I |
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Chair: Clementine Santamaria, FRIB/NSCL Room: Berkeley & Clarendon |
Wednesday, October 13, 2021 9:30AM - 10:06AM |
JF.00001: Recent Advances in Dynamic Nuclear Polarization Targets Invited Speaker: Elena A Long A new dynamic nuclear polarization (DNP) target has been constructed at the University of New Hampshire that is being used to develop new tensor enhancement techniques for upcoming experiments at Jefferson lab to measure the tensor polarized structure function b1 and the quasi-elastic tensor asymmetry Azz. This target utilizes a novel solid-state microwave system for driving both vector and tensor polarization enhancement and is capable of simultaneous EPR measurements, a recently constructed 1K liquid helium evaporative refrigerator, multiple NMR systems for polarization measurements, and 3D printed target ladders. Additionally, new methods for creating polarizable material utilizing slow-freezing techniques are being developed. An overview of these advances and experimental opportunities for this target will be presented. |
Wednesday, October 13, 2021 10:06AM - 10:18AM |
JF.00002: Axial and pseudoscalar form factors from charged-current neutrino-nucleon elastic scattering Oleksandr Tomalak We study the sensitivity to axial nucleon structure of single-spin asymmetries in (anti)neutrino charged-current elastic scattering on free nucleons. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large single-spin asymmetries. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundred MeV of energy or with tau (anti)neutrinos. Recoil and target longitudinal asymmetries are the most promising single-spin asymmetries for the extraction of the axial form factor at GeV energies. |
Wednesday, October 13, 2021 10:18AM - 10:30AM |
JF.00003: A New NMR System for Solid Polarized Targets James D Maxwell Solid polarized targets rely on continuous-wave Nuclear Magnetic Resonance techniques to provide measurements of the enhanced polarization from Dynamic Nuclear Polarization. For decades, Jefferson Lab has relied upon Liverpool Q-meters for NMR measurements, but these contain obsolete components and are no longer produced. To address the needs of coming polarized target experiments at JLab, we have developed a new NMR system with Q-meters based on the Liverpool design. In addition to new Q-meter circuits, this system adds electronic resonance tuning and phase shifting capabilities in modular hardware components. A new, FPGA-based data acquisition system allows control and measurement through an ethernet connection, interfaced via new Python software which brings additional data analysis tools to experimental runs. We will discuss the design and operation of this new system and plans for future NMR development at JLab. |
Wednesday, October 13, 2021 10:30AM - 10:42AM |
JF.00004: Polarized $^3$He Target in High Magnetic Field at CLAS12 Xiaqing Li, Dien T Nguyen, James D Maxwell A nuclear spin polarized $^3$He target has proven a successful effective polarized neutron target in spin-dependent measurements of electron scattering from the neutron. Polarized $^3$He targets in low magnetic fields have been well developed using the spin exchange optical pumping technique. However, the application of a polarized $^3$He target in a high-magnetic-field environment is limited due to the increased wall relaxation. Taking advantage of recent improvements in high-field metastability exchange optical pumping, a novel double-cell cryogenic target has been designed to accommodate to the 5-T solenoid in Hall B at Jefferson Lab for a proposed experiment of spin-dependent electron scattering from a polarized $^3$He target at CLAS12. In this talk, the target design and recent progress in the target development will be presented. |
Wednesday, October 13, 2021 10:42AM - 10:54AM |
JF.00005: Design of a Longitudinally Polarized Target for CLAS12 Victoria Lagerquist The upcoming Run Group C experiments in Hall B of Jefferson Lab will utilize the CLAS12 detector system and a new dynamically polarized target of irradiated NH3 and ND3 to study the nucleon spin structure. The dimensional constraints necessary for incorporation of this new target into the CLAS12 detector system, as well as utilization of its 5T central solenoid field, introduce unique design challenges. I will present an overview of our solutions to these challenges including precision magnetic field optimization, and an innovative, rapid material transport mechanism inside the target cryostat. |
Wednesday, October 13, 2021 10:54AM - 11:06AM |
JF.00006: First Tests of the New Longitudinally Polarized Target for CLAS12 Pushpa Pandey The Run Group C suite of experiments will measure multiple spin-dependent observables by scattering the energy-upgraded 11 GeV electron beam from longitudinally polarized nucleon targets inside the CLAS12 spectrometer in Hall B at Jefferson Lab. The dynamically polarized target built for these experiments has been extensively tested in the JLab Target Lab using an auxiliary 5 T magnet. We will report on the operational experience with the target, and the benchmarks achieved so far using various polarizable materials with the complete target setup. Our results show that all target components work well and that the project is on track for the scheduled experiment that will run during most of the year 2022. |
Wednesday, October 13, 2021 11:06AM - 11:18AM |
JF.00007: Spin-1 Polarized Target NMR Analysis Lillian M Soucy The UNH nuclear physics group produces polarized targets that are essential for the study of nucleon spin structure. The polarization of the material must be known to excellent precision to limit systematic uncertainties. Nuclear magnetic resonance (NMR) is used to determine the polarization of the target. The polarization is extracted by comparing the NMR lineshape to that of a reference signal where the polarization is known. Typically, the calibration is determined by measuring the lineshape at thermal equilibrium (TE) where Boltzmann statistics describe the equilibrium polarization. However, the signal to noise at equilibrium is extremely small which makes this calibration challenging. Maintaining the low temperature (1 K) and magnetic field (5 T) required for the TE over extended periods of time is a difficult experimental demand. |
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