Alkali-Hybrid Spin-Exchange Optically-Pumped Polarized 3HE Targets Used for Studying Neutron Structure

Singh, Jaideep, Department of Physics, University of Virginia
"Cates,Jr.", Gordon, Department of Physics, University of Virginia

This thesis describes the first application of alkali-hybrid spin-exchange optical pumping (SEOP) to polarized 3 He targets used in electron scattering experiments. Over the last decade, polarized 3 He targets have been used at the Thomas Jefferson National Accelerator Facility (JLab) to measure the structure of the neutron via its spin degrees of freedom. In this thesis, two experiments, E97110 & E02013, receive special attention. The first, E97110, measured the absolute inclusive cross section differences for a longitudinally polarized electron beam scattering from a traditional SEOP 3 He target polarized both parallel & perpendicular to the beam. These cross section differences were used to extract the 3 He spin structure functions g 1 (x, Q 2 ) & g 2 (x, Q 2 ) over a Bjorken-x range of 0.01 < x < 0.50 for Q 2 = 0.04, 0.06, 0.08, 0.10, 0.12, & 0.24 GeV 2 . Integrals of g 1 & g 2 over x were used to extract IA n (the generalized Gerasimov-Drell-Hearn integral) and Γn 1 (the first moment of g 1 ) for the neutron. Preliminary results for these quantities are used to test the predictions of Baryon Chiral Perturbation Theory. The second, E02013, measured the asymmetry for a longitudinally polarized electron beam scattering from an alkali-hybrid SEOP 3 He target polarized perpendicular to the q-vector. The electric form factor of the neutron, GE n , was extracted from this asymmetry for Q 2 = 1.7, 2.5, & 3.4 GeV 2 . Near final results for G n E are iv compared to predictions from a variety of nucleon models. Alkali-hybrid SEOP using rubidium & potassium ([K]/[Rb] ≈ 5 ± 2), coupled with narrowband (laser linewidth is roughly equal to Rb absorption linewidth) laser diode arrays, have resulted in a consistent & reliable in-beam 3 He polarization increase from 37% to 65%. We describe how to implement these improvements and why they are effective. Furthermore, we summarize what we've learned over the past decade about the 3 He polarization limits of SEOP. Finally, we present a detailed analysis of 3 He polarimetry based on nuclear magnetic resonance (NMR) and electron paramagnetic resonance frequency shifts (EPR), with a special emphasis on corrections due to magnetic field gradients and polarization gradients within the target cell.

Note: Abstract extracted from PDF text

PHD (Doctor of Philosophy)
All rights reserved (no additional license for public reuse)
Issued Date: