The Performance of a Novel Polarized ³He Target for the GEn-II SBS Experiment at Jefferson Lab

The Super Bigbite Spectrometer (SBS) experimental program is a series of experiments taking place in Hall A at Jefferson Lab that seeks to measure three of the nucleon elastic form factors at high values of Q². In particular, the aptly named GEn-II experiment was designed with the purpose of extracting the electric form factor of the neutron, G_Eⁿ, at Q² values of up to 9.7 GeV², higher than ever measured.

GEn-II makes use of a double-polarization technique which requires the use of a polarized ³He target as an effective neutron target. In order to achieve the necessary statistics for such a high Q² measurement, our target needed to reach a world-record Figure of Merit of approximately twice that of any previous polarized ³He experiment. Our target design consists of a 60cm long target chamber, the longest target chamber used to date, and a pumping chamber in which the ³He was polarized using alkali-hybrid spin exchange optical pumping.

In this talk, I will overview the preparation and performance of our targets during data taking. I will also go over the methods of measuring target polarization using Electron Paramagnetic Resonance and Nuclear Magnetic Resonance.