Jefferson Lab’s GEn-II Experiment: Using a Novel ³He Target for the Measurement of the Neutron Electric Form Factor at High Q²

Nucleon electromagnetic form factors offer insight into the internal structure of those nucleons. The Super Bigbite Spectrometer (SBS) program at Jefferson Lab conducts experiments measuring nucleon form factors at high Q² values. Previous electric form factor measurements for the proton, G_E^p , were measured for Q² = 8.5 GeV², where as the neutron’s, G_Eⁿ, had only been measured to Q² = 3.4 GeV².

By colliding a polarized electron beam with a polarized 3He target (with novel convection cell), experiment E12-09-016 (September 2022 - October 2023), GEn-II, measured the double spin asymmetry of the e − n cross section in order to extract the form factor ratio G_Eⁿ /G_Mⁿ at Q² values of 2.9, 6.6, and 9.7 GeV². The changes in the target cell’s geometry allowed for higher beam currents coupled with high SEOP (Spin Exchange Optical Pumping) polarizations. These effects helped lead to luminosities previously unattainable in polarized ³He experiments. This talk will cover performance aspects of the ³He target during GEn-II.