Polarized 3He Target Performance in the JLab SBS GEn Experiment, E12-09-016

The JLab Super Bigbite Spectrometer (SBS) program’s primary goal is to determine the elastic nucleon form factors at high momentum transfer. The SBS program includes a measurement of the neutron electric form factor, GEn, using the double-polarization technique with both a polarized electron beam and a polarized He-3 target. In order to obtain adequate statistics in the high Q² region, the polarized He-3 target has operated with a polarization-weighted luminosity approximately a factor of three above any previous polarized He-3 target used in an electron-scattering experiment. The target itself consists of a double-chambered glass cell, filled to approximately 7 atm of He-3 at room temperature, with a long cylindrical "target chamber" 60 cm in length. In order to maintain high polarization with electron beam currents up to 60uA, the target cells contain roughly 6 STP liters of He-3, twice the quantity of He-3 used in previous targets at JLab. This cell is polarized using alkali-hybrid spin-exchange optical pumping using up to 200W of near-infrared light from high-powered diode-laser arrays. The target polarization percentage is determined by a technique utilizing Electron Paramagnetic Resonance (EPR) as well as Nuclear Magnetic Resonance (NMR). Multiple target calibrations were carried out throughout the experiment in order to precisely determine the target polarization. This talk will include polarimetry results of all targets used during the GEn run period.