The Jefferson Lab Polarized 3He Target System

Jefferson Lab, a 5.7 GeV electron accelerator facility, has a broad program to study the structure of the neutron and the ³He nucleus using polarized ³He. The ³He gas target system designed for this program allows a wide range of scattering angles and maintains high polarization in a continuous electron beam. The ³He is contained in a high-pressure double-chambered glass cell centered in a 25 Gauss magnetic field. The ³He is polarized by spin-exchange with optically polarized rubidium vapor. Two independent methods of measuring the polarization have been integrated into this system: NMR, a water calibrated measurement of the nuclear magnetic resonance and EPR, a measurement of the shift in the electron paramagnetic resonance of rubidium before and after a helium nuclei spin-flip. These methods agree with each other to high precision and agree with the extracted polarization from an elastic asymmetry measurement.