Metastability Exchange Optical Pumping for Polarizing ³He in Varied Magnetic Fields and Pressures

Polarized ³He nuclear targets have proven essential as substitutes for polarized neutron targets in spin-dependent scattering experiments, providing critical insights into the quark and gluon structure of matter. Although traditional polarized ³He targets have experienced significant advancements over the past three decades, their application has largely been limited to low magnetic fields. Recent developments in high magnetic field metastability exchange optical pumping (MEOP) of ³He, initially designed for a polarized ³He ion source at RHIC and the EIC, now present a promising avenue for creating high field polarized ³He targets. By integrating these techniques with a double-cell cryogenic target design, we are employing MEOP of ³He nuclei at varying pressures using a fillable cell under magnetic fields ranging from 2 to 5 T. We will present the conceptual design for this target, highlight our progress in polarizing ³He at Jefferson Lab, and the test of a cryogenic stand, and outline the roadmap toward an experiment-ready target for JLab’s CLAS12 spectrometer.