Development of a Polarized 3He++ Ion Source for the EIC

Abstract

The capability of accelerating a high-intensity polarized $^{3}$He ion beam would provide an effective polarized neutron beam for new high-energy QCD studies of nucleon structure. This development is essential for the future Electron Ion Collider, which could use a polarized $^{3}$He ion beam to probe the spin structure of the neutron. The proposed polarized $^{3}$He ion source is based on the Electron Beam Ion Source (EBIS) currently in operation at Brookhaven National Laboratory. $^{3}$He gas would be polarized within the 5 T field of the EBIS solenoid via Metastability Exchange Optical Pumping (MEOP) and then pulsed into the EBIS vacuum and drift tube system where the $^{3}$He will be ionized by the 10 Amp electron beam. The goal of the polarized $^{3}$He ion source is to achieve $2.5 \times 10^{11}$ $^{3}$He$^{++}$/pulse at 70% polarization. An upgrade of the EBIS is currently underway. An absolute polarimeter and spin-rotator is being developed to measure the $^{3}$He ion polarization at 6 MeV after initial acceleration out of the EBIS. The source is being developed through collaboration between BNL and MIT.