Polarized 3He++ Ion Source for RHIC and an EIC

Abstract

The capability of accelerating a polarized 3 He ion beam in RHIC would demonstrate an effective polarized neutron beam for the study of new high-energy QCD studies of nucleon structure. This development would be particularly beneficial for the future plans of an Electron Ion Collider (EIC), 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 (BNL). 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 × 10 11 3 He ++ /pulse at 70% polarization. An upgrade of the EBIS is currently underway at BNL. The EBIS capability to produce polarized 3 He ++ is being developed through a collaboration between BNL and MIT.

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

“…Expanding on the preliminary results reported in 2017 [12], the entire Extended EBIS vacuum system has been modeled (see Fig. 5) to estimate the vacuum performance of the gas injection system and the efficiency of the gas ionization.…”

“…However, an EIC will require a much higher intensity and polarization than achieved by previously developed polarized 3 He ion sources [1,2,3]. For this reason, development of a polarized 3 He ion beam has been identified as an R&D priority for the EIC [4,5,6], and the BNL-MIT polarized 3 He ion source collaboration has pursued this R&D [7,8,9,10,11,12,13]. The design goal of the polarized 3 He ion source is 2.5 × 10 11 3 He ++ /s with 70% polarization in a 20 µs pulse, which equates to a peak current of ≈4 mA.…”