HEP-Astro Seminar | Realizing a Polarized 3He++ Ion Source at Brookhaven National Lab with Metastability Exchange Optical Pumping

A high intensity (2 x 10ˆ11 ions per pulse) polarized 3He++ ion source is being developed at BNL for use at the future Electron Ion Collider (EIC). The helium gas will be polarized using a novel technique based on metastability-exchange optical pumping (MEOP) in the 5T field of the existing Electron Beam Ion Source (EBIS), where it can be ionized and prepared for injection into the Booster. An infrared laser system has been developed for optical pumping and measuring the polarization of the gas inside of the EBIS field. Previous results in a test setup have shown up to 80% polarization for ultra-pure 3He in an “open” cell configuration, with isolation valve and refilling tubes closed. Now, the setup has been moved into an exact copy of the EBIS magnet to prepare for final integration and injection into the Booster. An absolute nuclear polarimeter and spin-rotator has been constructed to measure the 3He polarization near 6 MeV in the EBIS to Booster transit line. The ion source will be an essential component of future polarized neutron studies at the planned Electron Ion Collider (EIC).

In this seminar, I will provide a brief introduction to the theory behind the MEOP process and a discussion of relevant technical challenges in implementing the source at BNL. The status of the project and plans for integration and polarization measurements inside of EBIS during the 2026 RHIC shutdown will be presented.