  Since 2012, a BNL-MIT collaboration has worked to develop a polarized $^3$He
ion source for the Relativistic Heavy Ion Collider (RHIC) using the existing
Electron Beam Ionization Source (EBIS). $^3$He atoms are polarized using
optical pumping at high field and injected as neutral atoms into the EBIS. A
critical issue is the demonstration that the polarization of the extracted
$^3$He$^{++}$ ions from the source is high. In 2014, a concept to measure the
nuclear polarization was developed in this paper. Since then, the development
of the polarized $^3$He ion source has progressed, the polarimeter is under
construction, and the demonstration experiment is expected to take place in the
next several years.
