A direct current polarized H− ion source based on optically pumped rubidium

The TRIUMF optically pumped polarized H− ion source has been modified to operate with rubidium as the optically pumped medium. The intrinsic characteristics of rubidium as well as an increase in laser power, compared with the previous system based on sodium, have led to a large increase in beam polarization to over 75%. A proton current of 2.5 μA extracted from the TRIUMF cyclotron at 230 MeV was easily attained during initial operations.