Polarization Optimization Studies in the RHIC Optically-Pumped Polarized H-Ion Source

The performance of the RHIC Optically-Pumped Polarized H- Ion Source (OPPIS) in 2000-2002 runs in AGS and RHIC is reviewed. The OPPIS met the RHIC requirements for beam intensity with the reliable delivery of about 500 μA polarized H- ion current in 400 μs pulse duration (current can be increased to over 1.0 mA, if necessary). The beam intensity at 200 MeV was (5-6) 1011 H-/pulse, which is sufficient to obtain the required 2·1011 polarized protons per bunch in RHIC. The polarization dilution by molecular ions, which are produced in the ECR primary proton source is discussed. The molecular component can be reduced to about 5% by further ECR source-operation optimization. The molecular component is suppressed by optimization of the extraction electrode optics and by the decelerating einzel lens in the 35 keV LEBT line. As a result, the proton polarization of the accelerated beam was increased to over 80%, as measured in the 200 MeV proton-deuterium polarimeter