The Variable Energy Polarized Proton Beam at TRIUMF

A polarized H- current of 1 μA has been achieved within a normalized emittance of 0.3π mm-mrad from a Lamb-shift type source. 80% of the beam is routinely transported at 300 keV along the 45 m long electrostatic injection line to the cyclotron, where 200 nA can be accelerated to 500 MeV and extracted. A Wien filter, located near the entrance of the injection line, is used to compensate for the precession resulting from the cyclotron's fringe field and to align the spin vertically. Depolarization along the line has been calculated to be less than a few per cent. The polarization, enhanced with a diabatic zero crossing in the source, is approximately 80%; however, a slight loss in polarization has been measured in the cyclotron between 200 and 500 MeV.