An 800-MeV Spin Precessor for Polarized H- Beams Using H- to Ho Stripping

A new method is described for precessing the proton polarization axis of the incident H-polarized beam at LAMPF. The method uses a thin stripper to convert H-to Ho with ~50% efficiency at 800 MeV, and uses relatively small magnets to precess the HO spin. The large magnetic moment of the Ho relative to the charged ion (either H+ or H-) allows small magnets to produce any required spin orientation (with zero deflection of the neutral beam in the precession apparatus). Either Ho or H+ beam is delivered; for Ho, the magnitude of the proton polarization oscillates in proper time at the hyperfine frequency. The theory and test results will be summarized. Areas of possible application will be mentioned, including use for experiments and spin axis control where neutral beams can be used for injection of accelerated H-beams into storage rings or synchrotrons.