Unexpectedly wide rf-induced synchrotron sideband depolarizing resonances

Using an rf solenoid magnet, we studied the depolarization of a stored 104.1 MeV vertically polarized proton beam. The two primary rf depolarizing resonances were properly centered around the protons{close_quote} circulation frequency f{sub c}, at f{sub c}(3{minus}{nu}{sub s}) and f{sub c}({nu}{sub s}{minus}1), where {nu}{sub s} is the spin tune; moreover, each resonance was roughly consistent with the expected width of about 720 Hz. Each primary rf resonance had two synchrotron sideband resonances at the expected frequencies. The two {nu}{sub s}{minus}1 sidebands were deep dips while the two 3{minus}{nu}{sub s} sidebands were very shallow; this was not expected. Moreover, all four sideband resonances were unexpectedly wider than the two primary resonances. {copyright} {ital 1998} {ital The American Physical Society}