Unexpected reduction of rf spin resonance strength for stored deuteron beams

Stored beams of polarized protons, electrons, or deuterons can be spin flipped by sweeping an rf dipole’s or solenoid’s frequency through an rf spin resonance. Fitting such data to the modified Froissart-Stora equation’s spin resonance strength E_FS gave very large deviations from the ^*E_Bdl obtained from each rf magnet’s ∫B_rmsdl. We recently varied an rf dipole’s frequency sweep range Δf, and the momentum spread Δp/p and betatron tune ν_y of stored 1.85  GeV/c polarized deuterons. We found a sharp constructive interference when ν_y was near an intrinsic spin resonance. Moreover, over large Δf and Δp/p ranges, E_FS was about 7 times smaller than the predicted ^*E_Bdl.