We analyzed all available data on spin‐flipping stored beams of protons, deuterons and electrons. We first calculated the rf‐induced spin resonance strength ratio εFS/*εBdl; the εFS was obtained by fitting the measured polarization data to the modified Froissart‐Stora equation, while *εBdl was calculated using the ∫Bdl of the rf dipole or rf solenoid. We found that εFS/*εBdl was often 7 times lower than predicted for deuterons, and 12 to 170 times higher than predicted for protons. We studied these discrepancies with vertically polarized beams of 2.1 GeV/c protons and 1.85 GeV/c deuterons stored in the COSY ring in Jülich, Germany. These studies involved flipping their polarization direction, by sweeping the frequency of a water‐cooled ferrite rf dipole, of typically ∫Bdlrms = 0.60 ± 0.3 T⋅mm, through an rf‐induced spin resonance.
We studied the dependence of εFS/*Bdl on the beam size, the momentum spread and the distance from the nearest 1st‐order intrinsic spin resonance for both protons and deuterons, and on the frequency sweep range Δf for deuterons. We observed no measurable dependence of εFS/*Bdl on the beam’s size or momentum spread for either protons or deuterons. When we varied the vertical betatron tune νy near a 1st‐order intrinsic spin resonance, we observed a strong enhancement of εFS/*εBdl with a hyperbolic dependence on the distance from the 1st‐order intrinsic spin resonance for both protons and deuterons. This explained much of the proton discrepancy, but did not explain the deuteron’s very small εFS/*εBdl. All early deuteron data had small Δf values of 100–200 Hz; however, when Δf was increased from 100 to 3000 Hz, in four steps, there was no dependence of εFS/*εBdl on Δf Thus, this anomalously small εFS/*εBdl ratio may be due to some unexpected behavior of relativistic spin‐1 deuterons in an rf dipole.
