SPIN@COSY: Spin‐Manipulating Polarized Deuterons and Protons

We studied spin manipulation of 1.85 GeV/c polarized deuteron beam stored in COSY obtaining a spin‐flip efficiency of $97±1%.$ We first discovered experimentally and then explained theoretically interesting behavior of the deuteron tensor polarization. We, for the first time, studied systematically spin resonance strengths induced by rf dipoles and solenoids. We found huge disagreements between the strengths measured in controlled Froissart‐Stora sweeps and the theoretical values calculated using the well‐known formulae. These data instigated re‐examination of these formulae. We tested Chao’s proposed new matrix formalism for describing the spin dynamics due to a single spin resonance, which may be the first fundamental improvement of the Froissart‐Stora equation in that it allows analytic calculation of the beam polarization’s behavior inside a resonance. Our measurements of the deuteron’s polarization near and inside the resonance agreed precisely with the Chao formalism’s predicted oscillations. We tested Kondratenko’s proposal to overcome depolarizing resonances by ramping through them with a crossing pattern, which should force the depolarizing contributions to cancel themselves. Our first test of this idea with 2.1 GeV/c protons was not conclusive but a later test with 1.85 GeV/c deuterons demonstrated a rather substantial reduction in the depolarization compared to the tune jump at the same rate.