Overcoming Intrinsic Spin Resonances with an rf Dipole

A coherent spin resonance excited by an rf dipole was used to overcome depolarization due to intrinsic spin resonances at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory. We found that our data are consistent with a full spin flip of a polarized proton beam, without emittance growth, at $G\ensuremath{\gamma}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}12+{\ensuremath{\nu}}_{z}$ and $36\ensuremath{-}{\ensuremath{\nu}}_{z}$, by adiabatically exciting a vertical coherent betatron oscillation using a single rf dipole magnet. The interference pattern observed between the intrinsic spin resonance and the coherent spin resonance agrees well with multiparticle spin simulations based on a simple two-resonance model. The interference pattern can be used for beam diagnostics.