rf Wien filter in an electric dipole moment storage ring: The “partially frozen spin” effect

Abstract

An rf Wien filter (WF) can be used in a storage ring to measure a particle’s electric dipole moment (EDM). If the WF frequency equals the spin precession frequency without WF, and the oscillating WF fields are chosen so that the corresponding transverse Lorentz force equals zero, then a large source of systematic errors is canceled but the EDM signal is not. This effect, discovered by simulation, can be called the “partially frozen spin” effect.