Proposal for a cavity polarimeter at MIT-Bates

The possibility of successfully implementing a cavity polarimeter has been greatly improved by the discovery of a cavity mode for which the magnitude of the Stern-Gerlach force experienced by a magnetic moment traversing the cavity varies as the square of the relativistic factor gamma, so that the signal power varies as the fourth power of gamma. In addition, the interaction of this cavity mode with the beam charge varies as the inverse of the interaction with the magnetic moment, so that the background due to the beam charge varies as the inverse fourth power of gamma. If these gamma dependencies of moment and charge interaction with the pickup cavity do in fact exist, the possibility is opened for very fast, accurate, and inexpensive polarimetry at accelerators like MIT-Bates and RHIC. In addition, it might become possible to seriously consider Stern-Gerlach polarization of beams at LHC. We present details of a quick polarimeter test at the electron storage ring at MIT-Bates, and of an extension of this test to a working polarimeter in the RHIC rings.