Induced spin resonances of a polarized proton beam using a radio frequency solenoid.

Abstract

The spin dynamics of circulating beams must be thoroughly understood in order to provide polarized beams for high energy experiments exploring spin dependent particle interactions. A radio frequency solenoid was installed in the Cooler Ring of the Indiana University Cyclotron Facility where the energy spread of the proton beam is small hence facilitating high precision measurements. The measurements were made at a beam kinetic energy of 104.11 MeV. The rf-solenoid introduced a weak depolarizing field. The spin tune of the unperturbed synchrotron was measured by finding the resonance condition between the frequency of the weak depolarizing field and the spin's intrinsic precession frequency, the spin tune. The spin tune was measured to an accuracy of one part in 10$\sp5$ both with and without the presence of a full Siberian Snake. The spin vector of a circulating beam was observed to freely precess about the field of the rf-solenoid in the proximity of the resonance. The free spin precession demonstrated the high precision to which the spin vector can be manipulated. The synchrotron sidebands of an induced resonance were measured and found to have an unexpectedly large width. The width of the synchrotron sidebands can be described by the influence of the rf-solenoid on the beam's orbit dynamics thus emphasizing the coupling between spin and orbit dynamics. Specific recommendations are made for the improvement of the rf-solenoid and the design of similar oscillating field devices to be used as experimental tools in future polarized beam facilities.