Phase Locking the Spin Precession in a Storage Ring
The successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring has been realized in order to control both the precession rate (≈ 120kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a one standard deviation range of σ = 0.21rad. The minimum possible adjustment was 3.7mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.