Phase Locking the Spin Precession in a Storage Ring
AbstractThis Letter reports the successful use of feedback from a spin polarization measurement to the revolution
frequency of a 0.97 GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron (COSY)
storage ring in order to control both the precession rate (≈121 kHz) 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 1 standard deviation range
of σ = 0.21 rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz,
which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of
storage rings to look for an intrinsic electric dipole moment of charged particles.
N. Hempelmann et al. (JEDI Collaboration),
Physical Review Letters 119 (2017) 014801.
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