Phase Measurement for Driven Spin Oscillations in a Storage Ring

In this work we report the first simultaneous measurement of the horizontal and vertical components
of the polarization vector in a storage ring under the inuence of a radio frequency (rf) solenoid. The
experiments were performed at the Cooler Synchrotron COSY in Jülich using a vector polarized,
bunched 0.97 GeV/c deuteron beam.
Using the new spin feedback system, we set the initial phase difference between the solenoid field
and the precession of the polarization vector to a predefined value. The feedback system was then
switched of, allowing the phase difference to change over time, and the solenoid was switched on
to rotate the polarization vector. We observed the oscillation of the vertical polarization component
and the phase difference. The oscillations can be described using an analytical model.
The results of this experiment also apply to other rf devices with horizontal magnetic fields, such
as Wien filters. The precise manipulation of particle spins in storage rings is a prerequisite for
measuring the electric dipole moment (EDM) of charged particles.

Phys. Rev. Accel. Beams 21, 042002