Phase Measurement for Driven Spin Oscillations in a Storage Ring

TL;DR

This study demonstrates simultaneous measurement and control of spin polarization components in a storage ring using an rf solenoid, providing insights crucial for electric dipole moment experiments.

Contribution

First simultaneous measurement of horizontal and vertical polarization components under rf solenoid influence with a new spin feedback system.

Findings

Oscillation of vertical polarization observed

Analytical model successfully describes the oscillations

Results applicable to other rf devices like Wien filters

Abstract

This paper reports the first simultaneous measurement of the horizontal and vertical components of the polarization vector in a storage ring under the influence of a radio frequency (rf) solenoid. The experiments were performed at the Cooler Synchrotron COSY in J\"ulich using a vector polarized, bunched $0.97\,\textrm{GeV/c}$ 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 off, allowing the phase difference to change over time, and the solenoid was switched on to rotate the polarization vector. We observed an 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.