Speaker
Description
Permanent electric dipole moments (EDM) in elementary particles would violate CP-symmetry. The JEDI (J¨ulich
Electric Dipole moment Investigations) collaboration will measure the EDM of charged hadrons using a storage ring.
To keep the spin oscillation in phase with an external frequency, which is a requirement for EDM measurements in
magnetic storage rings, an active feedback system was developed and tested with a polarized deuteron beam at the
Cooler Synchrotron (COSY).
The feedback system determines the spin polarization using information from the polarimeter EDDA. Data
measured over a time of about one second are analyzed to determine the necessary correction. The phase of the
spin rotation is continuously adjusted by modifying the accelerator frequency, which changes the beam velocity and
hence the rate of spin precession.
The effects of the EDM in a storage ring were mimicked using an rf-solenoid whose frequency was locked with
respect to the spin oscillation. Like an EDM, the solenoid gradually tilts the spin from a horizontal to a vertical
direction.
The results of the tests of the feedback system demonstrate that the method is suitable for a future proof of
principle experiment for EDM measurements at COSY.
