Connection between zero chromaticity and long in-plane polarization lifetime in a magnetic storage ring
In this work, we demonstrate the connection between a magnetic storage ring with additional sextupole
fields set so that the x and y chromaticities vanish and the maximizing of the lifetime of in-plane
polarization (IPP) for a 0.97-GeV/c deuteron beam. The IPP magnitude was measured by continuously
monitoring the down-up scattering asymmetry (sensitive to sideways polarization) in an in-beam, carbon-
target polarimeter and unfolding the precession of the IPP due to the magnetic anomaly of the deuteron.
The optimum operating conditions for a long IPP lifetime were made by scanning the field of the storage
ring sextupole magnet families while observing the rate of IPP loss during storage of the beam. The beam
was bunched and electron cooled. The IPP losses appear to arise from the change of the orbit
circumference, and consequently the particle speed and spin tune, due to the transverse betatron
oscillations of individual particles in the beam. The effects of these changes are canceled by an appropriate
sextupole field setting.
