The connection between zero chromaticity and long in-plane polarization lifetime in a magnetic storage ring

TL;DR

This study shows that setting sextupole fields to eliminate chromaticity in a magnetic storage ring significantly extends the in-plane polarization lifetime of a deuteron beam, with implications for beam stability.

Contribution

It establishes a direct link between zero chromaticity conditions and enhanced polarization lifetime in a storage ring, demonstrating a practical method to optimize beam polarization.

Findings

Zero chromaticity conditions maximize IPP lifetime.

Optimal sextupole settings cancel orbit circumference changes.

Longer IPP lifetime reduces polarization loss during storage.

Abstract

In this paper, 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.