Polarized electron bunch refresh rates in an electron storage ring

TL;DR

This paper proposes a new scheme to equalize polarization bunch refresh rates in electron storage rings, which can improve accelerator operation and reduce systematic errors in high-energy physics experiments.

Contribution

It introduces an alternative policy for bunch refresh rates that are nearly independent of the radiative polarization level and emphasizes maximizing the buildup time constant.

Findings

The total bunch refresh rate is nearly independent of the asymptotic polarization level.

A scheme to equalize refresh rates of polarization bunches is proposed.

The approach can aid accelerator operation and reduce experimental systematic errors.

Abstract

When polarized electron bunches are injected and circulated in a high-energy storage ring, the polarization of the bunches relaxes to the asymptotic value of the radiative polarization, caused by the synchrotron radiation. Hence the bunches must be refreshed periodically, to maintain a predetermined time-averaged value of the bunch polarization. In general, the refresh rates of the "up" and "down" polarization bunches are different. We suggest an alternative policy. We point out that the total bunch refresh rate is almost independent of the asymptotic level of the radiative polarization. We also note that the true goal of so-called "spin matching" is to maximize the buildup time constant (not the asymptotic level) of the radiative polarization. We suggest a scheme to equalize the refresh rates of the "up" and "down" polarization bunches, which may be (i) helpful for accelerator operations, and also (ii) reduce systematic errors in HEP experiments.