Mitigation and control of instabilities in DAFNE positron ring

TL;DR

This paper discusses the various mitigation strategies implemented in the DAFNE positron ring to control e-cloud instabilities, including feedback systems, solenoids, and clearing electrodes, supported by diagnostic evaluations.

Contribution

It presents a comprehensive overview of the combined use of feedback, solenoids, and electrodes to mitigate instabilities in the DAFNE positron ring, with detailed diagnostic assessments.

Findings

Feedback systems effectively monitor instability growth rates.

Solenoids and electrodes reduce instability effects.

Diagnostics enable optimal device setup and performance evaluation.

Abstract

The positron beam in the DAFNE e+/e- collider has always been suffering from strong e-cloud instabilities. In order to cope with them, several approaches have been adopted along the years: flexible and powerful bunch-by-bunch feedback systems, solenoids around the straight sections of the vacuum chamber and, in the last runs, e-cloud clearing electrodes inside the bending and wiggler magnets. Of course classic diagnostics tools have been used to evaluate the effectiveness of the adopted measures and the correct setup of the devices, in order to acquire total beam and bunch-by-bunch currents, to plot in real time synchrotron and betatron instabilities, to verify the vertical beam size enlargement in collision and out of collision. Besides, to evaluate the efficacy of the solenoids and of the clearing electrodes versus the instability speed, the more powerful tools have been the special diagnostics routines making use of the bunch-by-bunch feedback systems to quickly compute the growth rate instabilities and the bunch-by-bunch tune spread in different beam conditions.