Bunch-by-bunch Beam Transverse Feedback Electronics Designed for SSRF

TL;DR

This paper presents the design and testing of a bunch-by-bunch transverse feedback electronics system for SSRF, improving beam stability by effectively suppressing instabilities with high-performance signal processing.

Contribution

It introduces a novel signal processor design for transverse feedback electronics, demonstrating performance that meets the stringent requirements of SSRF's beam stability system.

Findings

ENOB > 10 bits at 100 MHz input signal

Amplitude suppression > 35 dB at critical frequencies

Phase response uncertainty < 2 degrees

Abstract

Shanghai Synchrotron Radiation Facility (SSRF), is one of the third-generation high-beam current (3.5 GeV) synchrotron light sources. In the storage ring of SSRF, multi-bunch instabilities would increase beam emittance and energy spread, which degrade beam quality and even cause beam loss. To address the above issues, a Transverse Feedback System is indispensable for SSRF, in which the key component is the bunch-by-bunch transverse feedback electronics. The whole feedback system consists of five main parts: Beam Position Monitor (BPM), RF front-end, signal processor, RF amplifier, and vertical/horizontal transverse kickers. The dissertation focuses on the signal processor we design, which is the main part of the feedback electronics. We conducted initial testing on the signal processor to evaluate its performance and function. Test results indicate that ENOB of the Analog-to-Digital Conversion circuit is better than 10 bit with 100 MHz input signal, and remains better than 9.5 bit up to 300 MHz, which is good enough for the required 7.9 bit; the frequency response of the whole system also concords well with the simulation results, and the suppression in amplitude response at the critical frequency points is better 35 dB while the uncertainty of phase response is better than 2 degree, all meeting the application requirement.