Development of a real-time cavity-based injection efficiency monitor system at SSRF

Abstract

Injection efficiency is a critical parameter for synchrotron radiation facilities, especially those operating in top-up mode. The Shanghai Synchrotron Radiation Facility (SSRF) started top-up operation in 2012 committed to providing users with higher-quality light sources. During the top-up operation, a regular injection from the booster to the storage ring is required. A low-efficiency injection system will massively increase the radiation dose and seriously threaten the health of users. To evaluate the performance of the injection system, a real-time injection efficiency measurement system with high-resolution and high reliability is indispensable. Instead of using an integrating current transformer (ICT) that requires extremely careful shielding and grounding, a new system uses a novel dual-cavity monitor that can generate a high signal-to-noise ratio (SNR) and narrowband signal to detect bunch charges. It aims to reduce the influence of electromagnetic interference on the system and improve the reliability and resolution of the system. This paper describes the establishment of a cavity-based injection efficiency measurement system and focuses on bunch charge calibration and tests of the system resolution and injection efficiency. The test results show that the system resolution is 0.34% and the average injection efficiency is close to 90% at regular top-up operation.