Research into the sampling methods of digital beam position measurement

摘要

A fully digital beam position monitoring system (DBPM) has been designed for SSRF (Shanghai Synchrotron Radiation Facility). As analog-to-digital converter (ADC) is a crucial part in the DBPM system, the sampling methods should be studied to achieve optimum performance. Different sampling modes were used and com-pared through tests. Long term variation among four sampling channels, which would introduce errors in beam position measurement, is investigated. An interleaved distribution scheme was designed to address this issue. To evaluate the sampling methods, in-beam tests were conducted in SSRF. Test results indicate that with proper sampling methods, a turn-by-turn (TBT) position resolution better than 1 µm is achieved, and the slow-acquisition (SA) position resolution is improved from 4.28 µm to 0.17 µm.