Speaker
Description
Since the beginning of the ESRF-EBS storage ring in 2020, 11 BPM are affected by a phenomenon which generates un-physical position measurements, which depends on some beam parameter (mostly filling pattern and total current).
This issue is probably arising from a RF resonance at the BPM measurement frequency (352 MHz) present in the vicinity of the BPM block, inside the vacuum chamber. Early simulations done to find a possible resonant mode in this area were unsuccessful, indicating that subtle details of the vacuum chambers should be taken into account to explain the presence of such a mode.
After a deeper investigation, various measurements, tests and more advanced simulations, we now believe that we understand the origin of this resonance. We will show in this presentation how a resonance can occur even if the section of the vacuum chamber is not supposed to allow for it, the various measurements and tests which agree with this theory, and possible solutions to this issue.
