Cavity Beam Position Monitor at VELA
01 Sep 2015






A team of researchers and engineers from the John Adams Institute at Royal Holloway, University of London, FMB-Oxford and Daresbury Laboratory have commissioned the first prototype of a cavity beam position monitor (CBPM) system at VELA. Supported by STFC's Innovations Partnership Scheme (link opens in a new window), the development is aimed at providing future Free Electron Lasers (FEL) and similar linac-based facilities with a reliable high resolution position diagnostic. This industrialisation project will allow accelerator and FEL laboratories to purchase and install CBPMs without the requirement for in-house design and tuning expertise.

An important feature of CBPMs is their extremely high sensitivity which allows them to operate at very low beam charges and still provide micrometer-level position resolution, where standard electrostatic pick-ups usually cease to operate. So far, the measurements at VELA confirmed that the test system can operate below 10 pC bunch charge, and further work is underway to increase the system gain and provide position measurements at pC-level.

A new reference cavity will be added to the system to provide the charge normalisation and phase (which indicates positive or negative sign of the offset) information. Once these changes are implemented and commissioned, the CBPM system will become a useful diagnostic for VELA users interested in measurements at low bunch charge, including extremely short bunch operation, and help delivering the beam to their experiments.