First demonstration of coherent radiation imaging for bunch-by-bunch longitudinal compression monitoring

Abstract: Longitudinal bunch profile monitoring is a crucial diagnostic requirement in most accelerator facilities. This is particularly true in modern free-electron lasers and novel acceleration schemes, where bunch lengths are often <100 fs and standard instrumentation is invasive or lacks the required resolution. This paper proposes a new monitoring method in this challenging parameter space. Initial proof of principle results for relative compression monitoring via broadband imaging of coherent THz radiation are presented. The technique can utilize more conventional intensity monitoring or novel spatial distribution variation. Both techniques have been demonstrated using both invasive and non-invasive coherent radiation sources. These results pave the way for a future non-invasive longitudinal bunch profile monitor.