Electro-optical bunch arrival time measurement is a method to monitor the timing of bunches in predominantly linear electron accelerators to below femtosecond precision. Despite the method being well established, a stable and fully available measurement was reported only recently. DESY’s free-electron lasers FLASH and EuXFEL feature Bunch Arrival Time (BAM) diagnostics that serve as a standard operation data source for the facility’s longitudinal fast and slow stabilization, as well as an instrument available to the users for pump laser alignment and offline analysis. A comprehensive upgrade and R&D effort targeting the performance of DESY’s BAM was carried out in recent years. The complexity of the device poses challenges to its control layer, calibration, drift control, and operation setup. Solving these proved to be essential in reaching operational stability and high availability. We report on the updates to the BAM controls and the development of automation of numerous tasks that contributed a great deal to achieving long-term stability and full run availability.
Kral et al. (Fri,) studied this question.