LLRF System Design and Performance for XFEL Cryomodules Continuous Wave Operation

The cryomodule test bench (CMTB) at the Deutsches Elektronen Synchrotron (DESY) in Hamburg is equipped with a 100 kW inductive output tube (IOT) allowing the test of superconducting cryomodules in continuous wave (CW) operation mode. Although significantly different from the nominal pulsed operation mode of the European x-ray free electron laser (XFEL), CW operation can be handled by the same low-level radio frequency (LLRF) system, within minor firmware modifications. The hardware details of the LLRF setup at CMTB, the firmware and software architecture and performance results from the last CW test are presented in this contribution.