Status of cryomodule testing at cmtb for cw r&d

The CryoModule Test Bench (CMTB) is a facility to perform tests on superconducting accelerating modules. The 120 kW Inductive Output Tube (IOT) installed in the facility allows driving the eight superconducting cavities inside the module under test in a vector-sum or single cavity control fashion with average Continuous Wave (CW) gradients higher than 20 MV/m. The scope of these tests is to evaluate the feasibility of upgrading the European X-ray Free Electron Laser (EuXFEL) to CW operation mode. Following the successful tests done on a prototype module XM-3, the initial performance results on production module XM50 will be presented in this paper. Because of EuXFEL requirements, XM50.1 is equipped with modified couplers that allow a variable Loaded Quality factor (QL) to values higher than 4×107. A cost relevant open question is the maximum QL that can be operated at, while maintaining the system within the EuXFEL field stability specifications of 0.01 % in amplitude and 0.01 deg in phase. Because of this, the LLRF system capability of rejecting microphonics and RF disturbances, as well as Lorentz Force Detuning (LFD) related effects in open and closed loop is of prime interest.