Operating experience with SC resonators at the S-DALINAC

The recirculating electron accelerator S-DALINAC provides beams for a wide variety of nuclear and radiation physics experiments and since December 1996 it is also successfully used to drive a free electron laser (FEL) in the mid infrared wavelength region. The sc cavities of the S-DALINAC operate at 2997 MHz and therefore at a temperature of 2 K. Up to now the S-DALINAC has provided some 16000 h of beamtime for experiments. Guided by operational experience numerous developments concerning equipment directly associated with the superconducting (sc) cavities like tuners, rf couplers, etc., were performed. The operational principle and performance of the respective parts is discussed. Manufacturing of the sc cavities themselves, tuning for field flatness of the pi-mode, and treatment prior to installation as well as treatment after degradation is presented together with a summary of the current cavity and accelerator performance.