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 199 6 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 ha s provided some 16000 h of beamtime for experiments. Guided by operational experience numerous developments concerning equipment directly associated w ith the superconducting (sc) cavities like tuners, rf couplers, etc., were performed. The operational principle and performance of the respective part s is discussed. Manufacturing of the sc cavities themselves, tuning for fie ld flatness of the pi-mode, and treatment prior to installation as well as treatment after degradation is presented together with a summary of the cur rent cavity and accelerator performance.