Status of the superconducting CH-structure

The CH-Structure which has been developed at IAP in Frankfurt is the first superconducting multi-cell drift tube cavity for the low and medium energy range between 5 and 150 MeV. The prototype cavity which has been built consists of 19 accelerating cells and has an operation frequency of 360 MHz (see fig. 1). The cavity has been tested for several times, gradients of up to 4.7 MV/m have been achieved in cw operation. Presently the limitation is field induced quenching. To localize possible field emitting sites a detailed X-ray analysis has been performed. One main emitter could be identified. Additionally, warm measurements have been performed to test the tuning concept of the cavity. A tuning sensitivity of 400 kHz/mm has been measured.