Vertical test results on KEK-ERL 9-cell L-band superconducting cavity

Cenni, E.*; Furuya, Takaaki*; Sakai, Hiroshi*; Umemori, Kensei*; Shinoe, Kenji*; Sawamura, Masaru

In order to develop the Energy Recovery Linac, we are studying the performance of two prototype L-band superconducting cavities by means of vertical tests. The cavities were inspected through rotating X-ray and temperature mapping system. The performance limiting factor was found to be the field emissions. We observed X-ray emission and temperature raise along the cavity wall. The quench locations were determined with a good agreement between X-ray and temperature sensors. During vertical test we experienced some interesting phenomena such as quality factor degradation and X-ray burst. In the first case the degradation was observed even at low field, however we recovered it with a warming up to room temperature without additional surface treatment. In the latter case new emitters suddenly appeared after some quenches. They remained in the same location also after the warming up.