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

ERL9セル超伝導空洞の縦測定結果

Cenni, E.*; 古屋 貴章*; 阪井 寛志*; 梅森 健成*; 篠江 憲治*; 沢村 勝

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

エネルギー回収型リニアックの開発のため縦測定による空洞性能試験を行っている。空洞はX線と温度マッピングシステムを用いて観測し、空洞性能を制限するものが電界放出であることがわかった。空洞壁に沿ったX線や温度上昇が観測されクウェンチの場所を同定することができた。縦測定のとき二つの興味深い現象が観測された。一つはQ値の劣化で、低い電界でも観測されたが、室温に戻し、表面処理を行わず再度冷却を行うことで回復した。もう一つはX線バーストで何度かのクウェンチ後にできた新たなエミッタの突然の出現で、室温に戻すだけではエミッタの位置は変わらなかった。

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.