WEP009 　電子加速器　 8月2日 第1,2,3,4会議室他 13:00 - 15:00

薄膜超伝導体の高周波臨界磁場測定のためのマッシュルーム型空洞の設計研究

Design study of mushroom shaped cavity for evaluation of RF critical magnetic field of thin-film superconductor

○及川 大基，東口 武史（宇都宮大学），早野 仁司（高エネ研）

○Hiroki Oikawa, Takeshi Higashiguchi (Utsunomiya University), Hitoshi Hayano (KEK)

For more higher energy accelerator, we demand superconducting RF cavity that has high gradient of 45 MV/m or more. To obtain such a higher gradient, there has been proposed a method of increasing an RF critical magnetic field of the cavity inner surface by coating of multi-layer thin-film superconductor that has thickness close to the London penetration depth. By producing a multilayer film structure in cavity inner surface, it is believed to improve the RF critical magnetic field, and to connect directly to high gradient. To demonstrate a creation of a thin film on a surface of Nb samples, an RF cavity with a thin film coated Nb sample is needed to measure the RF critical field of the sample. To adapt it to the cavity, to cool to cryogenic temperature and to establish the sample to supply the RF power, it is necessary to design a cavity to produce a strong RF magnetic field parallel to the surface of the thin film sample. We designed a mushroom shaped cavity made of Nb and input coupler. Resonant frequency is 5.2 GHz by calculation. We calculated the resonant frequency and the field distribution, compared with the measured values for the model cavity.