WEP052 　加速構造　 8月8日 大展示ホール 13:10 - 15:10

３次高調波測定法を用いた薄膜超伝導体の下部臨界磁場測定

Lower critical field measurement of thin film superconductor using third harmonic method

○井藤 隼人（総合研究大学院大学），早野 仁司，佐伯 学行，久保 毅幸 （高エネルギー加速器研究機構），岩下 芳久，片山 領，頓宮 拓（京都大学化学研究所），及川 大基（宇都宮大学），伊藤 亮平，永田 智啓（アルバック）

○Hayato Ito (SOKENDAI ), Hitoshi Hayano, Takayuki Saeki, Takayuki Kubo (KEK), Yoshihisa Iwashita, Ryo Katayama, Hiromu Tongu (Kyoto University, ICR), Hiroki Oikawa (Utsunomiya University), Ryohei Ito, Tomohiro Nagata (ULVAC, inc.)

Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To measure the Hc1, we developed the measurement system using the third harmonic response of applied AC magnetic field. In order to control the temperature of the sample, we installed heaters and thermal anchors which could be moved by the motor. By this temperature control the sample state can be easily transferred from the Meissner state to the mixed state. By raising the temperature of the sample with applying AC magnetic field, Hc1 and transfer temperature, which is point of transfer from the Meissner state to the mixed state, can be determined at when the third harmonic response appears. By repeating the measurement for various applied AC magnetic field, the Hc1 vs temperature can be plotted. In this report, measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film sample will be discussed.