THPP32  ポスターセッション②  9月3日 ポスター会場 13:10-15:10
Measurement of vortex penetration field into NbN laminated thin-film structure
○井藤 隼人,早野 仁司,久保 毅幸,佐伯 学行,片山 領(高エネルギー加速器研究機構),岩下 芳久,頓宮 拓(京都大学化学研究所),伊藤 亮平,永田 智啓(アルバック)
○Hayato Ito, Hitoshi Hayano, Takayuki Kubo, Takayuki Saeki, Ryo Katayama (KEK), Yoshihisa Iwashita, Hiromu Tongu (Kyoto ICR), Ryohei Ito, Tomohiro Nagata (ULVAC, Inc.)
The maximum accelerating gradient (Eacc) of the SRF cavity can be increased by raising the vortex penetration field (Hv). A laminated thin-film structure, in which a superconductor layer (S’) such as NbN and an insulating layer (I) are coated on bulk Nb (S) (S’-I-S structure), has been proposed to increase the Eacc. By using the S’-I-S structure, the field is screened by the superconductor layer, reducing the field applied to the bulk Nb. Hence, the bulk Nb will withstand against a higher applied magnetic field. It means the cavity can achieve higher Eacc than conventional SRF cavities. S’-S structure in which a superconductor layer (S’) is coated on bulk Nb directly is also expected to increase the Eacc. In order to study the magnetic property of the laminated thin-film structure, we developed the Hv measurement system, which can apply the AC magnetic field locally without the influence of the sample edge effects. Measurements were performed to NbN-SiO2-Nb (S’-I-S structure) samples and NbN-Nb (S’-S structure) samples of various superconductor layer thicknesses. In this report, the measurement results of the NbN-SiO2-Nb samples and NbN-Nb samples will be discussed.