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TY - CONF AU - Ito, H. AU - Antoine, C.Z. AU - Four, A. AU - Hayano, H. AU - Ito, R. AU - Iwashita, Y. AU - Katayama, R. AU - Kubo, T. AU - Nagata, T. AU - Oikawa, H. AU - Saeki, T. AU - Tongu, H. ED - Schaa, Volker RW ED - Pei, Guoxi ED - Chin, Yong Ho ED - Fu, Shinian ED - Zhao, Ning TI - Lower Critical Field Measurement of Thin Film Superconductor J2 - Proc. of LINAC2018, Beijing, China, 16-21 September 2018 CY - Beijing, China T2 - Linear Accelerator Conference T3 - 29 LA - english AB - 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 investigate the Hc1, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. 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 Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film sample will be discussed. PB - JACoW Publishing CP - Geneva, Switzerland SP - 484 EP - 487 KW - solenoid KW - controls KW - experiment KW - SRF KW - embedded DA - 2019/01 PY - 2019 SN - 2226-0366 SN - 978-3-95450-194-6 DO - DOI: 10.18429/JACoW-LINAC2018-TUPO066 UR - http://jacow.org/linac2018/papers/tupo066.pdf ER -