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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 - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Lower Critical Field Measurement System of Thin Film Superconductor J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018 C1 - Vancouver, BC, Canada T2 - International Particle Accelerator Conference T3 - 9 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 performance of thin film, 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 stage and coil mount, the depth of thermal anchors attached to the stage and the mount can 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, performance of the measurement system is described. PB - JACoW Publishing CP - Geneva, Switzerland SP - 3882 EP - 3884 KW - controls KW - experiment KW - simulation KW - SRF KW - embedded DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-THPAL105 UR - http://jacow.org/ipac2018/papers/thpal105.pdf ER -