Application of high temperature superconductor in National Institute for Fusion Science

In the National Institute for Fusion Science (NIFS), the following three research items are being advanced as application of high temperature superconductor (HTS) to an experimental fusion plasma system, through collaboration with universities and laboratories. The first is an application of HTS in the large current feedthrough to a superconducting coil cooled with superfluid helium in order to reconcile low heat load and stable large current transport capability. A 20 kA current feedthrough from 4.4 K to 1.8 K has been being developed using YBCO bulk superconductors manufactured by the QMG process. The second is the development of a 30 kA HTS current lead. The Bi2212 bulk material fabricated by the diffusion process is considered as a candidate material for HTS current leads. The third is the development of the superconducting magnetic-levitation coil for Mini-RT wound with Bi2223 tape conductor. A magnetic-levitation coil operated in persistent-current mode has to levitate for 8 hours without a feed of refrigerant. Present status of these HTS application researches in NIFS is reported.