Thermal Analysis of PCS for an HTS Pancake Coil in Persistent Current Mode

It is well known that high temperature superconductors (HTS) are promising for a magnet application, but it has been almost impossible so far to apply them to the magnet in persistent current mode because of poor qualities of their superconducting joint at higher current as well as lower index values. In this paper, in order to get rid of the joints from an HTS superconducting magnet, a prototype HTS pancake coil using YBCO coated conductors by the technique of wind-and-flip pancake coil was made and will be tested later. This paper presents a design, fabrication, and thermal analysis of the prototype pancake coil. The coil will be cooled down around 20 K by conduction cooling using a GM cryocooler. The expected current drift rate for an MRI application has not been achieved, probably caused by large flux flow resistance of coated conductor at higher temperature, 77.3 K. A temperature dependency of temporal stability of the persistent current will be measured by monitoring the long-term drift of the magnetic field at different operating temperatures by Hall sensors.