Field enhancement in superconducting solenoids by holmium flux concentrators

Abstract The magnetic field strength in the bore of a 13 T superconducting solenoid was enhanced to 16 T in the 5.5 mm gap between two cylindrical holmium flux concentrators. This method is an economic way of extending the field region for measuring critical data of superconducting materials. The measured dependence of the gap field on coil current was reproduced in computer calculations by fitting the magnetization curve of holmium at 4.2 K. This curve may be used for optimizing the geometry of holmium flux concentrators at 4.2 K.