NbTi magnet cooled by SRDK-408 cryocooler-results and numerical model

Cooling down to the operation temperature and keeping the temperature on adequately low level by good thermal insulation and good cooling conditions decide on superconducting state in a superconducting device. In low temperature below 150 K significant changes of electrical and thermal parameters vs. temperature are observed. The paper presents the numerical model in FLUX2D of cooling a superconducting NbTi magnet (mass=1.46 kg) for an OGMS separator using the SRDK-408 cryocooler. The USER SUBROUTINES were used to define advanced temperature relations of physical properties in calculated regions and thermal flux to the cryocooler. Experimental results were used to verify the parameters of the numerical model. The NbTi magnet needs around 6 hours for achieving superconducting transition, but only 1 h and 40 min to reach 30 K.