Practical Application of Gas-Gap Thermal Switch in Conduction Cooled Superconducting Magnet System

A gas-gap thermal switch is developed to reduce the cool-down time of conduction cooled superconducting magnet. The main feature of the thermal switch is that it is sealed naturally at atmospheric environment in comparison with other gas-gap thermal switch, thereby it is much greater convenient during assembly. The switch is a closed container that contains several pairs of concentric tube-fins arranged in staggered way and it is located between first stage and second stage of GM cryocooler. At the beginning of the cool down, the thermal switch can transfer power from the first stage with the higher refrigeration capacity to the magnet. So the cool-down rate of the magnet is increased. To check the performance of the switch, we use a superconducting magnet for gyrotron whose weight is 41.5 kg as background device. The experiment shows that the cool-down time is shortened from 25 hours to 20 hours.