A system (100) for controlling temperature of a persistent current switch (120) operating in a background magnetic field includes a heat exchanger (138), a loop tube (135), a ball valve (245) and multiple electromagnets (251, 252). The heat exchanger disperses heat to a cryocooler (106). The loop tube enables flow of coolant to convectively transfer thermal energy generated by the persistent current switch to the heat exchanger. The ball valve is integrated with the loop tube between the persistent current switch and the heat exchanger, and contains a ferromagnetic ball (250). The electromagnets are positioned outside the loop tube adjacent to the ball valve, where energizing a first electromagnet of the multiple electromagnets magnetically moves the ferromagnetic ball to a first position opening the loop tube and enabling the flow of the coolant, and energizing a second electromagnets magnetically moves the ferromagnetic ball to a second position closing the loop tube and blocking the flow of the coolant.