System for controlling temperature of persistent current switch

A system for controlling transfer of thermal energy of a persistent current switch to a heat exchanger in thermal contact with a cryocooler, the system comprising:

• a loop tube positioned between the persistent current switch and the heat exchanger, wherein coolant selectively flows through the loop tube;
• a first ball valve on a first part of the loop tube between the persistent current switch and the heat exchanger, the first ball valve containing a first ferromagnetic ball, a first orifice adjoining a first opening of a first part of the loop tube, and a first notch adjacent to the first orifice;
• a second ball valve on a second part of the loop tube between the persistent current switch and the heat exchanger, the second ball valve containing a second ferromagnetic ball, a second orifice adjoining a second opening of a second part of the loop tube, and a second notch adjacent to the second orifice;
• a first solenoid and a second solenoid positioned outside the first part of the loop tube adjacent to the first ball valve;
• and
• a third solenoid and a fourth solenoid positioned outside the second part of the loop tube adjacent to the second ball valve,
• wherein the coolant is able to flow through the loop tube by energizing the first and third solenoids such that the first and second ferromagnetic balls move to the first and second notches, respectively, opening the first and second parts of the loop tube, and
• wherein the coolant is blocked from flowing through the loop tube by energizing the second and fourth solenoids such that the first and second ferromagnetic balls move to the first and second orifices, respectively, closing off the first and second parts of the loop tube.

A system for controlling transfer of thermal energy of a persistent current switch operating in a background magnetic field to a heat exchanger in thermal contact with a cryocooler, the system comprising:

• a loop tube positioned between the persistent current switch and the heat exchanger, wherein coolant selectively flows through the loop tube;
• a ball valve in the loop tube between the persistent current switch and the heat exchanger, the ball valve containing a ferromagnetic ball having a diameter greater than an inner diameter of the loop tube;
• a first solenoid positioned outside the loop tube adjacent to a first side of the ball valve;
• and
• a second solenoid positioned outside the loop tube adjacent to a second side of the ball valve,
• wherein the loop tube comprises a first end portion formed of a ferromagnetic material that partially extends into the first side of the ball valve, and a second end portion formed of the ferromagnetic material that partially extends into the second side of the ball valve, the first end portion defining one or more through-holes in sidewalls of the first end portion located within the ball valve,
• wherein the first end portion and the second end portion are magnetized by the background magnetic field when the first solenoid and the second solenoid are not energized,
• wherein energizing the first solenoid at least partially demagnetizes the first end portion, causing the ferromagnetic ball to move to the magnetized second end portion, covering an opening of the loop tube within the ball valve and blocking the flow of the coolant, and
• wherein energizing the second solenoid at least partially demagnetizes the second end portion, causing the ferromagnetic ball to move to the magnetized first end portion, covering another opening of the loop tube within the ball valve and enabling the flow of the coolant through the one or more through-holes.