Abstract: A superconducting magnet device includes a superconducting coil; a radiation shield that thermally protects the superconducting coil; a main cold head that cools the superconducting coil; a sub-cold head that cools the radiation shield; a common compressor that supplies a refrigerant gas to the main cold head and the sub-cold head; a first temperature sensor that measures a temperature of the radiation shield; a second temperature sensor that measures a temperature of the superconducting coil; and a controller configured to activate the sub-cold head for initial cooling of the superconducting magnet device, stop the sub-cold head based on an output of the first temperature sensor or the second temperature sensor, and operate the main cold head in a state where the sub-cold head is stopped.

Abstract: Argon gas and nitrogen gas are mixed together and cooled by a cooler to a liquefying temperature of argon gas specific to its pressure, to form argon fine droplets in the mixed gas. The gas is then jetted out of nozzles and blown into a vacuum chamber to adiabatically lower the temperature further and change fine droplets to solid fine particles which are used to clean the surface of an object.