FIELD

Embodiments described herein relate generally to a refrigeration system and a method for controlling the same.

BACKGROUND

A cryogenic refrigerator can cool, for example, a superconductive magnet. The cryogenic refrigerator is adopted to a refrigeration system. The refrigeration system is adapted for health-care equipment, such as an MRI (Magnetic Resonance Imaging) apparatus, or a heavy particle beam radiotherapy apparatus to treat cancer. When the cryogenic refrigerator is operated, oscillations and noises are generated, which burden the patient and impair precision equipment.

Another example of the cryogenic refrigerator is a low-oscillation cryogenic refrigerator, such as a pulse tube refrigerator. However, the low-oscillation cryogenic refrigerator is inferior in reliability and performance to a conventional cryogenic refrigerator using a displacer, for example, a GM (Gifford McMahon) refrigerator.

Therefore, when a high-reliability and high-performance conventional refrigerator, namely, a refrigerator using a displacer is operated, there is a demand that oscillations and noises generated from the refrigerator should be reduced.

The cryogenic refrigerator using the displacer adiabatically expands a refrigerant gas (working fluid), such as helium gas, compressed by a compressor by periodic reciprocation (upward and downward motions) of the displacer in a cylinder, and exchanges heat between the refrigerant gas and a cool storage device in the displacer, thereby cooling a cooling end. Furthermore, there is a known technique of measuring a temperature of the cooling end, and controlling a plurality of refrigerators to operate by a calculation controller, so that the measured temperature can be maintained at a target cooling temperature.

When refrigerators are operated while their cooling ends are thermally connected to one another, if peak timings of oscillations or noises coincide due to the reciprocations of the displacer in the cryogenic refrigerators, the oscillations and noises generated from a target to be cooled will be significant.

