Patent ID: 8544281

Claim:
A method for cooling a superconducting magnet enclosed in a cryostat of a magnetic resonance imaging system, the method comprising: introducing a gas into a cooling path in the cryostat from an input portion outside the cryostat; cooling a heat exchanger in the cooling path by a refrigerator outside the cryostat, wherein the heat exchanger is disposed within the cryostat, wherein the heat exchanger is positioned above a magnet cooling tube of the cooling path; cooling the gas at the heat exchanger as a cold gas or condensing the gas at the heat exchanger into a liquid cryogen; flowing, using gravity, the cold gas or liquid cryogen from the heat exchanger through at least a connection tube to the magnet cooling tube which is in thermal contact with the superconducting magnet; removing heat from the superconducting magnet by warming the cold gas into warm gas or by boiling the liquid cryogen into boiled-off gas; transmitting the warm gas or boiled-off gas back to the heat exchanger to re-cool the warm vas or re-condense the boiled-off gas for further cooling the superconducting magnet to a superconducting temperature; closing the input portion to make the cooling path as a closed-loop for maintaining the superconducting, magnet below the superconducting temperature; cooling a second heat exchanger disposed within the cryostat and positioned above a liquid cryogen container by the refrigerator outside the cryostat; introducing a second type of gas through a second inlet outside the cryostat, wherein the second type of gas has a higher liquefaction temperature than the said gas; cooling the second type of gas at the second heat exchanger for cooling or condensing the second type of gas into a second type of cold vas or a liquid cryogen; flowing, using gravity, the second type of cold gas or liquid cryogen to the liquid cryogen container through a connection tube between the second heat exchanger and the liquid cryogen container; and removing heat of the superconducting magnet through a thermal link having one end thermally contacting the liquid cryogen container and another end thermally contacting the superconducting magnet.