Superconducting magnet cooling system

A conductor and a device for cooling the conductor to the superconducting state, comprising:

• a supply of liquid coolant in the supercooled state, an inner conduit being coupled to said supply of liquid coolant and having within the interior thereof the conductor and said liquid coolant in contact with said conductor or the entire length thereof so that said conductor is in the superconducting state, a supply of boiling liquid coolant at lower temperature than said liquid coolant, an outer conduit being positioned about and separated from said inner conduit to form a channel between the outer wall of said inner conduit and the inner wall of said outer conduit, and means coupled to said channel and said supply of boiling liquid coolant for pumping said boiling liquid coolant through said channel, the conductor being so separated from the inner wall of said inner conduit that with heat being generated by the conductor at the superconducting state said heat is by convention within said supercooled liquid coolant carried from the conductor to the inner wall of said inner conduit and the flow rate of said boiling liquid coolant through said channel is of such value that sufficient liquid phase remains in said boiling liquid coolant over the length of said conductor to maintain the temperature of the supercooled liquid coolant at a relatively constant value over the length of the conductor.