Patent ID: 8291725
Filing Date: 2012-10-23
Classification: F25B,H01F

Abstract:
1. A method for cooling down at least one superconducting magnet, comprising: cooling down said at least one superconducting magnet by cooling said at least one superconducting magnet with a mixture of at least two helium streams that are at at least two different temperature levels; wherein the cooling down of said at least one superconducting magnet is carried out by cooling said at least one superconducting magnet with a first mixture, consisting essentially of a first helium stream at ambient temperature level and a second helium stream at a first lower temperature level, and then cooling said at least one superconducting magnet with a second mixture, consisting essentially of said second helium stream at said first lower temperature level and a third helium stream at a second lower temperature level, wherein said second lower temperature is a lower temperature than said first lower temperature level, said method further comprising compressing a helium stream in a compressor to provide a high pressure helium stream, subjecting said high pressure helium stream to a first indirect heat exchange wherein said high pressure helium stream undergoes heat exchange with liquid nitrogen, and dividing the resultant cooled high pressure helium stream into at least three portions, expanding a first portion of the resultant cooled high pressure helium stream to provide a first medium pressure helium stream, combining a second portion of the resultant cooled high pressure helium with said first medium pressure helium stream wherein at least portion of the resultant mixture of said second portion of the cooled high pressure helium stream and said first medium pressure helium stream is used as said second helium stream, and cooling a third portion of the resultant cooled high pressure helium in a second heat indirect exchange wherein said third portion of the cooled high pressure helium is cooled by heat exchange with said first medium pressure helium stream, and then expanding said third portion of the cooled high pressure helium to provide a second medium pressure helium stream, wherein at least a portion of said second medium pressure helium stream is used as said third helium stream.