Cryostat assembly

Abstract

A cryostat assembly comprises at least one substantially heat insulating wall surrounding a cooled region for restricting heat flow into the cooled region. A refrigeration system is provided having a heat absorbing portion coupled with the wall to enable heat to transfer to the heat absorbing portion, the refrigeration system also have a heat evacuating portion to enable absorbed heat to be evacuated from the cryostat assembly.

I claim: .[.1. A cryostat assembly comprising at least one substantially heat insulating wall defining a cooled region for restricting heat flow into said cooled region; a refrigeration system having a heat absorbing portion and a heat evacuating portion to enable absorbed heat to be evacuated from said cryostat assembly; and coupling means for coupling said heat absorbing portion with said wall to enable heat to transfer to said heat absorbing portion via said coupling means, said coupling means comprising at least one flexible, passive, heat conducting linkge..]. .[.2. An assembly according to claim 1, wherein said heat insulating wall comprises a heat radiation shield..]. .[.3. An assembly according to claim 1, wherein said wall is defined by at least part of a first coolant vessel..]. .[.4. An assembly according to claim 3, further comprising an inner heat radiation shield surrounding said region, said refrigeration system comprising a two stage refigeration system, said first stage of said system being coupled for heat transfer with said first coolant vessel and said second stage being coupled for heat transfer with said inner radiation shield..]. .[.5. An assembly according to claim 4, further comprising a second coolant vessel positioned within a volume defined by said inner radiation shield..]. .[.6. An assembly according to claim 1, wherein said wall is supported by a plurality of support rods, said refrigeration system being coupled for heat transfer with at least one of said support rods..]. .[.7. An assembly according to claim 6, wherein at least one of said support rods is coupled with another wall or vessel which itself is coupled with said refrigeration system whereby a heat flow path exists from said rod via said wall or vessel to said refrigeration system..]. .[.8. An assembly according to claim 1, wherein said coupling means comprises copper braid..]. .[.9. An assembly according to claim 1, wherein said refrigeration system further comprises a support housing, and a refrigeration unit removably mounted in said support housing, and wherein heat conducting contacts are provided on said unit and in said support housing connected with said coupling means whereby when said unit is fully mounted in said support housing said contacts engage one another to provide a heat path between said unit and said coupling means through said support housing, said support housing being adapted to restrict heat flow from outside said cryostat assembly to said coupling means..]. .[.10. An assembly according to claim 9, wherein said walls of the support housing are insulated against heat flow..]. .[.11. An assembly according to claim 9, wherein said coupling means comprises copper braid..]. 
     
        .Iadd.  .  A cryostat assembly comprising at least one substantially heat insulating wall and at least one coolant containing or evacuated vessel surrounding a cooled region for restricting heat flow into said cooled region; a refrigeration system comprising a support housing, and a refrigeration unit having a heat absorbing portion and a heat evacuating portion to enable absorbed heat to be evacuated from said cryostat assembly, said refrigeration unit being removably mounted in said support housing, cooperating heat conducting contacts being provided on said unit and in said support housing whereby when said unit is fully mounted in said support housing said contacts engage one another to provide a path for heat to flow between said support housing and said heat absorbing portion; and coupling means connected between said support housing and said wall to conduct heat from said wall to said support housing, the arrangement being such that said refrigeration unit can be disassembled from the rest of said cryostat assembly without purging said vessel, wherein the interior of said support housing is isolated from the interior 
     
     
        of each said coolant containing or evacuated vessel..Iaddend. .Iadd.13. An assembly according to claim 12, wherein said vessel contains liquid nitrogen or liquid helium..Iaddend. .Iadd.14. An assembly according to claim 12, wherein said wall coupled to said refrigeration unit is defined by at least part of said coolant containing or evacuated vessel..Iaddend. .Iadd.15. An assembly according to claim 12, further comprising an inner heat radiation shield surrounding said region, said refrigeration system comprising a two stage refrigeration system, said first stage of said system being coupled for heat transfer with said vessel and a second stage being coupled for heat transfer with said inner radiation shield..Iaddend. .Iadd.16. An assembly according to claim 15, further comprising another evacuated or coolant containing vessel positioned within a volume defined by said inner radiation shield..Iaddend. .Iadd.17. An assembly according to claim 12, wherein said wall is supported by a plurality of support rods, said refrigeration system being coupled for heat transfer with at least one of said support rods..Iaddend. .Iadd.18. An assembly according to claim 17, wherein at least one of said support rods is coupled with another wall or vessel which itself is coupled with said refrigeration system whereby a heat flow path exists from said rod via said wall or vessel to said refrigeration system..Iaddend. .Iadd.19. An assembly according to claim 12, wherein said coupling means comprises a flexible, highly heat conductive linkage..Iaddend. .Iadd.20. An assembly according to claim 19, wherein said coupling means comprises copper braid..Iaddend. .Iadd.21. An assembly according to claim 12, wherein the walls of said support housing are insulated against heat flow..Iaddend.