US 4,796,432 AGranted

Long hold time cryogens dewar

AssigneeUnisys Corporation

InventorsDale J. Fixsen, Roger N. Hastings, John A. Imsdahl

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Abstract

A liquid cryogen dewar is constructed in which two or more liquid cryogen chambers are suspended within a case wherein the innermost cryogens have a higher boiling, or sublimation, temperature than the cryogen in the next outermost chamber. The chambers may contain liquid helium, liquid nitrogen and solid CO.sub.2 proceeding from the innermost to the outermost chamber. Superconducting electronic circuitry such as SQUID devices may be connected to the outer case of the liquid helium cryogen chamber. An isothermal shield is also suspended outside the helium chamber. The elements of the dewar are supported by glass epoxy rods and polyester cords of low thermal conductivity. A fill and exhaust port is provided which communicates with fill and exhaust tubes that are heat sunk to various locations of the rods and the Dacron cords.

Claims20

Dependent claims

In a dewar for maintaining superconducting temperatures for an extended period of time comprising an outer case, comprising a plurality of cryogen containing chambers, the improved structure wherein the dewar is constructed so that each of said cryogen chambers completely surrounds the next innermost one of said cryogen chambers, and, except for the innermost one of said cryogen chambers, the cryogens contained in each of said chambers are maintained in states such that each cryogen has a progressively higher phase change temperature proceeding from the innermost one of said cryogen chambers to the outermost one of said cryogen chambers and isothermal suspension means for suspending all of said cryogen chambers within the dewar wherein the outermost one of said cryogen chambers is suspended in said dewar solely by isothermal suspension means comprising rods having a low thermal conductivity and all of said cryogen chambers, except said outermost cryogen chamber, are suspended in said dewar solely by isothermal suspension means comprising cords having a low thermal conductivity.

Dependencies are inferred from the claim text.