Cryostats including current leads for electronically powered equipment
A cryostat cooled by a pulse tube refrigerator and containing electrically powered equipment, wherein an electrical conductor is provided to the electrically powered equipment, said electrical conductor being in thermal and mechanical contact with one or more of the tubes of the pulse tube refrigerator.
1 . A cryostat cooled by a pulse tube refrigerator, itself comprising at least one pulse tube and at least one regenerator tube, and containing electrically powered equipment, wherein an electrical conductor is provided to the electrically powered equipment, said electrical conductor being in thermal and mechanical contact with one or more of the tubes of the pulse tube refrigerator, said electrical conductor also being conformal to an outer surface of said one or more tube(s).
2 . A cryostat according to claim 1 , wherein the outer surface of said one or more tube(s) is cylindrical.
3 . A cryostat according to claim 1 , wherein the electrical conductor is arranged to be brought out of thermal and mechanical connection with the tubes(s) of the pulse tube refrigerator when electrical current conduction is not required.
4 . A cryostat cooled by a pulse tube refrigerator, itself comprising at least one pulse tube and at least one regenerator tube, and containing electrically powered equipment, wherein an electrical conductor is provided to the electrically powered equipment, said electrical conductor being in thermal and mechanical contact with one or more of the tubes of the pulse tube refrigerator, wherein the electrical conductor is arranged to be brought out of thermal and mechanical connection with the tubes(s) of the pulse tube refrigerator when electrical current conduction is not required.
5 . A cryostat according to claim 1 , wherein an electrically insulating, thermally conductive layer is provided, interposed between the electrical conductor and the corresponding tube(s).
6 . A cryostat according to claim 1 , wherein the electrical conductor is in the form of two approximately half-cylindrical metal sheets, which are electrically insulated from the material of the tubes(s) of the pulse tube refrigerator.
7 . A cryostat according to claim 6 , wherein the electrical conductor consists of two approximately half-cylindrical sheets of brass, lined with a self-adhesive polyimide film, for electrical insulation.
8 . A cryostat according to claim 6 , wherein the electrical conductor consists of two approximately half-cylindrical sheets of brass, lined with epoxy resin filled with glass and/or aluminum oxide.
9 . A cryostat according to claim 1 , wherein a flow of cryogen gas is provided to cool the outer surface of the electrical conductor.
10 . A cryostat according to claim 1 , wherein the electrical conductor comprises a hollow electrically conductive member extending along the length of a pair of regenerator or pulse tubes of the pulse tube refrigerator; the conductive member being shaped to be conformal to the surfaces of the tubes on two sides wherein an electrically insulating, thermally conductive layer is provided, interposed between the hollow electrically conductive member and the corresponding tubes.
11 . A cryostat according to claim 10 , wherein the thermally conductive, electrically insulating layer comprises a self-adhesive polyimide film, or a composite material, or specifically epoxy resin filled with glass fiber and/or aluminum oxide.
12 . A cryostat according to claim 10 , wherein, in use as an electrical conductor, ohmic heating will cause the electrically conductive member to expand, pressing conformal surfaces into thermal and mechanical contact with the tubes; and, when not in use as an electrical conductor, the electrically conductive member cools and in doing so brings the conformal surfaces out of thermal and mechanical contact with the tubes 70 .
13 . A cryostat according to claim 10 , wherein the electrically conductive member is closed at each end, forming a gas-filled chamber, such that when the electrically conductive member is in use as an electrical conductor, ohmic heating causes expansion of the contained gas assisting in pressing the conformal surfaces into contact with the tubes, while the contrary contraction of the gas when ohmic heating ceases assists in displacing the conformal surfaces away from the tubes.
14 . A cryostat according to claim 6 , wherein one approximately half-cylindrical sheet is arranged to be connected to the positive side of a current source, while the other approximately half-cylindrical sheet is arranged to be connected to the negative side of the current source.
15 . A cryostat according to claim 1 , wherein two electrical conductors are provided to the electrically powered equipment, each electrical conductor being in thermal and mechanical contact with a respective tube of the pulse tube refrigerator, each connected to a respective one of positive and negative terminals of a current source.
16 . A cryostat cooled by a pulse tube refrigerator and containing electrically powered equipment, wherein an electrical conductor is provided to the electrically powered equipment, said electrical conductor coaxially arranged with respect to an individual pulse or regenerator tube of the pulse tube refrigerator, and isolated therefrom by a vacuum region.
17 . A cryostat according to claim 1 , wherein an electrical contact is provided such that the electrical contact is resiliently biased into electrical contact with the electrical conductor when the refrigerator is in its operating position, but is resiliently deformed by the refrigerator when the refrigerator is removed and replaced.