Supporting tie configuration for cryostat for cold shipment of NMR magnet
AssigneeGeneral Electric Company
InventorEvangelos T. Laskaris
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Abstract
A cryostat for use in magnets for NMR medical diagnostic imaging includes inner and outer vessels suspended by sets of at least three low thermal conductivity ties. The positioning of the tie anchoring points, particularly on the interior vessel, are selected in accordance with the present invention to preclude increased stresses in the supporting ties that occur as a result of thermal contraction. This configuration is particularly advantageous in that it permits the utilization of ties having smaller cross-sectional areas than would otherwise be required. The reduced cross-sectional area requirement is also therefore seen to increase the thermal isolation of the interior cryostat vessel. Cryostat vessels may be nested within one another.
Claims5
A cryostat comprising:
- an outer, evacuable vessel having an annular shape;
- an interior vessel having an annular shape and being wholly contained within said outer vessel so that the central axes of said interior vessel and said outer vessel lie substantially along the same line;
- a first set of at least three supporting ties extending transversely from attachment positions on a first end of said interior vessel to corresponding attachment points on the proximal end of said outer vessel, said attachment points on said first end of said interior vessel being substantially uniformly disposed about the periphery thereof and said corresponding attachment points on said outer vessel being substantially uniformly disposed about said outer vessel;
- and
- a second set of at least three supporting ties extending transversely from attachment points on a second end of said interior vessel to corresponding attachment points on the proximal end of said outer vessel, said attachment points on said second end of said interior vessel being substantially uniformly disposed about the periphery thereof and said corresponding attachment points on said outer vessel being substantially uniformly disposed about said outer vessel;
- said first and second set of said supporting ties each being disposed so that the angle .theta. between said tie and a line drawn from its attachment point on said interior vessel to said axis is given by .theta.=cos.sup.-1 (.DELTA.t/.DELTA.R), where .DELTA.t is the thermal contraction length of said tie and .DELTA.R is the thermal radial contraction length of said interior vessel.
Dependencies are inferred from the claim text.