US 2007/0182513 A1 · Cryogenic cooling of superconducting magnet systems below temperature of 4.2k

Abstract

A superconducting magnet system comprises a cryogenic vessel (1), a superconducting magnet (11) contained in an inner reservoir (16) within the vessel (1) to be cooled by liquid helium within the inner reservoir (16), and an outer reservoir (7) containing liquid helium and linked to the inner reservoir (16) by a feed tube (10) and a needle valve (9). In operation of the system current is supplied to the magnet (11) by a removable current lead (19) extending through the wall of the vessel (1) by way of a supply passage (17) in order to initiate superconducting current flow in the magnet. The supply of current to the magnet (11) is then stopped and the lead (19) is removed whilst the superconducting current flow persists in the magnet. After an extended period of superconducting current flow in the magnet (11) and without stopping such superconducting current flow, liquid helium at a temperature of about 4.2 K may be supplied to an upper part of the inner reservoir (16) above the magnet (11) from the outer reservoir (7) such that the magnet is still surrounded by liquid helium at a temperature of below 4.2 K. After a period of time the supply of liquid helium to the inner reservoir 16 is stopped, and the liquid helium in the inner reservoir (7) is cooled to a temperature below 4.2 K. Such a system is capable of being operated at very low temperatures down to below the lambda point, and of producing magnetic fields of high strengths and stability suitable for NMR spectroscopy.

Claims26

Dependent claims

A method of cryogenically cooling a superconducting magnet surrounded by liquid helium at a temperature of below 4.2 K within an inner chamber of a cryogenic vessel, the method comprising:

supplying current to the magnet by way of a removable current lead extending through a supply passage passing through the wall of the vessel in order to initiate superconducting current flow in the magnet;
stopping the supply of current to the magnet whilst the superconducting current flow persists in the magnet;
withdrawing the current lead from the supply passage;
after an extended period of superconducting current flow in the magnet without stopping such superconducting current flow, supplying by way of a valve liquid helium at a temperature of about 4.2 K to an upper part of the inner chamber above the magnet such that the magnet is still surrounded by liquid helium at a temperature of below 4.2 K;
stopping the supply of liquid helium to the inner chamber by closing the valve;
and
cooling the liquid helium in the upper part of the inner chamber to a temperature of below 4.2 K by reducing the pressure in the upper part of the inner chamber by pumping whilst the valve remains closed.

4 more elements

A superconducting magnet system comprising:

a cryogenic vessel;
a superconducting magnet contained in an inner chamber within the vessel to be cooled by liquid helium at a temperature of below 4.2 K within the inner chamber;
a removable current lead which supplies current to the magnet via a supply passage extending through the wall of the vessel in order to initiate superconducting current flow in the magnet, and subsequently stopping the supply of current to the magnet whilst the superconducting current flow persists in the magnet and the current lead is withdrawn from the supply passage;
a valve which supplies, after an extended period of superconducting current flow in the magnet and without stopping the superconducting current flow, liquid helium at a temperature of about 4.2 K to an upper part of the inner chamber above the magnet where the magnet is surrounded by liquid helium at a temperature of below 4.2 K, and subsequently stops the supply of liquid helium to the inner chamber by closing the valve;
and
cooling means, which cools the liquid helium in the upper part of the inner chamber to a temperature of below 4.2 K by reducing the pressure in the upper part of the inner chamber by pumping whilst the valve remains closed.

3 more elements

Dependencies are inferred from the claim text.

Cryogenic cooling of superconducting magnet systems below temperature of 4.2k

Life of this patent

Cryogenic cooling of superconducting magnet systems below temperature of 4.2k

Life of this patent

Abstract

Claims26