Cryogenic cooling apparatus and system
View Patent ↗Cryogenic cooling apparatus is disclosed for cooling a target region using the demagnetization cooling effect. The apparatus has a primary magnet for providing a magnetic field within the target region and a demagnetization magnet arranged to selectively provide conductive cooling to the target region. A primary shielding magnet substantially cancels the magnetic field from the primary magnet at least at a first position between the primary and demagnetization magnets. A demagnetization shielding magnet substantially cancels the magnetic field from the demagnetization magnet at least at the first position between the primary and demagnetization magnets. Each of the primary shielding magnet and demagnetization shielding magnet comprises a cylindrical superconducting coil having a geometric envelope which encloses the primary magnet and demagnetization magnet respectively. A conductive cooling assembly provides conductive cooling to each of the magnets. A cryogenic system including a cryostat, the apparatus and a refrigeration system is also provided.
1. Cryogenic cooling apparatus for providing cooling to a target region using the demagnetisation cooling effect, the apparatus comprising:
a primary magnet for providing a magnetic field within the target region;
a demagnetisation magnet arranged to selectively provide conductive cooling to the target region, wherein the primary magnet and the demagnetisation magnet are each formed from superconducting coils having rotational symmetry about an axis, and wherein the axis is common to each of the primary and demagnetisation magnets such that the magnets are arranged axially;
a primary shielding magnet for substantially cancelling the magnetic field from the primary magnet at least at a first position between the primary and demagnetisation magnets, wherein the first position is located along the axis, the primary shielding magnet comprising a cylindrical superconducting coil having a geometric envelope which encloses the primary magnet;
a demagnetisation shielding magnet for substantially cancelling the magnetic field from the demagnetisation magnet at least at the first position between the primary and demagnetisation magnets, the demagnetisation shielding magnet comprising a cylindrical superconducting coil having a geometric envelope which encloses the demagnetisation magnet, wherein the primary shielding magnet has an axial length which is greater than the dimension of the primary magnet by between 10 and 40%, and wherein the demagnetisation shielding magnet has an axial length which is greater than the dimension of the demagnetisation magnet by between 10 and 40%; and,
a conductive cooling assembly configured to be coupled to a refrigeration system, the conductive cooling assembly being arranged to provide conductive cooling to each of the the primary magnet, the demagnetisation magnet, the primary shielding magnet, and the demagnetisation shielding magnet.
2. Cryogenic cooling apparatus according to claim 1 , wherein:
a. the primary magnet and primary shielding magnet are each arranged as superconducting magnets which are powered by a first common superconducting current; and
b. the demagnetisation magnet and demagnetisation shielding magnet are each arranged as superconducting magnets which are powered by a second common superconducting current.
3. Cryogenic cooling apparatus according to claim 2 , wherein the first common superconducting current is independent of the second common superconducting current.
4. Cryogenic cooling apparatus according to claim 1 , wherein one or each of the primary shielding magnet and the demagnetisation shielding magnet are formed respectively as a single cylindrical solenoid coil.
5. Cryogenic cooling apparatus according to claim 1 , wherein the demagnetisation shielding magnet is configured to cool the target region to a temperature of 1 milliKelvin or less.
6. Cryogenic cooling apparatus according to claim 1 , wherein the target region comprises a sample holder.
7. Cryogenic cooling apparatus according to claim 1 , further comprising a heat switch located at the first position between the primary and demagnetisation magnets, the heat switch being arranged to provide the target region with conductive cooling in a selective manner from a demagnetisation member which is selectively magnetised by the demagnetisation magnet.
8. Cryogenic cooling apparatus according to claim 1 , further comprising one or more vacuum chambers within which the primary, primary shielding, demagnetisation and demagnetisation shielding magnets are contained, such that, when in use, the magnets are each located within a vacuum environment.
9. Cryogenic cooling apparatus according to claim 8 , wherein the conductive cooling assembly comprises one or more thermally conductive members for coupling with the refrigeration system.
10. A cryogenic system comprising:
a. a cryostat;
b. cryogenic apparatus according to claim 1 , contained within the cryostat; and,
c. the refrigeration system coupled to the conductive cooling assembly of the cryogenic apparatus.
11. A cryogenic system according to claim 10 , wherein the refrigeration system comprises a mechanical refrigerator arranged to cool the conductive cooling assembly.
12. A cryogenic system according to claim 11 , wherein the refrigeration system further comprises a dilution refrigerator for selectively thermally coupling to each of the target region and demagnetisation material to be selectively demagnetised by the demagnetisation magnet, the dilution refrigerator being cooled by the mechanical refrigerator when in use.
13. A cryogenic system according to claim 10 , wherein the conductive cooling assembly is configured to cool each of the magnets to a temperature of 3-5 Kelvin.
14. A cryogenic system according to claim 11 , wherein the conductive cooling assembly is configured to cool each of the magnets to a temperature of 3-5 Kelvin.
15. Cryogenic cooling apparatus according to claim 1 , wherein the conductive cooling assembly is configured to cool each of the magnets to a temperature of 3-5 Kelvin.