Superconducting quick switch
A magnet system for generating a magnetic field may include a superconducting magnet, a switch, and a heater element thermally coupled to the switch. The superconducting magnet is structured to generate magnetic fields, and the switch includes a non-inductive superconducting current carrying path connected in parallel to the superconducting magnet. In general, the switch is structured to only carry a level of current that is a portion of the current required to obtain a full field by the superconducting magnet.
1. A magnet system for generating a magnetic field, said system comprising:
a superconducting magnet structured to generate magnetic fields and having a predetermined full field current rating;
a non-reversing current flow non-persistent switch comprising a non-inductive superconducting current carrying path connected in parallel to said superconducting magnet, said switch configured to only carry a level of current that is less than 100% of the current required to obtain a full field by said superconducting magnet, said non-reversing switch being configured to be connected to a current supply and to supply current continuously to said superconducting magnet during generation of said magnetic fields, wherein the current supply is not removed from the magnet after the switch transitions back to the full field status; and
a heater element thermally coupled to said switch, said heater element being configured, in combination with said switch, to vary the current level applied to said superconducting magnet.
2. The magnet system according to claim 1 , further comprising:
a heater power source in electrical communication with said heater element, said switch capable of changing from a superconducting mode to a non-superconducting mode responsive to heat generated by said heater element.
3. The magnet system according to claim 1 , further comprising:
a non-conductive housing which contains said switch and said heater element.
4. The magnet system according to claim 3 , wherein said housing is adapted to be inserted into a vessel containing a cryogen, said housing including thermal material structured to inhibit heat transfer from said switch and said heater element to said cryogen.
5. The magnet system according to claim 1 , further comprising:
a first thermal link thermally coupled to said switch, said first thermal link structured to effectively cool said switch to a superconducting temperature; and
a second thermal link thermally coupled to said superconducting magnet, said second thermal link structured to effectively cool said superconducting magnet to a superconducting temperature.
6. The magnet system according to claim 5 , further comprising:
a cooler structured to provide said first thermal link and said second thermal link; and
a cooler controller structured to control said cooler and causing said first thermal link and said second thermal link to respectively cool said switch and said superconducting magnet to a desired superconducting temperature.
7. The magnet system according to claim 1 , further comprising:
a radio frequency (RF) shield positioned relative to said switch and said heater element to effectively reduce coupling of RF signals between said switch and said heater element.
8. The magnet system according to claim 1 , wherein said current carrying path is a thin-film current carrying path.
9. The magnet system according to claim 1 , wherein said switch comprises non-clad, bifilar wound, superconducting wire.
10. The magnet system according to claim 9 , wherein said superconducting wire includes a diameter of about 5 μm-125 μm.
11. The magnet system according to claim 1 , wherein said switch is structured to only carry a level of current that is about 1%-20% of said current required to obtain said full field of said superconducting magnet.
12. The magnet system according to claim 1 , wherein said switch is structured to only carry a level of current that is about 2%-7% of said current required to obtain said full field of said superconducting magnet.
13. The magnet system according to claim 1 , wherein said superconducting magnet comprises a solenoid.
14. The magnet system according to claim 1 , further comprising:
a protective element connected in parallel to said switch and structured to limit maximum voltage across said switch.
15. The magnet system according to claim 14 , wherein said protective element comprises an electrical circuit.
16. The magnet system according to claim 14 , wherein said protective element comprises at least two diodes.
17. The switch according to claim 1 , further comprising:
a first thermal link thermally coupled to said non-inductive superconductive current carrying path, said first thermal link structured to effectively cool said non-inductive superconductive current carrying path to a superconducting temperature.
18. The switch according to claim 17 , further comprising:
a cooler structured to provide said first thermal link; and
a cooler controller structured to control said cooler and causing said first thermal link to cool said non-inductive superconductive current carrying path to a desired superconducting temperature.
19. A magnet system for generating a magnetic field, said system comprising:
a superconducting magnet structured to generate magnetic fields;
means for maintaining electrical current supplied to said superconducting magnet during generation of said magnetic fields, wherein the current supply is not removed from the magnet after the switch transitions back to a full field status;
a non-persistent switch connected in parallel to said superconducting magnet, said switch structured to only carry a level of current that is less than 100% of current required to obtain the full magnetic field by said superconducting magnet;
means for selectively causing said non-persistent switch to transition between a superconducting mode and a non-superconducting mode; and
means for changing said electrical current to generate a desired magnetic field.
20. A method for generating magnetic fields, said method comprising:
maintaining during the generation of magnetic fields, electrical current supplied to a superconducting magnet structured to generate magnetic fields, wherein the current supply is not removed from the magnet after the switch transitions back to a full field status; and
changing said magnetic fields by:
(a) heating a non-persistent switch connected in parallel to said superconducting magnet to a critical temperature, said heating causing said non-persistent switch to transition to a non-superconducting mode, said switch structured to only carry a level of current that is less than 100% of the current required to obtain the full magnetic field by said superconducting magnet;
(b) changing said electrical current to generate a desired magnetic field; and
(c) allowing said switch to cool below said critical temperature, causing said switch to transition to a superconducting mode.
21. The method according to claim 20 , further comprising:
repeating operations (a) through (c) with different values for said electrical current to generate a corresponding different magnetic field.
22. The method according to claim 20 , further comprising:
cooling said superconducting magnet and said switch with a cryogen.
23. The method according to claim 20 , further comprising:
cooling said superconducting magnet and said switch.