Magnet coil system with active drift compensation for two independent current paths
A magnet coil system ( 2 ) which is at least partially superconducting at a cryogenic temperature, comprising at least two partial coils ( 3, 4, 5 ) which are connected in series and are each bridged by a superconducting switch ( 6, 7, 8 ), such that the partial coils form independent electric loops ( 11, 12, 13 ) when the superconducting switches ( 6, 7, 8 ) are closed, is characterized in that two electric loops ( 11, 12 ) have a common section and a flux pump ( 10 ) is provided which is circuited in the common section ( 14 ) of the electric loops ( 11, 12 ) of two partial coils ( 3, 4 ), wherein the sum of the currents of the two partial coils ( 3, 4 ) flows through the flux pump ( 10 ) in the operating state. In this fashion, the drifts of two independent electric loops can be compensated for with a few devices.
1. A magnet coil system which is at least partially superconducting at a cryogenic temperature, the magnet system comprising:
a first partial coil;
at least one second partial coil which is connected in series with said first partial coil;
a first superconducting switch bridging said first partial coil, said first partial coil and said first superconducting switch forming a first independent electric loop when said first superconducting switch is closed;
a second superconducting switch bridging said second partial coil, said second partial coil and said second superconducting switch forming a second independent electric loop when said second superconducting switch is closed, wherein said first and said second electric loop have a common section; and
a flux pump circuited in said common section, wherein a total sum of currents of said first and said second partial coils flows through said flux pump in an operating state.
2. The magnet coil system of claim 1 , wherein at least one of said first and said second partial coils at least partially consists of high-temperature superconducting material.
3. The magnet coil system of claim 1 , wherein the magnet coil system is structured and dimensioned for an NMR, MRI, EPR or FTMS spectrometer.
4. The magnet coil system of claim 3 , wherein said first and said second partial coils generate a sufficiently homogeneous partial magnetic field in the sample volume, such that a magnetic field is generated in the sample volume, which is sufficiently homogeneous for a respective application, despite current redistribution within said first and said second partial coils caused by said flux pump.
5. The magnet coil system of claim 4 , wherein an H2 field gradient of a corresponding partial magnetic field is smaller than 0.1 Gauss/(cm 2 A).
6. The magnet coil system of claim 1 , wherein at least said first and said second partial coils is substantially inductively decoupled from other partial coils.
7. The magnet coil system of claim 1 , wherein at least one of said first and said second partial coils are divided into subsections which are connected in series.
8. The magnet coil system of claim 7 , wherein said subsections are at least partially arranged on different radii.
9. The magnet coil system of claim 7 , wherein said subsections are at least partially oppositely polarized to act as active shielding of a stray field.
10. The magnet configuration comprising the magnet coil system of claim 1 , disposed in a cryostat having at least one cryogenic chamber, wherein a common power supply for said first and said second partial coils successively loads said first and said second coils with different currents via two common supply lines.
11. The magnet configuration of claim 10 , wherein said flux pump is disposed in a same cryogenic chamber as the magnet coil system.
12. A method of operating the magnet coil system of claim 1 , wherein said first and said second electric loops are connected to an external charging device for charging said first and said second partial coils, wherein operating currents of electric loops which contain said flux pump are selected such that those operating currents change by maximally 10% after removing the external charging device and switching on said flux pump, until a stationary state is reached.