Apparatus and methods for generating a pulsating, high-strength magnetic field
A magnetic field system is configured to generate intense, dynamically-varying magnetic fields to confine and control particles, objects, or plasmas. The magnetic fields may pulsate to impart and directly extract energy from a plasma.
1. A method of confining a plasma, the method comprising:
injecting the plasma into a container;
applying a first plurality of currents to a plurality of magnetic coils that are arranged to create a magnetic field within the container, wherein the magnetic field prepares the plasma in a first state, wherein a radius of a separatrix of the plasma in the first state has a first radial value and a length of the separatrix has a first length value when the plasma is in the first state;
applying a second plurality of currents to the plurality of magnetic coils that changes the magnetic field to transition the plasma from the first state to a second state, wherein the radius of the separatrix has a second radial value in the second state that is less than the first radial value and the separatrix has a second length value in the second state; and
applying a third plurality of currents to the plurality of magnetic coils that changes the magnetic field when the plasma transitions from the second state to a third state in which the plasma has more energy than in the second state and begins expanding beyond at least the second length value, wherein the third plurality of currents are selected to create a magnetic field that resists expansion of the radius of the separatrix from the second radial value over at least a portion of the length of the separatrix while the length of the separatrix increases beyond the second length value.
2. The method of claim 1 , wherein the third plurality of currents are selected to restrain the radius of the separatrix to approximately the second radial value over the portion of the length of the separatrix while the length of the separatrix increases beyond the second length value.
3. The method of claim 1 , wherein the plasma has a toroidal shape in the first state and an average beta value of the plasma is at least 0.3, wherein beta is a ratio of pressure of the plasma to a magnetic pressure on the plasma and is averaged over a surface of the plasma to obtain the average beta value.
4. The method of claim 1 , wherein applying the second plurality of currents further comprises reducing the length of the separatrix from the first length value of the separatrix in the first state to the second length value in the second state.
5. The method of claim 1 , wherein applying the second plurality of currents further comprises increasing at least one current of the first plurality of currents by a factor having a value in a range from 1.5 to 10,000.
6. The method of claim 1 , wherein applying the second plurality of currents further comprises increasing a magnitude of the magnetic field at a center of the container by a factor having a value in a range from 1.5 to 10,000.
7. The method of claim 1 , wherein applying the second plurality of currents further comprises reducing the radius of the separatrix from the first radial value by a factor having a value in a range from 1.5 to 5.
8. The method of claim 1 , wherein applying the second plurality of currents further comprises reducing the length the separatrix from the first length value by a factor having a value in a range from 1.5 to 50.
9. The method of claim 1 , wherein applying the first plurality of currents and applying the second plurality of currents both occur within a duration of time have a value in a range from 1 microsecond to 100 milliseconds.
10. The method of claim 1 , further comprising:
receiving current in at least one of the plurality of magnetic coils that is induced by an increase in magnetic flux produced as the plasma transitions to the third state.
11. The method of claim 10 , further comprising:
providing the current to an external load.
12. The method of claim 10 , further comprising:
repeating in a sequence of cycles the acts of injecting the plasma, applying the first plurality of currents, applying the second plurality of currents, applying the third plurality of currents, and receiving current, wherein the sequence of cycles includes at least 100 cycles.
13. The method of claim 12 , wherein each cycle of the sequence of cycles has a duration of time in a range from 1 microsecond to 1,000 milliseconds.
14. A system comprising:
a container to hold a plasma;
a plurality of magnetic coils arranged to produce a magnetic field within the container;
one or more supply circuits coupled to each of the plurality of magnetic coils; and
circuitry to control delivery of current to the plurality of magnetic coils, wherein the circuitry is configured to:
apply a first plurality of currents to the plurality of magnetic coils to create the magnetic field within the container that prepares the plasma in a first state, wherein a radius of a separatrix of the plasma in the first state has a first radial value and a length of the separatrix has a first length value when the plasma is in the first state;
apply a second plurality of currents to the plurality of magnetic coils that changes the magnetic field to transition the plasma from the first state to a second state, wherein the radius of the separatrix has a second radial value in the second state of the plasma that is less than the first radial value and the separatrix has a second length value in the second state; and
apply a third plurality of currents to the plurality of magnetic coils that changes the magnetic field when the plasma transitions from the second state to a third state in which the plasma has more energy than in the second state and begins expanding beyond at least the second length value, wherein the third plurality of currents are selected to create a magnetic field that resists expansion of the radius of the separatrix from the second radial value over at least a portion of the length of the separatrix while the length of the separatrix increases beyond the second length value.
15. The system of claim 14 , wherein the plurality of magnetic coils each has a center arranged along a linear axis to form a field reversed configuration generator.
16. The system of claim 14 , wherein the circuitry is further configured to apply the second plurality of currents by increasing at least one current of the first plurality of currents by a factor having a value in a range from 1.5 to 10,000.
17. The system of claim 14 , wherein the circuitry is further configured to apply the second plurality of currents by increasing a magnitude of the magnetic field at a center of the container by a factor having a value in a range from 1.5 to 10,000.
18. The system of claim 14 , wherein the circuitry is configured to apply the first plurality of currents and the second plurality of currents within a duration of time have a value in a range from 1 microsecond to 1,000 milliseconds.
19. The system of claim 14 , wherein the circuitry is further configured to cyclically repeat a sequence of applying the first plurality of currents, applying the second plurality of currents, and applying the third plurality of currents.
20. The system of claim 14 , wherein the circuitry comprises a controller communicatively coupled to each of the one or more supply circuits.
21. The system of claim 14 , wherein the circuitry comprises firing control circuitry configured to sequence the delivery of current to each of the plurality of magnetic coils in response to receiving a command signal to deliver current to a first magnetic coil of the plurality of magnetic coils.
22. The system of claim 21 , wherein the firing control circuitry is distributed among the one or more supply circuits coupled to each of the plurality of magnetic coils.
23. The system of claim 14 , wherein each supply circuit of the one or more supply circuits comprises:
a source to provide current;
an energy-storage component to receive current from the source; and
a first switch to deliver energy from the energy-storage component to a magnetic coil of the plurality of magnetic coils.
24. The system of claim 23 , wherein each supply circuit of the one or more supply circuits further comprises a second switch to recover energy from the magnetic coil and recharge the energy-storage component.
25. The system of claim 23 , wherein each supply circuit of the one or more supply circuits further comprises a third switch to provide current from the magnetic coil to an external load.