U.S. patent application number 16/223707 was filed with the patent office on 2020-06-18 for electromagnetic pulse source using quenching superconducting magnet.
This patent application is currently assigned to Massachusetts Institute of Technology. The applicant listed for this patent is Massachusetts Institute of Technology. Invention is credited to Daniel Brunner.
Application Number | 20200194153 16/223707 |
Document ID | / |
Family ID | 71071759 |
Filed Date | 2020-06-18 |
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United States Patent
Application |
20200194153 |
Kind Code |
A1 |
Brunner; Daniel |
June 18, 2020 |
Electromagnetic Pulse Source Using Quenching Superconducting
Magnet
Abstract
An electromagnetic pulse source comprises a superconducting
magnet comprising a coil of superconducting material. At least a
portion of the windings of the coil are separated by an electric
conductor. A charging circuit is coupled to the two terminals to
drive a current through the coil to charge the superconducting
magnet and configured to charge the coil to a condition such that
the coil enters a quench condition where current flows from one
turn of the coil to another turn of the coil through the electric
conductor. The quench event may cause a loss of inductance and
resulting electromagnetic radiation. A receiver circuit comprising
an inductive element is positioned so that the inductive element is
mutually-coupled to the coil and the electromagnetic radiation
causes a voltage to be induced across the inductive element.
Inventors: |
Brunner; Daniel; (Cambridge,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Massachusetts Institute of Technology |
Cambridge |
MA |
US |
|
|
Assignee: |
Massachusetts Institute of
Technology
Cambridge
MA
|
Family ID: |
71071759 |
Appl. No.: |
16/223707 |
Filed: |
December 18, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01F 6/06 20130101; H01F
6/02 20130101; H01F 6/04 20130101; H01F 6/008 20130101 |
International
Class: |
H01F 6/02 20060101
H01F006/02; H01F 6/06 20060101 H01F006/06; H01F 6/04 20060101
H01F006/04 |
Claims
1. A system comprising: a superconducting magnet comprising a coil
of superconducting material, the coil comprising two electrical
terminals, wherein at least a portion of the windings of the coil
are separated by an electric conductor; a charging circuit coupled
to the two terminals to drive a current through the coil to charge
the superconducting magnet, and configured to charge the coil to a
condition such that the coil enter a quench condition where current
flows from one turn of the coil to another turn of the coil through
the electric conductor, wherein a loss of inductance due to the
quench condition causes electromagnetic radiation; and a receiver
circuit comprising an inductive element positioned so that the
inductive element is mutually-coupled to the coil and the
electromagnetic radiation causes a voltage to be induced across the
inductive element.
2. The system of claim 1 wherein the charging circuit comprises a
current source to drive current through the coil.
3. The system of claim 1 wherein the charging circuit is configured
to drive a current through the coil that exceeds a superconducting
threshold of the coil to initiate the quench condition.
4. The system of claim 3 wherein the charging circuit is configured
to vary the current through the coil so that, during a first time
period, the current does not exceed the superconducting threshold
and the coil acts as a superconductor and, during a second time
period, the current exceeds the superconducting threshold and the
quench condition is initiated.
5. The system of claim 4 wherein the charging circuit is configured
to vary the current so that the current alternatingly exceeds and
does not exceed the superconducting threshold.
6. The system of claim 1 further comprising a cooling system to
cool the coil below a superconducting threshold temperature of the
coil.
7. The system of claim 6 wherein the cooling system comprises a
cooling controller circuit to control the temperature of the
coil.
8. The system of claim 6 wherein the cooling controller circuit is
configured to allow the temperature of the coil to exceed the
superconducting threshold temperature to initiate the quench
condition.
9. The system of claim 6 wherein the cooling controller is
configured to control the temperature of the coil so that, during a
first time period, the temperature of the coil does not exceed the
superconducting threshold temperature and the coil acts as a
superconductor and, during a second time period, the temperature of
the coil exceeds the superconducting threshold temperature and the
quench condition is initiated.
10. The system of claim 1 further comprising a heating system.
11. The system of claim 10 wherein the heating system is configured
to heat the coil to a temperature that exceeds a superconducting
threshold temperature to induce the quench event.
12. The system of claim 10 wherein the heating system comprises a
heating controller circuit to control the temperature of the
coil.
13. The system of claim 1 further comprising a magnetic source
circuit configured to generate a magnetic field about the coil that
exceeds a superconducting threshold magnetic field strength to
induce the quench event.
14. A method comprising: driving current through a superconducting
magnet comprising a coil of superconducting material, wherein at
least a portion of the windings of the coil are separated by an
electrical conductor; causing a quench event to occur by
controlling the current, by a control circuit, so that the current
exceeds a superconducting current threshold of the superconducting
magnet and flows through the electrical conductor, causing a
reduction in an inductance of the coil and generation of an
electromagnetic pulse; and converting, by a receiver circuit,
electromagnetic power of the electromagnetic pulse into electrical
power.
15. The method of claim 14 wherein the electromagnetic power is
used to drive a load.
16. The method of claim 14 wherein the electromagnetic power is
used to charge a battery.
17. The method of claim 14 wherein the receiver circuit comprises a
plasma stream.
18. The method of claim 14 further comprising detecting, by the
control circuit, when the quench event occurs.
19. The method of claim 14 further comprising repeatedly causing
the quench event, by the control circuit, by repeatedly recharging
the superconducting magnet and increasing the current beyond the
superconducting threshold.
20. The method of claim 14 further comprising heating and/or
cooling the superconducting magnet by a heating and/or cooling
system controlled by the control circuit.
21. The method of claim 20 further comprising causing, by the
control circuit, the quench event by controlling the heating and/or
cooling system to cause the temperature of the superconducting
magnet to exceed a superconducting threshold temperature.
22. The method of claim 21 further comprising repeatedly causing
the quench event by repeatedly cooling the superconducting magnet
below the superconducting threshold temperature and causing the
temperature of the superconducting magnet to exceed the
superconducting threshold temperature.
Description
FIELD
[0001] This disclosure relates to superconducting magnets and, more
particularly, to capturing electromagnetic pulse energy from quench
events of superconducting magnets.
BACKGROUND
[0002] One type of superconducting magnet is formed from a
superconducting material that is wound into a coil. When current
flows through the coil it produced a magnetic field. Because of the
zero resistance of superconductors, superconducting magnetics can
store energy loss lessly in magnetic fields, resulting in powerful
magnetic fields which can be used in applications such as fusion
power generation.
[0003] The superconducting material's temperature, current, and
magnetic field must be maintained below thresholds so that the
material acts as a superconductor. If any one of these factors
increases to a value above the threshold, the superconducting
material may lose its superconducting properties. When the
threshold is passed, many superconducting magnets will experience a
positive feedback of the loss of superconducting properties,
resulting in a quench of the magnet.
[0004] A class of "no-insulation" superconducting magnets has
normal conducting material, typically a metal such as steel or
copper, between its turns. This allows current to flow across turns
in the case of quench events. This cross-turn current flow results
in a decrease in the magnet inductance, which then drives a voltage
into inductively coupled structures in an attempt to maintain
magnetic flux. Such a quench propagates electromagnetically and has
been termed a "quench tsunami" and a "quench avalanche".
SUMMARY
[0005] In an embodiment, a system comprises a superconducting
magnet comprising a coil of superconducting material, the coil
comprising two electrical terminals, wherein at least a portion of
the windings of the coil are separated by an electric conductor; a
charging circuit coupled to the two terminals to drive a current
through the coil to charge the superconducting magnet, and
configured to charge the coil to a condition such that the coil
enter a quench condition where current flows from one turn of the
coil to another turn of the coil through the electric conductor,
wherein a loss of inductance due to the quench condition causes
electromagnetic radiation; and a receiver circuit comprising an
inductive element positioned so that the inductive element is
mutually-coupled to the coil and the electromagnetic radiation
causes a voltage to be induced across the inductive element.
[0006] One or more of the following features may be included.
[0007] The charging circuit may comprise a current source to drive
current through the coil.
[0008] The charging circuit may be configured to drive a current
through the coil that, exceeds a superconducting threshold of the
coil to initiate the quench condition.
[0009] The charging circuit may be configured to vary the current
through the coil so that, during a first time period, the current
does not exceed the superconducting threshold and the coil acts as
a superconductor and, during a second time period, the current
exceeds the superconducting threshold and the quench condition is
initiated.
[0010] The charging circuit may be configured to vary the current
so that the current alternatingly exceeds and does not exceed the
superconducting threshold.
[0011] A cooling system may be included to cool the coil below a
superconducting threshold temperature of the coil.
[0012] The cooling system may comprise a cooling controller circuit
to control the temperature of the coil.
[0013] The cooling controller circuit may be configured to cause
the temperature of the coil to exceed the superconducting threshold
temperature to initiate the quench condition.
[0014] The cooling controller may be configured to control the
temperature of the coil so that, during a first time period, the
temperature of the coil does not exceed the superconducting
threshold temperature and the coil acts as a superconductor and,
during a second time period, the temperature of the coil exceeds
the superconducting threshold temperature and the quench condition
is initiated.
[0015] A heating system may also be included
[0016] The heating system may be configured to heat the coil to a
temperature that exceeds a superconducting threshold temperature to
induce the quench event.
[0017] The heating system may comprise a heating controller circuit
to control the temperature of the coil.
[0018] A magnetic source circuit may be included. The magnetic
source circuit may be configured to generate a magnetic field about
the coil that exceeds a superconducting threshold magnetic field
strength to induce the quench event.
[0019] In another embodiment, a method comprises: driving current
through a superconducting magnet comprising a coil of
superconducting material, wherein at least a portion of the
windings of the coil are separated by an electrical conductor;
causing a quench event to occur by controlling the current, by a
control circuit, so that the current exceeds a superconducting
current threshold of the superconducting magnet and flows through
the electrical conductor, causing a reduction in an inductance of
the coil and generation of an electromagnetic pulse; and
converting, by a receiver circuit, electromagnetic power of the
electromagnetic pulse into electrical power.
[0020] The electromagnetic power may be used to drive a load.
[0021] The electromagnetic power may be used to charge a
battery.
[0022] The receiver circuit may include a plasma stream.
[0023] The control circuit may detect when the quench event
occurs.
[0024] The control circuit may repeatedly cause the quench event,
by repeatedly recharging the superconducting magnet and increasing
the current beyond the superconducting threshold.
[0025] The control circuit may heat and/or cool the superconducting
magnet by controlling a heating and/or cooling system controlled by
the control circuit.
[0026] The control circuit may cause the quench event by
controlling the heating and/or cooling system to cause the
temperature of the superconducting magnet to exceed a
superconducting threshold temperature.
[0027] The control circuit repeatedly causing the quench event by
repeatedly cooling the superconducting magnet below the
superconducting threshold temperature and causing the temperature
of the superconducting magnet to exceed the superconducting
threshold temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The foregoing features may be more fully understood from the
following description of the drawings. The drawings aid in
explaining and understanding the disclosed technology. Since it is
often impractical or impossible to illustrate and describe every
possible embodiment, the provided figures depict one or more
exemplary embodiments. Accordingly, the figures are not intended to
limit the scope of the invention. Like numbers in the figures
denote like elements.
[0029] FIG. 1 is a perspective view of a coiled superconducting
magnet.
[0030] FIG. 2 is a graph of a superconducting model of a
superconducting magnet.
[0031] FIG. 3 is a block diagram of a control system for
controlling a superconducting magnet and an electromagnetic pulse
receiver circuit.
[0032] FIG. 4 is a block diagram of a superconducting magnet and
plasma to receive an electromagnetic pulse.
[0033] FIG. 5 is a block diagram of a control system for
controlling a superconducting magnet.
[0034] FIG. 6 is a block diagram of a computing system.
DETAILED DESCRIPTION
[0035] This disclosure relates to systems for electromagnetically
transferring the magnetic energy stored in a superconducting magnet
quickly to another system.
[0036] FIG. 1 is a diagram of a superconducting magnet 108c, which
may be in the form of a superconducting tape 108b comprising a
superconducting material 108a. In embodiments, superconducting
magnet 108c may form a coil without insulation between the
individual coils of superconducting tape 108. For example,
superconducting tapes 108b may be coiled in a channel 106 of a
metallic, conductive plate 100. Plate 100 may include ridges 101
positioned between the coils. Although the metallic ridges are
conductors, their conductivity may be significantly lower than that
of superconductor 108a when superconductor 108a is in a
superconducting state. In this case, because the conductivity of
the plate is relatively lower than the conductivity of the
superconducting material, the conductive metal of plate 100 and/or
ridges 101 may act as an insulator when there are negligible
voltages in the magnet, for example when the magnet is operating in
steady state.
[0037] In embodiments, the superconducting magnet 108c may be
formed from superconductors having different geometries and shapes.
For example, superconducting tape 108b may be replaced by a
superconducting wire, a superconducting plate, or any other
geometry that can support superconducting tape 108b.
[0038] In certain embodiments, plate 100 may be a stacked-plate
assembly. Plate 100 may be disposed over another plate 102 such
that interface apertures 104 are aligned and can be used to fasten
the plates together.
[0039] Plate 102 may also contain a coil of superconducting tape
110. In embodiments, tape 108 and tape 110 may be electrically
coupled in series to form a longer winding of superconducting tape.
Coils of superconducting tape may be threaded throughout multiple
conducting plates to produce a superconducting tape coil that winds
along the entire length of the respective magnetic coil.
[0040] Although metallic plates are used as an example, other
materials and geometries may be used as long as the windings of the
magnetic material do not have traditional insulating material
between at least some of the turns. Rather, a conducting material
such as metal or a conductive ceramic may be placed between at
least some of the turns of the superconducting magnet.
[0041] As noted, in embodiments, superconducting magnet 108c may be
configured to operate without any turn-to-turn insulation. In other
words, turns of superconducting magnet 108c may be wound atop each
other and/or separated by a conductive material such as the metal
used to form plate 100. When conditions are met so that
superconductor 108a is operating as a superconductor, its
resistance to current may be much lower than the resistance of
other conductors such as the metal of plate 100. Under these
conditions, even though plate 100 is formed from a traditional
conducting metal, the path through superconductor 108a may be the
path of least resistance. Thus, when there are relatively low
voltages the current will be confined to flow primarily through the
superconductor 108a and will not substantially flow from turn to
turn of magnet 108c.
[0042] If, however, conditions change so that, during operation,
superconducting tape 108a loses (in whole or in part) its
superconducting properties, current may begin to flow from turn to
turn of superconducting magnet 108c, in a direction shown by arrow
112 instead of flowing through the superconducting turns. This
phenomenon, when the tape loses its superconducting properties and
the current begins to flow from turn to turn, may be referred to as
quenching.
[0043] Although the example shown in FIG. 1 includes metallic
plates that are used to hold superconducting tape 108b, this is not
a requirement. Any physical arrangement can be used so long as the
superconducting tape 108b does not include turn-to-turn insulation
and a quenching effect can be achieved, which will be discussed
below.
[0044] Referring to FIG. 2, the three-dimensional graph represents
an operating model 200 for superconductor 108a. The J axis
represents the current density flowing through the superconductor
108a, the B axis represents the magnetic field in the
superconductor 108a, and the T axis represents the temperature of
the superconductor 108a.
[0045] Curve 202 represents the boundary of superconductivity of
superconductor 108a. While superconductor 108a is operating at a
point below curve 202, it may act as a superconductor. However, if
the current density J, magnetic field B, and/or temperature T
becomes too high and the operating point moves above curve 202,
superconductor 108a may lose its superconducting properties, in
whole or in part, and begin to quench.
[0046] Referring to FIG. 3, a system 300 for controlling
superconducting magnet 108c may include control circuit 301.
Control circuit 301 may monitor the state of superconducting magnet
108c and induce a quenching effect to generate electromagnetic
pulses. Control circuit 301 may be coupled to a variable current
source 304 that drives current through superconducting magnet 108c,
and control circuit 301 may vary the current through
superconducting magnet 108c by controlling variable current supply
304.
[0047] Superconducting tape 108b may be supported by a conductive
substrate 303. In an embodiment, substrate 303 may be the same as
or similar to metallic plate 100. In other embodiments, substrate
303 may be formed from another type of conductive material and/or a
substrate having a different geometry, so long as current can flow
through substrate 303 from turn to turn when a quench occurs.
[0048] During normal operation, current source 304 may drive
current through superconducting magnet 108c below a current
threshold so that superconductor 108a acts as a superconductor.
However, to induce a quench, control circuit 301 may increase
and/or pulse the current through superconductor 108a to a point
above the superconducting threshold. As the current exceeds the
threshold, the superconductor 108a may cease to act as a
superconductor. When this happens, the conductivity of
superconductor 108a (or a portion of superconducting tape) may
decrease so that it is less than the conductivity of substrate 303.
Thus, current may flow through substrate 303 directly from one turn
of superconducting magnet 108c to another. This may result in a
rapid loss of inductance of superconducting magnet 108c and an
induced voltage in inductively coupled structures, which will be
discussed below.
[0049] In embodiments, the threshold value of the current (or
magnetic field B or temperature T) of superconductor 108a may be a
variable threshold based on a model 200 of superconductor 108a. For
example, the current threshold may be defined by the surface of
curve 202 (see FIG. 2), which may change depending on the operating
point of the magnetic field B and temperature T.
[0050] A cooling system may be coupled to superconducting magnet
108c to maintain and control temperature of superconductor 108a.
During normal operation, the cooling system may maintain the
temperature of superconductor 108a below a superconducting
threshold. However, to induce a quench, the cooling system may
allow the temperature of superconductor 108a to exceed the
threshold. In some embodiments, a heating system (e.g. comprising
heating channel 307) may be used to the temperature of
superconductor 108a to a temperature that exceeds the threshold.
The combination of a heating and cooling system may provide
increased control over the temperature of superconductor 108a as
well as increased speed in heating and cooling. The heating system
may include an electric heater (e.g. a resistor), a conduction
heating system, or any type of heating system that can heat
superconductor 108a. When the temperature of superconductor 108a
exceeds the superconducting threshold temperature, superconductor
may cease to operate as a superconductor and a quench condition may
be initiated.
[0051] In embodiments, the threshold value for the temperature of
superconductor 108a may be a variable threshold based on a model of
superconductor 108a. For example, the temperature threshold may be
defined by the surface of curve 202 (see FIG. 2), which may change
depending on the operating point of the magnetic field B and
current density J.
[0052] The heating and cooling system may include a liquid cooling
channel 306 and/or a heating channel 307 coupled to superconducting
magnet 108c. In embodiments, liquid cooling channel 306 and/or
heating channel 307 may be closely thermally coupled to
superconducting tape 302 to maximize the cooling that cooling
channel 306 can provide to the tape and the heating that heating
channel 307 can provide to the tape. For example, cooling channel
306 and/or heating channel 307 may be physically coupled to a
thermal conductor (such as a copper strip or plate, not shown),
which in turn is directly physically coupled to superconducting
tape 302.
[0053] In embodiments, cooling channel 306 may be a pipe or tube
that contains a cooling fluid. Pump 308 may pump the cooling fluid
through cooling channel 306 so that it circulates through
superconducting magnet 108c and removes heat. Although not shown,
the cooling system may also include a condenser, a compressor, a
cooling vat, a cooling tower, etc. Heating channel 307 may be (or
may include) an electrical (e.g. resistive) heater coupled to
control circuit 301. In other embodiments, heating channel 307 may
be a liquid or gas heat channel which may be coupled to pump 308,
etc.
[0054] Control circuit 301 may also be coupled to control the
heating and cooling systems. For example, control circuit 301 may
control pump 308, a condenser (not shown), a compressor (not
shown), an electric heater, or other elements of the cooling system
to provide heating and cooling to superconducting magnet 108c. In
general, control circuit 301 may be able to control the amount of
heating and cooling that the cooling system provides to
superconducting magnet 108c by operating pump 308 (or other heating
and cooling elements) at different speeds, by turning a compressor
or condenser or heating element on and off, etc.
[0055] Control circuit 301 may monitor the state of superconducting
magnet 108c. For example, control circuit 301 may be coupled to a
magnetic field sensor 310 to monitor the strength of the magnetic
field produced by superconducting magnet 108c. Although shown as a
loop sensor, magnetic field sensor 310 may be a Hall effect sensor,
a magnetoresistance element, or any type of magnetic field
detection device.
[0056] Control circuit 301 may also be coupled to temperature
sensor 312, which may be thermally coupled to superconducting
magnet 108c (and/or superconducting tape 302) so that control
circuit 301 can monitor the temperature of superconducting magnet
108c (and/or superconducting tape 302).
[0057] In embodiments, superconductor 108a may be a so-called high
temperature superconductor. In this case, the cooling system may be
configured to maintain the temperature of superconductor 108a
(and/or superconducting tape 108b at 4 Kelvin or higher to maintain
superconducting performance. If, however, a quench is desired, the
cooling system may allow the temperature to increase until
superconducting tape enters a quench state.
[0058] Additionally, because control circuit 301 controls current
source 304, control circuit 301 may monitor the amount of current
flowing through superconducting tape 302. In embodiments, system
300 may include a current sensor (e.g. coupled to superconducting
tape 108b, superconducting tape 302, and/or current source 304)
that can sense the amount of current flowing through
superconducting tape 108b. In this case, control circuit 301 may be
coupled to the current sensor and may use the current sensor to
monitor the current flowing through superconducting tape 108b.
[0059] Control circuit 301 may be implemented as a custom logic
circuit, a programmed FPGA, a general-purpose computer programmed
with software, a special-purpose computer programmed with software,
or any type of circuit, system, or computing device that can act as
a control system to control cooling to and current through
superconducting tape 108b. In embodiments, control circuit 301 may
include a memory 314 that can store data for use by control circuit
314. Memory 314 may be a non-volatile memory such as an EPROM, a
volatile memory that is loaded with the data required by control
circuit 301, or a hard-programmed memory such as a logic circuit
that acts as a memory. In embodiments, memory 314 may contain data
representing an operating model for superconductor 108a (and/or
superconducting tape 302).
[0060] System 300 may include a magnetic field source circuit 315
coupled to control circuit 301. Magnetic field source circuit 315
may be an electromagnet or other device that can generate a steady
state, repeating pulse, or single pulse magnetic field 317 in
response to a signal from control circuit 301. Also, magnetic field
source circuit 315 may be positioned in proximity to
superconducting magnet 108c so that magnetic field 317 can increase
the magnetic field B in and around superconducting magnet 108c. As
noted above, if the magnetic field B increases above a
superconducting threshold, superconductor 108a may cease to act as
a superconductor. Thus, control circuit 301 may control magnetic
field source circuit 315 to increase the magnetic field B around
superconducting magnet 108c to induce a quench event.
[0061] System 300 may also include a receiver circuit 310 to
receive electromagnetic pulses cause by the quench events of
superconducting magnet 108c. When a quench event occurs
superconductor 108a (or a portion of superconductor 108a) ceases to
act as a superconductor and current may flow through from turn to
turn of superconducting magnet 108c through substrate 303. This
reduces the number of turns and therefor reduces the magnet's
inductance. When this happens, superconducting magnet 108c may
induce a voltage in inductively coupled structures.
[0062] Receiver circuit 310 may comprise a coupled inductor 310
that will experience the induced voltage. Inductor 310 may be
coupled to a load 311 to put its induced voltage across the load.
Load 311 may be any type of load such as another circuit, a battery
that is charged by antenna 310, or the like.
[0063] In embodiments, control circuit 301 may detect when a quench
occurs by monitoring the temperature, current, and magnetic field
associated with superconducting magnet 108c. When a quench occurs,
the temperature may increase, the current through superconductor
108a may be reduced, and the magnetic field produced by
superconducting tape 108 may locally spike, for example. Control
circuit 301 may detect that quench has occurred by monitoring the
temperature, current, and magnetic field (e.g. with a magnetic
field sensor--not shown--such as a loop sensor, Hall effect
element, magnetoresistive element, etc.) to detect these
events.
[0064] Referring to FIG. 4, a toroidal plasma 400 may act as the
inductor to receive a voltage pulse from a quench event. For
example, a fusion power generator system may include a toroidal
plasma 400 used as fuel in a fusion reaction. Superconducting
magnet 108c may be positioned so that the electromagnetic pulse 404
generated by a quench event can be received by plasma 400. The
voltage induced by the electromagnetic pulse 400 may, for example,
drive electrical current through plasma 400. Thus, the
electromagnetic pulse may increase, decrease, or change the
direction of the current flowing through plasma 400. Although a
fusion power generator system is used as an example, any system
that includes an inductively coupled plasma stream may be used to
receive electromagnetic pulse 404.
[0065] In embodiments, data representing model 200 may be stored in
memory 314. Model 200 may be represented as a formula, a series of
formulas, a data table, a lookup table, or any other type of data
that can be used to represent the superconducting operating of
superconductor 108a.
[0066] Using model 200, control circuit 301 may be able to cause
superconductor 108a to quench. For example, assume that control
circuit 301 is operating superconducting tape at a point 206 near
the surface of curve 202 (see FIG. 2). Control circuit may increase
the current density J through superconductor 108a, allow the
temperature T to rise, and/or induce an external magnetic field so
that operating point 206 moves above the surface of curve 202,
which may result in superconductor 108a losing its superconducting
properties. When this happens, a quench event may occur.
[0067] In embodiments, a quench event may result in a quench
avalanche. For example, if one turn of superconducting magnet 108c
loses its superconducting properties, quenches, and the current
shorts to adjacent turns, it will cause induce a voltage on
adjacent turns, causing an increased current. This may result in
the adjacent turn also quenching and possibly causing another
adjacent coil to quench, and so on. Each quench event may result in
an electromagnetic pulse, or may increase the electromagnetic
pulse, which may be received by the receiver circuit.
[0068] Referring to FIG. 5, a block diagram illustrates a control
system 500 for controlling superconducting magnet 108c. Control
system 500 may be the same or similar to the control system
comprising control circuit 301 described above in connection with
FIG. 3.
[0069] Control system 500 may include a control circuit 502 with a
memory 504. In embodiments, memory 502 may contain data
representing an operating model 505 of a superconductor, like model
200 in FIG. 2. Control circuit 502 may be coupled to a heating and
cooling control circuit 506 that controls a heating and/or cooling
system 508. Cooling system 508 may be the same or similar to the
heating and cooling system described above in connection with FIG.
3.
[0070] Control circuit 502 may also be coupled to current control
circuit 510 which may control current source 512. Current source
512 may be the same or similar to current source 304 in FIG. 3.
[0071] Also, control circuit 502 may be coupled to a magnetic
source circuit 505 that can generate a steady or pulsed external
magnetic field. Magnetic source circuit 505 may be the same as or
similar to magnetic source circuit 315 in FIG. 3. Control circuit
502 may control magnetic source circuit 505 to create a steady
state or pulsed magnetic field to induce superconductor 108a to
quench.
[0072] In embodiments, cooling control circuit 506, current control
circuit 510, and control circuit 502 may be separate circuits. In
other embodiments, cooling control circuit 506 and current control
circuit 510 may be integrated into control circuit 502.
[0073] Magnetic field sensor 514 may measure the magnetic field
around superconducting magnet 108c and provide feedback signal
514a, representing the strength of the detected magnetic field, to
control circuit 502. Current sensor 516 may measure the value of
the current flowing through superconducting tape 108b and generate
feedback signal 516a, representing the value of the current. Also,
temperature sensor 518, which may be the same or similar to
temperature sensor 312, may measure the temperature of
superconducting tape and feed back signal 518a, representing the
temperature, to control circuit 502.
[0074] System 500 may provide a plurality of feedback loops for
controlling the superconducting magnet 108c. For example, system
500 may feed back temperature information (e.g. signal 518a),
current information (e.g. signal 516a), and magnetic field strength
information (e.g. signal 514a) to control circuit 502. Control
circuit 502 may use these signals and the model of superconducting
tape to control the current and cooling of the magnetic coil to
operate the magnetic coil
[0075] As described above regarding FIG. 3, control circuit 502 may
be able to cause superconducting magnet 108c to quench. For
example, assume that control circuit 301 is operating
superconductor at a point 206 on or near the surface of curve 202.
Control circuit 502 may increase the current density J through
superconductor 108a and/or allow the temperature T to rise so that
operating point 206 moves above the surface of curve 202, which
will result in superconducting tape losing its superconducting
properties. When this happens, a quench event may occur.
[0076] In embodiments, control circuit 502 and/or cooling circuit
506 and/or current control circuit 510 may be implemented as state
machines.
[0077] Control circuit 502 may be configured to repeatedly and/or
periodically cause quench events in superconducting magnet 108c. In
embodiments, control circuit 502 may charge superconducting magnet
108c until it is operating at the cusp of a quench event. Then,
control circuit 502 may increase the temperature or current or
magnetic field to initiate a quench event and the resulting
electromagnetic pulse. After the quench event, control circuit may
cool superconducting magnet 108c and drive current through
superconductor 108a so that it operates under curve 202 (see FIG.
2) and acts as a superconductor. Subsequently, control circuit 503
may again charge superconducting magnet 108c until it is operating
at the cusp of a quench event, and again increase the temperature
and/or current to initiate a subsequent quench event. Control
circuit 502 may repeat this process periodically or in response to
a trigger to cause electromagnetic pulses from quench events that
can be received by the receiver circuit.
[0078] Referring to FIG. 6, some or all of the algorithms
associated with control circuit 502, cooling control circuit 506,
and/or current control circuit 510 may be implemented as software
executing on a computing device, such as computing device 600.
Computing device 600 includes a processor 602, a random-access
memory (RAM) 604, and a storage device 606, which may be a hard
drive, a CD, a DVD, a flash drive, or any other type of
non-volatile memory. Software instructions may be stored in RAM 604
and/or storage device 606. Processor 602 may be coupled to storage
device 606 and/or RAM 604 so that processor 602 can read the
software instructions. As processor 602 reads the software
instructions, the software instructions may cause processor 602 to
perform operations, as described above in relation to control
circuit 502 and/or control circuit 301, for operating a magnetic
coil. Although not shown, processor 602 and/or computing device 600
may include other inputs and outputs, such as inputs for receiving
the signals from the sensing elements, GPIO, power inputs, or other
interfaces such as USB, SATA, HDMI, and the like.
[0079] Various embodiments are described in this patent. However,
the scope of this patent should not be limited to the described
embodiments, but rather should be limited only by the spirit and
scope of the following claims. All references cited in this patent
are incorporated by reference in their entirety.
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