U.S. patent application number 16/444784 was filed with the patent office on 2020-12-24 for control system for charging of non/partially insulated superconducting magnets and related techniques.
The applicant listed for this patent is Massachusetts Institute of Technology. Invention is credited to Daniel BRUNNER, Robert MUMGAARD.
Application Number | 20200402692 16/444784 |
Document ID | / |
Family ID | 1000004990453 |
Filed Date | 2020-12-24 |
![](/patent/app/20200402692/US20200402692A1-20201224-D00000.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00001.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00002.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00003.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00004.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00005.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00006.png)
![](/patent/app/20200402692/US20200402692A1-20201224-D00007.png)
United States Patent
Application |
20200402692 |
Kind Code |
A1 |
BRUNNER; Daniel ; et
al. |
December 24, 2020 |
CONTROL SYSTEM FOR CHARGING OF NON/PARTIALLY INSULATED
SUPERCONDUCTING MAGNETS AND RELATED TECHNIQUES
Abstract
A system comprises a superconducting magnet comprising a coil of
superconducting material. The coil includes two electrical
terminals. The windings of the coil are separated by a metallic
conductor. A control circuit is coupled to the two terminals to
drive a current through the coil to charge the superconducting
magnet and configured to provide a current through the coil that is
sufficiently small to avoid a quenching effect of the
superconducting magnet but also large enough to charge the magnet
within a predetermined time period. A cooling structure is
thermally coupled to the coil to remove heat caused by charging the
superconducting magnet with the current to allow for the current to
be sufficiently large to charge the magnet within the predetermined
time period without causing the quenching effect.
Inventors: |
BRUNNER; Daniel; (Cambridge,
MA) ; MUMGAARD; Robert; (Boston, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Massachusetts Institute of Technology |
Cambridge |
MA |
US |
|
|
Family ID: |
1000004990453 |
Appl. No.: |
16/444784 |
Filed: |
June 18, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01F 6/04 20130101; H01F
6/06 20130101; H01F 6/02 20130101 |
International
Class: |
H01F 6/06 20060101
H01F006/06; H01F 6/02 20060101 H01F006/02; 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 the windings of the coil are separated by a
metallic conductor; a control circuit coupled to the two terminals
to drive a current through the coil to charge the superconducting
magnet, and configured to provide a current through the coil that
is sufficiently small to avoid a quenching effect of the
superconducting magnet but also large enough to charge the magnet
within a predetermined time period; a cooling structure thermally
coupled to the coil to remove heat caused by charging the
superconducting magnet with the current to allow for the current to
be sufficiently large to charge the magnet within the predetermined
time period without causing the quenching effect.
2. The system of claim 1 wherein the cooling structure is
configured to maintain a temperature of the coil at 4 deg K or
higher.
3. The system of claim 1 wherein the control circuit further
comprises one or more feedback loops.
4. The system of claim 3 wherein the one or more feedback loops
feeds back a temperature of the coil.
5. The system of claim 3 wherein the one or more feedback loops
feeds back a current through the coil.
6. The system of claim 3 wherein the one or more feedback loops
feeds back a magnetic field of the coil.
7. The system of claim 1 wherein the control circuit comprises a
model of the coil.
8. The system of claim 7 wherein the model comprises a temperature
limit of the coil, a current limit of the coil, and a magnetic
field limit of the coil.
9. The system of claim 8 wherein the temperature limit, the current
limit, and the magnetic field limit define a region within which
the coil acts as a superconductor.
10. A method of controlling a superconducting magnetic coil
comprising: driving, by a variable current supply, a current
through the superconducting magnetic coil; monitoring, by a control
circuit, the current through the superconducting magnetic coil, a
temperature of the superconducting magnetic coil, and a magnetic
field about the superconducting magnetic coil; comparing, by the
control circuit, the temperature, current, and magnetic field to
model of the superconducting magnetic coil stored in the control
circuit to determine a current operating point of the
superconducting magnetic coil, wherein the model defines an
operating range for the superconducting magnetic coil within which
the coil acts as a superconductor; determining a maximum current
that can be used to charge the coil based on the operating point of
the superconducting magnetic coil and the operating range of the
superconducting magnetic coil; and adjusting the current to match
the maximum current to energize the superconducting magnetic
coil.
11. The method of claim 10 further comprising controlling, by the
control circuit, a cooling system to cool the superconducting
magnetic coil while applying the maximum current so that the
superconducting magnetic coil remains in the operating range.
12. The method of claim 11 wherein the cooling structure is
configured to maintain a temperature of the coil at 4 deg K or
higher.
13. The method of claim 10 wherein the control circuit further
comprises one or more feedback loops.
14. The method of claim 13 wherein the one or more feedback loops
feeds back a temperature of the coil.
15. The method of claim 13 wherein the one or more feedback loops
feeds back a current through the coil.
16. The system of claim 13 wherein the one or more feedback loops
feeds back a magnetic field of the coil.
17. The method of claim 10 wherein the model comprises a
temperature limit of the coil, a current limit of the coil, and a
magnetic field limit of the coil.
18. The method of claim 17 wherein the temperature limit, the
current limit, and the magnetic field limit define a region within
which the coil acts as a superconductor.
19. The method of claim 1 wherein windings of the superconducting
magnetic coil are separated by a metallic conductor.
Description
FIELD
[0001] This disclosure relates to superconducting magnets and, more
particularly, to superconducting magnets using partial- and
no-insulation.
BACKGROUND
[0002] As is known in the art, superconducting magnets having
partial- and/or no-insulation (PI/NI) between the superconducting
turns are used because they can be designed to be passively safe
during quenches. A quench is the transition from superconductor to
normal conductor due to the current in the superconductor exceeding
a threshold in the operating magnetic field, temperature, and/or
current density. A quench can deposit a significant amount of the
energy stored in the magnetic field as thermal energy in a small
volume of the magnet, which may cause damage to some or all
portions of the superconducting magnet. PI/NI magnets can avoid
this by allowing the current to flow around the quench zone to
adjacent superconducting turns and/or couples the quench
electromagnetically to adjacent turns.
SUMMARY
[0003] In accordance with one aspect of the concepts described
herein, it has been recognized that the reduction and/or entire
elimination of insulation in a superconducting magnet means that
voltages generated between the PI/NI superconducting layers (e.g.,
inductive voltages generated during charging and discharging) may
cause a current to flow through any electrically conductive layers.
This typically effectively places a resistance (R) in parallel with
an inductance (L) of the superconducting magnet thereby effectively
forming a parallel L-R circuit.
[0004] Such a situation can be problematic for at least two
reasons. First, superconducting magnets are often charged with a
current-controlled power source. In PI/NI magnets, the charging or
discharging time may be on the order of the LJR timescale, which
can be up to many hours for large-L, low-R PI/NI magnets. Because
of this, PI/NI superconducting magnets are typically only used for
DC magnets (i.e., ones that are turned on to a give field and held
there for long periods of time). Second, the current flowing
through the resistive portion of the magnet generates heat. This
heat must be removed by a cooling system and the resultant
temperature increase must be compatible with the superconducting
operation (it remains under the critical surface).
[0005] To overcome the limitation of slow charging times, the coil
terminals can effectively be overdriven, providing a much larger
inductive voltage to increase the ramp rate of current in the
superconductor. However, this also increases the current flowing
through the resistive portion of the magnet. Thus, in accordance
with the concepts, systems, circuits and techniques sought to be
protected herein, described is a control system that ramps (and
ideally, optimally ramps) or otherwise controls a current in a
superconductor while also controlling the effects of the current
flowing through a resistive element to ensure the magnet remains
superconducting.
[0006] In an embodiment, a system comprises a superconducting
magnet which itself comprises a coil of superconducting material.
The coil includes two electrical terminals. Windings of the coil
are separated by a metallic conductor. A control circuit is coupled
to the two terminals to direct or otherwise drive a current through
the coil to charge the superconducting magnet. Further, the control
circuit is configured to provide a current through the coil that is
sufficiently small to avoid a quenching effect of the
superconducting magnet but also large enough to charge the magnet
within a predetermined time period. A cooling structure is
thermally coupled to the coil to remove heat caused by charging the
superconducting magnet with the current to allow for the current to
be sufficiently large to charge the magnet within the predetermined
time period without causing the quenching effect.
[0007] One or more of the following features may be included either
individually or in combination.
[0008] The cooling structure may be configured to maintain a
temperature of the coil at 4 K or higher.
[0009] The control circuit may comprise one or more feedback
loops.
[0010] The one or more feedback loops may feed back a temperature
of the coil.
[0011] The one or more feedback loops may feedback a current
through the coil.
[0012] The one or more feedback loops may feedback a magnetic field
of the coil.
[0013] The control circuit may include a model of the coil.
[0014] The model may include a temperature limit of the coil, a
current limit of the coil, and a magnetic field limit of the
coil.
[0015] The temperature limit, the current limit, and the magnetic
field limit may define a region within which the coil acts as a
superconductor.
[0016] In another embodiment, a method of controlling a
superconducting magnetic coil includes driving, by a variable
current supply, a current through the superconducting magnetic
coil; monitoring, by a control circuit, the current through the
superconducting magnetic coil, a temperature of the superconducting
magnetic coil, and a magnetic field about the superconducting
magnetic coil; comparing, by the control circuit, the temperature,
current, and magnetic field to a model of the superconducting
magnetic coil stored in the control circuit to determine a current
operating point of the superconducting magnetic coil; determining a
maximum current that can be used to charge the coil based on the
operating point of the superconducting magnetic coil and the
operating range of the superconducting magnetic coil; and adjusting
the current to match the maximum current to energize the
superconducting magnetic coil. The model defines an operating range
for the superconducting magnetic coil within which the coil acts as
a superconductor
[0017] One or more of the following features may be included.
[0018] The control circuit may control a cooling system to cool the
superconducting magnetic coil while applying the maximum current so
that the superconducting magnetic coil remains in the operating
range.
[0019] The cooling structure may be configured to maintain a
temperature of the coil at 4 K or higher.
[0020] The control circuit may further comprise one or more
feedback loops.
[0021] The one or more feedback loops may feedback a temperature of
the coil.
[0022] The one or more feedback loops may feedback a current
through the coil.
[0023] The one or more feedback loops may feedback a magnetic field
of the coil.
[0024] The model may include a temperature limit of the coil, a
current limit of the coil, and a magnetic field limit of the
coil.
[0025] The temperature limit, the current limit, and the magnetic
field limit may define a region within which the coil acts as a
superconductor.
[0026] Windings of the superconducting magnetic coil may be
separated by a metallic conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] 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.
[0028] FIG. 1 is a block diagram of a magnetic coil and control
circuit.
[0029] FIG. 2 is a three-dimensional graph of an operational model
of a superconducting magnet.
[0030] FIG. 3 is a block diagram of an embodiment of a control
circuit for a superconducting magnet.
[0031] FIG. 4 is a perspective view of a simplified tokamak fusion
power system.
[0032] FIG. 4A is a block diagram of a portion of a magnetic coil
in a fusion power system.
[0033] FIG. 5 is a perspective view of a spiral plate and
superconducting tape for use in a superconducting magnet.
[0034] FIG. 6 is a block diagram of a computing device.
[0035] FIG. 7, an isometric partial cut-away view of an MRI system
which includes a control circuit which may be the same as or
similar to the control circuit of FIGS. 1 and 3.
DETAILED DESCRIPTION
[0036] This disclosure relates to control systems for
superconducting magnets for use in a wide variety of applications.
As will be discussed below, the superconducting magnets may
comprise a coil of superconducting material through which current
flows to generate a magnetic field.
[0037] Before proceeding with a description of illustrative control
circuits for use with superconducting magnets, some introductory
concepts are explained. It should be appreciated that while
reference may be made herein to specific applications, such
references are made solely to promote clarity in explaining the
broad concepts described herein. It should be appreciated that the
concepts, systems, circuits and techniques described herein find
use in a wide variety of different applications.
[0038] For example, after reading the description provided herein,
one of ordinary skill in the art will readily appreciate that the
concepts, systems, circuits and techniques described herein are
generally applicable for use in a wide range of applications (e.g.
a wide range of industrial uses) which may make use of high-field
magnets and that the described control concepts, control systems,
control circuits and control techniques may facilitate
commercialization of high-field magnets for use in a wide variety
of different applications. Such applications include but are not
limited to: applications in the medical and life sciences field
(e.g. magnetic resonance imaging and spectroscopy); applications in
the chemistry, biochemistry and biology fields (e.g. nuclear
magnetic resonance (NMR), NMR spectroscopy, electron paramagnetic
resonance (EPR), and Fourier-transform ion cyclotron resonance
(FT-ICR)); applications in particle accelerators and detectors
(e.g. for use in health care applications such as in instruments
for radiotherapy); application in devices for generation and
control of hot hydrogen plasmas; applications in the area of
transportation; applications in the area of power generation and
conversion; applications in heavy industry; applications in weapons
and defense; applications in the area of high-energy particle
physics; and applications in the area of fusion power plants (e.g.
compact fusion power plants).
[0039] Thus, although reference is sometimes made herein to the use
of high-field magnet assemblies including the subject control
circuits in connection with a specific application (e.g. fusion or
MRI) such references are not intended to be, and should not be
construed as, limiting. Rather, it should be appreciated that
control circuits and systems for high-field magnet assemblies
provided in accordance with the concepts described herein find use
in a wide variety of applications.
[0040] Referring now to FIG. 1, a system 100 for controlling
magnetic coil 102 may include control circuit 101 to monitor
magnetic coil 102, control (and ideally optimize) current ramping
and cooling as well as reduce (and ideally minimize) the occurrence
of quenching. Control circuit 101 may be coupled to a variable
current or voltage source 104 that drives current through magnetic
coil 102. Control circuit 101 may vary the current through magnetic
coil 102 by controlling variable current or voltage supply 104.
[0041] A cooling system may be coupled to magnetic coil 102 to
control the temperature of magnetic coil 102. In embodiments, the
value may be a variable threshold based on a model of magnetic coil
102, which will be discussed below. The cooling system may
minimally include a liquid cooling channel 106 coupled to magnetic
coil 102. In other embodiments, a conducting cooling system may be
used. In embodiments, liquid cooling channel 106 may be closely
thermally coupled to magnetic coil 102 to maximize the cooling that
cooling channel 106 can provide to the coil. For example, cooling
channel 106 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 magnetic coil 102.
[0042] In embodiments, cooling channel 106 may be a pipe or tube
that contains a cooling fluid. Pump 108 may pump the cooling fluid
through cooling channel 106 so that it circulates through magnetic
coil 102 and removes heat. Although not shown, the cooling system
may also include a condenser, a compressor, a cooling vat, a
cooling tower, etc.
[0043] In embodiments, magnetic coil 102 may be a so-called high
temperature superconductor. In this case, the cooling system may be
configured to maintain the temperature of magnetic coil 102 at 4
degrees Kelvin, 10 degrees Kelvin, or higher, or any temperature
above the boiling point of liquid Helium.
[0044] Control circuit 101 may also be coupled to control the
cooling system. For example, control circuit 101 may control pump
108, a condenser (not shown), a compressor (not shown) or other
elements of the cooling system to provide cooling to magnetic coil
102. In general, control circuit 101 may be able to control the
amount of cooling that the cooling system provides to magnetic coil
102 by operating pump 108 at different speeds, by adjusting valves,
by turning a compressor or condenser on and off, etc.
[0045] Control circuit 101 may also monitor the state of magnetic
coil 102. For example, control circuit 101 may be coupled to a
magnetic field sensor 110 to monitor the strength of the magnetic
field produced by magnetic coil 102. Although shown as a loop
sensor, magnetic field sensor 110 may be a Hall effect sensor, a
magnetoresistance element, or any type of magnetic field detection
device.
[0046] Control circuit 101 may also be coupled to temperature
sensor 112, which may be thermally coupled to magnetic coil 102 so
that control circuit 101 can monitor the temperature of magnetic
coil 102.
[0047] Additionally, because control circuit 101 controls current
source 104, control circuit 101 may monitor the amount of current
flowing through magnetic coil 102. In embodiments, system 100 may
include a current or voltage sensor (e.g. coupled to magnetic coil
102 and/or current source 104) that can sense the amount of current
flowing through magnetic coil 102. In this case, control circuit
101 may be coupled to the current or voltage sensor and may use the
current or voltage sensor to monitor the current flowing through
magnetic coil 102.
[0048] Control circuit 101 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 magnetic
coil 102. In embodiments, control circuit 101 may include a memory
114 that can store data for use by control circuit 101. Memory 114
may be a non-volatile memory such as an EPROM, a volatile memory
that is loaded with the data required by control circuit 101, or a
hard-programmed memory such as a logic circuit that acts as a
memory. In embodiments, memory 114 may contain data representing an
operating model for magnetic coil 102.
[0049] Referring now to FIG. 2, the three-dimensional graph
represents an operating model 200 for magnetic coil 102 (and/or
(and/or a superconducting tape). The J axis represents the current
density flowing through a coil or a superconducting tape, the B
axis represents the magnetic field to which a magnetic coil or
superconducting tape (e.g. coil 102 or tape 508) is exposed to
(produced by current flowing through the magnetic coil 102 as well
as any magnets external to the magnetic coil 102), and the T axis
represents the temperature of magnetic coil (e.g. coil 102) and/or
superconducting tape.
[0050] Curve 202 represents the boundary of superconductivity of a
magnetic coil (e.g. coil 102) and/or a superconducting tape. While
the magnetic coil (or tape) is operating 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, the magnetic coil (or tape)
may lose its superconducting properties, in whole or in part, and
begin to quench.
[0051] Using model 200, control circuit 101 may be able to provide
the maximum rate change of current to magnetic coil 102 in order to
energize magnetic coil 102 without allowing magnetic coil 102 to
quench. For example, assume that point 204 represents the state of
magnetic coil 102 at start-up, before any current is flowing
through magnetic coil 102 (i.e. point 204 occurs at a finite value
of temperature (T) and at zero current density (J) and zero
magnetic field (B)). To energize magnetic coil 102, control circuit
101 may provide a terminal current such that the current density J
in the superconductor is at or below point 206 without causing
magnetic coil 102 to quench. Generally, as the current density J
increases, the magnetic field B increases linearly. As the magnetic
field B and temperature T change, control circuit 101 can change
the amount of current flowing through magnetic coil 102 and/or the
amount of cooling provided to magnetic coil 102 so that magnetic
coil 102 remains in a superconducting state. Control circuit 101
may reduce (and ideally) minimize the time it takes to energize
magnetic coil 102 by providing an increased current (and ideally a
maximum or near maximum current) to magnetic coil 102 while keeping
the operating point of magnetic coil 102 below surface 202.
[0052] In embodiments, data representing model 200 may be stored in
memory 114. 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
magnetic coil 102.
[0053] Referring now to FIG. 3, a block diagram illustrates a
control system 300 for controlling a magnetic coil. Control system
300 may be the same as or similar to the control system described
above in connection with FIG. 1.
[0054] Control system 300 may include a control circuit 302 with a
memory 304. In embodiments, memory 304 may contain data
representing an operating model 305 of a magnetic coil, like the
operating model shown in FIG. 2. Control circuit 302 may be coupled
to a cooling control circuit 306 that controls a cooling system
308. Cooling system 308 may be the same as or similar to the
cooling system described above in connection with FIG. 1.
[0055] Control circuit 302 may also be coupled to current control
circuit 310 which may control current source 312. Current source
312 may be the same as or similar to current source 104 in FIG. 1.
Note that in other embodiments, current control circuit 310 may be
replaced by a voltage control circuit that controls voltage applied
to the superconducting magnet.
[0056] In embodiments, cooling control circuit 306, current control
circuit 310, and control circuit 302 may be separate circuits. In
other embodiments, cooling control circuit 306 and current control
circuit 310 may be integrated into control circuit 302.
[0057] Magnetic field sensor 314 may measure the magnetic field
around the magnetic coil and feedback signal 514a, representing the
strength of the detected magnetic field, to control circuit 302.
Magnetic field sensor 314 may be the same as or similar to magnetic
field sensor 110. Current sensor 316 may measure the value of the
current flowing through the magnetic coil and feedback signal 516a,
representing the value of the current. Also, temperature sensor
318, which may be the same or similar to temperature sensor 112,
may measure the temperature of the magnetic coil and feedback
signal 518a, representing the temperature, to control circuit
302.
[0058] System 300 may provide a plurality of feedback loops for
controlling the magnetic coil. For example, system 300 may feedback
temperature information (e.g. signal 518a), current information
(e.g. signal 516a), and magnetic field strength information (e.g.
signal 514a) to control circuit 302. Control circuit 302 may use
these signals and the operating model 305 to control the current
and cooling of the magnetic coil to operate the magnetic coil so it
remains in a superconducting state and does not quench. Also,
control circuit 302 may use these signals and the operating model
305 to minimize the time to energize the magnetic coil by providing
the maximum allowable current so that the magnetic coil remains in
a superconducting state.
[0059] In embodiments, control circuit 302 and/or cooling circuit
306 and/or current control circuit 310 may be implemented as state
machines.
[0060] The control systems described above may be used for various
embodiments including, but not limited to fusion power systems. As
an example, FIG. 4 is a diagram of a simplified tokamak system 400
for producing fusion power. The diagram includes a plasma tube 402
and a plurality of superconducting magnetic coils 404-410. These
coils may be the same as or similar to magnetic coil 102 described
above.
[0061] During energy generation, high temperature plasma (which
fuels the fusion reaction) circulates within plasma tube 402.
Because the plasma is at such high temperatures, if it were to
contact the walls of plasma tube 402 it could destroy plasma tube
402. Thus, system 400 generates magnetic fields that compress and
suspend the plasma into a stream within plasma tube 402 that does
not contact the walls of plasma tube 402.
[0062] To generate the magnetic field, tokamak system 400 has a
plurality of magnetic coils 404-410. These coils may comprise
superconducting magnets to produce the magnetic field that suspends
and compresses the plasma stream.
[0063] In embodiments, each magnetic coil 404-410 includes a series
of stacked plates 412. Each stacked plate may enclose a
superconducting magnet made from a coil of superconducting tape
material. As current flows through the coil of superconducting
tape, a magnetic field is generated.
[0064] FIG. 4A is a diagram of a portion 414 of magnetic coil 410.
As illustrated, magnetic coil 410 may comprise a series of stacked
plates 412. Each plate may contain a superconducting magnet, which
may be in the form of a coil, such as a coiled wire or tape for
example. Driving electrical current through the superconducting
tape may generate a magnetic field 416 that can compress plasma
stream 418 so that the plasma does not contact plasma tube 402.
[0065] Referring now to FIG. 5, shown is an example of
spiral-grooved plates stacked to form a so-called "double-pancake"
assembly 500. In this illustration, two identical spiral-grooved
plates 501, 502 are coupled back-to-back with an insulating
material (not visible in FIG. 5) inserted or otherwise disposed
therebetween. Spiral-grooved, stacked-plate superconducting magnets
and related spiral plates which may be the same as or similar to
assembly 500 are described in co-pending application Ser. No.
16/233,410 filed on Dec. 27, 2018 and application Ser. No.
16/416,781 filed on May 20, 2019 each of which are assigned to the
assignee of the present application and each of which applications
are hereby incorporated herein by reference in their
entireties.
[0066] In the illustrative embodiment of FIG. 5, a first plate 501
is disposed over a second plate 502 such that interface apertures
504 are aligned and can be used to fasten the plates together.
Plate 501 includes a spiral channel 506 defined by walls 507.
Channel 506 (also sometimes referred to herein as a grooved path or
a groove 506) is provided having a shape (i.e. a channel length, a
channel width and a channel height) selected to receive a tape
508.
[0067] Tape 508 may be provided as a high temperature
superconductor (HTS) tape stack that may include co-wind materials
is inserted into the grooved channel which executes an in-going
spiral on the top plate, a helix down to the bottom plate, and an
out-going spiral on the bottom plate. In embodiments, tape 508 may
be the same as or similar to the superconducting tape described in
co-pending applications 62/740,163 filed on Oct. 2, 2018, Ser. No.
16/233,410 filed on Dec. 27, 2018 and application Ser. No.
16/416,781 filed on May 20, 2019 each of which are assigned to the
assignee of the present application and each of which applications
are hereby incorporated herein by reference in their
entireties.
[0068] In some embodiments, tape 508 is continuously wound (i.e.
without breaks or segmentation) from a top surface to a bottom
surface of the pancake assembly. In some embodiments, tape 508 may
be provided as a non-insulating (NI) HTS tape (and co-wind stack
when used) which may be segmented or otherwise have breaks provided
therein (e.g. the path of one material may be broken and not
continuous). It should thus be appreciated that while the channel
may be described as more or less continuous (even though a
cross-sectional shape of a channel may change throughout the length
of the channel), the material loaded or otherwise disposed in the
channel may be continuous or may be provided in parts (e.g.
segmented).
[0069] In some embodiments, more than one HTS tape stack may be
disposed into the groove, with a material disposed between stacks
that may engage mechanically with the plate, such as via spiral
grooves, separately or in conjunction with the tape stacks. In some
embodiments, some or all of the co-wind materials may be disposed
to engage with the plate mechanically, such as via spiral grooves,
separately or in conjunction with the tape stacks. The co-wind
materials and surface coatings may be chosen to provide a desired
(and ideally, an optimized) magnet quench behavior.
[0070] Assembly 500 is suitable for use in providing a
superconducting magnet assembly such as may be used in any of the
applications described herein.
[0071] Similar to plate 501, plate 502 has a tape 510 disposed in a
channel thereof. In embodiments, tape 508 and tape 510 may be
electrically coupled in series to form a longer winding of
tape.
[0072] In embodiments, a superconducting magnet may be configured
to operate without any turn-to-turn insulation. In other words,
turns of tape 508 may be coiled atop each other and/or separated by
a conductive material such as the material from which plates 501,
502 are provided.
[0073] When conditions are met such that tape 508 exhibits
superconducting properties, its resistance to current may be
ideally zero and in any event much lower than the resistance of
normal conductors (conductors which do not exhibit superconducting
properties) such as the material (e.g. metal) from which plates
501, 502 are provided. Under these conditions of relatively low
voltages in the magnet, current is confined to and flows primarily
through the path defined by the channel in which tape 508 lies
(i.e. the current flows though the superconductor) and a relatively
small amount of current (and ideally no current) will pass from
turn to turn of tape 508 (i.e. current will not flow across walls
507 which define the channels in which the tape 508, 510 lies and
which separate the turns tape 508. 510).
[0074] If, however, conditions change so that, during operation,
superconducting properties are lost (lost either in-whole or
in-part), current may begin to flow from turn to turn of the
magnet, in a direction shown by arrow 512 instead of flowing around
the coil. 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.
[0075] Referring to FIG. 6, some or all of the algorithms
associated with control circuits 100 and 300, cooling control
circuit 306, and/or current control circuit 310 may be implemented
as software executing on a computing device, such as computing
device 600. Computing device 600 may be a computer, a
microprocessor, a custom processing circuit, an FPGA, or any type
of circuit or computing device that can execute software
instructions.
[0076] 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 302 and/or control circuit 101, 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.
[0077] In a system with multiple superconducting magnets, a number
of these control systems may be coupled together.
[0078] In embodiments, the concepts described may facilitate
commercialization of high-field magnets for use in fusion power
plants (e.g. compact fusion power plants) as well as in high-energy
physics applications. However, after reading the description
provided herein, one of ordinary skill in the art will readily
appreciate that the disclosed concepts are generally applicable for
use in a wide range of other applications (e.g. a wide range of
industrial uses) which may make use of high-field magnets. Such
applications include but are not limited to: applications in the
medical and life sciences field (e.g. magnetic resonance imaging
and spectroscopy); applications in the chemistry, biochemistry and
biology fields (e.g. nuclear magnetic resonance (NMR), NMR
spectroscopy, electron paramagnetic resonance (EPR), and
Fourier-transform ion cyclotron resonance (FT-ICR)); applications
in particle accelerators and detectors (e.g. for use in health care
applications such as in instruments for radiotherapy); application
in devices for generation and control of hot hydrogen plasmas;
applications in the area of transportation; applications in the
area of power generation and conversion; applications in heavy
industry; applications in weapons and defense; and applications in
the area of high energy particle physics.
[0079] As noted above, although reference is sometimes made herein
to the use of such high-field magnet assemblies in connection with
fusion power plants (e.g. compact fusion power plants) and fusion
research experiments (e.g. SPARC), such references are not intended
to be, and should not be construed as, limiting. It is appreciated
that control circuits and techniques provided in accordance with
the concepts described herein for use in and with high-field magnet
assemblies find use in a wide variety of different applications
[0080] For example, in the medical and life sciences field,
high-field magnets provided in accordance with the concepts
described herein may find use in magnetic resonance imaging (MRI)
and spectroscopy.
[0081] Referring to FIG. 7, an MRI system 700 comprises a patient
table 702 on which the patient is delivered into a tube 703 defined
by MRI system 700 for scanning. A scanner 704 uses magnets 706,
radio frequency (RF) coils 708, and gradient coils 710 to create
images. Maintaining such a large magnetic field requires a good
deal of energy, which can be accomplished by using superconductive
circuits. Thus, in embodiments, magnets 706 can be superconducting
magnets controlled by a control circuit which may be the same as or
similar to the control circuits described above in conjunction with
FIGS. 1 and 3. In this way, MRI system 700 may be configured to use
a strong magnetic field and radio waves to create detailed images
of organs and tissues within a person's body.
[0082] 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.
* * * * *