A superconducting MRI quench protection circuit

Abstract

The invention discloses a superconducting MRI quench protection circuit, which relates to the technical field of superconducting MRI, and comprises: a superconducting coil, an energy storage inductor, a first diode pair and an excitation power supply; the superconducting coil is connected in series with the excitation power supply; the energy storage inductor is connected in series with the first diode pair, and the energy storage inductor and the first diode pair are also connected in parallel with the superconducting coil to form a protection circuit. The present application stores the energy released when the superconducting coil quenches through the energy storage inductor, and uses the energy stored in the energy storage inductor to provide energy for the next excitation, thereby improving the recovery rate of the superconducting MRI quench energy.

Description

Technical Field

[0001] The present application relates to the technical field of superconducting MRI, and in particular to a superconducting MRI quench protection circuit. Background Art

[0002] When specific temperature, magnetic field, and current density conditions are met, the coil will exhibit superconducting properties. During normal operation of the MRI device, when specific operating conditions are destroyed, the coil will quench, and the Joule heat generated will cause the local temperature to rise too high, bringing the risk of burning the MRI device. At the same time, the high voltage generated instantly after the quench will cause the turns and layers of the coil to be broken down, generating an arc that burns the coil. In addition, the current mutation caused by the high voltage will cause the coil to be overstressed. Therefore, it is necessary to study the superconducting MRI quench protection circuit to avoid coil overheating and overcurrent damage to the MRI equipment during quench.

[0003] In the prior art, Chinese patent CN118841917A discloses a quench protection device, a quench protection method and a magnetic resonance system for a superconducting magnet, wherein the quench protection device comprises: a quench protection switch assembly; a heating branch, which is arranged in parallel at both ends of the quench protection switch and is thermally coupled with each magnet coil group; at least one quench heating circuit, which is connected in parallel with at least one magnet coil group and is connected with at least one first heater to form a quench heating loop, and is used for controlling at least one first heater to heat the quench protection switch when the voltage at both ends of at least one magnet coil group is greater than a first voltage and less than a second voltage, so that the heating branch heats each magnet coil group to perform quench propagation.

[0004] However, in the above-mentioned prior art, although the quench protection circuit consumes the quench energy of the superconducting coil through the heater, it causes a large energy loss and the recovery rate of the quench energy is low. Summary of the invention

[0005] The present application provides a superconducting MRI quench protection circuit, which is used to solve the problem that the existing quench protection circuit has a low recovery rate of quench energy.

[0006] On the one hand, the present application provides a superconducting MRI quench protection circuit, comprising: a superconducting coil L, an energy storage inductor L m , the first diode pair D1 and the excitation power supply E.

[0007] The superconducting coil L is connected to the excitation power source E in series.

[0008] The energy storage inductor L m Connected in series with the first diode pair D1, the energy storage inductor L m The first diode pair D1 is also connected in parallel with the superconducting coil L to form a protection loop.

[0009] In a possible implementation, a plurality of protection circuits are provided, and the plurality of protection circuits are connected in series to form a segmented protection circuit.

[0010] In a possible implementation, a first switch S1 is connected in series between the superconducting coil L at one end of the segment protection loop and the first diode pair D1.

[0011] The first switch S1 is connected in parallel with a heating branch.

[0012] The heating branch includes a plurality of heaters H connected in series, and each heater H is thermally coupled to a superconducting coil L.

[0013] In a possible implementation manner, a second diode pair D2 is connected in parallel to the segment protection loop.

[0014] In a possible implementation, the second diode pair D2 includes two diodes connected in reverse parallel.

[0015] In a possible implementation manner, a superconducting switch R is connected in parallel to the segment protection loop.

[0016] In a possible implementation, the first diode pair D1 includes two diodes connected in reverse parallel.

[0017] In a possible implementation, the excitation power source E is connected in series with a second switch S2.

[0018] A superconducting MRI quench protection circuit in the present application has the following advantages:

[0019] By placing the energy storage inductor L m After being connected in series with the first diode pair D1, they are connected in parallel with the superconducting coil L. The energy storage inductor L m The energy released when the superconducting coil L fails is stored and the energy storage inductor L m The stored energy provides energy for the next excitation, improving the recovery rate of the quench energy of superconducting MRI.

[0020] The proposed protection circuits are provided with several protection circuits, which are connected in series to form a segmented protection circuit. The segmented protection method improves the uniformity and efficiency of recycling the superconducting MRI quench energy.

[0021] The proposed first switch S1 is connected in parallel with a heating branch, and the heating branch includes a plurality of heaters H connected in series, each heater H is thermally coupled with a superconducting coil L. When a local quench occurs, the current flowing through the corresponding superconducting coil L is reduced, and the remaining current bypasses the first diode pair D1 and the heater H. Since each section of the heater H is connected in series, the current flowing through the remaining heaters H can accelerate the quench process and avoid the overheating and overvoltage hazards of the MRI equipment; at the same time, when a local quench occurs, the current flowing through the corresponding superconducting coil L is reduced, which also leads to a corresponding reduction in magnetic flux, thereby causing the magnetic flux in the heater H coil to change, generating an induced electromotive force and an induced current, and the current flows through the remaining heaters H, further accelerating the quench process; while the superconducting MRI quench energy is heated by the disconnection of the first switch S1, part of the energy is stored in the energy storage inductor L m In the process, the heating branch is short-circuited by closing the first switch S1, so that the energy storage inductor L m The energy stored in the magnet is released to provide energy for the next excitation.

[0022] The proposed segmented protection circuit is connected in parallel with the second diode pair D2 and the superconducting switch R. When the superconducting switch R is excited, it loses its superconducting power and its branch is in an open state. When the excitation ends, the superconducting switch R is closed, and the superconducting coil L forms a closed loop and starts to work normally. When the superconducting coil L loses its superconducting power, the second diode pair D2 is used to clamp the voltage generated on the superconducting coil L, thereby protecting the entire circuit.

[0023] The first diode pair D1 is used to isolate the inductor voltage during the excitation process and prevent the current from flowing through the energy storage inductor L m , while preventing the heater H from malfunctioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of a superconducting MRI quench protection circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] like Figure 1 As shown, the embodiment of the present application provides a superconducting MRI quench protection circuit, comprising: a superconducting coil L, an energy storage inductor L m , the first diode pair D1 and the excitation power supply E.

[0028] The superconducting coil L is connected to the excitation power source E in series.

[0029] The energy storage inductor L m Connected in series with the first diode pair D1, the energy storage inductor L m The first diode pair D1 is also connected in parallel with the superconducting coil L to form a protection loop.

[0030] Specifically, the energy storage inductor L m It is used to store the energy released when the superconducting coil L fails, and to provide energy for the next excitation.

[0031] Exemplarily, the protection circuits are provided in a plurality, and the plurality of protection circuits are connected in series to form a segmented protection circuit.

[0032] Specifically, the number of protection loops depends on the number of superconducting coils L, and each superconducting coil L corresponds to a protection loop.

[0033] Exemplarily, a first switch S1 is connected in series between the superconducting coil L at one end of the segmented protection loop and the first diode pair D1.

[0034] The first switch S1 is connected in parallel with a heating branch.

[0035] The heating branch includes a plurality of heaters H connected in series, and each heater H is thermally coupled to a superconducting coil L.

[0036] Specifically, the heater H is used to be activated by the terminal voltage of the superconducting coil L when the MRI device is quenched, consume a part of the quench energy, accelerate the quench process, and avoid overheating and overvoltage hazards of the MRI device. In this embodiment, the number of heaters H is equal to the number of superconducting coils L and corresponds one to one. In other possible embodiments, heating branches of other structures may also be provided.

[0037] Exemplarily, the segment protection loop is connected in parallel with a second diode pair D2.

[0038] Exemplarily, the second diode pair D2 includes two diodes connected in reverse parallel.

[0039] Exemplarily, a superconducting switch R is connected in parallel to the segment protection circuit.

[0040] Specifically, during excitation, the superconducting switch R quenches, and its branch is in an open state. When the excitation ends, the superconducting switch R closes, and the superconducting coil L forms a closed loop and starts to work normally. When the superconducting coil L quenches, the second diode pair D2 is used to clamp the voltage generated on the superconducting coil L, thereby protecting the entire circuit.

[0041] Exemplarily, the first diode pair D1 includes two diodes connected in reverse parallel.

[0042] Specifically, the first diode pair D1 is used to isolate the inductor voltage during the excitation process to prevent the current from flowing through the energy storage inductor L m , while preventing the heater H from malfunctioning.

[0043] Exemplarily, the excitation power source E is connected in series with a second switch S2.

[0044] Specifically, in this embodiment, the overall operation process of the superconducting MRI quench protection circuit is as follows: during the excitation process, the second switch S2 is closed, and the excitation power supply E provides current to the superconducting coil L; in the superconducting state, the second switch S2 is disconnected, the superconducting switch R is closed, and the MRI device enters a stable working state; when a quench occurs, the second switch S2 is disconnected, the heater H in the heating branch consumes part of the quench energy of the superconducting coil L, and the energy storage inductor L m Store another part of the quench energy; when the next excitation is required (i.e. the MRI device restores the superconducting state), the first switch S1 is closed, and the heating branch is short-circuited by the first switch S1, and the energy storage inductor L m The energy stored in the superconducting coil is released to provide energy for excitation; then the first switch S1 is opened and the second switch S2 is closed, and the excitation power supply E provides current to the superconducting coil L for excitation again.

[0045] In this embodiment of the present application, the energy storage inductor L m After being connected in series with the first diode pair D1, they are connected in parallel with the superconducting coil L. The energy storage inductor L m The energy released when the superconducting coil L fails is stored and the energy storage inductor L m The stored energy provides energy for the next excitation, improving the recovery rate of the quench energy of superconducting MRI.

[0046] The proposed protection circuits are provided with several protection circuits, which are connected in series to form a segmented protection circuit. The segmented protection method improves the uniformity and efficiency of recycling the superconducting MRI quench energy.

[0047] The proposed first switch S1 is connected in parallel with a heating branch, and the heating branch includes a plurality of heaters H connected in series, each heater H is thermally coupled with a superconducting coil L. When a local quench occurs, the current flowing through the corresponding superconducting coil L is reduced, and the remaining current bypasses the first diode pair D1 and the heater H. Since each section of the heater H is connected in series, the current flowing through the remaining heaters H can accelerate the quench process and avoid the overheating and overvoltage hazards of the MRI equipment; at the same time, when a local quench occurs, the current flowing through the corresponding superconducting coil L is reduced, which also leads to a corresponding reduction in magnetic flux, thereby causing the magnetic flux in the heater H coil to change, generating an induced electromotive force and an induced current, and the current flows through the remaining heaters H, further accelerating the quench process; while the superconducting MRI quench energy is heated by the disconnection of the first switch S1, part of the energy is stored in the energy storage inductor L m In the process, the heating branch is short-circuited by closing the first switch S1, so that the energy storage inductor L m The energy stored in the magnet is released to provide energy for the next excitation.

[0048] The proposed segmented protection circuit is connected in parallel with the second diode pair D2 and the superconducting switch R. When the superconducting switch R is excited, it loses its superconducting power and its branch is in an open state. When the excitation ends, the superconducting switch R is closed, and the superconducting coil L forms a closed loop and starts to work normally. When the superconducting coil L loses its superconducting power, the second diode pair D2 is used to clamp the voltage generated on the superconducting coil L, thereby protecting the entire circuit.

[0049] The first diode pair D1 is used to isolate the inductor voltage during the excitation process and prevent the current from flowing through the energy storage inductor L m , while preventing the heater H from malfunctioning.

[0050] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0051] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A superconducting MRI quench protection circuit, characterized in that: include: Superconducting coil L, energy storage inductor L m , a first diode pair D1 and an excitation power supply E; The superconducting coil L is connected in series with the excitation power supply E; The energy storage inductor L m Connected in series with the first diode pair D1, the energy storage inductor L m The first diode pair D1 is also connected in parallel with the superconducting coil L to form a protection loop; The protection circuits are provided with a plurality of protection circuits, which are connected in series to form a segmented protection circuit; A first switch S1 is connected in series between the superconducting coil L at one end of the segment protection loop and the first diode pair D1; The first switch S1 is connected in parallel with a heating branch; The heating branch includes a plurality of heaters H connected in series, and each heater H is thermally coupled to a superconducting coil L.

2. A superconducting MRI quench protection circuit according to claim 1, characterized in that: The segment protection circuit is connected in parallel with a second diode pair D2.

3. A superconducting MRI quench protection circuit according to claim 2, characterized in that: The second diode pair D2 includes two diodes connected in reverse parallel.

4. A superconducting MRI quench protection circuit according to claim 1, characterized in that: The segment protection circuit is connected in parallel with a superconducting switch R.

5. A superconducting MRI quench protection circuit according to claim 1, characterized in that: The first diode pair D1 includes two diodes connected in reverse parallel.

6. A superconducting MRI quench protection circuit according to claim 1, characterized in that: The excitation power source E is connected in series with a second switch S2.

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