JP5525810B2 - Superconducting magnet device and quench protection method thereof - Google Patents

Description

  The present invention relates to a superconducting magnet device and a quench protection method thereof.

  In a superconducting magnet device used in a particle accelerator beam line or the like, when a local normal conduction state occurs in a superconducting coil, the portion generates heat, the superconducting state in the vicinity is destroyed, and the superconducting state is It may cause quenching that breaks down rapidly. Since a large amount of magnetic energy is accumulated in the superconducting coil, it takes time to attenuate the current flowing through the superconducting coil, and if the magnetic energy accumulated in the superconducting coil is not consumed quickly when a quench occurs, Joule heat generation will occur. The superconducting coil may be damaged (especially burned out) or deteriorated.

  For this reason, the superconducting magnet device is provided with a quench protection device that protects the superconducting coil when a quench occurs. As this quench protection device, a circuit breaker, a protection resistor for energy absorption (consumption), and a quench detector are used, which are conventionally disclosed in Patent Documents 1 and 2 and configured as shown in FIG.

  In FIG. 8, a plurality of superconducting coils 1a to 1e are accommodated in a cryostat 2 and kept in a superconducting state, and these superconducting coils 1a to 1e are fed with power from an excitation power source 3 through a circuit breaker 4, Each superconducting coil 1a-1e is excited to generate a magnetic field. A protective resistor 5 is connected in parallel to these superconducting coils 1a to 1e, and a quench generated in the superconducting coils 1a to 1e is detected by a quench detector 6.

  During normal operation, the circuit breaker 4 is closed, a direct current is fed from the excitation power source 3 to the superconducting coils 1a to 1e via the circuit breaker 4, and the superconducting coils 1a to 1e generate magnetic fields.

  When a quench occurs in any of the superconducting coils 1a to 1e, the breaker 4 is opened in response to a quench detection signal from the quench detector 6. As a result, the current flowing from the exciting power source 3 to the superconducting coils 1a to 1e via the circuit breaker 4 is commutated from the superconducting coils 1a to 1e to the protective resistor 5 and accumulated in the superconducting coils 1a to 1e. Most of the magnetic energy is consumed by the protective resistor 5 installed outside the cryostat 2 and the resistance generated when the superconducting coils 1a to 1e are quenched, and the current flowing through the superconducting coils 1a to 1e is attenuated. . In this way, even when the superconducting coils 1a to 1e are quenched, the stored energy in the superconducting coils 1a to 1e is quenched without being heated inside the superconducting coils 1a to 1e.

  On the other hand, in the superconducting magnet device shown in FIG. 8, when quenching occurs in one of the plurality of superconducting coils 1a to 1, the quenching is not transmitted to the other superconducting coils. The flowing current cannot be rapidly reduced, and the quenched superconducting coil may generate abnormal heat.

  As a method of quenching the entire other superconducting coil in order to prevent quenching of one superconducting coil 7, external heaters 7a to 7e and a heater power supply 8 are provided as shown in FIG. A method (quenching back method) of heating and forcibly quenching a superconducting coil that has not been quenched is known and disclosed in Patent Documents 3 and 4. In the superconducting magnet device shown in FIG. 9, the same parts as those in the superconducting magnet device shown in FIG.

  In the superconducting magnet device of FIG. 9, during normal operation, the circuit breaker 4 is closed and a direct current is supplied from the excitation power supply 3 to the superconducting coils 1 a to 1 e.

  For example, when a quench occurs in the superconducting coil 1a, the breaker 4 is opened in response to a quench detection signal from the quench detector 6. As a result, the current flowing from the exciting power source 3 to the superconducting coils 1a to 1e via the circuit breaker 4 is commutated from the superconducting coils 1a to 1e to the protective resistor 5 and accumulated in the superconducting coils 1a to 1e. Most of the magnetic energy is consumed by the protective resistor 5, and the current flowing through the superconducting coils 1a to 1e is attenuated.

  Subsequently, the heater power supply 8 is activated and power is supplied to the external heaters 7a to 7e, so that the external heaters 7a to 7e generate heat, and the superconducting coils 1b to 1e that have not been quenched are heated and forcibly quenched. . This increases the in-coil resistance of the entire superconducting coils 1a to 1e, accelerates the decay of the current flowing through the superconducting coils 1a to 1e, and performs quench protection that avoids damage to the superconducting coil 1a.

JP-A-3-45163 JP 2006-319139 A Japanese Patent Laid-Open No. 7-235412 JP-A-11-102808

  Quench protection of conventional superconducting magnet devices has been performed as described above. However, in the quench protection using only the protection resistor 5 as shown in FIG. 8, if the resistance value of the protection resistor 5 is increased, the voltage drop becomes excessive, and as a result, the resistance value of the protection resistor 5 decreases. It takes time to attenuate the current flowing through the superconducting coils 1a to 1e, and damage to the superconducting coils 1a to 1e may not be avoided.

  In addition, as shown in FIG. 9, in the method of providing external heaters 7a to 7e and heater power supply 8 and forcibly quenching superconducting coils 1a to 1e that are not quenched by external heaters 7a to 7e, In addition, since the heater power supply 8 is required, the superconducting magnet device becomes complicated. Therefore, in the unlikely event that a heater driving device (not shown) or the heater power supply 8 fails, the quench protection operation cannot be performed or cannot be performed at an early stage, and the superconducting coils 1a to 1e may be damaged. There is.

  Furthermore, it is difficult to arrange the external heaters 7a to 7e arranged for obtaining a quench protection effect in an appropriate shape. For example, as shown in FIG. 10, when the external heaters 7a to 7e are arranged on the outer circumferences of the superconducting coils 1a to 1e at predetermined intervals, depending on the shapes and arrangement positions of the external heaters 7a to 7e. The temperature rise of each of the superconducting coils 1a to 1e becomes uneven due to the heating of each of the external heaters 7a to 7e. For this reason, there is a possibility that forced quenching of the superconducting coils 1a to 1e cannot be performed quickly.

  An object of the present invention is to provide a superconducting magnet device and a quench protection method thereof that can reliably protect a superconducting coil from damage and deterioration due to quenching.

A superconducting magnet device according to the present invention includes a plurality of superconducting coils that generate a magnetic field, a cryostat that houses the superconducting coils and maintains a superconducting state, and supplies power to the superconducting coils via a breaker. In a superconducting magnet device configured to have an excitation power source for exciting the superconducting coil, a plurality of heaters and energization control means connected in series with each other are connected in parallel to the superconducting coil, Each of the heaters is arranged to be able to heat each of the superconducting coils in the cryostat, and the heater wire constituting the heater has a thermal contraction rate equivalent to that of the coil conductor constituting the superconducting coil. , is constituted by metal resistance at very low temperature is equal to the resistance value at cryogenic temperatures of the coil conductor, further the diameter of the coil conductor When the quenching is detected in the superconducting coil, the circuit breaker is opened, and the power supply from the excitation power source to the superconducting coil is cut off. Simultaneously with this interruption, the current flowing through the superconducting coil can be commutated to all of the heaters by the energization control means.

Further, the quench protection method for a superconducting magnet device according to the present invention includes a plurality of superconducting coils that generate a magnetic field, a cryostat that accommodates the superconducting coils and maintains a superconducting state, and a breaker to the superconducting coils. In the quench protection method of a superconducting magnet device configured to supply power via the excitation power to excite the superconducting coil, a plurality of heaters connected in series with each other are connected in parallel to the superconducting coil And each of the heaters is arranged to be able to heat each of the superconducting coils in the cryostat, and a heater wire constituting the heater is equivalent to a coil conductor constituting the superconducting coil. and has a heat shrinkage, resistance in the cryogenic temperature is constituted by a metal to be equal to the resistance value at cryogenic temperatures of the coil conductor, The diameter of the coil conductor is set in a range of 0.5 to 2 times the diameter of the coil conductor, the quench is detected in the superconducting coil, the circuit breaker is opened, and the excitation power source is connected to the superconducting coil. when the power supply is cut off, the cut-off at the same time, the current flowing through the superconductive coil commutated to all of the heater, in a manner characterized by heating each of said superconducting coil by each of the heater is there.

  According to the superconducting magnet device and the quench protection method thereof according to the present invention, when quenching is detected in the superconducting coil and the power supply to the superconducting coil is cut off, the superconducting coil flows simultaneously with the interruption. Since the current is commutated to the heater and the superconducting coil is heated by the heater, the unquenched superconducting coil or the unquenched part of the superconducting coil can be quickly and forcibly quenched, and the superconducting coil It is possible to attenuate the current flowing through the whole. As a result, the superconducting coil can be reliably protected from damage (burnout, etc.) and deterioration due to quenching.

The present invention is a block diagram showing a first embodiment of a superconducting magnet device. The perspective view which shows the single superconducting coil in FIG. FIG. 3 is a half cross-sectional view showing the lower half portion of the superconducting coil of FIG. FIG. 4 is a partial sectional view showing a part of FIG. 3 in an enlarged manner. Explanatory drawing explaining the non-inductive winding of the heater coil in FIG. The graph which shows the change of the electric current which flows through the whole superconducting coil, when quenching generate | occur | produces in the superconducting coil of FIG. The half sectional view which shows the superconducting coil of 2nd Embodiment in the superconducting magnet apparatus which concerns on this invention in the cross-sectional state corresponding to FIG. The block diagram which shows an example of the conventional superconducting magnet apparatus. The block diagram which shows another example of the conventional superconducting magnet apparatus. The perspective view which shows the single superconducting coil in FIG. 9 with a heater.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[A] First embodiment (FIGS. 1 to 6)
FIG. 1 is a configuration diagram showing a first embodiment of a superconducting magnet device according to the present invention. The superconducting magnet device 10 shown in FIG. 1 generates a uniform magnetic field by a plurality of superconducting coils 11a to 11e maintained in a superconducting state. The superconducting coils 11a to 11e, the cryostat 12, An excitation power supply 13, a circuit breaker 14, heater coils 15 a to 15 e, a diode 16, a quench detector 17, and a control circuit 18 are configured.

  The heater coils 15a to 15e function as heaters, and the diode 16 functions as energization control means. Moreover, the circuit breaker 14, the heater coils 15a-15e, the diode 16, the quench detector 17, and the control circuit 18 are comprised as the quench protection apparatus 20 of the superconducting coils 11a-11e. The quench protection device 20 does not require a separate heater power supply for supplying power to the heater coils 15a to 15e.

  The superconducting coils 11a to 11e are connected in series with each other, and each generates a magnetic field by feeding power from the excitation power source 13. As shown in FIGS. 2 and 3, each of these superconducting coils 11 a to 11 e is formed by winding a coil conductor 22 around a winding frame 21 having a U-shaped half section in multiple layers using a winding machine (not shown). Composed. A magnetic field generated in each of the superconducting coils 11a to 11e is indicated by an arrow B in FIG. Moreover, the code | symbol O in FIG.2 and FIG.3 shows each center of the superconducting coils 11a-11e.

  As shown in FIG. 1, the cryostat 12 accommodates a plurality of superconducting coils 11a to 11e so as to be at a very low temperature (for example, about 4K), and keeps these superconducting coils 11a to 11e in a superconducting state. The excitation power source 13 is connected in series with a plurality of superconducting coils 11a to 11e via a circuit breaker 14, and feeds power to these superconducting coils 11a to 11e so that these superconducting coils 11a to 11e are supplied. Energize.

  The quench detector 17 detects that a quench that transitions from the superconducting state to the normal conducting state has occurred in any or all of the superconducting coils 11a to 11e, and this quench detection signal is the control circuit. 18 is transmitted. The control circuit 18 opens the circuit breaker 14 when the quench detection signal is executed. The circuit breaker 14 is closed during normal operation of the superconducting magnet device 10 to allow power supply from the excitation power supply 13 to the superconducting coils 11a to 11e, but when the control circuit 18 is opened, the excitation power supply The power supply from 13 to the superconducting coils 11a to 11e is cut off.

  A plurality of the heater coils 15 a to 15 e are connected in series and are connected in series to the diode 16. Further, the heater coils 15a to 15e and the diode 16 are connected in parallel to the superconducting coils 11a to 11e and are disposed in the cryostat 12. Of these, each of the heater coils 15a to 15e is disposed close to each of the superconducting coils 11a to 11e as described later, so that each superconducting coil 11a to 11e can be heated.

  The diode 16 functions to prevent power supply from the excitation power supply 13 to the heater coils 15a to 15e during normal operation of the superconducting magnet device 10. However, any or all of the superconducting coils 11a to 11e are quenched. When generated, the voltage generated in the superconducting coils 11a to 11e upon occurrence of quenching functions to commutate the current flowing in the superconducting coils 11a to 11e to the heater coils 15a to 15e.

  The function of commutating the current flowing through the superconducting coils 11a to 11e to the heater coils 15a to 15e is the same as when any or all of the superconducting coils 11a to 11e are quenched. To the superconducting coils 11a to 11e are cut off at the same time. There are one diode 16 or a plurality of diodes 16 connected in series, and the number of diodes 16 is determined by the output voltage of the excitation power supply 13.

  As shown in FIGS. 3 and 4, each of the heater coils 15 a to 15 e is the same as the superconducting coils 11 a to 11 e by using the same winding machine as that in the case where the heater wire 23 is, for example, the superconducting coils 11 a to 11 e. It is configured to be wound in a coil shape in the direction. Further, each of the heater coils 15a to 15e is close to the innermost layer between the innermost layer of the superconducting coils 11a to 11e and the winding frame 21 over the entire inner circumference of the innermost layer. Be placed.

  In addition, the diameter of each heater wire 23 of the heater coils 15a to 15e is set in a range of half to twice the diameter of each coil conductor 22 of the superconducting coils 11a to 11e. For example, when the diameter of the coil conductor 22 is 1.0 mm, the diameter of the heater wire 23 is set in the range of 0.5 to 2.0 mm. The reason is based on the viewpoint of improvement in enforcement efficiency such that the heater coils 15a to 15e can be wound using the same winding machine as the superconducting coils 11a to 11e.

  Furthermore, as shown in FIG. 5, each heater wire 23 of the heater coils 15a to 15e includes two elements 24 and 25 in which one side ends 24A and 25A are short-circuited. Heater coils 15 a to 15 e are formed by non-inductive winding in which these elements 24 and 25 are wound in a coil shape as one heater wire 23. In this non-inductive winding, currents in opposite directions flow through the elements 24 and 25, so that no magnetic field is generated around one heater wire 23 composed of these elements 24 and 25. As a result, each heater coil An induced voltage (self-induced voltage) hardly occurs in 15a to 15e.

  Moreover, each heater wire 23 (that is, elements 24 and 25) of the heater coils 15a to 15e shown in FIG. 4 has a thermal contraction rate (linear expansion rate) substantially equal to the coil conductor 22 of the superconducting coils 11a to 11e. It is made of a metal and has a resistance value at an extremely low temperature (for example, about 4K) that is substantially equal to the coil conductor 22 of the superconducting coils 11a to 11e. Specifically, the heater wire 23 is configured by using a wire made of copper or aluminum as a covered heater covered wire. In particular, when the coil conductor 22 of the superconducting coils 11a to 11e is made of niobium titanium, the heater wire 23 is made of copper having a resistance value close to that of niobium titanium.

  Next, the operation of the superconducting magnet device 10 shown in FIG. 1 will be described.

  During normal operation of the superconducting magnet device 10, the circuit breaker 14 is closed, and direct current is supplied from the exciting power supply 13 to the superconducting coils 11a to 11e via the circuit breaker 14, and the superconducting coils 11a to 11e A magnetic field is generated in the direction indicated by the arrow B in FIG.

  For example, when a quench occurs in the superconducting coil 11a among the superconducting coils 11a to 11e, the quench detector 17 detects the quench and a quench detection signal is transmitted from the quench detector 17 to the control circuit 18. The control circuit 18 opens the circuit breaker 14. As a result, the direct current flowing from the excitation power supply 13 to the superconducting coils 11a to 11e via the circuit breaker 14 is interrupted, and simultaneously with this interruption, the direct current flowing through the superconducting coils 11a to 11e is converted into a heater by the action of the diode 16. It commutates to coils 15a-15e.

  By this commutation, most of the magnetic energy stored in the superconducting coils 11a to 11e during normal operation of the superconducting magnet device 10 is consumed by the resistance of the heater coils 15a to 15e, and the heater coils 15a to 15e generate heat. The current flowing through the superconducting coils 11a to 11e is attenuated. The superconducting coils 11b to 11e that have not been quenched are heated and forcedly quenched by the heat generated by the heater coils 15a to 15e. As a result, the in-coil resistance of the superconducting coils 11a to 11e is increased, and the current flowing through the entire superconducting coils 11a to 11e is further attenuated. This avoids damage (burnout) and deterioration of the superconducting coil 11a where the quench has occurred.

  Here, FIG. 6 is a graph showing the time change of the current flowing through the superconducting coils 11a to 11e when quenching occurs in any of the superconducting coils 11a to 11e. A solid line β indicates the case of a conventional superconducting magnet device (FIG. 8) that does not perform forced quenching, and a solid line α indicates that current flowing through the superconducting coils 11a to 11e is commutated to the heater coils 15a to 15e. The case of this Embodiment which forcedly quenches the superconducting coils 11a-11e is shown. In this Embodiment, it turns out that the electric current which flows into the superconducting coils 11a-11e has attenuate | damped rapidly from the time t when quenching generate | occur | produced in any of the superconducting coils 11a-11e.

  With the configuration as described above, the following effects (1) to (5) are achieved according to the present embodiment.

  (1) When the quench detector 17 detects a quench in the superconducting coil 11a, for example, and the power supply to the superconducting coils 11a to 11e is cut off by the opening operation of the circuit breaker 14, the diode 16 The current flowing through the superconducting coils 11a to 11e is commutated to the heater coils 15a to 15e, and the superconducting coils 11a to 11e are heated by the heater coils 15a to 15e. The current flowing through the entire superconducting coils 11a to 11e can be attenuated. As a result, in particular, the quenched superconducting coil 11a can be reliably protected from damage (burnout, etc.) and deterioration due to quenching.

  (2) Since each of the heater coils 15a to 15e is disposed along the inner circumference inside the innermost layer of each of the superconducting coils 11a to 15e, each of the heater coils 15a to 15e can be used as a superconducting coil. Each of 11a-11e can be heated uniformly. For this reason, the forced quench of superconducting coils 11a-11e can be implemented rapidly.

  (3) Since the heater coils 15a to 15e are formed by winding the heater wire 23 (elements 24 and 25) in a coil shape by non-inductive winding, generation of an induction voltage can be suppressed during energization. As a result, when a high voltage is generated, the high voltage protection circuit that cuts off the power supply to the heater coils 15a to 15e and protects the heater coils 15a to 15e becomes unnecessary. As a result, when quenching of the superconducting coils 11a to 11e occurs, the heater coils 15a to 15e can generate heat at a fast response speed, and the forced quenching of the superconducting coils 11a to 11e can be performed quickly.

  (4) Since the heater wire 23 constituting the heater coils 15a to 15e is made of a metal having a thermal contraction rate substantially equal to that of the coil conductor 22 constituting the superconducting coils 11a to 11e, these superconducting coils 11a. To 11e and heater coils 15a to 15e are cooled to a cryogenic temperature by the cryostat 12 to prevent the two (superconducting coils 11a to 11e and heater coils 15a to 15e) from separating due to a difference in thermal contraction rate. it can. For this reason, when quenching of the superconducting coils 11a to 11e occurs, the superconducting coils 11a to 11e can be quickly heated by the heater coils 15a to 15e to perform forced quenching. Further, since the heater wire 23 and the coil conductor 22 are made of a metal having substantially the same heat shrinkage rate, it is possible to suppress the occurrence of thermal distortion in the heater coils 15a to 15e and the superconducting coils 11a to 11e.

  (5) Since the resistance value at the cryogenic temperature of the heater wire 23 constituting the heater coils 15a to 15e is provided to be approximately the same as the resistance value at the cryogenic temperature of the coil conductor 22 constituting the superconducting coils 11a to 11e. The voltage at the time of initial current energization to heater coils 15a-15e can be controlled. For this reason, when quenching of the superconducting coils 11a to 11e occurs, the heater coils 15a to 15e can generate heat at a fast response speed, and the forced quenching of the superconducting coils 11a to 11e can be performed quickly.

[B] Second embodiment (FIG. 7)
FIG. 7 is a half sectional view showing the superconducting coil of the second embodiment in the superconducting magnet device according to the present invention in a sectional state corresponding to FIG. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description is simplified or omitted.

  The superconducting magnet device of the present embodiment is different from the superconducting magnet device 10 of the above embodiment in the arrangement positions of the heater coils 15a to 15e with respect to the superconducting coils 11a to 11e. That is, each of the heater coils 15a to 15e of the present embodiment is arranged close to the outermost layer over the entire outer circumference of the outermost layer of each of the superconducting coils 11a to 11e.

  Generally, in the large superconducting coils 11a to 11e, when a current is passed through the superconducting coils 11a to 11e having a large radius in a uniform magnetic field generated by the self, a relatively large electromagnetic force is applied to the superconducting coils 11a to 11e. The superconducting coils 11a to 11e are pulled outward. At this time, if each of the heater coils 15a to 15e is disposed inside the innermost layer of each of the superconducting coils 11a to 11e, each of the superconducting coils 11a to 11e is separated from each of the heater coils 15a to 15e. Thus, heating of the superconducting coils 11a to 11e by the heater coils 15a to 15e becomes insufficient.

  On the other hand, when each of the heater coils 15a to 15e is disposed outside the outermost layer of each of the superconducting coils 11a to 11e, the heater coils 15a to 15e can be used even when a large electromagnetic force acts as described above. The separation of each of 15e and each of superconducting coils 11a-11e is prevented, and each of superconducting coils 11a-11 can be uniformly and satisfactorily heated by each of heater coils 15a-15e.

  Therefore, in this embodiment, in addition to the effects (1) and (3) to (5) of the above embodiment, the following effect (6) is obtained.

  (6) Since each of the heater coils 15a to 15e is disposed close to the outermost layer along the outer periphery of the outermost layer of each of the superconducting coils 11a to 11e, each of the superconducting coils 11a to 11e. Also, the electromagnetic force generated in each prevents the superconducting coils 11a to 11e from separating from the heater coils 15a to 15e. For this reason, each of the superconducting coils 11a to 11e can be uniformly and satisfactorily heated by each of the heater coils 15a to 15e. Therefore, the forced quenching of each of the superconducting coils 11a to 11e can be quickly performed by this heating. Can do.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.

  For example, in the present embodiment, the superconducting magnet device 10 having a plurality of superconducting coils 11a to 11e has been described. However, the present invention can be applied even when there is a single superconducting coil. In this case, the unquenched portion of a single superconducting coil can be forced to quench by a single or multiple heater coils.

DESCRIPTION OF SYMBOLS 10 Superconducting magnet apparatus 11a-11e Superconducting coil 12 Cryostat 15 Excitation power supply 14 Breaker 15a-15e Heater coil (heater)
16 Diode (energization control means)
20 Quench protector 22 Coil conductor 23 Heater wire

Claims (2)

A plurality of superconducting coils that generate a magnetic field; a cryostat that houses the superconducting coils and maintains the superconducting state; and an excitation power source that feeds power to the superconducting coils via a circuit breaker to excite the superconducting coils. In the superconducting magnet device configured to have,
A plurality of heaters and energization control means connected in series with each other are connected in parallel to the superconducting coil, and each of the heaters is arranged to be able to heat each of the superconducting coils in the cryostat,
The heater wire constituting the heater is made of a metal having a thermal contraction rate equivalent to that of the coil conductor constituting the superconducting coil and having a resistance value at a cryogenic temperature equivalent to a resistance value at the cryogenic temperature of the coil conductor. Further, the diameter is set in the range of 0.5 to 2 times the diameter of the coil conductor,
When a quench is detected in the superconducting coil, the circuit breaker is opened, and power supply from the excitation power source to the superconducting coil is interrupted, simultaneously with this interruption, the current flowing through the superconducting coil is A superconducting magnet device characterized in that it can be commutated to all of the heaters by means of energization control means. A plurality of superconducting coils that generate a magnetic field; a cryostat that houses the superconducting coils and maintains the superconducting state; and an excitation power source that feeds power to the superconducting coils via a circuit breaker to excite the superconducting coils. In a quench protection method of a superconducting magnet device configured to have,
A plurality of heaters connected in series with each other are connected in parallel to the superconducting coil, and each of the heaters is arranged to be able to heat each of the superconducting coils in the cryostat,
The heater wire constituting the heater is made of a metal having a thermal contraction rate equivalent to that of the coil conductor constituting the superconducting coil and having a resistance value at a cryogenic temperature equivalent to a resistance value at the cryogenic temperature of the coil conductor. Further, the diameter is set in the range of 0.5 to 2 times the diameter of the coil conductor,
Wherein said circuit breaker quench the superconducting coil is detected is opening operation, when the power supply from the excitation power supply to the superconducting coil is cut off, the cut-off at the same time, the current flowing through the superconducting coil A quench protection method for a superconducting magnet apparatus, wherein the superconducting coil is commutated to all of the heaters and each of the superconducting coils is heated by each of the heaters.

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