JP2014216412A - Operation method of high-temperature superconducting coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of a high-temperature superconducting coil which can be operated in such a manner that an oxide superconducting wire rod can be prevented from being burnt even in the case of normal conduction transition of a superconducting wire rod.SOLUTION: The present invention relates to an operation method of a high-temperature superconducting coil which is characterized that, when operating the high-temperature superconducting coil by setting an electrification current to an oxide superconducting layer while using the high-temperature superconducting coil formed from an oxide superconducting wire rod including an intermediate layer, the oxide superconducting layer and a metal stabilization layer on a substrate, such a maximum current is grasped as to prevent superconducting characteristics of the oxide superconducting layer from being deteriorated by heat generated by a diversion of the electrification current to the metal stabilization layer during normal conduction transition, and the high-temperature superconducting coil is operated with a current equal to or lower than the maximum current as the electrification current.

Description

  The present invention relates to a method for operating a high temperature superconducting coil.

  The low-temperature superconducting coil provided with a low-temperature superconducting wire such as NbTi has a low critical temperature of the low-temperature superconducting wire constituting the coil as low as 10K or less and an operating temperature as low as about 4K. Therefore, the low-temperature superconducting coil has a small specific heat. For this reason, if a normal conduction transition occurs from a superconducting state for some reason in a part of a low-temperature superconducting coil, Joule heat generation due to the normal conduction transition → temperature rise → decrease in critical current → heat generation → temperature rise repeatedly, Normal conduction transition occurs. Therefore, when a low temperature superconducting coil is operated, a method for detecting a normal conduction transition by detecting a voltage generated by the normal conduction transition or detecting a balance voltage has been put into practical use.

However, high-temperature superconducting wires having a critical temperature of about 90K such as RE-123-based superconducting wires represented by Y-based (REBa ₂ Cu ₃ O _7-x : RE is a rare earth element including Y and Gd) are used as refrigerators. It is assumed that the motor is operated at an operating temperature that can reduce power consumption, such as about 20K. Assuming that the operating temperature is 20 K, the specific heat of the high-temperature superconducting wire is large, and even if the normal conduction dislocation occurs partially, its propagation speed is slow. In addition, since normal conduction dislocations are generally generated locally, it is assumed that normal conduction dislocations do not propagate to a sufficient length for generating a voltage in a high-temperature superconducting wire. For this reason, it has been pointed out that there is a high possibility that the normal conduction transition of the high temperature superconducting wire cannot be detected satisfactorily even if the method for detecting the normal conduction transition by voltage measurement, which has been studied for conventional low temperature superconducting wires, is used.

Conventionally, as an example of a normal conductive transition detection method of high-temperature superconducting wire, Bi-based superconducting wires _{(Bi 2 Sr 2 CaCu 2 O} 8 + δ: Bi2212, Bi 2 Sr 2 Ca 2 Cu 3 O 10 + δ: Bi2223) superconducting coil using an Protection devices against this have been studied. For example, a voltage detector that detects a voltage portion V that is the difference between the entire voltage or a part of the voltage of the high-temperature superconducting coil or a region, and a current detector that detects the voltage I flowing through the high-temperature superconducting coil are provided. A protection device is known (see Patent Document 1).
This protective device is provided with a protective device that performs a protective operation of the high-temperature superconducting coil, a current breaker, and a protective resistor as a commutation circuit based on the ratio of current I to voltage V, V / I.

JP 2006-041274 A

The protective device described in the above-mentioned Patent Document 1 has a function of monitoring the first-order differential value dV / dt in addition to the ratio of the current I and the voltage V, V / I, and determining the abnormality of the high-temperature superconducting coil, The second-order differential value d ² V / dt ² is monitored to determine the abnormality of the high-temperature superconducting coil, and the inspection accuracy is improved.
However, the protection device described in Patent Document 1 is a technology reflecting the result of study on a superconducting coil provided with a Bi-based oxide superconducting wire, and this technology includes an RE123-based oxide superconducting wire having a different structure. It is unclear whether it can be applied to high-temperature superconducting coils. In addition, the RE123-based oxide superconducting wire has a structure in which an intermediate layer and an oxide superconducting layer are laminated on a tape-shaped substrate, and a metal stabilizing layer is coated on the oxide superconducting layer. However, at present, a method for selecting the thickness of the metal stabilizing layer has not been established. In particular, with regard to the RE123-based oxide superconducting wire, what is the thickness of the metal stabilizing layer and what is the operating current, whether burnout of the oxide superconducting wire can be prevented when the normal conducting transition occurs. The situation has not yet been fully discussed.

  The present invention has been made in view of the above circumstances, and provides a method for operating a high-temperature superconducting coil that can be operated so as to prevent burning of the oxide superconducting wire even if the oxide superconducting wire undergoes normal conduction transition. With the goal.

The operation method of the high-temperature superconducting coil according to the present invention uses a high-temperature superconducting coil made of an oxide superconducting wire having an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer on a base material, and supplies the current to the oxide superconducting layer. When operating a high-temperature superconducting coil with a current set, it is characterized in that a current equal to or less than the maximum current that can be passed through the metal stabilization layer without degrading the oxide superconducting layer during normal conduction transition is operated as an energizing current. To do.
The high-temperature superconducting coil is operated with a current that is less than the maximum current that does not degrade the characteristics of the oxide superconducting layer due to the resistance heating that occurs in the metal stabilizing layer during the normal conducting transition. Even when a current flows, the characteristics of the oxide superconducting layer do not deteriorate. Therefore, a high temperature superconducting coil made of an oxide superconducting wire provided with a metal stabilizing layer can be operated safely.

The operation method of the high-temperature superconducting coil according to the present invention is characterized in that it is operated as an energized current having a maximum current density corresponding to the maximum current that can be passed through the metal stabilizing layer during the normal conducting transition is 1780 A / mm ² or less. To do.
Since the high-temperature superconducting coil is operated as an energizing current with a maximum current density of 1780 A / mm ² or less flowing through the metal stabilization layer during the normal conducting transition, the oxide superconducting layer is in a normal conducting state by any chance. Thus, even when an energizing current flows through the metal stabilizing layer, the characteristics of the oxide superconducting layer do not deteriorate. Therefore, a high temperature superconducting coil made of an oxide superconducting wire provided with a metal stabilizing layer can be operated safely.

A voltage detecting means for detecting a voltage generation of 50 mV or more accompanying the normal conduction transition of the oxide superconducting wire is connected to the metal stabilizing layer, and the oxide superconducting wire is connected to the oxide superconducting wire based on the voltage detection result of the voltage detecting means. An energization stopping means for stopping energization is connected.
By detecting the generation of a voltage of 50 mV or more during the normal conduction transition and stopping the energization of the oxide superconducting wire, the operation can be stopped without impairing the superconducting characteristics of the oxide superconducting wire. Even if a current flows through the metal stabilization layer due to the normal conduction transition and resistance heat generation occurs in the metal stabilization layer, it is energized before the deterioration of the characteristics of the oxide superconducting layer due to heat generation by detecting the generation of a voltage of 50 mV or more. You can stop. For this reason, after the normal conducting transition occurs, the oxide superconducting wire can be energized again and used without any trouble. That is, the safe operation of the high temperature superconducting coil can be performed.

The operation method of the high-temperature superconducting coil according to the present invention is characterized by connecting an energization stopping unit that stops energization to the oxide superconducting wire within 100 msec based on a voltage detection result of the voltage detecting unit. .
By detecting the generation of a voltage of 50 mV or more at the normal conduction transition and stopping the energization to the oxide superconducting wire within 100 msec, the operation can be stopped without impairing the superconducting characteristics of the oxide superconducting layer. Even if current flows in the metal stabilization layer with the normal conduction transition and resistance heat generation of the metal stabilization layer with the normal conduction transition occurs, the voltage generation of 50 mV or more is detected, and the current is stopped within 100 msec. Energization can be reliably stopped before the characteristics of the superconducting layer deteriorate. Therefore, the oxide superconducting wire can be energized again after the normal conducting transition and used without any trouble. That is, the safe operation of the high temperature superconducting coil can be performed.

  According to the present invention, the high-temperature superconducting coil is operated with an energizing current that does not deteriorate the superconducting characteristics of the oxide superconducting layer due to the resistance heat generated in the metal stabilizing layer during the normal conducting transition. Even when the superconducting layer is in a normal conducting state and an energizing current flows through the metal stabilizing layer, the high-temperature superconducting coil can be operated so that the oxide superconducting layer does not deteriorate. Therefore, the high temperature superconducting coil can be operated safely.

FIG. 1A is a schematic cross-sectional view showing an example structure of an oxide superconducting wire provided in a high-temperature superconducting coil according to the present invention, and FIG. 1B is a high temperature obtained by winding the oxide superconducting wire around a winding drum. The side view which shows an example structure of a superconducting coil. The schematic block diagram which shows the voltage measuring device, power supply device, and control apparatus which were connected to the oxide superconducting wire shown in FIG. The block diagram which shows an example of the superconducting apparatus incorporating the high-temperature superconducting coil which consists of the simulation oxide superconducting wire of the structure equivalent to the oxide superconducting wire shown in FIG. 1, a voltage measuring device, a power supply device, and a control apparatus.

Hereinafter, a first embodiment of a high-temperature superconducting coil and its operating method applied to the present invention will be described with reference to the drawings.
FIG. 1A is a schematic cross-sectional view showing an example of the structure of an oxide superconducting wire for constituting a high-temperature superconducting coil applied to the present invention, and this oxide superconducting wire 1 is shown in FIG. A case where the high-temperature superconducting coil 29 is configured and the high-temperature superconducting coil 29 is an operation target will be described below.
In order to obtain a safe operating current of the high temperature superconducting coil 29 to be operated, a plurality of measurement points are defined on the simulated oxide superconducting wire having the same structure as that of the oxide superconducting wire as shown in FIG. This is obtained by incorporating a simulated oxide superconducting wire having defined points into the superconducting device 30 shown in FIG.

An oxide superconducting wire 1 according to this embodiment shown in FIG. 1 (A) has a diffusion prevention layer 3, a bed layer 4, an orientation layer 5, and a cap layer 6 on a tape-like long metal base 2. The oxide superconducting layer 7, the first metal stabilizing layer 8, and the second metal stabilizing layer 9 are laminated. In this embodiment, the diffusion prevention layer 3, the bed layer 4, the alignment layer 5, and the cap layer 6 constitute an intermediate layer T. In this embodiment, the oxide superconducting layer 7 is formed on the substrate 2 via the intermediate layer T. Are stacked. In the intermediate layer T, the diffusion preventing layer 3 and the bed layer 4 are not essential, and one or both of them may be omitted depending on circumstances.
Note that the oxide superconducting wire 1 shown in FIG. 1A is exaggerated for the sake of convenience in order to make the characteristics of the present invention easier to understand, but the oxide superconducting wire of the present embodiment is shown. 1 has a thin tape shape as a whole. Also, in each of the drawings showing the following embodiments, in order to make the features of the present invention easier to understand, the main part may be shown in an enlarged manner, and the dimensional ratio of each component is the same as the actual one. Not always.

  The substrate 2 is preferably in the form of a tape in order to be long, and is made of a high-strength metal material excellent in heat resistance such as a nickel alloy typified by Hastelloy (trade name, manufactured by Haynes, USA). Among them, any type of Hastelloy, such as Hastelloy B, C, G, N, and W, having different component amounts such as molybdenum, chromium, iron, and cobalt can be used. Moreover, as the base material 2, an oriented Ni—W alloy tape base material in which a texture is introduced into a nickel alloy can also be applied. What is necessary is just to adjust the thickness of the base material 2 suitably according to the objective, and it can be set as the range of 10-500 micrometers.

The diffusion preventing layer 3 is formed for the purpose of preventing the diffusion of the constituent elements of the base material 2, and silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), GZO (Gd ₂ Zr ₂ O). ₇ ) and the like, and is formed to a thickness of, for example, 10 to 400 nm by a film forming method such as a sputtering method.
The bed layer 4 has high heat resistance and is used for reducing interfacial reactivity, and is used for obtaining the orientation of a film formed thereon. The bed layer 4 is made of Y ₂ O ₃ , Er ₂ O ₃ , CeO ₂ , Dy ₂ O _3, Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , La ₂ O ₃ or the like. The bed layer 4 is formed by a film forming method such as a sputtering method, and the thickness thereof is, for example, 10 to 100 nm.

The orientation layer 5 is formed from a biaxially oriented material in order to control the crystal orientation of the cap layer 6 thereon. Specifically, the alignment layer 5 is made of Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O. ₃ , metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ can be exemplified.
If the alignment layer 5 is formed with good biaxial orientation by IBAD (Ion-Beam-Assisted Deposition) method, the crystal orientation of the cap layer 6 can be improved, and the film is formed thereon. The superconducting property can be exhibited by improving the crystal orientation of the oxide superconducting layer 7.
The cap layer 6 is formed on the surface of the alignment layer 5 and is made of a material that allows crystal grains to self-orient in the in-plane direction. Specifically, CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , It consists of Gd ₂ O ₃ , ZrO ₂ , YSZ, Ho ₂ O ₃ , Nd ₂ O ₃ , LaMnO _{3 and the} like.
Among them, the CeO ₂ layer can be formed at a high film formation rate by PLD method (pulse laser deposition method), sputtering or the like, and good crystal orientation can be obtained. The film thickness of the cap layer 6 can be formed in the range of 50 to 5000 nm.

The oxide superconducting layer 7 may be a known high-temperature superconductor, specifically, REBa ₂ Cu ₃ O _y (RE is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, An example is a material made of Tb, Dy, Ho, Er, Tm, Yb, and Lu. Examples of the oxide superconducting layer 7 include Y123 (YBa ₂ Cu ₃ O _7-X ) or Gd123 (GdBa ₂ Cu ₃ O _7-X ).
The oxide superconducting layer 7 is laminated by a physical vapor deposition method such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, chemical vapor deposition (CVD), or thermal coating decomposition (MOD). In particular, from the viewpoint of productivity, the PLD (pulse laser deposition) method, the TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method) or the CVD method may be used. it can.

  The first metal stabilizing layer 8 (protective layer) is formed as a layer having good conductivity, such as Ag or an Ag alloy, having a low contact resistance with the oxide superconducting layer 7, and a good compatibility. The reason why the first metal stabilizing layer 8 is made of Ag is that oxygen is easily transmitted to the oxide superconducting layer 7 side in the oxygen annealing step of doping the oxide superconducting layer 7 with oxygen. it can. The base material of the oxide superconducting layer manufactured by the film formation method is an insulator. However, when oxygen is incorporated by oxygen annealing, the oxide superconducting layer has a well-structured crystal structure and exhibits superconducting properties. In order to form the first metal stabilizing layer 8, a film forming method such as a sputtering method is employed, and the thickness can be formed to about 1 to 30 μm.

The second metal stabilizing layer 9 is preferably made of a relatively inexpensive conductive metal material such as copper, a copper alloy such as a Cu—Zn alloy or a Cu—Ni alloy, aluminum or an alloy thereof, or stainless steel. The second metal stabilizing layer 9 commutates the current of the oxide superconducting layer 7 together with the first metal stabilizing layer 8 when the oxide superconducting layer 7 tries to shift from the superconducting state to the normal conducting state. Acts as a bypass. Further, when the oxide superconducting wire 1 is used for a superconducting fault current limiter, the stabilization layer is used to instantaneously suppress an overcurrent that occurs when the normal conducting transition occurs and shifts to the normal conducting state. In the case of this application, examples of the material used for the second metal stabilization layer 9 include high-resistance metals such as Ni-based alloys such as Ni—Cr. The thickness of the 2nd metal stabilization layer 9 can be 10-300 micrometers, for example.
In order to form the second metal stabilization layer 9, for example, a stabilization tape in which a Sn plating solder layer for connection is formed on the back surface side of the tape material made of the above-described material is used, and the first metal stabilization layer 8 is formed. The second metal stabilization layer 9 can be formed thereon by soldering. Alternatively, the second metal stabilization layer can be formed by covering the entire periphery of the laminate on which the substrate 2 to the first metal stabilization layer 8 are formed with Cu plating. Alternatively, the second metal stabilization layer is formed by plastic processing of the tape material so that the laminate formed from the base material 2 to the first metal stabilization layer 8 is surrounded by the tape material made of the aforementioned material. You can also.

The oxide superconducting wire 1 configured as described above is usually formed by winding an insulating tape such as a polyimide tape so as to surround the entire circumference or by forming an insulating protective layer attached vertically to form an insulating structure. Used for superconducting equipment applications such as superconducting coils.
FIG. 1B shows an example high-temperature superconducting coil 29 configured using the oxide superconducting wire 1, and the high-temperature superconducting coil 29 in this example is insulated from a bobbin 35 including a winding drum 36 and a flange plate 37. An oxide superconducting wire 1 having a structure is wound. The high-temperature superconducting coil 29 in this example is a coil having a structure in which a pancake coil P formed by winding the oxide superconducting wire 1 is laminated in the length direction of a plurality of winding drums 36. In the high-temperature superconducting coil 29 shown in FIG. 1 (B), six pancake coils P are stacked, and each time two pancake coils P are stacked, a metal disk cooling plate 28 is interposed therebetween. Has been. Note that the above-described high-temperature superconducting coil 29 is an example, and the high-temperature superconducting coil applicable in the present embodiment is not limited to the structure shown in FIG. 1B, and the single oxide superconducting wire 1 is wound on the winding drum 36. The whole structure may be wound, and the number of laminated pancake coils P may be any number.

  In order to grasp the safe operating current when operating the high temperature superconducting coil 29 having the structure shown in FIG. 1B, in the present embodiment, the above-described oxide superconducting wire 1 and A simulated high temperature superconducting coil 32 having a structure in which a simulated oxide superconducting wire 1A having an equivalent structure is wound is used. The simulated oxide superconducting wire 1A of the present embodiment is an oxide superconducting wire having the same structure as that of the oxide superconducting wire 1, and is wound around the winding drum 36 several times, for example, three times. That is, the simulated oxide superconducting wire 1A has the same structure prepared by cutting out part of the oxide superconducting wire 1 constituting the high-temperature superconducting coil 29, or a laminated structure equivalent to the laminated structure of the oxide superconducting wire 1 The simulated oxide superconducting wire 1A having the same thickness and required superconducting characteristics is used.

In the present embodiment, in the simulated oxide superconducting wire 1A wound around the winding drum 36 shown in FIG. 3, the surface of the second stabilizing layer 9 at an arbitrary position in the longitudinal direction is simulated oxidation as shown in FIG. A reference measurement area S0 having a predetermined length is defined along the length direction of the superconductor wire 1A, reference voltage measurement points 10 and 11 are provided at both ends thereof, and a heater 12 is provided at the center of the reference measurement area S0. Is installed. Further, in the simulated oxide superconducting wire 1A, the first measurement area S1 is partitioned so as to extend the same distance in the length direction (left and right direction in FIG. 2) of the simulated oxide superconducting wire 1A including the reference measurement area S0. First voltage measurement points 17 and 18 are installed at both ends.
The heater 12 is installed to forcibly transfer the simulated oxide superconducting wire 1A from the superconducting state to the normal conducting state.
The distance between the measurement areas S0 and S1 provided along the simulated oxide superconducting wire 1A may be arbitrary.

A voltage measuring device for individually measuring the voltage V0 generated between the reference voltage measuring points 10 and 11 and the voltage V1 generated between the first voltage measuring points 17 and 18 with respect to the simulated oxide superconducting wire 1A. 19 is connected. Each of the measurement points 10, 11, 17, 18 is connected to a voltage measuring device 19 through wirings 10a, 11a, 17a, 18a connected to them, and is configured to measure a voltage generated at each measurement point. Yes.
The voltage measuring device 19 can measure the voltages V0 and V1. Also, what is indicated by reference numeral 24 in FIG. 2 is a thermoelectric device that is installed in the vicinity of the reference voltage measurement point 10 and measures the surface temperature of the second metal stabilization layer 9 (temperature of the simulated oxide superconducting wire 1). It is a pair.
In the structure of the present embodiment, voltage measurement means are configured by the voltage measurement points 10, 11, 17, 18, the wirings 10 a, 11 a, 17 a, 18 a connected thereto, and the voltage measurement device 19. This voltage measuring means is for measuring a voltage generated when a current flows through the metal stabilizing layers 8 and 9 of the simulated oxide superconducting wire 1A.

  Next, a switch device (energization stopping means) 22 and a power supply device 23 are connected to both ends of the simulated oxide superconducting wire 1A via connection wires 20 and 21, and the simulated oxide superconducting wire is connected from the power supply device 23. The 1A oxide superconducting layer 7 can be energized. In addition, a control device 25 is electrically connected to the switch device 22 and the power supply device 23 via connection lines 26 and 27, and the control device 25 switches the on / off operation of the switch device 22 to simulate the oxide. The superconducting wire 1 </ b> A is configured so as to be able to control the on / off of energization to the oxide superconducting layer 7.

Next, the simulated oxide superconducting wire 1A, the switch device 22, the power supply device 23, and the control device 25 shown in FIG. 2 are more specifically connected to the superconducting device 30 having the structure shown in FIG.
The superconducting device 30 of the present embodiment includes a simulated high temperature superconducting coil 32 inside a storage container 31 such as a vacuum container, and a refrigerator 33 for cooling the simulated high temperature superconducting coil 32 inside the storage container 31 to a critical temperature or lower. It is configured with. The storage container 31 of this embodiment is connected to a vacuum pump 34 and configured to be able to depressurize the interior to a desired degree of vacuum.

  The simulated high temperature superconducting coil 32 is formed by winding the simulated oxide superconducting wire 1A described above around a bobbin composed of a winding drum 36 and a saddle plate 37 in a coil shape, and is formed on both ends of the winding drum 36. It is installed on the bottom side of the receiving container 31 with the gutter plate 37 oriented horizontally and the winding drum 36 oriented vertically. The winding body 36 is wound by covering the simulated oxide superconducting wire 1A having the above laminated structure with a coating layer and performing insulation treatment, but the measurement points described above with reference to FIG. The wiring to the heater, the wiring of the heater, and the like are wired so as to be appropriately drawn out from the coating layer.

Next, a direct current power supply device 23 is connected to the container 31 for energizing the simulated oxide superconducting wire 1A of the simulated high temperature superconducting coil 32, and the simulated oxide superconductivity inside the power supply device 23 and the container 31 is connected. The wire 1 </ b> A is connected by connecting wires 20, 21 so that the simulated oxide superconducting wire 1 </ b> A can be energized from the power supply device 23. In addition, the current controller 23a is attached to the power supply apparatus 23 of this embodiment, and it is comprised so that an electricity supply test can be performed, adjusting the electric current value applied to the simulation oxide superconducting wire 1A in steps.
Further, the heater 12 installed in the reference measurement area S0 of the simulated oxide superconducting wire 1A in the simulated high temperature superconducting coil 32 is connected via a connecting line 38 to a heater power source 37 separately provided outside the container 31. The reference measurement area S0 of the simulated oxide superconducting wire 1A can be heated with a target calorific value according to the voltage value supplied from the heater power supply 37.
Inside the container 31, an overall heater 40 for controlling the overall temperature of the simulated oxide superconducting wire 1A constituting the simulated high temperature superconducting coil 32 and an overall temperature sensor 41 for controlling the temperature are provided. These are electrically connected to a temperature controller 42 provided outside the container 31 by a connection line 42a so that the overall temperature of the simulated oxide superconducting wire 1A can be controlled by the control of the temperature controller 42. It is configured.

A recording device 43 and a data collecting / measuring instrument 44 are installed outside the storage container 31, and these are each measurement points in the measurement areas S 0 to S 1 of the simulated oxide superconducting wire 1 A inside the storage container 31 via a connection line 45. 10, 11, 17, and 18, and configured to be able to individually measure and record the voltages of the measurement areas S <b> 0 to S <b> 1, and these measurement results are data processing devices 46 connected to the data collection measuring instrument 44. Is input.
The data processing device 46 and the control device 25 are electrically connected by a connection line 47, and when data processing is performed in the control device 25, voltage measurement of each measurement area S0 to S3 stored in the data processing device 46 is performed. The connection line 47 is also connected to the temperature controller 42 while being configured so that the result can be referred to.
With the above configuration, the control device 25 is configured to be able to perform operation control of the power supply device 23, operation control of the heater power supply 37, and operation control of the temperature regulator 42.

Next, a method of operating the high-temperature superconducting coil 29 by evaluating the voltage behavior of the simulated oxide superconducting wire 1A during normal conduction transition using the superconducting device 30 having the configuration shown in FIG. 3 will be described below.
The simulated oxide superconducting wire 1A of the superconducting device 30 is operated at a constant operating temperature lower than the critical temperature, for example, 77K, 50K, or 20K while maintaining a constant temperature, and the simulated oxide superconducting wire 1A is used for the purpose. Confirm that the superconducting current flows.
After that, the heater 25 is operated by operating the heater power source 37 by the control device 25, the second metal stabilizing layer 9 of the simulated oxide superconducting wire 1A is heated, and the oxide superconducting layer 7 underneath is heated. Transition to normal conducting state.
When the heater 12 is energized and the oxide superconducting layer 7 in the reference measurement area S0 is forcibly changed to the normal conduction state, the voltage V0 in the reference measurement area S0 increases with time.

Next, when a bypass current flows through the stabilization layers 8 and 9 during the normal conduction transition in the simulated oxide superconducting wire 1A by performing a test as described below, the stabilization layers 8 and 9 are heated by resistance heating. The maximum current density at which the oxide superconducting layer 7 does not deteriorate even if it rises can be obtained.
In order to measure the maximum current density of the stabilization layer, the superconducting device 30 shown in FIG. 3 provided with the superconducting coil 32 made of the simulated oxide superconducting wire 1A is used, and the simulated oxide superconducting wire 1A is used as shown in FIG. The provided measurement points 10 and 11 are used.
In the superconducting device 30 shown in FIG. 3, the temperature of the simulated oxide superconducting wire 1 </ b> A is maintained at a predetermined temperature lower than the critical temperature by conducting cooling of the refrigerator 33, and a predetermined current is supplied from the power supply device 23 to simulate the superoxide superconducting wire Confirm that a stable superconducting current flows at 1A.

Thereafter, the heater 12 is energized to forcibly transfer a part of the simulated oxide superconducting wire 1A to normal conduction, and the voltage behavior is investigated. The voltage V0 is measured using the measurement system shown in FIG.
The thermocouple 24 is delayed in response by several hundred msec compared to the temperature conversion from the voltage due to heat conduction, but the measured temperature by the thermocouple in the above measurement is almost the same as the value converted from the voltage except for the response delay. I was able to confirm that there was. The minimum voltage detection sensitivity of this measurement system is 0.01 mV, and the time when the voltage is generated (= time when the normal conduction rearrangement occurs) is 0 sec.

When the voltage generated as described above reaches 50 mV to 100 mV, the switch device 22 of the power supply device 23 is turned off. For a very short time until the power supply from the power supply device 23 was turned off, the oxide superconducting layer 6 was flowing in the first metal stabilizing layer 8 and the second metal stabilizing layer 9 of the simulated oxide superconducting wire 1A. Shunt current. Since the first metal stabilizing layer 8 and the second metal stabilizing layer 9 have inherent resistances, they generate resistance by an energizing current, and the simulated oxide superconducting wire 1A is heated by this resistance heating.
After stopping energization as described above, the presence or absence of deterioration of the superconducting characteristics of the simulated oxide superconducting wire 1A is confirmed. In order to confirm the presence or absence of deterioration, the simulated oxide superconducting wire 1A is again put into a superconducting state and is confirmed by measuring the critical current value Ic of the simulated oxide superconducting wire 1A.
The critical current value Ic can be measured by carrying out the four-terminal method using the voltage measurement points 10, 11 or 17, 18 provided in the simulated oxide superconducting wire 1A by energizing from the power supply device 23.

As described above, an energization test is performed using the high-temperature superconducting coil 32 shown in FIG. 3 using the simulated oxide superconducting wire 1A having a specific structure, and a part of the simulated oxide superconducting wire 1A is forced by the heater 12. By performing a measurement operation for conducting a current test on the first metal stabilization layer 8 and the second metal stabilization layer 9 for a very short time until the current conduction is stopped after the normal conduction transition, the corresponding current is applied to the high temperature superconducting coil. It is possible to grasp whether the current is safe for the operation of 32.
The current value to be passed through the simulated oxide superconducting wire 1A is changed variously and the same measurement operation is repeated, and it is investigated whether the superconducting characteristic of the simulated oxide superconducting wire 1A is deteriorated at any current.
If the current value to be energized is gradually increased and the same measurement operation is repeated, and the critical current value of the simulated oxide superconducting wire 1A decreases, the energized current used for the measurement operation corresponds to the corresponding simulated oxide superconductivity. This is the limit of the energization current when operating the wire 1A. Therefore, the operating current when operating the high-temperature superconducting coil 29 constructed using the oxide superconducting wire 1 having the same structure as the simulated oxide superconducting wire 1A is the limit obtained from the test using the above-described simulated oxide superconducting wire 1A. Therefore, the practical high-temperature superconducting coil 29 composed of the oxide superconducting wire 1 can be safely operated.

In the oxide superconducting wire 1 having a laminated structure shown in FIG. 1A, the first metal stabilizing layer 8 and the second metal stabilizing layer 9 have different specific resistances depending on the forming material, and the width and film thickness of each layer. There is a difference in the amount of heat generated when the energization current is bypassed according to the thickness.
For this reason, the structure equivalent to the oxide superconducting wire applied to the superconducting coil to be actually operated (the structure in which the material, film thickness, and width of the first metal stabilizing layer 8 and the second metal stabilizing layer 9 are equivalent) 3) and a plurality of turns are wound around the bobbin 32 of the bobbin 32 shown in FIG. 3 to form a simulated high temperature superconducting coil 32 for simulation testing. If the current test is repeated and the limit current density in the metal stabilization layer of the simulated high-temperature superconducting coil 32 is grasped, the safe operating current of the high-temperature superconducting coil used for practical operation can be obtained.
If the operation current for the practical high-temperature superconducting coil is determined and operated in accordance with the operation current thus obtained, the normal conduction transition will occur unexpectedly for some reason, and the operation current will be different from that of the first metal stabilizing layer 8. Even if the current flows in the second metal stabilization layer 9, the operating current is cut off when it is detected that the current flowing in the metal stabilization layer exceeds 50 mV before the oxide superconducting wire 1 deteriorates in characteristics. The energization can be stopped, and the superconducting characteristics of the high temperature superconducting coil 29 do not deteriorate. For this reason, the high temperature superconducting coil 29 can be safely operated by applying the operating current determined as described above.

Hereinafter, examples in which a safe operating current of a high-temperature superconducting coil is obtained using an oxide superconducting wire having a practical structure will be described. However, the present invention is not limited to the following examples.
On a tape-like base material having a width of 5 mm or 10 mm and a thickness of 100 μm made of Hastelloy C-276 (trade name: manufactured by Haynes, USA), a diffusion preventing layer having a thickness of 100 nm made of Al ₂ O ₃ and a thickness of 20 nm. Y ₂ O ₃ bed layer, MgO 10 nm thick IBAD alignment layer, CeO ₂ 400 nm thick cap layer, and YBa ₂ Cu ₃ O _7-x composition 1 μm thick oxide superconducting layer A plurality of laminates were prepared by laminating a first metal stabilizing layer made of Ag having a thickness of 2 μm. These laminates were subjected to oxygen annealing treatment in an oxygen atmosphere at 500 ° C. for 10 hours.
For each of the obtained laminates, a metal stabilization tape made of copper having various thicknesses (0.04 to 0.3 mm) shown in Table 1 below is bonded and bonded via an Sn plating solder layer. A simulated oxide superconducting wire was obtained.
These simulated oxide superconducting wires were wound three turns around a cylindrical cylindrical body made of brass having an inner diameter of 110 mm to constitute a high-temperature superconducting simulated coil for testing. The high-temperature superconducting simulated coil was incorporated into a superconducting device having the configuration shown in FIG. 3, and an energization test described below was performed to obtain the maximum current density that could be passed through the metal stabilizing layer.

  The simulated oxide superconducting wire wound around the winding drum is provided with a reference measurement area S0 including reference voltage measurement points 10 and 11 shown in FIG. 2, and the width of the reference measurement area S0 is set to 10 mm. A heater was placed in the center of the measurement area S0.

The refrigerator of the superconducting device shown in FIG. 3 was operated and maintained at the predetermined temperature shown in Table 1 by conduction cooling, and a predetermined current was passed through the simulated oxide superconducting wire to confirm that a stable superconducting current flowed. Thereafter, the heater provided in the reference measurement area of the simulated oxide superconducting wire was operated to forcibly transfer the simulated oxide superconducting wire to normal conduction, and the voltage behavior was investigated.
The voltage minimum detection sensitivity of the apparatus shown in FIG. 2 is 0.01 mV, and the time when the voltage is generated (= the time when the normal conduction rearrangement occurs) is set to 0 sec.

When the voltage was generated from 50 mV to 100 mV, power supply from the power supply device to the simulated oxide superconducting wire was stopped, and after the test, the presence or absence of deterioration of the simulated oxide superconducting wire was examined. The presence or absence of superconducting property deterioration was determined by examining the critical current value (Ic) that can be measured when the simulated oxide superconducting wire is cooled below the critical temperature.
The critical current was measured by the four-terminal method using the voltage measurement points 10, 11 or 17, 18 after energization from the power supply device 23. The critical current measurement standard (voltage) is 1 μV / cm.

  The above results are listed in Table 1 below. The following Examples 1 to 15, 17 and Test Examples 13 and 18 are test results using a simulated oxide superconducting wire having a width of 5 mm, and Example 16 is a test result using a simulated oxide superconducting wire having a width of 10 mm. It is. In the case of Examples 1 to 17, the energization stop is a switch operation using a current breaker that stops energization after 0.5 S when a voltage exceeding 50 mV is generated. It is a test result by a switch operation using a current breaker that stops energization after 100 msec when a voltage exceeding 50 mV is generated.

Table 1 shows operating temperatures when the oxide superconducting wire is cooled by a refrigerator. The operating temperature was set to four types of 77K, 65K, 50K, and 20K.
Table 1 shows the substrate thickness (the thickness of the tape substrate made of Hastelloy C-276 (trade name: manufactured by Haynes, USA)) and the stabilized copper thickness (second metal stability) when a simulated oxide superconducting wire is produced. The thickness of the Cu tape constituting the stabilization layer), the stabilization layer thickness (the thickness of the first metal stabilization layer of Ag + the thickness of the second metal stabilization layer of Cu), the energization current, the stabilization copper current The density (current density of Cu tape only) and stabilization layer current density (total value of Cu tape and Ag stabilization layer) are described.
Further, when conducting an energization test, a superconducting magnet was installed in the vicinity of some of the high-temperature superconducting coils, an external magnetic field having the strength shown in Table 1 was applied, and a similar test was performed to examine the influence of the external magnetic field.

From the results shown in Table 1, even in the high-temperature superconducting coil using any of the simulated oxide superconducting wires of Examples 1 to 12 and Examples 14 to 17, the critical current was measured again after turning off the energizing current. However, no abnormality was found, and it was confirmed that there was no problem even if it was reused after transition to normal conduction.
From the results shown in Table 1, the stabilized copper thickness of 0.04 mm to 0.3 mm, in other words, for the simulated oxide superconducting wire with the stabilization layer thickness of 0.05 mm to 0.31 mm, The high-temperature superconducting coil could be operated without any problem in the range. In these samples, the current density flowing in the metal stabilization layer is 65 A / mm ^{2 to} 545 A / mm ² , and the high-temperature superconducting coil made of the simulated oxide superconducting wire of these examples has a critical current value after the normal conducting transition. Since no decrease is seen, it can be determined that safe driving has been achieved.

For these, samples increased the stabilizing layer current density to 727A / mm ² Test Example 13, samples increased the stabilizing layer current density up to 1000A / mm ² Test Example 18 critical after normal conductive transition A decrease in current value was observed.
From the above results, in Examples 1 to 17 where the current was cut off at 0.5 S after the voltage exceeding 50 mV was generated, the current density acting after the normal conduction transition on the metal stabilizing layer was less than 727 A / mm ^2. For example, it was found that if the range is from 65 A / mm ^{2 to} 545 A / mm ² , the simulated oxide superconducting wire will not be abnormally heated or burned, and good superconducting characteristics can be maintained. Therefore, when operating a high-temperature superconducting coil made of a simulated oxide superconducting wire in which an intermediate layer, an oxide superconducting layer, a first metal stabilizing layer, and a second metal stabilizing layer are laminated on a base material, On the other hand, if the operation is performed by energizing the current density acting after the normal conduction transition to be less than 727 A / mm ² , it can be determined that a safe operation is possible.

Examples 1 to 17 and Test Examples 13 and 18 shown in Table 1 were current interruptions by circuit breakers that could be interrupted after 0.5 S. However, when a commercially available general current circuit breaker was used, 50 to 100 msec. Processing time. The samples of Example 19 and Test Example 20 in Table 1 show the results of testing using a current breaker that can cut off the current at 100 msec after detecting a voltage of 50 mV. Under this condition, there was no problem even if the current density was 1780 A / mm ² , but the superconducting characteristics deteriorated in Test Example 20 in which the current density was 2590 A / mm ² .
In addition, for a sample having the same structure as the sample of Test Example 13 shown in Table 1, after detecting a voltage of 50 mV, again using a current breaker capable of interrupting current at 100 msec, again under the same conditions as those in Test Example 13 When tested, no deterioration occurred in the superconducting characteristics after the current was turned off. Further, for a sample having the same structure as the sample of Test Example 18 shown in Table 1, after detecting a voltage of 50 mV, again using a current breaker capable of interrupting current at 100 msec, again under the same conditions as those of Test Example 18 When tested, no deterioration occurred in the superconducting characteristics after the current was turned off.

Depending on whether 0.5S or 100msec is required to interrupt the current, the resistance heating value of the metal stabilizing layer varies. When the interruption time is long, the oxide superconducting layer is heated to a higher temperature. The The oxide superconducting layer does not deteriorate even when heated to about 300K. Although it is considered that the oxide superconducting layer does not easily deteriorate even when the temperature rises to about 500K, it is desirable that the oxide superconducting layer be 300K in view of the margin. Therefore, taking into consideration the ability of a standard commercially available current breaker instead of a current interruption by 0.5S, and taking into account the rate of temperature rise until the interruption is required when current interruption is possible at 100 msec, metal stabilization It can be seen that even when a current of up to about 1780 A / mm ^{2 is} passed through the layer as in Example 19, the metal stabilizing layer becomes high temperature and the oxide superconducting layer does not deteriorate with a commercially available current breaker.
From the above background, the limit current density that can be passed through the metal stabilization layer of the oxide superconducting wire when using a current breaker with a general breaking speed (100 msec) can be regarded as 1780 A / mm ² .

  DESCRIPTION OF SYMBOLS 1 ... Oxide superconducting wire, 1A ... Simulated oxide superconducting wire, 2 ... Base material, 3 ... Diffusion prevention layer, 4 ... Bed layer, 5 ... 1st intermediate | middle layer, 6 ... 2nd intermediate | middle layer, 7 ... Oxidation Superconducting layer, 8 ... first stabilization layer, 9 ... second stabilization layer, 10, 11 ... reference voltage measurement point, 12 ... heater, 13, 17, 18 ... voltage measurement point, 19 ... voltage measurement Device: S0 ... Reference measurement area, S1 ... First measurement area, 22 ... Switch device, 23 ... Power supply device, 25 ... Control device, 29 ... Simulated high temperature superconducting coil, 31 ... Container, 32 ... Simulated high temperature superconducting coil, 33 Refrigerator, 35 ... Bobbin, 36 ... Winding drum, 37 ... Plate, P ... Pancake coil, 44 ... Data collection measuring instrument, 46 ... Data processing device.

Claims (4)

  When operating a high-temperature superconducting coil using a high-temperature superconducting coil made of an oxide superconducting wire provided with an intermediate layer, an oxide superconducting layer, and a metal stabilizing layer on a base material, and setting an energizing current to the oxide superconducting layer A method for operating a high-temperature superconducting coil, wherein a current equal to or less than a maximum current that can be passed through the metal stabilization layer without deteriorating the oxide superconducting layer during normal conduction transition is operated as an energizing current. The operation of the high-temperature superconducting coil according to claim 1, wherein the operation is performed as an energized current having a maximum current density corresponding to a maximum current that can flow through the metal stabilizing layer at the time of the normal conducting transition is 1780 A / mm ² or less. Method.   A voltage detecting means for detecting a voltage generation of 50 mV or more accompanying the normal conduction transition of the oxide superconducting wire is connected to the metal stabilizing layer, and the oxide superconducting wire is connected to the oxide superconducting wire based on the voltage detection result of the voltage detecting means. The method for operating a high-temperature superconducting coil according to claim 1 or 2, wherein an energization stopping means for stopping energization is connected.   4. The high-temperature superconductivity according to claim 2, further comprising an energization stop unit that stops energization of the oxide superconducting wire within 100 msec based on a voltage detection result of the voltage detection unit. How to operate the coil.

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