JPH10177900A - Superconducting wiggler exciting method and superconducting wiggler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting wiggler exciting method and a superconducting wiggler using this method, capable of suppressing the consumption of very low temperature coolant for cooling a superconducting element, continuously operating the superconducting wiggler for a long time, and easily controlling a magnetic field level. SOLUTION: A mobile magnetic field type flux pump 1 in which a superconducting disc part 17 is set inside a very low temperature coolant bath, and a magnet rotor part 15 is set outside the bath is arranged, the magnet rotor is rotated, magnetic flux is accumulated in a superconducting circuit, and a superconducting coil connected to the superconducting disc is excited. A magnet rotor of the magnet rotor part 15 has a horizontal arm, and permanent magnets are preferable to be fixed to both ends of the arm in the different polarity direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of exciting a superconducting coil group of a superconducting wiggler which is inserted into an electron beam accelerator ring or the like to generate radiation, and a superconducting wiggler using the method. The present invention relates to a superconducting coil excitation method and a superconducting wiggler that enable continuous operation for a long period of time by suppressing heat conduction to a coil and suppressing consumption of a refrigerant such as liquid helium.

[0002]

2. Description of the Related Art In recent years, a strong magnetic field can be generated as a device for generating a radiation light by applying a magnetic field distributed in a wave shape in the traveling direction to an electron beam traveling on an electron beam accelerator ring or the like to meander. A superconducting wiggler using a superconducting coil has been used. A superconducting wiggler generally consists of a central magnet for generating radiation and side magnets for adjusting the electron orbit and returning to the original orbit, but is housed in a cryostat to maintain the superconductivity of the superconducting coil. Need to be cooled to extremely low temperatures.

[0003] The mainstream of the means for exciting the superconducting coil is to supply a current from a dedicated DC power supply and to energize the coil from a current-carrying busbar outside the device through a current lead inside the device. As a current lead structure, for example, there is a current lead structure in which a cooling gas shield type current lead is inserted into a cryogenic refrigerant bath and connected to a superconducting coil. This cooling gas shield type current lead is a system in which heat conduction is suppressed by cooling Joule heat with a refrigerant evaporating gas such as liquid helium. However, since there is residual heat of about several W, consumption by evaporation of the refrigerant is reduced. Inevitable.

Further, in recent years, examples of using a high-temperature superconducting current lead practically used in place of the cooling gas shield type current lead are increasing. The high-temperature superconducting current lead is shown in FIG.
As shown in FIG. 0, the lower end of the high-temperature superconducting current lead is connected to the superconducting lead connected to the superconducting coil immersed in the liquid helium bath, and a cooling plate cooled by a small refrigerator is provided with an insulating layer on the upper end of the high-temperature superconducting current lead. It is equipped so that the current leads can be maintained in a superconducting state by being connected and cooled through. A braided copper wire is connected to the upper end of the high-temperature superconducting current lead, and the braided conductor is connected to an external DC power supply provided via an external terminal provided on the outer wall of the cryostat. The exciting current is supplied to the superconducting coil through the electric circuit thus formed. In addition, there is a method using a liquid nitrogen tank instead of cooling by a refrigerator. When a high-temperature superconducting current lead is used, no Joule heat is generated, and only one lead conducts heat between a portion cooled by a refrigerator at the upper end and a portion cooled by a cryogenic refrigerant such as liquid helium at the lower end. 0 per hit. The problem of heat penetration into the cryogenic refrigerant is significantly improved as compared with 1W and the cooling gas shield type current lead.

By the way, in the method of generating radiation light by a superconducting wiggler, in order to maintain the position of the electron beam orbit,
It is necessary to simultaneously excite several superconducting coil groups while maintaining mutual matching, and twice as many current leads as the number of coils must be connected to the superconducting coils in the cryostat. The larger the number, the greater the conduction heat from the current leads, or the Joule heat, which causes the refrigerant,
For example, the evaporation of liquid helium increases. For this reason,
When a cooling gas shield type current lead is used, the heat input to the refrigerant is 10 to 20 W from the current lead alone,
Since the refrigerant is largely evaporated, long-term operation cannot be performed without supplying the refrigerant. Further, even when a high-temperature superconducting current lead with improved thermal conditions is used, there is still a conduction heat of 0.5 to 1 W, and there is still dissatisfaction with the long-term operation without refrigerant supply.

Furthermore, these excitation methods require that a dedicated large DC power supply for excitation be provided externally. In addition, since the conventional DC power supply for excitation controls the output current by stepwise switching, it is difficult to adjust the current to match the required change in the magnetic field, and may overshoot the upper limit level in the design. When a value that matches the magnetic field level at which the electron beam is stable cannot be obtained, a movement may occur in which the output current flows around the target value.

As an exciting method that does not use such an exciting DC power supply, there is an exciting method using a flux pump. When a flux pump is used, a large current power supply is not required, and a small power supply for controlling the rotation of the motor can supply energy to the superconducting coil. In addition, since the generated current value can be continuously controlled by the rotation of the motor and can be demagnetized, it is possible to obtain a change pattern of the magnetic field adjusted so as to make a soft landing at the electron beam stable magnetic field level. it can.

The main types of flux pumps are roughly classified into a moving magnetic field type and a rectifying type. At present, a moving magnetic field type flux pump is more suitable for the purpose of exciting a superconducting coil. The flux pump cannot penetrate magnetic flux into the superconducting circuit or superconductor, but when the superconducting state in the superconducting circuit breaks and the magnetic flux penetrates into the part where the normal conducting region occurs, this part returns to the superconducting state once. Utilizing the property that the invading magnetic flux remains trapped in the circuit.

The moving magnetic field type flux pump is also called a power generation type flux pump, and applies a magnetic field of a permanent magnet or the like to a superconducting plate forming a part of a superconducting circuit to form a normal conducting region in that portion and move the magnet. As a result, the normal conduction region is moved, and an eddy current is generated around the normal conduction region. When the normal conduction region returns to the superconducting state, the eddy current generated there is added to the current in the superconducting circuit and is taken in. The eddy current accumulated in the superconducting plate is supplied to the superconducting coil via the superconducting connection line. It is called a flux pump because it accumulates and accumulates a current corresponding to the invading magnetic flux in the circuit every time the magnetic field moves. If the magnet does not move, no eddy current is generated simply because magnetic flux has entered, and no current is generated in the circuit. In the case of demagnetization, if the direction of movement of the magnet is reversed, the direction of the eddy current is reversed and the current is reduced, so that the superconducting coil can be demagnetized. As described above, the flux pump is a generator essentially utilizing a superconducting phenomenon, unlike a so-called superconducting generator in which a field winding or an armature winding is made superconducting.

FIG. 12 is a drawing showing the operating principle of a Volger type flux pump which is a typical moving magnetic field type flux pump. Instead of linearly moving a permanent magnet for injecting magnetic flux into a superconducting disk, a bolger type flux pump is attached to the tip of an arm provided on a rotating shaft, and is rotated at a rotation speed corresponding to a required excitation speed, for example, about 6 to 1200 rpm. The permanent magnet rotates and orbits a circular orbit having a predetermined radius centered on the center of the disk. Then, every time the arm makes one rotation, the predetermined magnetic flux is confined,
The current corresponding to the confined magnetic flux is added to the current flowing in the superconducting circuit to which the superconducting coil is connected. Therefore, the amount of increase in the current flowing through the superconducting coil is proportional to the rotation speed of the arm, and the current decreases when the rotation direction is reversed. Thus, the excitation of the superconducting coil using the flux pump can be controlled continuously.

[0011] The moving magnetic field type flux pump further includes an Atherton type flux pump. The Atherton type flux pump has a structure in which a superconducting plate is formed into a cylindrical shape, and a plurality of permanent magnets rotate around the cylindrical shape. The superconducting cylindrical plate may be a single continuous plate or may have slits. This flux pump may be considered to be connected in parallel with the number of permanent magnets of a type in which eddy currents are confined by the translation of the permanent magnets on the superconducting plate.

A Beelen type flux pump is also known. Beren type flux pump is U
A superconducting plate is adhered and fixed to the arc-shaped inner surface of the U-shaped electromagnet or the permanent magnet, and a plate-shaped soft iron rotor orthogonal to the axis is inserted inside the arc-shaped magnet and rotates around a concentric axis.
The magnets are fixed, and when the rotor comes between the opposing magnets, a magnetic circuit is formed between the opposing magnetic poles, and the corresponding portion of the superconducting plate is made normal. Therefore, when the rotor rotates, the normal conducting region moves together with the magnetic flux, and an eddy current is generated in the superconducting plate.

FIG. 11 is a diagram showing a method of exciting a superconducting coil by a flux pump. The power generation part of the flux pump is immersed in liquid helium, a motor for rotating the rotating shaft is installed in the normal temperature part outside the cryostat, and a rotating conduction system that transmits the rotational motion penetrates from the normal temperature part to the liquid helium area Have been. Since the flux pump is essentially a power generation method that requires superconductivity, no Joule heat is generated at the time of excitation.However, since the rotational conduction system transfers heat from the room temperature part to the liquid helium tank, a special Without elaboration, evaporation of the refrigerant cannot be suppressed.

As described above, in the conventional superconducting wiggler excitation method including the method using the flux pump, when exciting the superconducting coil, heat is transferred to the superconducting coil via a current lead or a rotary conduction system which is also a good conductor of heat. As a result, the refrigerant in the cryostat is evaporated, so that it is necessary to operate while frequently supplying the refrigerant. Therefore, in order to extend the replenishment interval of the refrigerant and enable long-term continuous operation, it is necessary to minimize the heat conduction through the current leads and the like. This contrivance is a major factor in complicating the insulation structure of the cryostat of the conductive wiggler and increasing the size of the wiggler.

[0015]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method of exciting a superconducting wiggler capable of reducing the size of the entire apparatus without using a large-scale power supply, and a superconducting method using the method. The wiggra is provided. Further, the present invention provides a superconducting wiggler capable of continuously changing the excitation speed of a superconducting coil. Still another object of the present invention is to provide a superconducting wiggler excitation method capable of suppressing long-term continuous operation by suppressing evaporation of a refrigerant in a cryostat and a superconducting wiggler using the method.

[0016]

In order to solve the above-mentioned problems, a superconducting wiggler exciting method according to the present invention comprises a superconducting disk unit installed in a cryogenic refrigerant tank of a cryostat and a magnet rotor unit installed outside the tank. A magnetic flux pump is provided, and a magnetic flux is accumulated in a superconducting circuit by rotating a magnet rotor to excite a superconducting coil connected to a superconducting disk. In addition, it is preferable that the magnet rotor of the magnet rotor section has a horizontal arm, and rotates by fixing permanent magnets at both ends in directions having different polarities.

Further, an iron core is provided between the permanent magnets of the horizontal arm, and the core is brought into contact with the superconducting disk portion via an insulator inside the superconducting disk. Is preferably configured to be closed. Further, a non-contact magnetic joint can be inserted in the middle of a rotating shaft for rotating the magnet rotor to suppress heat conduction, and the non-contact magnetic joint can be cooled by a refrigerator. Furthermore, the magnet rotor rotating shaft is translated in advance in the axial direction, the magnet rotor is brought into contact with the surface of the cryogenic refrigerant tank to cool it, and it is possible to rotate the magnet rotor away from the surface of the cryogenic refrigerant tank immediately before the start of excitation. can do.

In order to solve the above-mentioned problems, a superconducting wigler according to the present invention comprises a flux pump having a superconducting disk part installed in a cryogenic refrigerant tank and a magnet rotor part installed outside the tank. A coil is connected. Further, the magnet rotor is provided with a horizontal arm in which permanent magnets are fixed at both ends in directions having different polarities and an iron core is provided between the permanent magnets, and the superconducting disk portion contacts the inside of the superconducting disk via an insulator. An iron core may be provided. In addition, a non-contact magnetic joint is provided in the middle of the rotating shaft for rotating the magnet rotor, a refrigerator for cooling the non-contact magnetic joint is provided, and the rotating shaft is translated in the axial direction to the room temperature side end of the magnet rotor rotating shaft. Preferably, means are provided.

According to the superconducting wiggler excitation method according to the present invention, the excitation of the superconducting coil is performed by the flux pump incorporated in the apparatus, so that the superconducting DC power supply outside the apparatus is connected via a current lead or the like in the wiggler apparatus. Compared with the conventional excitation method in which current is supplied and excited, a motor for controlling the rotation of a magnet rotor of a flux pump may be provided as power instead of a large-capacity DC power supply for excitation provided outside the apparatus, Since an energizing cable connecting the DC power supply and the superconducting coil is not required, the entire system of the superconducting wiggler can be made compact. Further, since there is no current lead as a source of large Joule heat and conduction heat in the wiggler device, evaporation of the refrigerant such as liquid helium for cooling the superconducting coil can be reduced, and the operation time can be prolonged. .

Further, according to the excitation method of the present invention, the superconducting disk portion of the flux pump is installed in the cryogenic refrigerant tank and the magnet rotor is installed in the adiabatic vacuum space outside the tank. The stationary part of the superconducting disk, in which the rotating drive part and the superconducting and normal conducting elements are mixed, is mechanically separated while being magnetically coupled across the tank wall and is in non-contact, so the liquid helium tank is connected via the rotation conduction system of the flux pump. Can reduce the heat conducted to the heat sink.

In the conventional excitation method using a superconducting DC power supply, the excitation speed of the superconducting coil can be changed only in steps, whereas the excitation speed of the flux pump is proportional to the rotation speed of the magnet rotor. Moreover, the current can be increased or decreased by changing the rotation direction. Therefore, by using a servomotor or the like capable of controlling the speed with high precision for the rotation of the magnet rotor, the excitation speed to the superconducting coil group can be changed continuously and in both directions of increasing and decreasing the magnetic field. Can be fine-tuned. In the conventional method, the electron beam deviates from its original position in the process of changing the excitation state of the superconducting wiggler step by step, and has a bad influence on the stability of the electron beam. Since the method can follow continuously, such a problem is greatly reduced.

When the magnet rotor rotates a horizontal arm having a pair of permanent magnets fixed at opposite ends in directions having different polarities, magnetic fluxes of the same density in the opposite direction to the superconducting plate are generated in the opposite direction. The eddy current induced in the superconducting plate is doubled as compared to a bolger type flux pump with one arm rotating with one permanent magnet, and the magnetic flux trapped in the superconducting circuit on the superconducting disk side Can be doubled. That is, the method of the present invention is equivalent to a case where a conventional bolger type flux pump is arranged in two stages in series.

Further, when an iron core is provided between the permanent magnets of the horizontal arm and the iron core is fixedly arranged on the side of the superconducting disk via an insulator on the inside of the superconducting disk, the permanent magnet rotates every moment. Then, when it comes to a position facing the iron core on the superconducting disk side, a normal conducting region is formed and the magnetic circuit is closed. At this time, since the leakage magnetic flux from the portion of the cryogenic refrigerant tank wall sandwiched between the permanent magnet and the iron core is minimized, it is possible to secure the magnetic flux trapped in the superconducting circuit, enhance this, and obtain a peak current. it can. In addition, even when the magnet rotor deviates from the position facing the iron core on the superconducting disk side, if the magnetic field generated by the magnet is larger than the critical magnetic field of the superconducting disk, a normal conducting region is formed. An electric current can be obtained. Thus, the excitation speed of the superconducting coil can be improved.

When a non-contact magnetic joint made of opposed permanent magnets is inserted into the middle of the rotation axis of the magnet rotor, and the non-contact magnetic joint is cooled by a refrigerator, the temperature of the low-temperature part from the room temperature section via the rotation shaft is reduced. Liquid helium from the flux pump is cut off by blocking the heat flow conducted to the part at the position of the magnetic joint, and cooling the position of the magnetic joint on the support column that protects and supports the rotating shaft to offset the heat conduction from the room temperature part. Evaporation of the cryogenic refrigerant can be suppressed by making the final heat input to the tank only radiant heat. In the case where the support column can be moved up and down, it is preferable that cooling is performed at each refrigeration stage of the small refrigerator through a flexible copper thermal anchor. In addition, in the case where the magnet rotor rotation axis is translated in the axial direction, first, the magnet rotor is brought into contact with the surface of the cryogenic refrigerant tank to sufficiently cool it, and then an appropriate distance is maintained from the surface of the cryogenic refrigerant tank. By operating the flux pump by pulling it apart
Radiant heat transmitted from the magnet rotor side of the rotating shaft to the superconducting circuit side can be suppressed.

According to the superconducting wiggler according to the present invention, the superconducting disk unit is provided in the cryogenic refrigerant tank, and the flux pump is provided with the magnet rotor unit provided outside the tank. The superconducting disk is connected to the superconducting coil. Therefore, the excitation of the superconducting coil can be precisely controlled by a servomotor or the like having a capacity sufficient to rotate the magnet rotor unit, without using a conventional high-current DC power supply. In addition, a current supply cable for connecting the DC power supply and the superconducting coil is not required, and heat conduction can be suppressed and the structure of the cryostat can be simplified, so that the entire wiggler device can be made compact.

Further, a magnet rotor having a pair of permanent magnets fixed to both ends of a horizontal arm in directions having different polarities and an iron core provided between the permanent magnets, and a flux pump having an iron core inside an opposing superconducting disk When the permanent magnet rotates and comes to a position facing the iron core on the superconducting disk side, the part becomes normal conduction and the magnetic circuit is closed, and the leakage magnetic flux from the part of the cryogenic refrigerant tank wall becomes small. Therefore, the excitation speed of the superconducting coil can be improved.

A non-contact magnetic coupling is provided in the middle of the rotating shaft of the magnet rotor portion, the non-contact magnetic coupling is cooled by a refrigerator, and a means for axially translating the rotating shaft of the magnet rotor is provided. Since the heat transmitted through the rotating shaft is cut off on the way, it is cooled to an appropriate low temperature by the refrigerator, and the rotor can be sufficiently cooled by a cryogenic refrigerant such as liquid helium before starting the operation. The heat transmitted from the outside normal temperature region becomes extremely small. For this reason, long-term continuous operation is possible without replenishing refrigerant.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The superconducting wiggler excitation method according to the present invention and the superconducting wiggler using the same will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view showing an exciting means of a superconducting wiggler including a magnetic coupling and a flux pump according to one embodiment of the present invention, FIG. 2 is a perspective view showing an operating state of an exciting portion in the present embodiment, and FIG. FIG. 4 is a diagram illustrating an operation state of the embodiment.

The flux pump 1 used for exciting the superconducting wiggler in the present embodiment shown in FIG. 1 can be said to be an improved type of a Volger type flux pump, and a power generation unit 3 attached to a partition wall of a cryogenic refrigerant tank, A lower rotating shaft 5 for rotating the magnet rotor in the power generation unit, an upper rotating shaft 7 for rotating the lower rotating shaft, and a rotating drive source 9 installed in the outermost room of the cryostat at room temperature to control the rotation of the upper rotating shaft. Become. The lower rotary shaft 5 is protected by a lower support column 11, and the upper rotary shaft 7 is protected by an upper support column 13. The power generation unit 3 includes a magnet rotor unit 15 and a superconducting disk unit 17, and moves the magnet rotor unit 15 out of the cryogenic refrigerant tank.
Further, by disposing the superconducting disk portion 17 in the cryogenic refrigerant tank with the cryogenic refrigerant tank wall 19 interposed therebetween, the two parts are separated from each other and brought into non-contact.

Further, the rotating shaft which normally continuously penetrates from the normal temperature portion to the low temperature portion of the cryostat device is also separated into a lower rotating shaft 5 and an upper rotating shaft 7, and comprises permanent magnets 21 and 23 opposed to each other at an intermediate position. The rotation is transmitted in a non-contact manner with the magnetic coupling 25 interposed therebetween. The permanent magnet pair of the magnetic joint 25 has a gap with the heat transfer disk 27 interposed therebetween, and is made non-contact so as to cut off conduction heat flowing into the cryogenic refrigerant tank via the rotating shaft.

The heat transfer disk 27 is connected to a first stage of a refrigerator (not shown) through a flexible copper thermal anchor so that the heat transfer disk 27 can be maintained at a medium-low temperature state. It has the effect of removing radiation heat and reducing the temperature difference with the lower rotary shaft 5 to reduce radiation. The heat transfer disk 27 is further fixed to the support columns 11 and 13 by the magnetic coupling housing 29 to remove conduction heat from the normal temperature portion and suppress conduction heat to the cryogenic portion. The upper rotary shaft 7 has a shaft sealing joint 31 at the upper end.
The shaft seal joint 31 is supported by the bellows 3
3 and is supported by the outer cryostat tank 35. The distance between the shaft sealing joint 31 and the outer tank 35 is adjusted by the position adjusting screw 3.
7 can be adjusted and fixed. By adjusting the position adjusting screw 37, the entire portion outside the cryogenic refrigerant tank in the flux pump 1 is translated and the position can be adjusted vertically.

Therefore, before the excitation, the magnet rotor portion 15 is cooled by bringing it into contact with the outer wall 19 of the cryogenic refrigerant tank, and is slightly returned, and the excitation operation can be performed after the non-contact. Then, radiant heat transmitted from the rotor section to the cryogenic refrigerant tank during operation is reduced, and evaporation of the refrigerant due to heat input is suppressed. At the lower end of the support column 11, a flexible copper thermal anchor 39 connected to the second stage of the refrigerator is attached, which is maintained at an extremely low temperature and removes heat conducted through the support column 11. It has become. With this configuration, the heat input from the excitation source to the wall of the cryogenic refrigerant tank is
Only radiant heat of about several mW per unit is provided, and the heat input condition is far improved compared to other excitation methods, so that the refrigerant-free supply operation can be performed for a long time.

FIG. 2 is a perspective view for explaining the operation of the power generation unit 3 of the flux pump 1 in this embodiment. Elements having the same functions as the elements described in FIG. 1 are denoted by the same reference numerals, and description thereof will be simplified. The conventional bolger type flux pump has a structure composed of one permanent magnet fixed to the tip of a rotating one arm and a superconducting disk facing the permanent magnet as shown in FIG. Magnetic flux can be accumulated once.

On the other hand, the flux pump 1 of the present invention
Then, a horizontal arm 41 made of an iron core is provided at the end of the lower rotary shaft 5 for rotating the magnet rotor, and two permanent magnets 43 and 45 are arranged at both ends of the iron core so that the polarities are opposite to each other. One superconducting disk 47 as a V-shaped magnet rotor
And rotate it. At this time, two normal conducting regions 49, 5 generated in the superconducting disk 47 by two permanent magnets 43, 45 of different polarities attached to the tip of the arm.
Since the eddy currents around 1 are in the same direction, the current flowing in the superconducting coil 53 connected to the superconducting disk 47 is twice that in the case of one permanent magnet. That is, the superconducting circuit accumulates a predetermined amount of magnetic flux twice each time the magnet rotor rotation shaft 5 makes one rotation. If the two permanent magnets 43 and 45 have the same polarity, the two eddy currents generated in the superconducting disk 47 are in opposite directions and cancel each other, so that no current flows to the superconducting coil 53 side. And the effect of the present invention cannot be obtained.

In this embodiment, the superconducting disk 4
A U-shaped iron core 55 having the same shape as the U-shaped magnet rotor is fixedly disposed inside the U-shaped magnet 7. When the magnet rotor rotates and reaches a position facing the U-shaped iron core 55 fixed and arranged, a magnetic circuit is formed between the horizontal arm 41 of the U-shaped magnet rotor and the U-shaped iron core 55, and the leakage magnetic flux is formed. Is minimized, and a peak current is obtained. Even when the magnet rotor is at a position deviated from the U-shaped iron core 55, if the magnetic field generated by the magnet is larger than the critical magnetic field of the superconducting disk, a normal conducting region is formed in the superconducting disk 47, so that the magnet rotor is at the facing position An eddy current can be obtained although it is smaller than at the time.

As described above, disposing the U-shaped iron core 55 inside the superconducting disk 47 can prevent leakage of the superconducting disk 47 when the superconducting disk 47 is disposed with the cryogenic refrigerant tank wall separated from the magnet rotor. This has the effect of reducing magnetic flux. Further, the change of the excitation mode in the flux pump 1, that is, the switching between the magnetization increase and the demagnetization can be performed by switching the rotation direction of the magnet rotor. This means that the magnetic flux accumulated in the superconducting circuit during the magnetizing process is rewound by switching the rotation direction of the magnet rotor.

Further, the change of the magnetizing / demagnetizing speed can be performed by changing the rotation speed of the magnet rotor. With the conventional method of exciting a superconducting wiggler from a DC power supply, the magnetizing and demagnetizing speeds can usually only be changed stepwise, so that the operation of adjusting the magnetic field to the magnetic field region where the electron beam exists stably can be performed freely. Often, the stability of the electron beam was impaired. In a method of exciting a superconducting wiggler with a conventional DC power supply,
For example, when exciting as a target value the upper limit magnetic field level at which a stable electron beam can be obtained, if the magnetization is continued at a predetermined speed selected toward a design allowable magnetic field level higher than the stability limit, Often the magnetic field level at which the beam can stabilize is too large. When the demagnetization is performed for the correction, a predetermined demagnetization speed that exists in a stepwise manner is also selected so as to move toward the beam stabilizing magnetic field, and this time, it will overshoot downward. As described above, while the magnetic field adjustment is repeated several times, the stability of the electron beam is impaired and the electron beam strays.

In the present invention, the superconducting wiggler is excited by the flux pump. Therefore, by using a servomotor capable of high-precision speed control as the rotation source of the magnet rotor,
Since the speed of increase and decrease of the magnetization of the superconducting coil can be continuously varied, and the operation of adjusting the magnetic field to the beam stable magnetic field region can be freely finely adjusted, the stability of the electron beam is less likely to be impaired. That is, even if the beam stabilizing magnetic field excessively passes during the magnetizing process as shown by a short dotted line in FIG. 3, it can be immediately returned to the beam stabilizing magnetic field as shown by a solid line by performing fine adjustment. If the beam stabilizing magnetic field level is known in advance, as shown by the long broken line in the figure, it is possible to softly land on the beam stabilizing magnetic field while finely adjusting the excitation speed gently, thereby impairing the stability of the electron beam. It will not be. In the figure, the horizontal axis indicates time, and the vertical axis indicates magnetic field strength.

[0039]

FIG. 4 shows an embodiment of the present invention, and shows the overall structure of a superconducting wiggler for exciting a superconducting coil group by incorporating two flux pumps having a structure as schematically shown in FIG. I have. In addition, in order to facilitate understanding,
Components having the same function are denoted by the same reference numerals as in the previous drawings, and the description is simplified.

Cryostat 61 for superconducting wiggler
Has a cylindrical cryogenic refrigerant tank 63 containing a superconducting coil and an iron yoke, a two-stage heat shield plate 65 surrounding it, an outer tank 67 forming an adiabatic vacuum layer at the outermost periphery thereof, It comprises a small refrigerator 69 for cooling the shield plate, an outer tank, a cryogenic refrigerant tank, a beam chamber 71 penetrating through the center of the superconducting coil group, and the like. The two flux pumps 1 penetrate from the outer tank room temperature section on which the rotary drive source 9 is mounted to the inner tank low temperature section where the power generation section 3 is installed.
The magnetic coupling 25 is provided in the rotation transmission system 73 between them. In order to prevent conduction heat or radiant heat from the flux pump 1 from invading into the cryogenic refrigerant tank 63, one small refrigerator 69 is connected to the two flux pumps 1 via the flexible thermal anchors 75 and 77. Rotational transmission system 7
3 and the power generation unit 3 are cooled.

The flux pump 1 according to the present invention has a rotary drive source 9 in the outer tank room temperature part of the cryostat 61,
A rotary conduction system 73 having a magnetic coupling 25 as shown in FIG. 5 in the middle thereof penetrates the adiabatic vacuum layer, and has a power generation unit structure 3 as shown in FIG. The rotation drive source 9 includes a servomotor 79 capable of speed control and the flux pump 1
It comprises a bellows joint 33 and a shaft seal joint 31 for enabling the position adjustment in the overall height direction and the introduction of the rotation transmission system 73 into the cryostat in a vacuum-resistant manner. In the height direction adjustment, the surface of the magnet rotor 15 of the power generation unit 3 is contact-cooled beforehand with the cryogenic refrigerant tank shell 19 before excitation, and then the magnet rotor 15 surface is separated from the cryogenic refrigerant tank shell 19 to properly adjust the position. This is performed in order to suppress the final stage radiant heat by maintaining the contact gap. The position adjustment in the height direction is performed by a position adjustment screw and a nut 37 provided around the flange of the bellows joint 33.

The rotary transmission system 73 is divided into two stages between the rotary drive source 9 and the magnetic coupling 25 and between the magnetic coupling 25 and the power generation unit 3. And the upper rotary shaft 7 that extends between the magnetic coupling 25 and the servomotor 79 are accommodated in the lower support column 11 and the upper support column 13, respectively. At both ends of the upper and lower support columns 11 and 13, a bearing for suppressing shaft run-out and maintaining a shaft end gap and a bearing housing for accommodating the bearing are mounted.

FIG. 5 is a sectional view showing the structure of a magnetic coupling portion 25 connecting the upper support column 13 and the lower support column 11. The magnetic joint 25 has an upper rotary shaft 7 and a lower rotary shaft 5 with a copper heat transfer disk 27 interposed therebetween.
The half-joint which has a high degree of vertical symmetry has a non-contact and magnetic coupling in a vertically symmetrical structure, and transmits rotational motion. In the magnetic joint 25, permanent magnets 21 and 23 having different polarities and iron cores 101 and 103 are incorporated in each of the upper and lower half joints, and a pair of left and right magnetic circuits 105 are formed in the vertical direction. Strong magnetic coupling is provided.

A flexible thermal anchor 75 connected to the first stage of the small refrigerator is connected to the heat transfer disk 27, as indicated by a one-dot chain line in the figure. The thrust bearings 10 housed in the upper and lower bearing housings 107 and 111, respectively, in order to eliminate vertical displacement due to the attractive force of the magnet and penetration of conduction heat due to mutual contact.
9 and 113, the positions of the half joints are kept in a non-contact state. In addition, a through hole is drilled in the axis of the magnetic coupling portion 25, and a sheath thermocouple 115 for measuring the temperature of the power generation unit penetrates.

FIG. 6 is a sectional view showing a power generation unit of the flux pump according to the present embodiment. 7 is a detailed cross-sectional view of the portion A in FIG. 6, and FIG. 8 is a view taken along the line BB in FIG. Here also, components having the same functions are denoted by the same reference numerals as in the previous drawings, and the description is simplified. As shown in FIG. 6, the magnet rotor portion 15 and the superconducting disk portion 17 of the power generation unit 3 are each divided into an outside and an inside with a cryogenic refrigerant tank shell 19 interposed therebetween, and oppose each other with a slight gap between adiabatic vacuum spaces. doing. For this reason, the flux pump can excite the superconducting coil group by the following power generation unit structure and mechanism.

In the magnet rotor 15, two permanent magnets 43 and 45 having different polarities (N pole and S pole) are arranged and fixed in a U-shape at both ends of an iron core 41, and are fixed in a rotating disk 131 made of a nonmagnetic material. Buried and fixed. The rotating disk 131 is attached to the tip of the lower rotating shaft 5. On the other hand, in the superconducting disk portion 17, as shown in FIG. 7, which is an enlarged view of the portion A in FIG. 6, the superconducting disk 47 is arranged inside the inner tank shell 19 via the electric insulating film 133, and further inside. A U-shaped iron core 55 having the same shape as the magnet rotor is arranged via the electric insulating film 135. The superconducting disk 47 and the U-shaped iron core 55 are non-magnetic.
It is fixed in a mounting flange 137 of an electric insulator, and is mounted inside the cryogenic refrigerant tank shell 19 by the flange 137.

FIG. 8 is a partially cutaway view of a part of the superconducting disk unit 17 incorporated into the mounting flange 137 as viewed from the surface of the flange. The superconducting disk 47 has a concave notch 139 at a vertically symmetrical position, and at the right and left symmetrical position shifted by 90 °, the inner wall 14 of the mounting flange 137.
1 and a superconducting joint 143 is provided at the tip thereof, to which a superconducting wire 145 connected to a superconducting coil group (not shown) is connected. The U-shaped iron core 55 is disposed in the horizontal direction in the figure. The magnet rotor 15 rotates, and the surfaces of the permanent magnets 43 and 45 are
When the surface of the U-shaped iron core 55 is opposed to and coincides with the surface of the U-shaped iron core 55, a set of magnetic circuits 147 is formed to minimize the leakage magnetic flux, so that the peak current is sent to the superconducting coil group.

Even when the permanent magnet surface deviates from the U-shaped iron core 55, a normal conduction region is formed in the superconducting disk 47, so that an exciting current can be obtained although it is smaller than that at the time of facing and matching. Further, when the surfaces of the permanent magnets 43 and 45 reach the concave cutout position 139 of the superconducting disk 47, the entire surface of the disk is in a superconducting state, the current is in a resting phase, and the whole circuit is in the most superconducting stable phase. Become. Thus, the current sent to the superconducting coil group within one rotation of the magnet rotor changes from the peak value to the intermediate value to zero.

The magnet rotor portion 15 prevents attraction by forming a magnetic circuit between the magnet rotor surface and the U-shaped iron core surface, and the superconducting disk 47 and the permanent magnet 43 of the magnet rotor
45, a thrust bearing 149 is attached to a shaft coupling that extends to the rotating disk 131,
The bearing housing 151 accommodating it and the lower support column 11 itself are positioned by a height position adjusting mechanism 37 attached to the rotation drive source 9 in the room temperature section. Further, the bearing housing 151 of the magnetic rotor unit 15 is connected to the second stage of the small refrigerator through the thermal anchor 77.
Further, a small hole is formed in the shaft center of the bearing housing 151, and the thermocouple 115 is inserted therein.

The superconducting wiggler of the present embodiment described in detail above can cut off the heat input to the cryogenic refrigerant tank 63 by cutting off the conduction heat and the radiant heat in each part structure of the flux pump 1. For this reason, the factor of heat input from the flux pump 1 to the cryogenic refrigerant tank 63 is greatly reduced as compared with the case where the high-temperature superconducting current lead is used, and the superconducting wiggler can be operated continuously for a long period of time.

First, the conduction heat transmitted through the support columns 11 and 13 of the upper and lower rotary transmission system 73 is transferred to the flexible thermal anchor 75 which branches the upper and lower bearing housings 29 of the magnetic coupling portion 25 from the first stage of the small refrigerator. By cooling the bearing housing 151 of the power generation unit / magnet rotor unit 15 to about 20K through the flexible thermal anchor 77 from the second stage of the small refrigerator, the temperature of each stage of the small refrigerator is reduced to about 80K. Offset by refrigeration capacity.

The superconducting disk portion 17 of the power generation unit 3
Is in contact with the cryogenic refrigerant (liquid helium) and is cooled to about the boiling point of the refrigerant (4.2 K) to maintain the superconducting state. With respect to the conduction heat transmitted through the upper and lower rotary shafts 5 and 7 in the support column, the rotary shaft is only in point contact with the bearing ball and the shaft peripheral surface in the bearings 109 and 113, so that the small refrigerator is used. Even if the bearing housings 107 and 111 are subjected to heat transfer cooling, a large heat blocking effect cannot be expected. For this reason, conduction heat is cut off based on the non-contact / separation function of the non-contact magnetic joint 25 in the rotation transmission system 73 and the magnet rotor 15 and the superconducting disk 17 in the power generation unit 3.

Further, since the half joints of the magnetic joint 25 are also in non-contact opposition to the heat transfer disk 27 in a cooled state due to the first stage refrigerating capacity of the small refrigerator, the lower rotary shaft 5 and the upper rotary shaft 7 Radiant heat between them is also suppressed.
In addition, during operation, the magnet rotor 15 of the power generation unit 3 is kept in a non-contact state with the cryogenic refrigerant tank shell 19 with a slight gap therebetween, so that heat transmitted through the rotating shaft 5 is transferred to the cryogenic refrigerant tank shell 19. Without conduction, only radiant heat from the surface of the magnet rotor 15 becomes a factor of heat input to the cryogenic refrigerant tank 63. This radiant heat can also be sufficiently reduced by pressing the surface of the magnet rotor 15 against the cryogenic coolant tank shell 19 in advance by the height position adjusting mechanism 37 attached to the rotation drive source 9 at room temperature before starting the excitation.
3, 45, iron core 41, rotating disk 131, shaft coupling system 151
Is cooled, and then separated and brought into non-contact by the height position adjusting mechanism 37 to reduce the amount.

In order to monitor the cooling temperatures of the magnets 43 and 45, the rotating disk 131, the bearing housing 151, etc. before the excitation,
A sheath thermocouple 115 is inserted in this part. The sheath thermocouple 115 penetrates the center of the rotating shaft and is connected to a terminal provided at the shaft sealing joint portion 31 of the rotating drive source 9 at the room temperature, and transmits a detection output to a measuring instrument. Since the heat input from the flux pump 1 to the cryogenic refrigerant tank 63 can be reduced to about 50 mW / m ² by the above heat input prevention measures, for example, the diameter of the magnet rotor surface is reduced to 30 cW / m ^2.
m, the heat input is about 10 mW with two flux pumps. Therefore, the amount of refrigerant (liquid helium) evaporated can be much smaller than in the conventional method using a high-temperature superconducting current lead.

FIG. 9 shows an example of an excitation control circuit for exciting a superconducting coil group by two flux pumps 1 in this embodiment. The superconducting coil group includes a pair of main coils 201 and 20 facing each other across the beam chamber.
2 and a pair of upstream side coils 203 and 204 disposed upstream of the main coil, and a pair of downstream side coils 205 and 206 disposed downstream of the main coil.
Consists of The superconducting disk of the first flux pump 211 generates an exciting current for the main coils 201 and 202, and the superconducting disk of the second flux pump 212 generates an exciting current for the upstream side coils 203 and 304 and the downstream side coils 205 and 206. Occurs.

The magnet rotor of the first flux pump 211 is rotated by a small power source 213 for rotation, and the small power source for rotation is supplied via a rotation control circuit 215 to a wiggler control circuit 217.
The operation is controlled by. The wiggler control circuit 217 has the first
In accordance with the flux pump 211, the second small power source for rotation 214 is driven via the second rotation control circuit 216 to control the rotation of the magnet rotor of the flux pump 212.
A permanent current switch 221 is inserted in series with the superconducting disk of the first flux pump 211. The first superconducting circuit formed by the superconducting disk of the flux pump 211, the permanent current switch 221 and the superconducting main coils 201 and 202 has a diode 223 in parallel.
And a first quench protection circuit including a protection resistor 225. The first superconducting circuit is further provided with a quench detector 227 for detecting the occurrence of quench from the voltage difference before and after the superconducting coil, and a heater power supply 229 for supplying a current to the heater of the permanent current switch 221 by the output of the quench detector. Have been.

Similarly, a permanent current switch 222 is inserted into the superconducting disk of the second flux pump 212,
The superconducting disk of the flux pump 212, the permanent current switch 222, and two pairs of superconducting side coils 203 and 20
In the second superconducting circuit formed by 4, 205, 206,
The second is composed of a diode 224 and a protection resistor 226 in parallel.
Quench protection circuit is provided. The quench detector 228 and the heater power supply 230 are also provided in the second superconducting circuit.
Is provided.

The superconducting discs of the flux pumps 211 and 212, the permanent current switches 221 and 222, and the diode 22 included in a portion 231 surrounded by a one-dot chain line in the circuit diagram.
The circuit elements 3 and 224 and the protection resistors 225 and 226 are housed together with the superconducting coil group in a cryogenic refrigerant tank, and the operation circuits and devices for these are remotely operated outside the wiggler device. During the excitation operation by the flux pumps 211 and 212 or immediately after the end of the excitation, if the superconducting coil is stably generating a magnetic field, the permanent current switch 221 is used.
Reference numeral 222 denotes an ON state (connected state), and no current flows through the protection circuits connected in parallel.

However, when a quench occurs for some reason in the superconducting circuit, the heater power supplies 229 and 230 are activated by the signals from the quench detectors 227 and 228 to energize the heaters of the permanent current switches 221 and 222.
The permanent current switches 221 and 222 are in the OFF state (cutoff state). At this time, a voltage is generated at both ends of the switch, and the current flowing in the superconducting circuit flows to the protection circuit side. Thus, when a quench occurs, the permanent current switch 22
By automatically operating the superconducting coils 1 and 222, the magnetic energy accumulated on the superconducting coil side is diverted to the protection circuit side, so that the superconducting coil and the superconducting disk 21 of the flux pump are separated.
1,212 can be protected from quench.

A servo motor 79 whose speed can be controlled is used for rotationally driving the magnet rotors of the flux pumps 211 and 212. The speed of the servo motor is controlled by the wiggler control circuit 2.
In accordance with a programmed signal generated by a computer in the computer 17 or a signal from a beam monitor that monitors the position of an electron beam, the computer is controlled via the small power supplies for rotation 213 and 214 and the rotation control circuits 215 and 216. Thus, the excitation speed of the flux pump can be appropriately controlled so as not to deviate the optimal position of the electron beam in the beam chamber.

In this embodiment, a pair of permanent magnets is used for the magnet rotor portion or the magnetic joint portion. However, it goes without saying that the efficiency can be improved by using a plurality of permanent magnet pairs. In addition, although a simple mechanism using a bolt and a nut is used as a height position adjusting mechanism of the flux pump, it goes without saying that various mechanisms can be used. Further, a refrigerator is used for cooling the rotational motion transmission system, but a cooling method using a refrigerant may be used.

[0062]

As described above, according to the superconducting wiggler excitation method of the present invention and the superconducting wiggler using the method, if there is a small power supply device for controlling a relatively small servomotor for driving a flux pump, Often, a dedicated high-current DC power supply and a current-carrying cable are not required as in the conventional method, so that the entire wiggler apparatus is made compact. Further, since the excitation speed of the superconducting coil can be continuously changed by controlling the rotation of the flux pump, soft landing to the target beam stable magnetic field level can be easily achieved. Further, the long-term continuous operation of the superconducting wiggler is enabled by suppressing the inflow of heat from the outside and extending the replenishment interval of the refrigerant.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an exciting means of a superconducting wiggler including a magnetic coupling and a flux pump according to the present invention.

FIG. 2 is a perspective view showing an operating state of an exciting portion shown in FIG.

FIG. 3 is a diagram showing an operation state of an excitation part shown in FIG. 1;

FIG. 4 is a partial sectional view showing one embodiment of the superconducting wiggler of the present invention.

FIG. 5 is an enlarged sectional view of a magnetic coupling part in the embodiment shown in FIG.

FIG. 6 is an enlarged sectional view of a flux pump portion in the embodiment shown in FIG.

FIG. 7 is a sectional view showing a portion A in FIG. 6;

8 is a view taken in the direction of arrows BB in FIG. 6;

FIG. 9 is a circuit diagram illustrating an example of a control circuit according to the present embodiment.

FIG. 10 is a view showing a conventional superconducting wiggler excitation method.

FIG. 11 is a drawing showing another example of the conventional superconducting wiggler excitation method.

FIG. 12 is a view for explaining the operation of a conventional flux pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flux pump 3 Power generation part 5, 7 Rotating shaft 9 Rotation drive source 11, 13 Support column 15 Magnet rotor part 17 Superconducting disk part 19 Cryogenic refrigerant tank wall 21, 23 Permanent magnet of magnetic joint 25 Magnetic joint 27 Heat transfer disk 29 Magnetic joint housing 31 Shaft seal joint 35 Cryostat outer tank 37 Position adjusting screw 39 Flexible copper thermal anchor 43, 45 Permanent magnet of flux pump 47 Superconducting disk 49, 51 Normal conduction area 53 Superconducting coil 55 U-shaped iron core 61 For superconducting wiggler Cryostat 63 Cryogenic refrigerant tank 65 Heat shield plate 67 Outer tank 69 Refrigerator 71 Beam chamber 73 Rotating conduction system 75, 77 Flexible thermal anchor 79 Servo motor 101, 103 Iron core of magnetic joint 109, 113 Thrust bearing 1 Reference Signs List 15 sheath thermocouple 131 rotating disk 133, 135 electric insulating film 139 concave cutout 143 superconducting joint 145 superconducting wire 149 thrust bearing 201, 202 main coil 203, 204, 205, 206 side coil 211, 212 flux pump 213, 214 Small power supply for rotation 215, 216 Rotation control circuit 217 Wiggler control circuit 221, 222 Permanent current switch 223, 224 Diode 225, 226 Protection resistor 227, 228 Quench detector 229, 230 Heater power supply

Claims (8)

[Claims] 1. A superconducting disk comprising: a superconducting disk; a moving magnetic field type flux pump in which a magnet rotor section including a magnet rotor is installed outside the tank; and a superconducting coil including a superconducting coil by rotating the magnetic rotor. A superconducting wiggler excitation method comprising: accumulating magnetic flux in a circuit; and exciting a superconducting coil connected to a superconducting disk unit by an accumulated current. 2. A superconducting wiggler exciting method according to claim 1, wherein said magnet rotor has a horizontal arm and fixedly rotates permanent magnets at both ends in directions having different polarities. 3. When an iron core is provided between the permanent magnets, and the superconducting disk portion abuts the iron core on the inside of the superconducting disk via an insulator, and the permanent magnet of the magnet rotor comes to a position facing the permanent magnet. 3. The superconducting wiggler exciting method according to claim 2, wherein the magnetic circuit is closed. 4. A non-contact magnetic coupling is inserted in the middle of a rotating shaft for rotating the magnet rotor, heat conduction from the rotating shaft is suppressed, and the non-contact magnetic coupling is cooled by a refrigerator. Item 4. The superconducting wiggler excitation method according to any one of Items 1 to 3. 5. The cooling system according to claim 1, wherein the rotating shaft is translated in the axial direction before starting the excitation by the flux pump so that the magnet rotor is brought into contact with the surface of the cryogenic refrigerant tank to cool it. 5. The superconducting wiggler excitation method according to claim 1, wherein the superconducting wiggler is rotated away from the surface. 6. A superconducting disk comprising a flux pump in which a superconducting disk section is installed in a cryogenic refrigerant tank and a magnet rotor section including a magnetic rotor is installed outside the tank, and a superconducting coil is connected to the superconducting disk. Wiggra. 7. The magnet rotor comprises a horizontal arm having permanent magnets fixed at both ends in directions of different polarities and an iron core provided between the permanent magnets, and the superconducting disk portion is provided with an insulator inside the superconducting disk. The superconducting wiggler according to claim 6, further comprising an iron core abutting through the wire. 8. A non-contact magnetic joint is provided in the middle of a rotating shaft for rotating the magnet rotor of the magnet rotor portion, a refrigerator for cooling the non-contact magnetic joint is provided, and the rotating shaft is provided at an end of the rotating shaft. 8. A method for exciting a superconducting wiggler according to claim 6, further comprising means for translating the superconducting wiggler in the axial direction.