JP6517112B2 - Superconducting lead structure - Google Patents

Description

  The present invention relates to superconducting lead structures.

  Conventionally, as a technology in such a field, a superconducting lead structure described in Patent Document 1 below is known. The superconducting lead structure positions the lead body including the tape-like superconducting lead, the electrodes joined to both ends of the superconducting lead, the superconducting wire and the electrode to have a predetermined distance between the electrodes. And a reinforcing member to be accommodated in the closed state.

JP, 2015-032612, A

  As described above, by covering the superconducting lead with the reinforcing member, careless mechanical damage to the superconducting lead can be avoided. In this case, the reinforcing member needs to have electrical insulation, but since the insulating material generally exhibits a very high coefficient of thermal expansion as compared to the superconducting lead, the heat between the superconducting lead and the reinforcing member Due to the difference in expansion coefficient, thermal stress may occur in the lead body during cooling or temperature change. Then, the thermal stress may cause damage to the electrode and the superconducting lead.

  It is an object of the present invention to provide a superconducting lead structure that covers the superconducting lead and reduces the possibility of electrode and superconducting lead damage due to thermal fluctuations.

  The superconducting lead structure of the present invention is a superconducting lead structure for supplying a current to a superconducting coil, and includes a first electrode and a second electrode provided on a current path, a first electrode, and a second electrode. A superconducting lead which is bridged between the electrodes and electrically connects the first electrode and the second electrode, and which surrounds the superconducting lead at least in part of the region between the first electrode and the second electrode The lead protective portion has one end side fixed to the first electrode and the other end side unconstrained to the second electrode.

  In this superconducting lead structure, since the lead protection portion is in a non-constrained state to the second electrode, even if the distance between the first electrode and the second electrode changes due to the thermal deformation of the superconducting lead, There is no need for the lead protector to follow the change. Therefore, the generation of thermal stress due to the difference in the thermal expansion coefficient between the lead protection portion and the superconducting lead is suppressed, and the possibility of damage to the superconducting lead due to thermal fluctuation is reduced.

  As a specific configuration of the superconducting lead structure, a gap may be formed between the other end of the lead protection portion and the second electrode.

  Further, the superconducting lead structure of the present invention may further include a thermal anchor portion attached to the first electrode to cool the first electrode. As described above, in the configuration in which the first electrode is cooled by the thermal anchor portion, the above-described configuration is effective.

  In addition, one end side of the lead protection portion may be sandwiched between the first electrode and the thermal anchor portion. Essentially, it is necessary to electrically insulate the first electrode from the thermal anchor portion. According to the above configuration, the lead protection portion can also serve as the insulating material between the first electrode and the thermal anchor portion. .

  According to the present invention, it is possible to provide a superconducting lead structure that covers the superconducting lead and reduces the possibility of damage to the electrode and the superconducting lead due to thermal fluctuations.

1 is a cross-sectional view showing a cyclotron to which a superconducting lead structure according to an embodiment of the present invention is applied. It is a disassembled perspective view of a superconducting lead structure. It is sectional drawing which shows a superconducting lead structure and a heat shield pipe | tube. It is sectional drawing which expands and shows lower end vicinity of the lead | read | reed protection part which concerns on a modification. It is sectional drawing which expands and shows the lower end vicinity of the lead | read | reed protection part which concerns on another modification.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same parts or corresponding parts are denoted by the same reference numerals, and redundant description will be omitted.

  The cyclotron 1 shown in FIG. 1 uses the superconducting lead structure according to the present embodiment, and exhibits a circular shape centered on a vertical central axis C in a plan view. 1, the left side of the central axis C shows a cross section along the vertical plane including the central axis C and the load support 12, and the right side of the central axis C shows the central axis C and the current introducing portion 20. It shows a cross section along the vertical plane that it contains.

  As shown in FIG. 1, the cyclotron 1 supplies charged particles from an ion source (not shown) into the acceleration space G, accelerates the charged particles in the acceleration space G, and outputs a charged particle beam. It is a circular accelerator. Examples of charged particles include protons and heavy particles (heavy ions). The cyclotron 1 is used, for example, as an accelerator for charged particle beam therapy.

  The cyclotron 1 includes a superconducting electromagnet device 5 in addition to the ion source. The superconducting electromagnet device 5 has poles 3 and 4, a yoke 6, superconducting coils 7 and 8, a coil support frame (coil support) 9, and a vacuum vessel 10.

  The poles 3 and 4 are spaced apart in the central axis line of the superconducting coils 7 and 8 (central axis of winding of the superconducting coils 7 and 8) C. The cyclotron 1 is used by being disposed so that the central axis C is vertical. The pole 3 is an upper pole disposed above the acceleration space G, and the pole 4 is a lower pole disposed below the acceleration space G. Further, an electrode (di electrode, not shown) is provided between the poles 3 and 4. By applying a high frequency to this electrode, an electric field is formed.

  The yoke 6 is a hollow disk-shaped block, in which the poles 3 and 4 and the vacuum vessel 10 are disposed. The yoke 6 is for preventing the lines of magnetic force generated by the superconducting coils 7 and 8 and the poles 3 and 4 from leaking to the outside.

  The upper superconducting coil 7 is wound around the central axis C so as to cover the outer periphery of the pole 3, and the lower superconducting coil 8 is wound so as to cover the outer periphery of the pole 4. The superconducting coil 7 and the superconducting coil 8 are disposed side by side in the central axis C direction and accommodated in the coil support frame 9. The superconducting coils 7 and 8 have a coil body of a configuration in which a superconducting wire is wound, and a high temperature superconducting wire may be used as the superconducting wire. As the high temperature superconducting wire, an oxide superconductor (for example, Bi2223, Bi2212, Y123), MgB2 or the like may be used. A low temperature superconducting wire may be used as the superconducting wire. In the superconducting coils 7 and 8, for example, the inner frame (or the inner winding frame) is not provided on the inner peripheral side, and the inner peripheral surface of the coil (the wire and the adhesive for fixing the wire) is bonded by another member -It is an air core coil which is not fixed. The coil support frame 9 is fixed to and supported by the yoke 6 via the load support 12. The load supports 12 are disposed at, for example, four locations in the circumferential direction around the central axis C.

  The vacuum vessel 10 communicates with the coil accommodating portion 10a extending annularly around the central axis C, the cylindrical support accommodating portion 10b communicating with the coil accommodating portion 10a and extending vertically, and the coil accommodating portion 10a. And a cylindrical electrode storage portion 10c extending upward. The superconducting coils 7 and 8 attached to the coil support frame 9 are accommodated in the coil accommodating portion 10a. The load support 12 described above is accommodated in the support accommodating portion 10 b. The electrode accommodating portion 10 c accommodates a current introducing portion 20 for introducing a current to the superconducting coils 7 and 8 from the outside. The cyclotron 1 is provided with a pair of positive and negative current introducing parts 20, but only one of the current introducing parts 20 appears on the cross section of FIG. Since the pair of current introducing units 20 have the same configuration, in the following, only the configuration of one current introducing unit 20 is shown and described in each drawing, and the overlapping description is omitted.

  Further, a refrigerator 13 for cooling the superconducting coils 7 and 8 is connected to the vacuum vessel 10. The refrigerator 13 is, for example, a GM refrigerator, and can cool the superconducting coils 7 and 8 to, for example, 4K. The refrigerator is not limited to the GM refrigerator (Gifford-McMahon cooler), and may be, for example, a Stirling refrigerator or another refrigerator.

  An input terminal 15 for introducing a current is provided on the upper surface of the electrode housing portion 10 c so as to be exposed to the outside of the vacuum vessel 10. The current introducing unit 20 includes a superconducting lead structure 25 for guiding current to the superconducting coils 7 and 8, and a copper plate 23 for connecting the superconducting lead structure 25 and the input terminal 15. The current input from the external power source through the input terminal 15 is sent to the superconducting coils 7 and 8 through the copper plate 23 and the superconducting lead structure 25. A part of the superconducting lead structure 25 is housed inside the heat shield cylinder 27. The heat shield cylinder 27 is housed in the electrode housing portion 10c, and has a cylindrical shape extending to a position halfway along the electrode housing portion 10c. The heat shield cylinder 27 is connected to a low temperature head (not shown) of the refrigerator 13, and the heat shield cylinder 27 is cooled to about 50K. The heat shield cylinder 27 is made of, for example, copper.

  Subsequently, the superconducting lead structure 25 will be described with reference to FIGS. 2 and 3. The superconducting lead structure 25 has a first electrode block 31 (first electrode) provided on a current path, a second electrode block 32 (second electrode), and a superconducting lead 35. . The superconducting lead structure 25 further includes a vertical support 37. The upper end of the first electrode block 31 is connected to the lower end of the copper plate 23 described above. The lower end portion of the second electrode block 32 is connected to the superconducting coils 7 and 8 through other electrodes. The first electrode block 31 and the second electrode block 32 are made of copper and have a square shape in plan view. The first electrode block 31 and the second electrode block 32 are connected by a vertical support post 37 made of stainless steel. The superconducting lead 35 extends parallel to the vertical support column 37, is bridged between the first electrode block 31 and the second electrode block 32, and electrically connects the first electrode block 31 and the second electrode block 32. doing. The superconducting lead 35 is made of a superconducting material such as bismuth.

  The superconducting lead 35 is preferably in the form of a thin plate and relatively low in mechanical strength, so it is preferable that the superconducting lead 35 be physically protected. For this reason, the superconducting lead structure 25 is provided with a lead protection portion 41 surrounding the superconducting lead 35 in the region between at least the first electrode block 31 and the second electrode block 32. The lead protection portion 41 is made of, for example, an electrically insulating material such as GFRP (glass fiber reinforced plastic). The lead protective portion 41 has a rectangular cylindrical shape extending in a direction parallel to the superconducting lead 35, and the superconducting lead 35 and the vertical support 37 are accommodated in the hollow portion of the lead protective portion 41. The upper end portion of the lead protection portion 41 is fixed to the first electrode block 31, and the inner peripheral surface of the upper end portion of the lead protection portion 41 is in contact with the outer peripheral surface of the first electrode block 31.

  As a method of fixing the lead protecting portion 41 to the first electrode block 31, as described later, it may be bolted together with other members, or an adhesive may be used. The lead protection portion 41 is formed of a combination of four heat insulating plate members 41 a fixed to four side surfaces of the first electrode block 31. Further, the lead protection portion 41 extends downward from the first electrode block 31 toward the second electrode block 32, and the lower end of the lead protection portion 41 is in a non-restraint state with respect to the second electrode block 32. . In the unconstrained state, when the second electrode block 32 is displaced in the extending direction of the superconducting lead 35, the lower end of the lead protective portion 41 follows and is not displaced, and the second electrode block 32 and the lead protective portion In this state, the lower end of 41 is independently displaceable in the extending direction of the superconducting lead 35.

  As a specific configuration of the non-restraint state, the length of the lead protection portion 41 is set such that the lower end of the lead protection portion 41 does not reach the second electrode block 32. Then, as shown in FIG. 3, when the upper end portion of the lead protection portion 41 is fixed to the first electrode block 31, the vertical direction between the lower end of the lead protection portion 41 and the upper end of the second electrode block 32 is A gap A is formed, and the lead protection portion 41 and the second electrode block 32 are not in contact with each other.

  Furthermore, the superconducting lead structure 25 includes a thermal anchor portion 43 that mediates the thermal connection between the first electrode block 31 and the thermal shield cylinder 27. The heat anchor portion 43 is made of, for example, copper. The heat anchor portion 43 is an L-shaped member, and the bottom surface of the horizontal piece of the heat anchor portion 43 is fixed to the top surface of the heat shield cylinder 27. Then, the side surface of the vertical piece of the thermal anchor portion 43 is fixed to the side surface of the first electrode block 31 via the heat insulating plate 41 a. That is, the upper end portion of the heat insulating plate 41 a is sandwiched between the thermal anchor portion 43 and the first electrode block 31. For example, the heat anchor portion 43 and the heat insulation plate 41 a are fixed to the first electrode block 31 by fastening the heat anchor portion 43 to the side surface of the first electrode block 31 with a bolt penetrating the heat insulation plate 41 a. Ru. In this case, the bolt is made of an electrically insulating material.

  With this configuration, the first electrode block 31 is cooled to a temperature (about 50 K) equivalent to that of the heat shield cylinder 27 through the heat insulating plate 41 a and the heat anchor portion 43. On the other hand, since the heat insulating plate 41a is interposed between the first electrode block 31 and the thermal anchor portion 43, the first electrode block 31 and the thermal anchor portion 43 are electrically insulated, and the superconducting coil It is avoided that the supply current to 7 and 8 leaks to the heat shield cylinder 27 side.

  The operation and effect of the superconducting lead structure 25 described above will be described.

  In the superconducting lead structure 25, the presence of the lead protection portion 41 avoids inadvertent mechanical damage to the superconducting lead 35. Further, only the upper end (one end) of the lead protection portion 41 is fixed to the first electrode block 31, and the lower end (the other end) of the lead protection portion 41 is in a non-restraint state to the second electrode block 32. With this configuration, even if the distance between the first electrode block 31 and the second electrode block 32 changes due to the thermal deformation of the superconducting lead 35, the lead protection unit 41 does not have to follow the change. Accordingly, the occurrence of thermal stress due to the difference in the thermal expansion coefficient between the lead protection portion 41 and the superconducting lead 35 is suppressed, and the possibility of damage to the superconducting lead 35 due to thermal fluctuation is reduced. In addition, since it is not necessary to consider the thermal expansion coefficient of the lead protection portion 41, the range of material selection of the lead protection portion 41 can be broadened.

  Further, since it is necessary to electrically insulate the first electrode block 31 and the thermal anchor portion 43, the upper end portion of the lead protection portion 41 is sandwiched between the first electrode block 31 and the thermal anchor portion 43. According to the configuration, since the lead protecting portion 41 doubles as the insulating material between the first electrode block 31 and the thermal anchor portion 43, the number of parts can be reduced.

  The present invention can be carried out in various forms including various modifications and improvements based on the knowledge of those skilled in the art, including the embodiments described above. Moreover, it is also possible to constitute the modification explained below using the technical matter described in the embodiment mentioned above. You may use combining the structure of each embodiment suitably.

  For example, it is not essential to form the lead protection part 41 by the four heat insulation board | plate materials 41a, and the square cylindrical lead protection part 41 may be integrally formed. In addition, a gap may be generated between the adjacent heat insulating plate members 41a.

  In addition, as an example of a configuration in which the lead protection portion 41 is in a non-restraint state with respect to the second electrode block 32, a structure as shown in FIG. 4 or FIG. That is, as shown in FIG. 4, a gap in the radial direction (direction orthogonal to the extending direction of the superconducting lead 35) between the inner peripheral surface of the lead protection portion 41 and the outer peripheral surface of the second electrode block 32. B may be formed. Further, as shown in FIG. 5, the inner peripheral surface of the lead protection portion 41 is in sliding contact with the outer peripheral surface of the second electrode block 32, and the inner peripheral surface of the lead protection portion 41 is the second electrode block 32 during thermal deformation. You may make it slide on the outer peripheral surface of. In addition, the superconducting lead structure of the present invention is not limited to a superconducting cyclotron, but is a device using another superconducting electromagnet (a deflection electromagnet of a charged particle beam therapy apparatus, a silicon single crystal by a magnetic field applied Czochralski method (MCZ) The present invention is also applicable to pulling devices and the like.

  7, 8: superconducting coil, 25: superconducting lead structure, 31: first electrode block (first electrode), 32: second electrode block (second electrode), 35: superconducting lead, 41: lead protection Part, 43: thermal anchor part, A, B: gap.

Claims (4)

A superconducting lead structure for supplying current to a superconducting coil, wherein
First and second electrodes provided on the path of the current;
A superconducting lead which is bridged between the first electrode and the second electrode and electrically connects the first electrode and the second electrode;
An insulating lead protector surrounding the superconducting lead in at least a part of a region between the first electrode and the second electrode;
The lead protection unit is
One end side is fixed to the first electrode, and the other end side is unconstrained to the second electrode ,
It further comprises a thermal anchor for cooling the first electrode,
The superconducting lead structure , wherein the one end side of the lead protection portion is in contact with the first electrode and is sandwiched between the first electrode and the thermal anchor portion .   The superconducting lead structure according to claim 1, wherein a gap is formed between the other end of the lead protection portion and the second electrode. The superconducting lead structure according to claim 1 , wherein the thermal anchor portion is in contact with the one end side of the lead protection portion . It further has a heat shield cylinder that accommodates the superconducting lead and the other end side of the lead protection unit,
The heat anchor portion has an L shape having a horizontal piece and a vertical piece, the horizontal piece is fixed to the heat shield cylinder, and the vertical piece contacts the one end side of the lead protection portion The superconducting lead structure according to claim 1.

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