KR100429777B1 - A bobbin for the superconductive magnet using the gm cryocooler - Google Patents

Abstract

The present invention relates to a bobbin for a superconducting electromagnet of a conduction cooling method that is conduction-cooled by using a GM cryogenic cooler, wherein the bobbin has an upper end and a lower end having a central insulator and one end fastened to both ends of the insulator. A bobbin made of a conductive part and having a superconducting coil wound on an outer circumferential surface thereof so that both ends thereof are fixed to one side of the edge part; Rectangle thermal capacitor is fixed to the top of the head and the top of the GM cooler at right angles; A conductive cooling rod having one end coupled to both ends of the other side of the thermal capacitor and an insulating member interposed therebetween, and the other end coupled to one side of an edge portion of the bobbin; A bead line, which is a current inlet coupled to one side of the edge portion to apply power to the bobbin from a power source; And a pair of diodes connected in parallel to the protrusions formed on the other side of the edge portion, and the bobbin according to the present invention electrically insulates the current inlet and the bobbin through a bobbin coupled to three stages of upper and lower conductive parts and a central insulating part. The thermal conductivity is improved through the thermal capacitor, the conductive cooling part, and the thermal anchor, and the mechanical strength can be improved through the pressing plate, the soldering recess, and the thermal anchor. Energy was released as thermal energy to prevent local concentration of heat.

Description

Bobbin for superconducting electromagnet using GM cooler {A BOBBIN FOR THE SUPERCONDUCTIVE MAGNET USING THE GM CRYOCOOLER}

The present invention relates to a bobbin for a conduction-cooling superconducting electromagnet that is conduction-cooled using a 4K GM (Gifford-McMahon) cryogenic chiller (hereinafter referred to as 'GM cooler'). The upper and lower conducting portions at the boundary eliminates the need for electrical insulation of the current-carrying part and the bobbin, resulting in a superconducting electromagnet with improved performance.

Superconductivity, which is a property of disappearing electrical resistance at cryogenic temperatures near 4K, is being applied to devices using high magnetic field superconducting electromagnets such as MRI and NMR. These devices mainly use expensive liquid helium as a refrigerant to generate cryogenic conditions, and use a cryogenic container that is thermally well designed / manufactured to suppress evaporation of helium. Recently, with the development of GM cooler capable of cooling below 4K, a superconducting electromagnet of conduction cooling method, which maintains superconductivity by directly cooling the bobbin of the electromagnet without using refrigerant, has been developed and applied to a small high magnetic field generating electromagnet. .

Such a conductive cooling superconducting electromagnet has the advantages of simple structure and operation method and low maintenance cost compared to the previous method using liquid helium as a refrigerant. However, there is a disadvantage that the superconducting electromagnet is vulnerable to thermal disturbance because it is placed in a vacuum and there is no refrigerant around.

In the cryogenic state, mechanical vibrations may occur because the mechanical stress is concentrated in the portion where the current flows into the superconducting electromagnet during thermal contraction of the bobbin. In addition, even when the support structure for the superconducting coil is weak, vibration due to the electromagnetic force during the excitation of the electromagnet may be generated. The mechanical vibration caused by the above causes heat to destroy the superconducting properties of the current inlet, thereby destroying the superconducting state of the whole electromagnet. In particular, since the current inlet and bobbin are electrically insulated and thus in thermal insulation, the heat generated by the mechanical vibration as described above is not eliminated in the conductive cooling superconducting electromagnet without refrigerant. Interferes with cooling, which is fatal to the superconducting state.

Furthermore, if the superconducting properties are destroyed during operation of the electromagnets, the electromagnets may be converted into phase conductors, which will release considerable heat. Conventional conduction cooling superconducting electromagnets employ a method of releasing energy generated at this time using a thermally separated diode circuit. However, the conduction cooling electromagnet has a problem that heat energy is concentrated on a part of the electromagnet so that the superconducting coil can be burned because there is no refrigerant around.

The present invention has been made to solve the problems posed by the conventional conductive cooling superconducting electromagnet as described above, the bobbin for a superconducting electromagnet using the GM cooler according to the present invention is

First, to provide a structure of the bobbin that can eliminate the difficulty of electrically insulating the current inlet and the bobbin,

Secondly, to provide a means to improve the cooling efficiency by improving the thermal conductivity of the bobbin,

Third, according to this, by directly coupling the current inlet to the bobbin to improve the mechanical strength to eliminate the generation of unnecessary thermal energy,

Fourth, to provide a means for securely fixing the superconducting coil,

Fifth, the object of the present invention is to provide a conductive means for electrically insulated from the GM cooler to the bobbin while improving electrical conductivity.

Sixth, the object of the present invention is to provide a superconducting electromagnet of the conduction cooling method with improved performance by ensuring stable operation of the electromagnet through the bobbin according to the present invention.

In order to achieve the above object, the bobbin for superconducting electromagnet using the GM cooler according to the present invention has a superconducting coil formed on the outer circumferential surface of the superconducting portion having a central insulation portion and an upper / conductive portion having one end coupled to both ends of the insulation portion and having an edge portion formed at the other end thereof. The bobbin is wound so that both ends are fixed to one side of the edge portion; Rectangle thermal capacitor is fixed to the top of the head and the top of the GM cooler at right angles; A conductive cooling rod having one end coupled to both ends of the other side of the thermal capacitor and an insulating member interposed therebetween, and the other end coupled to one side of an edge portion of the bobbin; A bead line, which is a current inlet coupled to one side of the edge portion to apply power to the bobbin from a power source; And a pair of diodes connected in parallel to the protrusions formed at the other side of the edge portion.

The thermal capacitor is formed by stacking / fixing a plurality of copper plates between upper and lower outer PI films for insulation and lower pressing plates spaced apart from each other by a certain degree, and it is preferable that the thermal capacitors are bolted through the conductive cooling rod and the flange part.

In addition, the bent wire combined with the lower edge portion is fixed by the thermal anchor at the upper edge portion and the corresponding position in order to improve the cooling and fixing effect, the insulating plate is interposed between the anchor and the upper edge portion mechanical durability And insulation can be improved.

In addition, the edges of the bobbin and the fixing of both ends of the superconducting coil are soldered to the grooves having the coil insertion holes formed in the edges to ensure reliable fixing.

1 is a perspective view showing a coupling relationship between a superconducting electromagnet bobbin and a GM cooler according to the present invention;

2 is an exploded perspective view of the bobbin of the present invention,

3 is a perspective view of a bobbin showing a groove for a superconducting coil,

4 is a perspective view illustrating a coupling relationship between a GM cooler, a thermal capacitor, and a conductive cooling rod;

5 is a schematic diagram showing a coupling relationship between a diode and a superconducting coil;

Figure 6 is a perspective view showing the flow of heat and current in the bobbin when breaking superconducting electromagnets.

<Description of Symbols for Major Parts of Drawings>

1: bobbin 3, 5: upper and lower conductive parts

3a, 5a: rim 3b, 5b: protrusion

3c, 5c: Diode coupling hole 3d, 5d: Groove for superconducting coil

3f, 5f: female thread part 7: center insulation part

7a: male thread portion 9a, 9b: ring

10: GM cooler 11: head part

20: thermal capacitor 21a, 21b: copper plate

23a, 23b: PI film 25a, 25b: pressure plate

31.33: conduction cooling rod 35, 37: electric wire

37a: thermal anchor 37b: insulation plate

39a, 39b: diode C: superconducting coil

I: current flow T: heat flow

Hereinafter, described in detail by the accompanying drawings of the present invention.

1 is a perspective view showing a coupling relationship between a superconducting electromagnet bobbin and a GM cooler according to the present invention, Figure 2 is an exploded perspective view of the bobbin of the present invention, first the bobbin 1 according to the present invention for mechanical strength and electrical insulation Oxygen-free copper having excellent thermal conductivity in the vicinity of the center insulation portion 7 made of a material such as FRP, and 4K having one end fastened to both ends of the insulation portion 7 and the edge portions 3a and 5a formed at the other end. It is composed of three stages consisting of upper and lower conductive parts 3 and 5 made of a material such as tough pitch copper and aluminum. Fastening of the insulating portion 7 and the conductive portion 3, 5 is preferably screwed through the female screw portion (3f, 5f) and the male screw portion (7a) as shown in FIG. In addition, between the insulating part 7 and the conductive part 3, 5, rings 9a and 9b made of metal having high thermal conductivity and ductility (for example, indium (In), lead, and aluminum) are provided to improve thermal contact. It is more preferable to interpose.

A superconducting coil C (refer to FIG. 5) is wound around the outer circumferential surface of the three-stage coupled bobbin 1 so that both ends thereof are fixed to one side of the edge portions 3a and 5a. As shown in FIG. 3, the superconducting coil C and the bobbin 1 are fixed to the insertion holes 3e and 5e of the grooves 3d and 5d formed in the edge portions 3a and 5a of the bobbin 1. Both ends of the coil C are preferably inserted into and soldered to each other.

Next, the components for improving the conduction cooling of the bobbin 1 through the GM cooler 10 are composed of a thermal capacitor 20 and a conduction cooling rods 31 and 33. The thermal capacitor 20 has a rectangular shape in which the lower end of the head portion 11 and the upper end of one side of the GM cooler 10 are orthogonally fixed. As shown in FIG. 4, the thermal capacitor 20 has a top and bottom outer PI (polyimide) film (for example, Kapton ^{R manufactured by} DuPont) arranged below to thermally connect and electrically insulate. ) Film) (23a, 23b) and copper plate (21a, 21b) is preferably laminated between the lower pressing plate (25a, 25b) made of the same material spaced apart from each other to some extent, conductive cooling rod It can be firmly fixed to the bolt (B) through the (31, 33) and its flanges (31a, 33a). The structure of the pressure plates 25a and 25b spaced apart is to improve thermal conductivity by firmly pressing the stacked thermal capacitors 20 with the upper and lower conductive cooling rods 31 and 33 and the bolts B. If the height of 20) and the gap between the flanges 31a and 33a of the conductive cooling rods 31 and 33 do not coincide, the compression of the thermal capacitor 20 is difficult, so the thermal capacitor is separated into two parts and the vertical conductive cooling rod is separated. (31,33) The flanges 31a, 33a are pressed / fixed through the pressing plates 25a, 25b and the bolts B. FIG. However, it is apparent that such a shape may be a thermal capacitor laminated in one layer, but not in a separate structure. Meanwhile, the thermal capacitor 20 may also be fixed to the head portion 11 of the GM cooler 10 with a bolt (B).

In FIG. 1, the conductive cooling rods 31 and 33 conducting the cold air of the GM cooler 10 from the thermal capacitor 20 to the bobbin 1 may be formed at both ends of the other side of the thermal capacitor 20 and the insulating members 23a,. One end is coupled while the other end is in contact with 23b), and the other end is coupled to one side of the edge portions 3a and 5a of the bobbin 1. The conductive cooling rods 31 and 33 may be anoxic copper having high conductivity, tough pitch copper, or aluminum rod.

Meanwhile, in FIG. 1, the power inlet for applying power to the bobbin 1 from the power source is coupled to one side of the bobbin 1 edges 3a and 5a and in the drawing a side away from the cooling rods 31 and 33. Bead lines 35 and 37. The bead lines 35 and 37 and the solder grooves 3d and 5d to which the superconducting coils C are fixed are connected together. Preferably, the lead wire 37 coupled to the lower edge portion 5a is fixed by the thermal anchor portion 37a and a thermal anchor 37a at a corresponding position to improve the cooling and fixing effect. It is good. In the case where the anchor 37a is a metal material which is excellent in thermal conductivity and is an electrical conductor such as oxygen-free copper, the anchor 37a and the upper edge portion (to prevent a short circuit from the upper edge portion 3a) It is preferable that the insulating plate 37b is interposed between 3a).

1 and 5, a pair of diodes are provided on the protrusions 3b and 5b formed on the other side of the edge portions 3a and 5a so as to be conducted when the electromagnets are broken and bypass electric current to release electrical energy. 39a and 39b are connected in parallel. As shown in FIG. 3, coupling holes 3c and 5c for diodes are formed in the protrusions 3b and 5b of the edge portions 3a and 5a.

Referring to the operation and effects of the conductive cooling superconducting electromagnet of the present invention described above are as follows.

The bobbin 1 according to the present invention is composed of a central insulation portion 7 and three ends conductive parts 3 and 5 separated in three stages, and the bobbin 1 has both ends conductive parts 3 and 5 drawing power and current. It is electrically connected through the densely sealed wires 35 and 37, but is electrically bisected through the central insulator 7. Both ends of the superconducting coil C wound on the bobbin 1 are electrically connected to the soldering recesses 3d and 5d of the bobbin. The bobbin (1) conduction portion (3,5) can act as a current inlet, while mechanically fixing both ends of the superconducting coil (C) through the groove (3d, 5d) and the insertion hole (3e, 5e). In addition, the bobbin 1 has a thermally strong binding force through the GM cooler 10, the thermal capacitor 20, and the conductive cooling parts 31 and 33, and thus the superconducting coil C and the bead lines 35 and 37. The thermal bond is also strengthened. Since the lead wire 37 is mechanically and thermally strengthened through the thermal anchor 37a and electrically insulated from the upper edge portion 3 through the insulating plate 37b, the bobbin 1 has a very high thermal conductivity as a whole. It is in an improved state, and thus the conduction cooling efficiency is excellent.

The superconducting electromagnet is cooled to 4K or less by the GM cooler 10 and enters the superconducting state. When the GM cooler 10 is operated, the bobbin (1) and the current inlet coupled to the bobbin (1) are electrically cooled by conduction cooling. Wires 35 and 37 and diodes 39a and 39b are cooled to cryogenic temperatures. The heat of each component is discharged to the outside through the thermal capacitor 20 and the conductive cooling parts 31 and 33. In particular, the thermal capacitor 20 of the present invention is manufactured by stacking thin copper plates 21a and 21b to facilitate coupling and not to apply stress to the head of the GM cooler 10 during heat shrinkage.

When the superconducting electromagnet enters the superconducting state after cooling for several tens of hours, a current is applied to the rods 35 and 37 which are current inlets. At this time, the superconducting magnet is operated below the forward voltage of the diode to prevent conduction of current to the diodes 39a and 39b. The diodes 39a and 39b are coupled in parallel with the superconducting coil C (see Fig. 5), and do not conduct current at a voltage below the forward voltage.

If the superconducting electromagnet is separated from the superconducting state due to mechanical vibration or abnormal operation of the GM cooler 10, a part of the superconducting electromagnet becomes a phase conduction state, and the electromagnet generates a voltage exceeding the forward voltage of the diode. . At this time, the diodes 39a and 39b are turned on, bypassing the current flowing through the electromagnet, and converting electrical energy into thermal energy. At this time, as indicated by the dotted arrow (I) in Figure 6, since the diode is located in the opposite direction to the lead wires (35, 37) as the current inlet, the current (I) is the bobbin (1) through the conductive portion (3) 5) to flow across. Since the electrical resistance exists in the conductive parts 3 and 5 of the bobbin 1 made of oxygen-free copper, heat is generated by the current. This heat generation diffuses through the bobbin 1 as indicated by the solid line arrow T in FIG. 6, thereby preventing the concentration of thermal energy in the local part of the electromagnet.

As described above, the bobbin for a superconducting electromagnet using the GM cooler according to the present invention

First, it eliminates the difficulty of electrically insulating the current inlet and the bobbin through the bobbin coupled to the upper and lower conductive parts and the central insulator.

Secondly, through the thermal capacitor, conduction cooling unit, and thermal anchor, the cooling efficiency was improved by improving the thermal conductivity not only of the bobbin itself but also of the bobbin and GM cooler.

Thirdly, the mechanical strength of the entire bobbin is improved through the pressing plate, the soldering recess, and the thermal anchor, eliminating unnecessary heat energy.

Fourth, through the pressing plate, PI film, insulation plate, central insulation, and ring, the insulation between the components of bobbin and between bobbin and GM cooler is improved while also electrically insulating.

Sixth, it is electrically connected in parallel with the bobbin, and unlike the conventional diode, it bypasses the current at the time of breakdown through the thermally connected diode to prevent the local concentration of heat by releasing electrical energy as thermal energy.

Seventh, in the end, through the bobbin according to the present invention by forcibly conducting heat to prevent the concentration of heat at the initial point of destruction when the breakdown caused by various causes to prevent the burning of the electromagnet can ensure stable operation of the electromagnet and performance This improved conduction cooling superconducting electromagnet can be provided.

Claims (5)

A superconducting coil (C) is formed on the outer circumferential surface of the central insulator 7 and the upper / conductive units 3 and 5 having one end fastened to both ends of the insulator 7 and having edges 3a and 5a formed at the other end thereof. Bobbin (1) is wound so that both ends are fixed to one side of the edge portion (3a) (5a); A rectangular thermal capacitor 20 in which the lower end of the head portion 11 of the GM cooler 10 and one upper end thereof are orthogonally fixed; Conduction cooling rods 31 and 33 having one end coupled to both ends of the other side of the thermal capacitor 20 and an insulating member interposed therebetween and the other end coupled to one side of the edge portions 3a and 5a of the bobbin 1; Bead lines 35 and 37 which are current inlets coupled to one side of the edge portions 3a and 5a to apply power to the bobbin 1 from a power source; And Bobbin for a superconducting electromagnet using a GM cooler comprising a pair of diodes (39a, 39b) connected in parallel to the protrusions (3b, 5b) formed on the other side of the edge (3a, 5a). The method of claim 1, Superconductivity using a GM cooler, characterized in that the ring (9a, 9b) for enhancing the thermal contact is interposed between the central insulator (7) of the bobbin (1) and the upper and lower conductive parts (3) (5) Bobbins for electromagnets. The method of claim 1, The thermal capacitor 20 is formed by stacking / fixing a plurality of copper plates 21a and 21b between upper and lower outer PI films 23a and 23b for insulation and lower press plates 25a and 25b spaced apart from each other by a certain degree. Bobbins for superconducting electromagnets using a GM cooler, characterized in that they are fixed by bolts (B) through conduction cooling rods (31, 33) and flanges (31a, 33a). The method according to any one of claims 1 to 3, The lead wire 37 coupled with the lower edge portion 5a is fixed by the thermal anchor 37a at the upper edge portion 3a and the corresponding position to improve the cooling and fixing effect. Bobbins for superconducting electromagnets using a GM cooler, characterized in that an insulating plate (37b) is interposed between the top border (3a). The method of claim 1, The edges 3a and 5a of the bobbin 1 and the ends of the superconducting coils C are fixed to grooves 3d and 5d having coil insertion holes 3e and 5e formed in the edges 3a and 5a. Bobbins for superconducting electromagnets using a GM cooler, characterized by being soldered.