JPH0529137A - Superconducting electromagnet - Google Patents

Superconducting electromagnet

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Publication number
JPH0529137A
JPH0529137A JP3184946A JP18494691A JPH0529137A JP H0529137 A JPH0529137 A JP H0529137A JP 3184946 A JP3184946 A JP 3184946A JP 18494691 A JP18494691 A JP 18494691A JP H0529137 A JPH0529137 A JP H0529137A
Authority
JP
Japan
Prior art keywords
superconducting
coil
resistor
resistance
ring
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP3184946A
Other languages
Japanese (ja)
Inventor
Takaaki Bono
敬昭 坊野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fuji Electric Co Ltd
Original Assignee
Fuji Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fuji Electric Co Ltd filed Critical Fuji Electric Co Ltd
Priority to JP3184946A priority Critical patent/JPH0529137A/en
Publication of JPH0529137A publication Critical patent/JPH0529137A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/02—Quenching; Protection arrangements during quenching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)

Abstract

PURPOSE:To obtain a superconducting electromagnet providing a protection resistor which reliably protects a permanent current switch and makes small a time constant of current attenuation for urgent demagnetization by connecting in series a diode to a protective resistor and then thermally and approximately providing a protective resistor in the side of external diameter of at least a pair of ring coils. CONSTITUTION:A main coil 1 consisting of a plurality of ring coils 11A to 13B which are coaxially and symmetrically provided in the axial direction, a superconducting coil formed by an active shield 10 consisting of a plurality of ring coils 14A to 15B which are coaxially and symmetrically provided in the axial direction in the side of external diameter of the main coil 1 and a protective resistor 3 which is connected in parallel with the superconducting coil are housed within a low temperature housing. In such a superconducting electromagnet, a diode 8 is connected in series with the protective resistor 3 with the a positive voltage side during activation connected in the positive pole side and a protective resistor 3 is provided thermally and approximately in the external diameter side of at least a pair of ring coils 14A, 14B. For example, the protective resistor 3 is formed by a metal thin film of the predetermined shape.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】この発明は、医療診断装置である
核磁気共鳴装置（以下、ＭＲＩ装置と略称する）の超電
導電磁石、特に漏れ磁場を超電導コイルで打ち消す方式
であるアクティブシールド形超電導電磁石に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting electromagnet of a nuclear magnetic resonance apparatus (hereinafter abbreviated as MRI apparatus) which is a medical diagnostic apparatus, and more particularly to an active shield type superconducting electromagnet which is a method of canceling a leakage magnetic field with a superconducting coil. .

【０００２】[0002]

【従来の技術】超電導電磁石が超電導状態を維持するた
めには、温度、電流及び発生磁束密度の三要素から制限
を受け、その臨界点はそれぞれ臨界温度、臨界電流及び
臨界磁束密度と呼ばれている。この３種類の臨界点以下
にある場合に限り超電導状態が維持されるが、このうち
の１つでも臨界点を越えてしまうと超電導状態から常電
導状態へと転移してしまう。この超電導状態から常電導
状態へのに転移は一般にクエンチと呼ばれている。2. Description of the Related Art In order for a superconducting electromagnet to maintain a superconducting state, it is limited by three factors of temperature, current and generated magnetic flux density, and its critical points are called critical temperature, critical current and critical magnetic flux density, respectively. There is. The superconducting state is maintained only when the temperature is below these three types of critical points, but if even one of the critical points exceeds the critical point, the superconducting state transitions to the normal conducting state. The transition from the superconducting state to the normal conducting state is generally called quench.

【０００３】超電導電磁石を励磁中、巻線に発生磁束密
度と励磁電流との積に比例した電磁力がかかり、巻線の
変位により摩擦熱が発生し臨界温度を越えてしまうなど
種々の原因によりクエンチが発生する。その際、超電導
電磁石に蓄積された磁気エネルギーはジュール熱として
放出され、大量の冷媒の蒸発を引き起こす。また、前述
のジュール熱のために超電導電磁石を構成する超電導線
材の温度が上昇し、焼損する恐れもある。このような理
由で、クエンチは超電導電磁石にとって有害なものであ
ることはよく知られている。While exciting the superconducting electromagnet, an electromagnetic force proportional to the product of the generated magnetic flux density and the exciting current is applied to the winding, frictional heat is generated due to the displacement of the winding, and the temperature exceeds the critical temperature. Quench occurs. At this time, the magnetic energy accumulated in the superconducting electromagnet is released as Joule heat, causing evaporation of a large amount of refrigerant. Moreover, the temperature of the superconducting wire forming the superconducting electromagnet may rise due to the Joule heat described above, and there is a risk of burning. For this reason, it is well known that quench is harmful to superconducting electromagnets.

【０００４】超電導電磁石は、クエンチ時に電磁石に蓄
えられた磁気エネルギーをジュール熱として放出する
が、この際、超電導線材の焼損を防ぐために電磁石と並
列に保護用の抵抗を挿入し、磁気エネルギーの一部をこ
の保護抵抗で消費させて、超電導線の温度が許容温度以
下になるような方式が採用されている。この保護抵抗
は、一般に超電導電磁石を収納している低温容器の外部
に設置されるが、近年実用されているＭＲＩ装置や磁気
浮上列車などに使用されている超電導電磁石はいわゆる
永久電流モードで超電導電磁石が運転されるため、低温
容器外に設置することが難しい。特に、ＭＲＩ装置の超
電導電磁石では極低温冷媒の液体ヘリウムの蒸発量をで
きるだけ少なくするために、通常の永久電流モードでは
電流リードも除去されて運転される。このような状態で
運転される超電導電磁石における保護抵抗は必然的に低
温容器内に設置する構成が採用される。The superconducting electromagnet releases the magnetic energy stored in the electromagnet as Joule heat at the time of quenching. At this time, a protective resistor is inserted in parallel with the electromagnet to prevent burning of the superconducting wire, and the A system is adopted in which the temperature of the superconducting wire becomes lower than the allowable temperature by consuming the part with this protective resistance. This protective resistance is generally installed outside the cryogenic container that houses the superconducting electromagnet, but the superconducting electromagnet used in recent years such as MRI devices and magnetic levitation trains is a so-called permanent current mode superconducting magnet. Since it is operated, it is difficult to install it outside the cryogenic container. In particular, in the superconducting electromagnet of the MRI apparatus, in order to reduce the evaporation amount of liquid helium of the cryogenic refrigerant as much as possible, the current lead is also removed and operated in the normal permanent current mode. The protective resistance in the superconducting electromagnet which is operated in such a state is necessarily installed in the cryogenic container.

【０００５】超電導電磁石を用いたＭＲＩ装置では、広
い空間に高い磁場を安定に発生できる利点がある。一
方、ＭＲＩ装置の周囲に広がる漏れ磁場の範囲も大きい
という問題もある。この漏れ磁場を低減する方式とし
て、超電導電磁石を強磁性の磁気シールドで覆って漏れ
磁場を吸収させるセルフシールドと称されている方式
と、反対方向に電流を流す超電導コイルを外径側に設け
て漏れ磁場の漏れ出しを抑制するアクティブシールドと
称される方式とがある。アクティブシールド方式の超電
導電磁石はセルフシールド方式に比べて軽量であるとい
う長所があり、均一磁場を主に生成する超電導コイルは
主コイル、シールド作用を持たせる超電導コイルはアク
ティブシールドと称されており、これら超電導コイルは
同じ低温容器に収納される。An MRI apparatus using a superconducting electromagnet has an advantage that a high magnetic field can be stably generated in a wide space. On the other hand, there is a problem that the range of the leakage magnetic field spread around the MRI apparatus is large. As a method of reducing this leakage magnetic field, a method called a self-shield that absorbs the leakage magnetic field by covering the superconducting electromagnet with a ferromagnetic magnetic shield, and a superconducting coil that flows current in the opposite direction are provided on the outer diameter side. There is a method called an active shield that suppresses leakage of a leak magnetic field. The superconducting electromagnet of the active shield method has the advantage that it is lighter than the self-shielding method, the superconducting coil that mainly generates a uniform magnetic field is called the main coil, and the superconducting coil that has a shielding effect is called the active shield. These superconducting coils are stored in the same low temperature container.

【０００６】図５はアクティブシールド形超電導電磁石
の断面図である。この図において、図示のｚ方向が対称
軸の方向であり、この図はこの対称軸を含む面による断
面図である。主コイル１は巻枠４１に、アクティブシー
ルド１０は巻枠４２に巻回されており、巻枠４１と巻枠
４２の両側を側板４３で、巻枠４２の外径側を外枠４４
でそれぞれ覆うことによって液体ヘリウム容器としての
低温容器４が構成されている。液体ヘリウムを冷却媒体
とした超電導コイルが収納され極低温に保持されるため
の容器は一般にクライオスタットと呼ばれている。この
クライオスタットは低温容器４を最内容器とし、図示し
ない真空容器を最外層容器として、この真空容器と低温
容器４の間の空間が真空に保持されるとことによって魔
法瓶と同じ原理によって低温容器４への外部空間からの
熱侵入を最小にする構成が採用されている。真空容器や
真空容器と低温容器４との間には熱絶縁層が設けられる
がこの図ではそれも省略してある。FIG. 5 is a sectional view of an active shield type superconducting electromagnet. In this figure, the z direction shown is the direction of the axis of symmetry, and this figure is a cross-sectional view taken along a plane including this axis of symmetry. The main coil 1 is wound around the winding frame 41, and the active shield 10 is wound around the winding frame 42. The both sides of the winding frame 41 and the winding frame 42 are side plates 43, and the outer diameter side of the winding frame 42 is the outer frame 44.
The low temperature container 4 as a liquid helium container is constituted by covering each of them with. A container for accommodating a superconducting coil using liquid helium as a cooling medium and maintaining it at a cryogenic temperature is generally called a cryostat. In this cryostat, the cryogenic container 4 is the innermost container, the vacuum container (not shown) is the outermost layer container, and the space between the vacuum container and the cryogenic container 4 is maintained in vacuum. A configuration is adopted that minimizes heat ingress to the exterior space. Although a heat insulating layer is provided between the vacuum container and the vacuum container and the low temperature container 4, it is also omitted in this figure.

【０００７】主コイル１は軸方向に対称な３対のリング
コイルからなっている。リングコイル１１Ａと１１Ｂ、
１２Ａと１２Ｂ、１３Ａと１３Ｂとがそれぞれ対称であ
り、アクティブシールド１０も同様に２対のリングコイ
ル１４Ａと１４Ｂ、１５Ａと１５Ｂとからなっている。
ＭＲＩ装置では高度に均一な静磁場としての均一磁場５
の生成が要求されるので、このように複数のリングコイ
ル対の寸法、巻数及び配置を適切に設定することによ
り、数ppm という高度な均一性を確保することのできる
超電導電磁石とすることが可能になる。The main coil 1 is composed of three pairs of ring coils which are symmetrical in the axial direction. Ring coils 11A and 11B,
12A and 12B and 13A and 13B are symmetrical, and the active shield 10 is also composed of two pairs of ring coils 14A and 14B and 15A and 15B.
In the MRI device, a uniform magnetic field as a highly uniform static magnetic field 5
Therefore, it is possible to obtain a superconducting electromagnet that can secure a high degree of uniformity of several ppm by appropriately setting the dimensions, number of turns, and arrangement of multiple ring coil pairs in this way. become.

【０００８】主コイル１とアクティブシールド１０との
磁気能率の絶対値を一致させ方向を逆にすると、外部に
漏れ出す磁場を最小にできることが知られており、実際
にコイルに電流を流して漏れ磁場が外部に漏れださない
ようにすることから、磁気シールドとして使用されるコ
イルのことを前述のようにアクティブシールドと呼ばれ
ている。It is known that when the absolute values of the magnetic efficiencies of the main coil 1 and the active shield 10 are made to coincide with each other and the directions thereof are reversed, the magnetic field leaking to the outside can be minimized. A coil used as a magnetic shield is called an active shield as described above because the magnetic field does not leak outside.

【０００９】保護抵抗２は巻枠４１の凸部に取付けられ
た支持具８に支持されて主コイル１とアクティブシール
ド１０との間の空間に配置されている。この空間は均一
磁場５を形成する磁束の殆どが戻りに通る磁気回路にな
っていて、構造物を収納するために設けられた空間では
ないので、この空間を利用して保護抵抗２を始め永久電
流スイッチ６もこの空間に配置する構成が採用されてい
る。The protective resistor 2 is supported by a supporting member 8 attached to the convex portion of the winding frame 41 and is arranged in the space between the main coil 1 and the active shield 10. Since this space is a magnetic circuit through which most of the magnetic flux forming the uniform magnetic field 5 passes back, and is not a space provided for housing the structure, the space is used to start the protective resistance 2 and the permanent resistance. The current switch 6 is also arranged in this space.

【００１０】保護抵抗２の抵抗値、吸収すべき熱容量な
どの仕様値は超電導電磁石や後述の永久電流スイッチの
仕様から決定される。実際に使用される材料や寸法の選
択はこの仕様値から決められる。アクティブシールド１
０が設けられない超電導電磁石の場合に比べてアクティ
ブシール形超電導電磁石が蓄積する磁気エネルギーは大
きい値になるので、超電導コイルが通電中に超電導状態
から常電導状態に転移する現象であるクエンチが生じた
ときに解放されるエネルギーが大きいことから、このエ
ネルギーを吸収するための保護抵抗２の熱容量も大きい
ものが必要である。そのため、図示のように保護抵抗２
の軸方向寸法を主コイル１の軸方向寸法に近い寸法まで
大きくとってある。Specification values such as the resistance value of the protective resistor 2 and the heat capacity to be absorbed are determined from the specifications of the superconducting electromagnet and the permanent current switch described later. The selection of the materials and dimensions actually used is determined from this specification value. Active shield 1
Since the magnetic energy accumulated in the active seal type superconducting magnet has a larger value than in the case of the superconducting magnet in which 0 is not provided, quenching, which is a phenomenon in which the superconducting coil transitions from the superconducting state to the normal conducting state, occurs during energization. Since the energy released when the energy is released is large, the heat capacity of the protective resistor 2 for absorbing this energy is also required to be large. Therefore, the protection resistor 2
The axial dimension of the main coil 1 is increased to a dimension close to the axial dimension of the main coil 1.

【００１１】図６は図５に示したアクティブシールド形
超電導電磁石の回路図である。この図において、主コイ
ル１とアクティブシールド１０とは直列接続されて永久
電流スイッチ６で両端が短絡されている。主コイル１を
構成するリングコイル１１Ａ，１２Ａ，１３Ａ, １１
Ｂ，１２Ｂ，１３Ｂ、及びアクティブシールド１０を構
成するリングコイル１４Ａ, １５，１４Ｂ，１５Ｂには
それぞれ保護抵抗２１Ａ, ２２Ａ，２３Ａ，２４Ａ，２
１Ｂ，２２Ｂ，２３Ｂ，２４Ｂが並列接続されている。
ただ、リングコイル１１Ａと１２Ａをまとめて１つの保
護抵抗２１Ａが、同様にしてリングコイル１１Ｂと１２
Ｂとをまとめて保護抵抗２１Ｂがそれぞれ並列接続され
ている。FIG. 6 is a circuit diagram of the active shield type superconducting electromagnet shown in FIG. In this figure, the main coil 1 and the active shield 10 are connected in series, and both ends of the permanent current switch 6 are short-circuited. Ring coils 11A, 12A, 13A, 11 constituting the main coil 1
B, 12B, 13B and ring coils 14A, 15, 14B, 15B forming the active shield 10 have protective resistors 21A, 22A, 23A, 24A, 2 respectively.
1B, 22B, 23B and 24B are connected in parallel.
However, the ring coils 11A and 12A are combined into one protection resistor 21A, and the ring coils 11B and 12A are similarly arranged.
The protection resistors 21B are collectively connected in parallel with B.

【００１２】このように保護抵抗２を分割した保護抵抗
２１Ａ, ２２Ａ，２３Ａ，２４Ａ，２１Ｂ，２２Ｂ，２
３Ｂ，２４Ｂをそれぞれ対応するリングコイルに並列に
接続する回路構成は、１つのリングコイルにクエンチが
発生した場合、そのリングコイルの電流のみが並列接続
されている保護抵抗に分流するため、クエンチ時に発生
する電圧やリングコイル内部の温度を低く抑えることが
可能になるという利点がある。The protective resistors 21A, 22A, 23A, 24A, 21B, 22B, 2 obtained by dividing the protective resistor 2 in this way are described.
In the circuit configuration in which 3B and 24B are connected in parallel to the corresponding ring coils, respectively, when a quench occurs in one ring coil, only the current of the ring coil is shunted to the protection resistor connected in parallel. There is an advantage that the generated voltage and the temperature inside the ring coil can be kept low.

【００１３】超電導電磁石を励磁する際には、永久電流
スイッチ６を「開」の状態にして電流リード７１，７２
を介して図示しない直流電源によって直流電圧を印加
し、この電圧と主コイル１とアクティブシールド１０を
包含した超電導電磁石の自己インダクタンスとで決まる
上昇速度で電流を上昇させる。定格電流になったところ
で電圧を零にするとともに永久電流スイッチ６を「閉」
にする。主コイル１、アクティブシールド１０、永久電
流スイッチ６とこれらを接続するリードは全て超電導線
からなっているので、これらで形成する閉回路の抵抗が
実質的に零になることから、この閉回路を流れる電流は
数年の長い期間にわたって流れ続ける。このような状態
は永久電流モードと呼ばれており、閉回路を形成するた
めのスイッチは前述のように永久電流スイッチと呼ばれ
ている。電流リード７１，７２は永久電流スイッチ６を
「閉」にした後取り外されるようになっている。When exciting the superconducting electromagnet, the permanent current switch 6 is set to the "open" state and the current leads 71, 72 are placed.
A DC voltage is applied from a DC power source (not shown) via the, and a current is increased at a rate of increase determined by this voltage and the self-inductance of the superconducting electromagnet including the main coil 1 and the active shield 10. When the rated current is reached, the voltage is set to zero and the permanent current switch 6 is closed.
To Since the main coil 1, the active shield 10, the permanent current switch 6 and the leads connecting them are all made of superconducting wire, the resistance of the closed circuit formed by them becomes substantially zero. The flowing current continues to flow for a long period of several years. Such a state is called a persistent current mode, and the switch for forming the closed circuit is called a persistent current switch as described above. The current leads 71 and 72 are designed to be removed after the permanent current switch 6 is closed.

【００１４】図７は保護抵抗２の右半分の斜視図であ
り、この図は厚さ寸法を誇張して図示してある。この図
において、保護抵抗２は図の左右の方向が超電導電磁石
の軸方向に、上下の方向が周方向になるように配置され
る。したがって、超電導電磁石内に組み込まれた保護抵
抗２は図のθ方向に断面が湾曲した形状になっている。
図５の保護抵抗２の断面は図７のＣ−Ｃ断面を表してあ
る。FIG. 7 is a perspective view of the right half of the protective resistor 2, which is exaggerated in the thickness dimension. In this figure, the protection resistors 2 are arranged so that the left and right directions in the figure are the axial direction of the superconducting electromagnet and the up and down directions are the circumferential direction. Therefore, the protection resistor 2 incorporated in the superconducting electromagnet has a cross section curved in the θ direction in the figure.
The cross section of the protective resistor 2 of FIG. 5 represents the CC cross section of FIG. 7.

【００１５】保護抵抗２は０．２mm程度の薄いステンレ
ス板を両側から切れ目を入れて波状に形成され適当な位
置から端子２５，２６，２７，２８，２９が引き出され
ている。端子２５と２６の間が保護抵抗２１Ａになり、
同じようにして、端子２６，２７間が単位保護抵抗２２
Ａ、端子２７，２８間が単位保護抵抗２３Ａ、端子２
８，２９間が単位保護抵抗２４Ａとなっている。それぞ
れの単位保護抵抗の抵抗値はそれぞれの端子の引き出し
位置によって決まることになる。電流の流れる方向は主
に図の上下方向になるので、隣同士の板には反対方向の
電流が流れることから自己インダクタンスの小さな構成
となっている。The protective resistor 2 is formed by corrugating a thin stainless steel plate having a thickness of about 0.2 mm from both sides, and terminals 25, 26, 27, 28 and 29 are drawn out from appropriate positions. Between the terminals 25 and 26 becomes the protection resistor 21A,
Similarly, the unit protection resistor 22 is provided between the terminals 26 and 27.
A, unit protection resistor 23A between terminals 27 and 28, terminal 2
A unit protection resistor 24A is provided between 8 and 29. The resistance value of each unit protection resistor is determined by the lead position of each terminal. Since the current flows mainly in the vertical direction in the figure, the current flows in the opposite direction to the adjacent plates, so that the self-inductance is small.

【００１６】保護抵抗２の抵抗値やジュール熱を吸収す
るための熱容量などの値は、超電導電磁石や永久電流ス
イッチの仕様値によって決定され、これに基づいて使用
材料やその寸法が決定される。一般には前述のような材
料と厚さのものが使用されることが多い。ちなみに、そ
れぞれの抵抗値などの概数は、永久電流スイッチ６が
「開」のときの抵抗値が約２０Ω、保護抵抗２が約０．
２Ω、常電導状態に変移したときの超電導コイル１００
が約１０Ωである。また、超電導コイル１００の自己イ
ンダクタンスは約２０Ｈである。Values such as the resistance value of the protective resistor 2 and the heat capacity for absorbing Joule heat are determined by the specification values of the superconducting electromagnet and the persistent current switch, and the materials used and the dimensions thereof are determined based on the specifications. In general, the materials and thicknesses described above are often used. By the way, the approximate values such as the resistance values are about 20Ω when the permanent current switch 6 is “open” and about 0.
2Ω, superconducting coil 100 when transitioned to normal conducting state
Is about 10Ω. The self-inductance of the superconducting coil 100 is about 20H.

【００１７】図８は超電導電磁石の励磁時の回路図であ
り、超電導電磁石は図６のそれに比べて簡略化して表示
してある。この図において、リングコイル、保護抵抗と
もに直列接続されているので、それぞれ構成された超電
導コイル、保護抵抗で等価的に置き換えることができ、
それぞれ超電導１００、保護抵抗２とする。永久電流ス
イッチ６は超電導コイル６１とヒータ６２とからなって
いて、前述のように液体水素に浸された状態で使用され
る。永久電流スイッチ６を「開」にするにはヒータ６２
に図示しない電源から電流を流した加熱しその熱で超電
導コイル６１に強制的にクエンチを起こさせる。超電導
６１が超電導状態にあるときは抵抗値が零であるのに対
してクエンチを起こして常電導状態に変移するとその抵
抗値は前述のようにっ約２０Ωと大きくなって実質的に
「開」になる。FIG. 8 is a circuit diagram when the superconducting electromagnet is excited, and the superconducting electromagnet is shown in a simplified form as compared with that of FIG. In this figure, since the ring coil and the protection resistor are connected in series, they can be equivalently replaced by the superconducting coil and the protection resistor, respectively.
Superconductivity 100 and protection resistance 2 are used, respectively. The permanent current switch 6 is composed of a superconducting coil 61 and a heater 62, and is used in a state of being immersed in liquid hydrogen as described above. The heater 62 is used to open the permanent current switch 6.
The heating is performed by applying an electric current from a power source (not shown), and the heat causes the superconducting coil 61 to be forcibly quenched. When the superconducting 61 is in the superconducting state, the resistance value is zero, whereas when it is quenched and changes to the normal conducting state, the resistance value becomes as large as about 20Ω as described above, and is substantially "open". become.

【００１８】超電導コイル１００を励磁すると回路には
超電導コイル１００のインダクタンスＬと励磁速度（ d
ｉC ／ dｔ）の積に等しい電圧ＶC がかかり、この電圧
ＶC に対応して永久電流スイッチ６に電流ｉp 、保護抵
抗２に電流ｉr が分流して流れる。前述の抵抗値を基に
計算すると、永久電流スイッチ６の電流ｉp は保護抵抗
２の電流ｉr の約１００分の１であり、消磁のために永
久電流スイッチ６を「開」にしたときも同様である。When the superconducting coil 100 is excited, the inductance L of the superconducting coil 100 and the exciting speed (d
i C / dt) takes a voltage equal V C to the product of the current i p in the persistent current switch 6 in response to the voltage V C, flows diverted current i r protection resistor 2. When calculated based on the resistance value of the above, the current i p of the permanent current switch 6 is about 100 minutes of one of the current i r protection resistance 2, when the persistent current switch 6 to the "open" for demagnetization Is also the same.

【００１９】前述のように、保護抵抗２は液体ヘリウム
に浸されているため、保護抵抗２に電流が流れるとジュ
ール熱により保護抵抗２の温度が上昇することにより液
体ヘリウムが蒸発する。励磁速度を早くすると、励磁時
間は短縮されるが、同時に液体ヘリウム蒸発量も増加す
る。そのため、励磁中の液体ヘリウムの消費量を少なく
することを考慮すると、保護抵抗２の抵抗値はできるだ
け大きいことが望ましい。As described above, since the protective resistor 2 is immersed in liquid helium, when a current flows through the protective resistor 2, the temperature of the protective resistor 2 rises due to Joule heat and liquid helium evaporates. When the excitation speed is increased, the excitation time is shortened, but at the same time, the evaporation amount of liquid helium is increased. Therefore, in consideration of reducing the consumption of liquid helium during excitation, it is desirable that the resistance value of the protective resistor 2 be as large as possible.

【００２０】また、前述のように、永久電流モードにお
ける永久電流スイッチ６にクエンチが発生した場合の永
久電流スイッチ６の保護を考えると、永久電流スイッチ
６の温度を許容値以下に抑えるためにはできるだけ多く
の電流が保護抵抗２に分流するようにすればよく、その
ためには保護抵抗２の抵抗値をできるだけ小さくするこ
とが望ましい。As described above, considering the protection of the permanent current switch 6 when the permanent current switch 6 is quenched in the persistent current mode, in order to keep the temperature of the permanent current switch 6 below the allowable value. It suffices that as much current as possible be shunted to the protective resistance 2. For that purpose, it is desirable to make the resistance value of the protective resistance 2 as small as possible.

【００２１】ＭＲＩ装置では何らかの異常事態が発生し
たために超電導電磁石を緊急に消磁する必要が生じるこ
とがあり、このようなことが考慮されて、近年、このよ
うな所定の時間内で消磁できる機能がＭＲＩ装置の仕様
として要求される傾向にある。このような永久電流モー
ドで定格運転中に超電導電磁石を消磁する場合、取り外
してある電流リード７１，７２を再度接続して電源と接
続して電流を減衰させて消磁を行うという方法は時間的
な点から実質的に不可能である。In the MRI apparatus, it may be necessary to urgently demagnetize the superconducting electromagnet due to some abnormal situation. In consideration of such a situation, in recent years, a function capable of degaussing within such a predetermined time has been provided. It tends to be required as a specification of the MRI apparatus. When demagnetizing the superconducting electromagnet during rated operation in such a permanent current mode, the method of reconnecting the removed current leads 71 and 72 and connecting to the power source to attenuate the current to perform degaussing is time-consuming. From the point of view it is virtually impossible.

【００２２】そこで、緊急消磁時には、永久電流スイッ
チ６の開閉用のヒータ６２を加熱し、永久電流スイッチ
６の超電導コイル６１を強制的にクエンチさせることに
よって永久電流モードを破壊するという方法がとられ
る。そして、保護抵抗２に電流がバイパスしジュール発
熱することによって超電導コイル１００に蓄積されてい
たエネルギーを消費させて電流を減衰させる。この電流
の減衰時定数τは保護抵抗２の抵抗値に反比例するので
消磁の時定数を小さくするためには保護抵抗２の抵抗値
を大きくすればよいが、大きくし過ぎるとバイパスする
電流値が小さくなるために常電導状態になった永久電流
スイッチ６に流れる電流値が大きくなり、永久電流スイ
ッチ６の保護としての役目を果たさなくなる危険性も大
きくなる。ちなみに、前述の超電導コイル１００の自己
インダクタンスと保護抵抗２の抵抗値とから時定数を求
めると約１００秒になる。Therefore, at the time of emergency demagnetization, a method of destroying the persistent current mode by heating the heater 62 for opening and closing the persistent current switch 6 and forcibly quenching the superconducting coil 61 of the persistent current switch 6 is adopted. . Then, the current bypasses the protection resistor 2 and Joule heat is generated to consume the energy accumulated in the superconducting coil 100 to attenuate the current. Since the decay time constant τ of this current is inversely proportional to the resistance value of the protection resistor 2, it is sufficient to increase the resistance value of the protection resistor 2 in order to reduce the demagnetization time constant. Since the size of the permanent current switch 6 becomes smaller, the value of the current flowing through the permanent current switch 6 in the normal conduction state increases, and the risk of not serving the role of protecting the permanent current switch 6 also increases. By the way, when the time constant is calculated from the self-inductance of the superconducting coil 100 and the resistance value of the protective resistor 2, it takes about 100 seconds.

【００２３】[0023]

【発明が解決しようとする課題】前述のように、励磁時
には保護抵抗２の抵抗値は大きいほどよく、消磁時の永
久電流スイッチ６の保護のためには小さいほどよい。緊
急消磁の場合を考慮する必要のない場合にはこれら相反
する事項を総合的に判断して適切な保護抵抗値が設定さ
れ図６に示すようにリングコイルに並列に接続する構成
が採用される。しかし、緊急消磁の場合を考慮すると、
図６のような保護抵抗の並列接続は妥当ではなく、また
前述の適切に設定された保護抵抗値では電流減少の時定
数が長くなり過ぎ、緊急消磁に関する仕様を満足するこ
とができないという問題が生ずる。As described above, the larger the resistance value of the protective resistor 2 during excitation, the better, and the smaller the protection value of the permanent current switch 6 during demagnetization. When it is not necessary to consider the case of emergency degaussing, these contradictory matters are comprehensively determined, an appropriate protection resistance value is set, and a configuration is adopted in which the ring coil is connected in parallel as shown in FIG. . However, considering the case of emergency demagnetization,
The parallel connection of the protection resistors as shown in FIG. 6 is not appropriate, and there is a problem that the time constant of the current decrease becomes too long with the above-mentioned properly set protection resistance value, and the specifications regarding the emergency demagnetization cannot be satisfied. Occurs.

【００２４】この発明の目的は、このような問題を解決
し、永久電流スイッチ６を確実に保護できる保護抵抗を
備え、しかも緊急消磁における電流減衰の時定数を仕様
を満足する程度に小さくすることのできる超電導電磁石
を提供することにある。An object of the present invention is to solve such a problem, to provide a protective resistor capable of reliably protecting the permanent current switch 6, and to make the time constant of current attenuation in emergency demagnetization small enough to satisfy the specifications. Another object of the present invention is to provide a superconducting electromagnet that can be manufactured.

【００２５】[0025]

【課題を解決するための手段】上記課題を解決するため
に、この発明によれば、同軸かつ軸方向に対称の複数の
リングコイルからなる主コイル及びこの主コイルの外径
側に同軸かつ軸方向に対称の複数のリングコイルからな
るアクティブシールドで構成された超電導コイルと、こ
の超電導コイルに並列接続された保護抵抗とが低温容器
に収納されてなる超電導電磁石において、前記保護抵抗
に直列に、励磁時の正電圧側を正極側にしたダイオード
を接続し、保護抵抗を少なくとも１対のリングコイルの
外径側に熱的に接近して設けてなるものとし、また、保
護抵抗が、所定の寸法形状の金属薄板からなるものと
し、また、保護抵抗が、金属線をアクティブシールドの
両端のリングコイルの外径側に巻回してなるものとす
る。In order to solve the above-mentioned problems, according to the present invention, a main coil composed of a plurality of coaxial and axially symmetrical ring coils, and a coaxial and axial shaft on the outer diameter side of the main coil are provided. A superconducting coil composed of an active shield consisting of a plurality of ring coils symmetrical in the direction, and a protective resistance connected in parallel to the superconducting coil in a superconducting electromagnet that is housed in a low temperature container, in series with the protective resistance, It is assumed that a diode whose positive voltage side is the positive side at the time of excitation is connected and a protection resistor is provided thermally close to the outer diameter side of at least one pair of ring coils. It is assumed that it is made of a thin metal plate having a dimension and shape, and that the protective resistance is formed by winding a metal wire around the outer diameter side of the ring coil at both ends of the active shield.

【００２６】[0026]

【作用】この発明の構成において、保護抵抗に直列に、
励磁時の正電圧側を正極側にしたダイオードを接続する
ことによって、励磁時に保護抵抗に流れる電流が遮断さ
れるので、永久電流スイッチを保護するに充分なように
保護抵抗を小さくしても差し支えなくなる。保護抵抗を
少なくとも１対のリングコイルの外径側に熱的に接近し
て設けることによって、緊急消磁時に永久電流スイッチ
を「開」の状態にして永久電流スイッチに流れていた電
流を保護抵抗に転流させたときに、保護抵抗に発生する
抵抗損による熱がリングコイルの超電導線に伝わって温
度が上がり強制的なクエンチが生じる。これによって緊
急消磁時の抵抗値はこのクエンチを起こしたリングコイ
ルの分が加算されることになり、リングコイルの常電導
状態での抵抗値は保護抵抗のそれよりもはるかに大きい
のが普通なので、保護抵抗を前述のように小さな値に設
定しても緊急消磁で要求される短い減衰時定数で電流を
減衰させることが可能になる。In the structure of the present invention, the protection resistor is connected in series,
By connecting a diode with the positive voltage side to the positive side during excitation, the current flowing through the protective resistance is cut off during excitation.Therefore, it is possible to reduce the protective resistance enough to protect the permanent current switch. Disappear. By providing the protection resistors thermally close to the outer diameter side of at least one pair of ring coils, the permanent current switch is set to the "open" state at the time of emergency demagnetization, and the current flowing through the permanent current switches is used as the protection resistor. When commutated, the heat due to the resistance loss generated in the protective resistance is transferred to the superconducting wire of the ring coil to raise the temperature and a forced quench occurs. Due to this, the resistance value at the time of emergency demagnetization will be added by the amount of the ring coil that caused this quenching, and the resistance value of the ring coil in the normal conduction state is usually much larger than that of the protection resistance. Even if the protection resistance is set to a small value as described above, the current can be attenuated with the short damping time constant required for the emergency demagnetization.

【００２７】また、保護抵抗を、従来の保護抵抗と同様
に所定の寸法形状の金属薄板で形成してもよく、また、
リングコイルの外径に抵抗線を巻回する構成でもよい。
抵抗線を使用する場合、巻回時に所要の張力をかけるこ
とによってリングコイルを締付ける力を与えることがで
きるので、クエンチの原因である半径方向電磁力による
微動が生ずる可能性の高いアクティブシールドの両端の
リングコイルに巻回することによってクエンチ発生の確
率が低減する。Further, the protective resistance may be formed of a thin metal plate having a predetermined size and shape like the conventional protective resistance.
The resistance wire may be wound around the outer diameter of the ring coil.
When a resistance wire is used, the ring coil can be tightened by applying the required tension during winding, so both ends of the active shield that are likely to cause micromotion due to the radial electromagnetic force that causes quenching. The probability of occurrence of quench is reduced by winding around the ring coil.

【００２８】[0028]

【実施例】以下この発明を実施例に基づいて説明する。
図１はこの発明の実施例を示す超電導電磁石の回路図で
あり、図６と同じ回路要素に対しては共通の符号を付け
て詳細な説明を省略する。この図において、保護抵抗３
は２つの直列接続された保護抵抗３Ａ，３Ｂで構成さ
れ、これらに直列にダイオード８が接続されている。図
は電流リード７１，７２が接続されている励磁時を示し
ており、正極側である電流リード７１の側にダイオード
８の正極端子が接続されているので、励磁時にはダイオ
ード８で電流が遮断されて保護抵抗３には電流が流れな
い。EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a circuit diagram of a superconducting electromagnet according to an embodiment of the present invention. The same circuit elements as those in FIG. 6 are designated by the same reference numerals and detailed description thereof will be omitted. In this figure, the protection resistor 3
Is composed of two protection resistors 3A and 3B connected in series, and a diode 8 is connected in series to these. The figure shows the current leads 71 and 72 connected at the time of excitation, and since the positive terminal of the diode 8 is connected to the side of the current lead 71 which is the positive side, the current is cut off by the diode 8 at the time of excitation. Therefore, no current flows through the protection resistor 3.

【００２９】保護抵抗３Ａ，３Ｂはそれぞれリングコイ
ル１４Ａ，１４Ｂに接近した位置を図示してあるが、こ
れは後述するように保護抵抗３Ａをリングコイル１４Ａ
の、保護抵抗３Ｂをリングコイル１４Ｂの、それぞれ外
径側に接して設けてあることを示すものである。保護抵
抗３に電流が流れて抵抗損が発生し温度が上がると、リ
ングコイル１４Ａ，１４Ｂが加熱されて温度を上げクエ
ンチが起こるようにしてある。The protection resistors 3A and 3B are shown in the positions close to the ring coils 14A and 14B, respectively.
2 shows that the protective resistors 3B are provided in contact with the outer diameter side of the ring coil 14B, respectively. When a current flows through the protective resistor 3 to cause resistance loss and the temperature rises, the ring coils 14A and 14B are heated to raise the temperature and cause a quench.

【００３０】前述のように励磁時には保護抵抗３には電
流が流れないので、このような強制的なクエンチは生じ
ない。前述のように緊急消磁のために永久電流スイッチ
６のヒータ巻線６２に電流を流して強制的に超電導コイ
ル６１にクエンチを起こさせて永久電流スイッチ６を
「開」の状態にすると、永久電流スイッチ６に流れてい
た電流は保護抵抗３とダイオード８の直列回路に転流す
る。このときの電流はダイオード８の順方向なので、僅
かの電圧降下はあるにせよ遮断されることなく電流が流
れる。As described above, since no current flows through the protective resistor 3 during excitation, such a forced quench does not occur. As described above, for emergency demagnetization, when a current is passed through the heater winding 62 of the permanent current switch 6 to forcibly cause the superconducting coil 61 to quench and the permanent current switch 6 to be in the "open" state, The current flowing through the switch 6 commutates to the series circuit of the protection resistor 3 and the diode 8. Since the current at this time is in the forward direction of the diode 8, the current flows without interruption even if there is a slight voltage drop.

【００３１】保護抵抗３に電流が流れることによって前
述のように保護抵抗３Ａ，３Ｂが加熱されて温度が上が
り、この温度がリングコイル１４Ａ，１４Ｂに伝達され
てこれらの超電導線の温度が上がりクエンチが生じ循環
回路の中の抵抗にリングコイル１４Ａ，１４Ｂの常電導
状態の抵抗値が加算される。一般に常電導状態のリング
コイル１４Ａ，１４Ｂの抵抗値は保護抵抗３の抵抗値よ
りもはるかに大きいので電流の減衰時定数は保護抵抗３
の抵抗値だけの場合に比べてはるかに短くなり、実質的
にリングコイル１４Ａ，１４Ｂ常電導状態の抵抗値で殆
ど決まってしまう。ちなみに前述の超電導コイル１００
の抵抗値１０Ωの中に占めるリングコイル１４Ａ，１４
Ｂの抵抗値の和は約２Ωなので、これと前述の自己イン
ダクタンス値とから電流の減衰時定数を計算すると約１
０秒となる。As described above, the current flows through the protective resistor 3 to heat the protective resistors 3A and 3B to raise the temperature, and this temperature is transmitted to the ring coils 14A and 14B to raise the temperature of these superconducting wires and to quench. Occurs and the resistance value of the ring coils 14A and 14B in the normal conducting state is added to the resistance in the circulation circuit. Generally, the resistance values of the ring coils 14A and 14B in the normal conducting state are much larger than the resistance value of the protection resistor 3, so that the decay time constant of the current is 3
The resistance value is much shorter than the case where only the resistance value is, and the resistance value in the normal conducting state of the ring coils 14A and 14B is substantially determined. By the way, the above-mentioned superconducting coil 100
Of the ring coil 14A, 14 in the resistance value of 10Ω
Since the sum of the resistance values of B is about 2Ω, the decay time constant of the current is calculated from this value and the self-inductance value mentioned above.
It will be 0 seconds.

【００３２】保護抵抗３Ａ，３Ｂをリングコイル１４
Ａ，１４Ｂに設けた理由は、後述するようにリングコイ
ル１４Ａ，１４Ｂを保護抵抗３Ａ，３Ｂで外径側から締
付けて微動を生じにくくすることを考慮したためであ
る。この考慮が不要の場合にはアンペアターンが最も大
きい主コイル１の両端のリングコイル１３Ａ，１３Ｂに
保護抵抗３Ａ，３Ｂを設けてももよい。The protection resistors 3A and 3B are connected to the ring coil 14
The reason why the ring coils A and 14B are provided is that the ring coils 14A and 14B are tightened from the outer diameter side by the protection resistors 3A and 3B to make it difficult to cause fine movement, as will be described later. If this consideration is not necessary, protection resistors 3A and 3B may be provided on the ring coils 13A and 13B at both ends of the main coil 1 having the largest ampere-turn.

【００３３】図２は図１の超電導電磁石の断面図であ
り、図５と同じ部材については共通の符号を付けて詳細
な説明を省略する。また、図３は図２のＡ部拡大断面図
ある。これらの図において、保護抵抗３Ａ，３Ｂは図７
と同様に薄い金属板からなるもので、全周にわたって巻
回されているのではないので図の下の断面図には示され
ていない。このような保護抵抗３ではリングコイル１４
Ａ，１４Ｂを締付ける作用は期待できないのでリングコ
イル１３Ａ，１３Ｂの外径側に設けてもよい。FIG. 2 is a sectional view of the superconducting electromagnet of FIG. 1. The same members as those in FIG. 5 are designated by the same reference numerals and detailed description thereof will be omitted. Further, FIG. 3 is an enlarged cross-sectional view of a portion A of FIG. In these figures, the protection resistors 3A and 3B are shown in FIG.
It is not shown in the sectional view below the figure because it is made of a thin metal plate and is not wound all around. In such a protection resistor 3, the ring coil 14
Since the action of tightening A and 14B cannot be expected, it may be provided on the outer diameter side of the ring coils 13A and 13B.

【００３４】前述のように、ダイオード８を直列に挿入
したために保護抵抗３の抵抗値は小さくてよくまた消磁
時にはリングコイル１４Ａ，１４Ｂの抵抗が働くことか
ら、保護抵抗３の容量は小さくてよくなるので図のよう
に２つのリングコイル１４Ａ，１４Ｂにだけ設ける程度
に小さな保護抵抗３でもよい。保護抵抗３Ａとリングコ
イル１４Ａとの間は絶縁層５Ａで絶縁してある。巻枠４
２も金属製なのでこれとの間の絶縁をとることも必要で
あるがその構成の図示は省略してある。As described above, the resistance value of the protection resistor 3 may be small because the diode 8 is inserted in series, and the resistance of the ring coils 14A and 14B works during demagnetization, so that the capacitance of the protection resistor 3 may be small. Therefore, as shown in the figure, the protection resistor 3 may be small enough to be provided only in the two ring coils 14A and 14B. The protection resistor 3A and the ring coil 14A are insulated by an insulating layer 5A. Reel 4
Since 2 is also made of metal, it is necessary to insulate it from the metal 2, but its construction is not shown.

【００３５】図４はこの発明の別の実施例を示す拡大断
面図であり、図３と異なる点は保護抵抗３０Ａが抵抗線
３１を巻回してなることである。すなわち、絶縁層５Ａ
をリングコイル１４Ａの上に設けた後その上に張力をか
けながら抵抗線３１を軸方向に並べて巻回する。これに
よってリングコイル１４Ａには締付け力がかかる。励磁
によって電流が増大するに伴って増大するリングコイル
１４Ａ，１４Ｂの電磁力は外径側に向かう半径方向力が
主なのでこの半径方向力を締付け力が打ち消すことにな
って超電導線の微動が起こりにくくなる。FIG. 4 is an enlarged sectional view showing another embodiment of the present invention. What is different from FIG. 3 is that the protective resistance 30A is formed by winding a resistance wire 31. That is, the insulating layer 5A
Is provided on the ring coil 14A, and then the resistance wire 31 is axially arranged and wound while applying tension on the ring coil 14A. As a result, a tightening force is applied to the ring coil 14A. The electromagnetic force of the ring coils 14A and 14B, which increases as the current increases due to the excitation, is mainly a radial force toward the outer diameter side, so the tightening force cancels this radial force, and a slight movement of the superconducting wire occurs. It gets harder.

【００３６】抵抗線３１として図では丸線を図示してあ
るが、角線であっても差し支えなく、これらは絶縁被覆
されたものを使用するのが普通である。また、図では１
層だけ巻回してあるが、更に半径方向に重ねて複数層を
形成するものであってもよい。Although a round wire is shown as the resistance wire 31 in the drawing, it may be a square wire, and it is usual to use a wire covered with an insulating coating. Also, in the figure, 1
Although only the layers are wound, the layers may be overlapped in the radial direction to form a plurality of layers.

【００３７】前述の実施例ではアクティブシールド１０
の両端のリングコイル１４Ａ，１４Ｂに保護抵抗３Ａ，
３Ｂもしくは３０Ａ，３０Ｂを設ける構成を示したが、
このように１対のリングコイルだけに保護抵抗を設ける
構成ではなく例えば主コイル１３Ａ，１３Ｂを加えた２
対のリングコイルに４分割した保護抵抗を設ける構成を
採用することもできる。アクティブシールド形超電導電
磁石は通常図示したように５対のリングコイルで構成さ
れるのでこれら５対全部に保護抵抗を設けることもも可
能である。ただ、消磁時の電流減衰の時定数は超電導コ
イル１００に誘起される電圧に反比例するので、余り時
定数を小さくするのも支障が生ずることから、こられの
要因を総合的に判断して保護抵抗の値や接して設けるリ
ングコイル対の決定などを行うことになる。In the above embodiment, the active shield 10
To the ring coils 14A and 14B on both ends of the protective resistor 3A,
Although the configuration in which 3B or 30A, 30B is provided is shown,
As described above, the main coil 13A, 13B is added instead of the structure in which the protective resistance is provided only for the pair of ring coils.
It is also possible to employ a configuration in which a pair of ring coils is provided with a protective resistance divided into four. Since the active shield type superconducting electromagnet is usually composed of five pairs of ring coils as shown in the figure, it is possible to provide protective resistance to all of these five pairs. However, since the time constant of current decay during demagnetization is inversely proportional to the voltage induced in the superconducting coil 100, making the time constant too small can be a hindrance. The value of resistance and the pair of ring coils provided in contact with each other are determined.

【００３８】[0038]

【発明の効果】この発明は前述のように、保護抵抗に直
列に、励磁時に保護抵抗に電流が流れないようにダイオ
ードを挿入することによって、励磁時での保護抵抗の電
流が零になるので、永久電流スイッチを保護するに充分
なように保護抵抗を小さくしても差し支えなくなる。保
護抵抗を１対かそれ以上のリングコイルの外径側に熱的
に接して設けることによって、緊急消磁時に永久電流ス
イッチを「開」の状態にして永久電流スイッチに流れて
いた電流を保護抵抗に転流させたときに、保護抵抗は抵
抗損によって温度が上昇しこの温度が接しているリング
コイルの超電導線に伝わって加熱されクエンチが生じて
こリングコイルは常電導状態に変移する。これによって
緊急消磁時の抵抗値はこのリングコイルの常電導状態で
の抵抗値が加算されて、保護抵抗を前述のように小さな
値に設定しても緊急消磁時に要求される短い減衰時定数
で電流を減衰させることが可能になるという効果が得ら
れる。As described above, according to the present invention, by inserting a diode in series with the protection resistor so that a current does not flow through the protection resistor during excitation, the current of the protection resistor during excitation becomes zero. However, it does not matter if the protective resistance is made small enough to protect the permanent current switch. By providing a protective resistance in thermal contact with the outer diameter side of one or more pairs of ring coils, the permanent current switch is placed in the "open" state during emergency demagnetization, and the current flowing through the permanent current switch is protected. When commutated to, the protective resistance increases in temperature due to resistance loss and is transmitted to the superconducting wire of the ring coil which is in contact with this temperature to be heated to cause quenching, and the ring coil changes to the normal conducting state. As a result, the resistance value at the time of emergency demagnetization is the resistance value of this ring coil in the normal conduction state added, and even if the protection resistance is set to a small value as described above, it has the short damping time constant required at the time of emergency demagnetization. The effect that the current can be attenuated is obtained.

【００３９】また、保護抵抗を、従来の保護抵抗と同様
に所定の寸法形状の金属薄板で形成してもよく、また、
リングコイルの外径に抵抗線を巻回する構成でもよい。
抵抗線を巻回して保護抵抗とする場合、巻回時に所要の
張力をかけることによってリングコイルを締付ける力を
与えることができるので、クエンチの原因である半径方
向電磁力による微動が生ずる可能性の高いアクティブシ
ールドの両端のリングコイルに巻回することによってク
エンチ発生の確率が低減するという効果も得られる。The protective resistor may be formed of a thin metal plate having a predetermined size and shape like the conventional protective resistor.
The resistance wire may be wound around the outer diameter of the ring coil.
When a resistance wire is wound to form a protective resistance, the ring coil can be tightened by applying the required tension during winding, so there is a possibility of micromotion due to the radial electromagnetic force that causes quenching. By winding around the ring coils at both ends of the high active shield, it is possible to obtain an effect that the probability of occurrence of quench is reduced.

【図面の簡単な説明】[Brief description of drawings]

【図１】この発明の実施例を示す超電導電磁石の回路図FIG. 1 is a circuit diagram of a superconducting electromagnet showing an embodiment of the present invention.

【図２】この発明の実施例を示すアクティブシールド形
超電導電磁石の断面図FIG. 2 is a sectional view of an active shield type superconducting electromagnet according to an embodiment of the present invention.

【図３】図２のＡ部の要部断面図FIG. 3 is a sectional view of a main part of a portion A of FIG.

【図４】図３とは別の実施例を示す図２のＡ部の要部断
面図FIG. 4 is a cross-sectional view of an essential part of a portion A of FIG. 2 showing an embodiment different from that of FIG.

【図５】従来のアクティブシールド形超電導電磁石を示
す断面図FIG. 5 is a sectional view showing a conventional active shield type superconducting electromagnet.

【図６】図５に示す超電導電磁石の回路図FIG. 6 is a circuit diagram of the superconducting electromagnet shown in FIG.

【図７】図６に示す保護抵抗の斜視図7 is a perspective view of the protective resistor shown in FIG.

【図８】図５に示す超電導電磁石の励磁時の回路図FIG. 8 is a circuit diagram when the superconducting electromagnet shown in FIG. 5 is excited.

【符号の説明】[Explanation of symbols]

１００ 超電導コイル １ 主コイル １０ アクティブシールド １１Ａ リングコイル １１Ｂ リングコイル １２Ａ リングコイル １２Ｂ リングコイル １３Ａ リングコイル １３Ｂ リングコイル １４Ａ リングコイル １４Ｂ リングコイル １５Ａ リングコイル １５Ｂ リングコイル ２ 保護抵抗 ２１Ａ 保護抵抗 ２１Ｂ 保護抵抗 ２２Ａ 保護抵抗 ２２Ｂ 保護抵抗 ２３Ａ 保護抵抗 ２３Ｂ 保護抵抗 ２４Ａ 保護抵抗 ２４Ｂ 保護抵抗 ３ 保護抵抗 ３Ａ 保護抵抗 ３Ｂ 保護抵抗 ６ 永久電流スイッチ ７１ 電流リード ７２ 電流リード 100 superconducting coil 1 main coil 10 active shield 11A ring coil 11B ring coil 12A ring coil 12B ring coil 13A ring coil 13B ring coil 14A ring coil 14B ring coil 15A ring coil 15B ring coil 2 protection resistance 21A protection resistor 21B Protection resistance 22A protection resistor 22B protection resistance 23A protection resistor 23B protection resistor 24A protection resistance 24B protection resistance 3 Protection resistance 3A protection resistance 3B protection resistor 6 Permanent current switch 71 Current lead 72 Current lead

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｇ０１Ｒ 33/38 Ｈ０１Ｌ 39/14 ＺＡＡ Ｚ 8728−4Ｍ 7621−2Ｊ Ｇ０１Ｒ 33/22 ＺＡＡ Ｎ ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 5 Identification code Internal reference number FI Technical display location G01R 33/38 H01L 39/14 ZAA Z 8728-4M 7621-2J G01R 33/22 ZAA N

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】同軸かつ軸方向に対称の複数のリングコイ
ルからなる主コイル及びこの主コイルの外径側に同軸か
つ軸方向に対称の複数のリングコイルからなるアクティ
ブシールドで構成された超電導コイルと、この超電導コ
イルに並列接続された保護抵抗とが低温容器に収納され
てなる超電導電磁石において、 前記保護抵抗に直列に、励磁時の正電圧側を正極側にし
たダイオードを接続し、保護抵抗を少なくとも１対のリ
ングコイルの外径側に熱的に接近して設けてなることを
特徴とする請求項１記載の超電導電磁石。1. A superconducting coil composed of a main coil composed of a plurality of coaxial and axially symmetrical ring coils, and an active shield composed of a plurality of coaxial and axially symmetrical ring coils on the outer diameter side of the main coil. In the superconducting electromagnet in which the protection resistor connected in parallel to this superconducting coil is housed in a low temperature container, the protection resistor is connected in series with a diode with the positive voltage side at the time of excitation being the positive electrode side, and the protection resistor is connected. The superconducting electromagnet according to claim 1, wherein the superconducting electromagnet is provided so as to be thermally close to the outer diameter side of at least one pair of ring coils. 【請求項２】保護抵抗が、所定の寸法形状の金属薄板か
らなることを特徴とする請求項１記載の超電導電磁石。2. The superconducting electromagnet according to claim 1, wherein the protective resistance is made of a thin metal plate having a predetermined size and shape. 【請求項３】保護抵抗が、金属線をアクティブシールド
の両端のリングコイルの外径側に巻回してなることを特
徴とする請求項１記載の超電導電磁石。3. The superconducting electromagnet according to claim 1, wherein the protective resistance is formed by winding a metal wire around the outer diameter side of the ring coil at both ends of the active shield.
JP3184946A 1991-07-25 1991-07-25 Superconducting electromagnet Pending JPH0529137A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP3184946A JPH0529137A (en) 1991-07-25 1991-07-25 Superconducting electromagnet

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP3184946A JPH0529137A (en) 1991-07-25 1991-07-25 Superconducting electromagnet

Publications (1)

Publication Number Publication Date
JPH0529137A true JPH0529137A (en) 1993-02-05

Family

ID=16162124

Family Applications (1)

Application Number Title Priority Date Filing Date
JP3184946A Pending JPH0529137A (en) 1991-07-25 1991-07-25 Superconducting electromagnet

Country Status (1)

Country Link
JP (1) JPH0529137A (en)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH075235A (en) * 1992-12-11 1995-01-10 Philips Electron Nv Magnetic resonance device with superconducting magnet
JPH07235412A (en) * 1994-02-24 1995-09-05 Mitsubishi Electric Corp Superconducting magnet device
EP1065513A2 (en) * 1999-07-02 2001-01-03 Bruker AG Active shielded superconductive magnet with compensation of field disturbance
US7104217B2 (en) 2000-04-18 2006-09-12 Tokyo Electron Limited Plasma processing apparatus
JP2007335616A (en) * 2006-06-15 2007-12-27 Mitsubishi Electric Corp Superconductive magnet
JP2011138892A (en) * 2009-12-28 2011-07-14 Toshiba Corp Superconducting magnet device, and quenching protecting method thereof
JP2011210920A (en) * 2010-03-30 2011-10-20 Japan Superconductor Technology Inc Protection resistor of superconducting magnet, and superconducting magnet device equipped with the same
CN102651265A (en) * 2011-02-23 2012-08-29 英国西门子公司 Superconducting electromagnet comprising coils bonded to a heated support structure
WO2014118390A2 (en) * 2013-02-04 2014-08-07 Siemens Plc Superconducting magnet coil arrangement
USRE45942E1 (en) 2012-02-21 2016-03-22 Siemens Plc Superconducting electromagnets comprising coils bonded to a support structure
EP4303896A3 (en) * 2022-07-06 2024-05-01 General Electric Renovables España, S.L. Coil support structure for superconducting coils in a superconducting machine

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH075235A (en) * 1992-12-11 1995-01-10 Philips Electron Nv Magnetic resonance device with superconducting magnet
JPH07235412A (en) * 1994-02-24 1995-09-05 Mitsubishi Electric Corp Superconducting magnet device
EP1065513A2 (en) * 1999-07-02 2001-01-03 Bruker AG Active shielded superconductive magnet with compensation of field disturbance
EP1065513A3 (en) * 1999-07-02 2001-03-07 Bruker AG Active shielded superconductive magnet with compensation of field disturbance
US7104217B2 (en) 2000-04-18 2006-09-12 Tokyo Electron Limited Plasma processing apparatus
JP2007335616A (en) * 2006-06-15 2007-12-27 Mitsubishi Electric Corp Superconductive magnet
JP4699293B2 (en) * 2006-06-15 2011-06-08 三菱電機株式会社 Superconducting magnet
JP2011138892A (en) * 2009-12-28 2011-07-14 Toshiba Corp Superconducting magnet device, and quenching protecting method thereof
JP2011210920A (en) * 2010-03-30 2011-10-20 Japan Superconductor Technology Inc Protection resistor of superconducting magnet, and superconducting magnet device equipped with the same
CN102651265A (en) * 2011-02-23 2012-08-29 英国西门子公司 Superconducting electromagnet comprising coils bonded to a heated support structure
JP2012175110A (en) * 2011-02-23 2012-09-10 Siemens Plc Superconducting electromagnet comprising coils bonded to support structure
USRE45942E1 (en) 2012-02-21 2016-03-22 Siemens Plc Superconducting electromagnets comprising coils bonded to a support structure
WO2014118390A2 (en) * 2013-02-04 2014-08-07 Siemens Plc Superconducting magnet coil arrangement
WO2014118390A3 (en) * 2013-02-04 2014-10-23 Siemens Plc Superconducting magnet coil arrangement
JP2016507159A (en) * 2013-02-04 2016-03-07 シーメンス パブリック リミテッド カンパニーＳｉｅｍｅｎｓ ｐｌｃ Superconducting magnet coil device
EP3252784A1 (en) * 2013-02-04 2017-12-06 Siemens Healthcare Limited Superconducting magnet coil arrangement
US10365337B2 (en) 2013-02-04 2019-07-30 Siemens Healthcare Limited Superconducting magnet coil arrangement
EP4303896A3 (en) * 2022-07-06 2024-05-01 General Electric Renovables España, S.L. Coil support structure for superconducting coils in a superconducting machine

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