JP3727122B2 - Superconducting bulk magnet - Google Patents
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Description
【０００１】
【発明の属する技術分野】
この発明は、高温超電導体のバルクを用いたマグネットに関する。
【０００２】
【従来の技術】
高温超電導体の開発に伴い、これら超電導体を利用した超電導磁石が開発されてきている。例えば、特開平３−２８９３４４号公報には、超電導コイルを界磁側に用いて通電により磁場を発生させ、電機子に回転力を与える超電導モーターが提案されている。
【０００３】
しかしながら、上記装置では超電導線材のコイルに通電して磁場を発生させるため、超電導状態のコイルにクエンチが発生する恐れがある。クエンチとは、局所的に発生した常電導状態が雪崩的に拡大し、超電導体全体が急激に常電導状態に転移することをいう。クエンチが発生すると、超電導線材のコイルに所望の特性が得られないばかりでなく、常電導状態で発生する大きなジュール熱により装置に損傷が生じるおそれもあるため、クエンチの発生は極力排除する必要がある。上記クエンチは線材において特に発生しやすい。
【０００４】
クエンチの発生を防止して超電導磁石の安定化を図る方法としては、超電導線材の表面を高純度銅等でシールする冷却安定化法や、極細多芯化した超電導線材を用いる断熱安定化法などがあるが、いずれも高コスト化や装置の大型化を免れることはできない。
【０００５】
一方、近年開発されたＲ（希土類）−Ｂａ−Ｃｕ−Ｏ系超電導体は第２種超電導体であって、溶融法で作成したバルク体（固片）であってもピン止め制御が可能であり、液体窒素温度でも高い臨界電流が達成されている。従来の超電導バルク体は比熱が小さいため小さな外乱で超電導が破れるという欠点があったが、上記Ｒ（希土類）−Ｂａ−Ｃｕ−Ｏ系超電導体のバルク体は比熱が大きく、外乱に対する耐性が高い。
【０００６】
そこで、この特質を利用した特開平７−８７７２４号公報や特開平７−１１１２１３号公報に記載されているような、超電導体のバルク（固片）を利用した超電導磁石が提案されている。
【０００７】
特開平７−８７７２４号公報に記載の超電導モーターには、超電導バルク体の周囲に着磁用コイルを巻回した構造の超電導磁石が使用されている。この超電導磁石は、ピン止め効果の高い第２種超電導体を用いており、着磁用コイルにパルス電流を供給し、発生した磁束を超電導バルク体のピン止め点に固定するものである。着磁用コイルによる磁場の発生が終了しても、超電導体はピン止め点に固定した磁束を保持しようとするため、超電導体内部にピン止め点を中心とした永久電流が発生し、磁束は保存される。すなわち、超電導バルク体自体が磁石となる。
【０００８】
一方、特開平７−１１１２１３号公報において、▲１▼超電導バルク体を芯として周囲をコイルで包囲した構造の複合磁石、▲２▼コイルを中心としてその周囲をリング状の超電導バルク体で包囲した構造の複合磁石、▲３▼超電導バルク体を芯として周囲をコイルで包囲し、さらにその外側にリング状の超電導バルク体を配した構造の複合磁石が提案されている。
【０００９】
上記▲１▼の複合磁石は、コイルで付与する磁場によってバルク超電導磁石の磁場強度を自由に変化できる。また、▲２▼の複合磁石は、低温超電導体コイルを用いた場合に磁場が外縁部で曲がることを妨げて発生磁場を向上できる。そして、▲３▼の複合磁石は、低温超電導体コイルを用いた場合に発生磁場を向上するとともに、コイルがクエンチしてもバルクが超電導状態を保つので急激な変化が緩和できるものである。
【００１０】
【発明が解決しようとする課題】
しかし、上記各公報に記載の超電導磁石では、超電導バルク体の内側若しくは外側の一方のみに着磁コイルを配置するため、バルクに印加される磁場に偏りが生じる。例えば、超電導バルク体の外側のみに着磁コイルを配置した場合には、バルクの外側に印加される磁場はバルクの内側に印加される磁場よりも大きくなる。また、超電導バルク体の内側のみに着磁コイルを配置した場合には、バルクの内側に印加される磁場はバルクの外側に印加される磁場よりも大きくなる。
【００１１】
したがって、上記超電導磁石では、超電導バルク体全体に着磁しようとすると、着磁コイル付近の超電導バルク体には必要以上の磁場を印加することになってしまう。一般に超電導体の臨界電流密度は磁場依存性を有しており、磁場が大きくなると臨界電流密度は低下してしまうので、超電導バルク体に必要以上の磁場を印加することは好ましくない。
【００１２】
また、上記超電導磁石の着磁コイルに超電導線材のコイルを用いる場合には、超電導線材自体の臨界電流密度の問題も生じる。すなわち、着磁コイルで発生させる磁場が大きいほど、超電導線材自体の経験する磁場も大きくなり臨界電流密度が低下するため、超電導着磁コイルに大電流を流して大きな磁場を発生させるには超電導着磁コイルを大型化しなければならない。したがって、磁石の小型化・軽量化の観点からは、同じだけの磁束を超電導バルクに捕捉させるために印加する磁場は小さいほどよい。
【００１３】
本発明は、超電導バルク体と着磁コイルとからなる超電導バルク体マグネットであって、超電導バルク体に必要以上の磁場を印加することがなく、また各着磁コイルで発生させる磁場が小さく、着磁コイルが超電導バルク体を効率的に着磁させる構造の超電導バルク体マグネットを提供することを目的とする。
【００１４】
【課題を解決するための手段】
上記目的を達成するために、本発明は、以下の構成を要旨とする。
（１）内周側着磁コイルを中心とし、その周りを筒状のピン止め効果のある第２種超電導体からなる超電導バルク体で包囲し、さらに超電導バルク体の外側を外周側着磁コイルで包囲した超電導バルク体マグネットであって、筒状の超電導バルク体に、互いに逆向きの電流を通電する内周側着磁コイルと外周側着磁コイルとをそれぞれの中心軸を共有するように配置し、前記中心軸と同じ向きの磁場を超電導バルク体に印加することを特徴とする超電導バルク体マグネット。
（２）超電導バルク体の材質が微細な２１１相が分散した１２３相のＲＢａＣｕＯ系（Ｒは希土類元素を示す）若しくはＮｄ系の酸化物超電導体であることを特徴とする前記（１）に記載の超電導バルク体マグネット。
（３）内周側着磁コイルと外周側着磁コイルが発生する磁場を重ね合わせたものが、超電導バルク体に均一な磁場を印加することを特徴とする前記（１）または（２）に記載の超電導バルク体マグネット。
【００１５】
【発明の実施の形態】
本発明において、超電導バルク体の形状は中空筒型としたが、より具体的には、中空とした円筒状、穴開き直方体状、中空とした楕円円筒状等があげられる。超電導バルク体の材質としては、微細な２１１相が分散した１２３相のＲＢａＣｕＯ系（Ｒは希土類元素を示す）若しくはＮｄ（ネオジウム）系の酸化物超電導体が好ましい。これらの超電導体は第２種超電導体であって、高いピン止め効果を有し、高磁場中でも高い臨界電流密度が得られる。これら超電導体の構成成分の組成・製造方法等に関しては特に限定するものではなく、ピン止め効果の高い第２種超電導体であればよい。製造方法としては、例えば特公平７−５１４６３号公報に記載の溶融凝固法に粉砕工程を付加したＭＰＭＧ法があげられる。また、超電導バルク体は、直接中空筒型に製造してもよいし、一旦穴のない中実形状に製造した超電導バルク体に機械加工等によって穴を開け筒状に成形するようにしてもよい。
【００１６】
本発明の内周側着磁コイル及び外周側着磁コイルは、例えば銅線やアルミ線などの常電導体の線材、あるいは、例えばＢｉ系銀シース線材などの超電導体の線材よりなるコイルである。内周側着磁コイルの材質と外周側着磁コイルの材質とは、別なものを用いてもよい。
【００１７】
本発明は、上記した超電導バルク体の内外周に、内周側着磁コイルと、外周側着磁コイルとを、それぞれ中心軸を共有するように配置する。
【００１８】
ここで、内外両着磁コイルに互いに逆向きの電流を通電すれば、図１に概略的に示すように、内側着磁コイルが発生させる磁束▲２▼と外側着磁コイルが発生させる磁束▲１▼とは、両コイルに挟まれた空間では同じ方向となる。すなわち、内外両着磁コイルに互いに逆向きの電流を通電すれば、内外両着磁コイルが超電導バルク体に印加する磁場は同じ方向となり、超電導バルク体には内外両着磁コイルの発生する磁場が重ね合わさって印加される。
【００１９】
したがって、従来の超電導バルク体と着磁コイルを用いた超電導磁石よりも、各着磁コイルが発生させる磁場は小さくてよい。このため着磁コイルに常電導線材のコイルを用いる場合には、着磁コイルに通電する電流が小さくできるので、発熱を低減できる。また、着磁コイルに超電導線材のコイルを用いる場合には、各着磁コイルが経験する磁場を小さくできるので、超電導線材の臨界電流密度の低下を抑制できる。このため超電導着磁コイルの小型化・軽量化が可能となる。図２（ａ）に半径ａ、内径ｂの筒状超電導バルク体の外周側のみに着磁コイルを配置した場合に超電導バルク体に印加される磁場分布を、図２（ｂ）に外径ａ、内径ｂの筒状超電導バルク体の内周側と外周側との両方に着磁コイルを配置した場合の磁場分布をそれぞれ示す。
【００２０】
図２（ａ）に示したように、片側のみに着磁コイルを配置した場合には、着磁コイル側の印加磁場が大きくなり臨界電流密度が低下してしまう。そして、バルク全体に磁場を印加しようとすると、バルクに印加される磁場の偏りはかなり大きくなる。
【００２１】
これに対して、本発明のように筒状超電導バルク体の両側に着磁コイルを配置すれば、両側の着磁コイルから磁場を印加するため、図２（ｂ）に示したようにバルクに印加される磁場の最大値を低減することができる。
【００２２】
さらに、内周側着磁コイルと外周側着磁コイルとが超電導バルク体に印加する磁場が均一になるようにすれば、超電導バルク体の捕捉する磁束の密度が均一となり、超電導体に必要以上に大きな磁場が印加されることがなくなるため、臨界電流密度の低下を防ぎ、捕捉できる磁束の密度が大きくできる。
【００２３】
超電導バルク体に印加する磁場を均一するには、内周側着磁コイルと外周側着磁コイルの形状、巻数および通電する電流の大きさを調整する。形状、巻数および通電する電流の大きさを最適に組み合わせることで均一度を向上できる。
【００２４】
本発明の超電導バルク体マグネットは、予め筒状超電導バルク体を臨界温度以下に冷却してから、その内周側と外周側とに配置した着磁コイルにより超電導体に磁場を印加する。あるいは、着磁コイルにより超電導体に磁場を印加しながら超電導バルク体を臨界温度以下に冷却する。
【００２５】
超電導バルク体の冷却方法としては、浸漬冷却と伝導冷却がある。浸漬冷却の場合には、冷媒として液体ヘリウム、液体窒素、液体ネオン等を使用する。伝導冷却の場合は、超電導バルク体を断熱部材で囲み、熱伝導部材を冷凍機により冷却する。
【００２６】
ここで、バルクに印加する外部磁場の強さが下部臨界磁界以上、かつ上部臨界磁界以下であれば、バルクは混合状態となり局所的に外部磁場が侵入する。侵入した磁束は超電導体のピン止め点に捕捉され、その周囲に渦状の永久電流が発生し、バルクに印加する磁場を無くしてもピン止め点に捕捉された磁束は保存される。従って、超電導バルク体自体が磁化された状態となる。
【００２７】
超電導バルク体を臨界温度以下に冷却してから、着磁コイルにより磁場を印加する場合には、着磁コイルにはパルス電流を流すようにしてもよい。パルス電流は反復して着磁コイルに流してもよい。
【００２８】
着磁コイルに超電導コイルを用いると、着磁コイルからの発熱が抑えられるため超電導バルク体の超電導状態を維持する上で有利である。ただし、この場合は着磁コイル（超電導コイル）も臨界温度以下に冷却する必要がある。冷却方法は、超電導バルク体の冷却方法と同様である。
【００２９】
【実施例】
以下、本発明の実施例を説明する。
図３に、本発明の一実施例である超電導バルクマグネットの概略断面図を示す。この超電導バルクマグネットは、主として円筒状の超電導バルク体１、該バルク体１の内周に沿って配置される内周側着磁コイル３、同バルク体１の外周に沿って配置される外周側着磁コイル５からなっている。
【００３０】
超電導バルク体１は、Ｙ−Ｂａ−Ｃｕ−Ｏ超電導材料を外径４６mm、高さ２０mmの円柱状バルク体に溶融法で作製し、この円柱状バルク体に径２０mmの穴を開けて円筒状とした。この超電導バルク体１の内側に、外径２０mm、内径１６mm、高さ２０mmで銅線を巻いた内周側着磁コイル３を挿入し、さらに超電導バルク体１の外側に外径５０mm、内径４６mm、高さ２０mmで内周側着磁コイルと同じ向きに銅線を巻いた外周側着磁コイル５を配置して超電導バルクマグネットを構成した。各コイルと超電導バルク体とは、中心軸を共有するように配置した。また、超電導バルク体と着磁コイルとは、上面が同じ高さになるようにした。
【００３１】
この超電導マグネットの外周側着磁コイル５にのみ５０００Ａ／ｃｍ2 の電流を流した場合の超電導バルク体部分の磁場を図４に実線で示す。この場合には、超電導バルク体部分の磁場の最低値は内周側で５３ｍＴであるのに対して、最大値は外周側で８４ｍＴに達する。
【００３２】
また、内周側着磁コイル３にのみ電流を流して、超電導バルク体１に５３ｍＴ以上の磁場を印加しようとすると、内周側着磁コイル３に７３８１０Ａ／ｃｍ2 の電流を流す必要があり、超電導バルク体１に印加される磁場の最大値は１７５ｍＴにも達する。
【００３３】
一方、外周側着磁コイル５と内周側着磁コイル３の両方に電流を流した場合、磁場の最低値が５３ｍＴであって、かつ超電導体バルク体１に印加される磁場が最も均一になるのは、内周側着磁コイル３に６７９５Ａ／ｃｍ2 、外周側着磁コイル５には逆向きに３３００Ａ／ｃｍ2 の電流を流したときであった。この時の超電導バルク体部分の磁場を図４に点線で示す。図４に示した通り、超電導バルク体１には５３ｍＴ以上の磁場が印加されていながら、磁場の最大値は６０ｍＴに抑えられている。
【００３４】
そして、この磁場を超電導バルク体１に印加しながら超電導バルク体１を臨界温度以下に冷却した後、内周側着磁コイル３と外周側着磁コイル５の電流を同時に切断したところ、超電導バルク体１は磁束を保持して磁石となった。
【００３５】
【発明の効果】
この発明の超電導マグネットによれば、内周側と外周側とに配置した両着磁コイルが超電導バルク体に磁場を印加するため、各着磁コイルが印加する磁場は小さくて済む。そのため、常電導着磁コイルを用いる場合には発生熱量が低減できるため超電導バルク体の温度が上昇しにくく、超電導着磁コイルを用いる場合には臨界電流密度の磁場による劣化を抑えることができる。また、超電導バルク体に印加する磁場をほぼ均一にできるため、超電導バルク体に磁束を捕捉させる上でも有利である。
【図面の簡単な説明】
【図１】内外両着磁コイルに互いに逆向きの電流を通電した際に発生する磁場の模式図である。
【図２】（ａ）外周側のみに着磁コイルを配置した場合の磁場分布の概略図。
（ｂ）内周側と外周側とに着磁コイルを配置した場合の磁場分布の概略図。
【図３】この発明の超電導マグネットの一実施例の概略断面図。
【図４】この発明の超電導マグネットの一実施例における超電導体バルク体部分の磁場分布の概略図。
【符号の説明】
１ 超電導バルク体
３ 内周側着磁コイル
５ 外周側着磁コイル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnet using a bulk of a high-temperature superconductor.
[0002]
[Prior art]
With the development of high-temperature superconductors, superconducting magnets using these superconductors have been developed. For example, Japanese Patent Application Laid-Open No. 3-289344 proposes a superconducting motor that generates a magnetic field by energization using a superconducting coil on the field side and applies a rotational force to the armature.
[0003]
However, in the above apparatus, since a magnetic field is generated by energizing the coil of the superconducting wire, quenching may occur in the superconducting coil. Quenching means that the normal conducting state generated locally expands like an avalanche, and the entire superconductor rapidly changes to the normal conducting state. When a quench occurs, not only the desired characteristics of the coil of the superconducting wire are not obtained, but also the device may be damaged by the large Joule heat generated in the normal conduction state, so it is necessary to eliminate the occurrence of the quench as much as possible. is there. The quench is particularly likely to occur in the wire.
[0004]
Methods for stabilizing the superconducting magnet by preventing the occurrence of quenching include a cooling stabilization method that seals the surface of the superconducting wire with high-purity copper, an adiabatic stabilization method that uses a superconducting wire with ultrafine multi-core, etc. However, none of them can avoid the increase in cost and the size of the apparatus.
[0005]
On the other hand, recently developed R (rare earth) -Ba-Cu-O-based superconductors are type 2 superconductors, and pinning control is possible even for bulk bodies (solid pieces) prepared by the melting method. High critical current is achieved even at liquid nitrogen temperature. The conventional superconducting bulk body has a drawback that the superconductivity is broken by a small disturbance because the specific heat is small. However, the bulk body of the R (rare earth) -Ba-Cu-O based superconductor has a large specific heat and high resistance to the disturbance. .
[0006]
Therefore, a superconducting magnet using a bulk (solid piece) of a superconductor as described in Japanese Patent Application Laid-Open No. 7-87724 and Japanese Patent Application Laid-Open No. 7-111213 using this characteristic has been proposed.
[0007]
A superconducting magnet described in JP-A-7-87724 uses a superconducting magnet having a structure in which a magnetizing coil is wound around a superconducting bulk body. This superconducting magnet uses a type 2 superconductor having a high pinning effect, supplies a pulse current to the magnetizing coil, and fixes the generated magnetic flux to the pinning point of the superconducting bulk body. Even after the generation of the magnetic field by the magnetizing coil is completed, the superconductor tries to maintain the magnetic flux fixed at the pinning point, so that a permanent current is generated inside the superconductor around the pinning point, and the magnetic flux is Saved. That is, the superconducting bulk body itself becomes a magnet.
[0008]
On the other hand, in JP-A-7-111213, (1) a composite magnet having a structure in which a superconducting bulk body is surrounded by a coil, and (2) a periphery of the coil is surrounded by a ring-shaped superconducting bulk body. There has been proposed a composite magnet having a structure, (3) a composite magnet having a structure in which a superconducting bulk body is surrounded by a coil and a ring-shaped superconducting bulk body is disposed on the outside thereof.
[0009]
The composite magnet of (1) can freely change the magnetic field strength of the bulk superconducting magnet by the magnetic field applied by the coil. Further, the composite magnet of (2) can improve the generated magnetic field by preventing the magnetic field from bending at the outer edge when the low temperature superconductor coil is used. The composite magnet (3) improves the generated magnetic field when a low-temperature superconductor coil is used, and can relieve abrupt changes since the bulk remains superconductive even when the coil is quenched.
[0010]
[Problems to be solved by the invention]
However, in the superconducting magnets described in the above publications, the magnetizing coil is disposed only on the inner side or the outer side of the superconducting bulk body, so that the magnetic field applied to the bulk is biased. For example, when the magnetizing coil is disposed only outside the superconducting bulk body, the magnetic field applied to the outside of the bulk is larger than the magnetic field applied to the inside of the bulk. Further, when the magnetizing coil is disposed only inside the superconducting bulk body, the magnetic field applied to the inside of the bulk becomes larger than the magnetic field applied to the outside of the bulk.
[0011]
Therefore, in the superconducting magnet, if an attempt is made to magnetize the entire superconducting bulk body, an excessive magnetic field will be applied to the superconducting bulk body in the vicinity of the magnetizing coil. In general, the critical current density of a superconductor has a magnetic field dependency. When the magnetic field increases, the critical current density decreases. Therefore, it is not preferable to apply an excessive magnetic field to the superconducting bulk body.
[0012]
In addition, when a coil of a superconducting wire is used as the magnetizing coil of the superconducting magnet, there arises a problem of critical current density of the superconducting wire itself. That is, the greater the magnetic field generated by the magnetizing coil, the greater the magnetic field experienced by the superconducting wire itself, and the critical current density decreases. Therefore, superconducting deposition is required to generate a large magnetic field by flowing a large current through the superconducting magnetizing coil. The magnet coil must be enlarged. Therefore, from the viewpoint of reducing the size and weight of the magnet, the smaller the applied magnetic field is, the better it is to capture the same amount of magnetic flux in the superconducting bulk.
[0013]
The present invention is a superconducting bulk magnet composed of a superconducting bulk body and a magnetizing coil, which does not apply an excessive magnetic field to the superconducting bulk body, and generates a small magnetic field in each magnetizing coil. An object of the present invention is to provide a superconducting bulk magnet having a structure in which a magnetic coil efficiently magnetizes the superconducting bulk body.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the gist of the present invention is as follows.
(1) The inner periphery side magnetized coil is the center, the surroundings are surrounded by a superconducting bulk body made of a cylindrical superconducting type 2 superconductor, and the outer side of the superconducting bulk body is surrounded by the outer periphery side magnetizing coil. A superconducting bulk magnet surrounded by a cylindrical superconducting bulk magnet so that the inner and outer magnetized coils that pass currents in opposite directions to each other share a central axis. A superconducting bulk magnet characterized by being arranged and applying a magnetic field in the same direction as the central axis to the superconducting bulk body.
(2) The superconducting bulk material is a 123 phase RBaCuO-based (R represents a rare earth element) or Nd-based oxide superconductor in which fine 211 phases are dispersed. Superconducting bulk magnet.
(3) In the above (1) or (2), the superposition of the magnetic field generated by the inner peripheral side magnetizing coil and the outer peripheral side magnetizing coil applies a uniform magnetic field to the superconducting bulk body. The superconducting bulk magnet described.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the shape of the superconducting bulk body is a hollow cylindrical shape, but more specifically, a hollow cylindrical shape, a perforated rectangular parallelepiped shape, a hollow elliptical cylindrical shape, and the like can be given. The material of the superconducting bulk material is preferably a 123-phase RBaCuO-based (R represents a rare earth element) or Nd (neodymium) -based oxide superconductor in which fine 211 phases are dispersed. These superconductors are type 2 superconductors, have a high pinning effect, and can obtain a high critical current density even in a high magnetic field. There are no particular limitations on the composition, manufacturing method, and the like of the constituent components of these superconductors, and any type of superconductor having a high pinning effect may be used. An example of the production method is the MPMG method in which a pulverization step is added to the melt solidification method described in JP-B-7-51463. Further, the superconducting bulk body may be directly manufactured into a hollow cylindrical shape, or may be formed into a cylindrical shape by drilling a hole in the superconducting bulk body once manufactured into a solid shape without a hole by machining or the like. .
[0016]
The inner circumference side magnetized coil and the outer circumference side magnetized coil of the present invention are coils made of a normal conductor wire such as a copper wire or an aluminum wire, or a superconductor wire such as a Bi-based silver sheath wire, for example. . Different materials may be used for the inner peripheral magnetizing coil and the outer peripheral magnetizing coil.
[0017]
In the present invention, the inner circumference side magnetized coil and the outer circumference side magnetized coil are arranged on the inner and outer circumferences of the superconducting bulk body so as to share the central axis.
[0018]
Here, if currents in opposite directions are applied to both the inner and outer magnetized coils, as shown schematically in FIG. 1, the magnetic flux (2) generated by the inner magnetized coil and the magnetic flux generated by the outer magnetized coil (▲) 1 ▼ is the same direction in the space between the two coils. That is, if currents in opposite directions are applied to both the inner and outer magnetized coils, the magnetic field applied to the superconducting bulk body by the inner and outer magnetized coils will be the same direction, and the magnetic field generated by the inner and outer magnetized coils in the superconducting bulk body Are superimposed and applied.
[0019]
Therefore, the magnetic field generated by each magnetizing coil may be smaller than that of a conventional superconducting magnet using a superconducting bulk body and a magnetizing coil. For this reason, when the coil of a normal conducting wire is used for the magnetizing coil, the current flowing through the magnetizing coil can be reduced, so that heat generation can be reduced. In addition, when a superconducting wire coil is used as the magnetizing coil, the magnetic field experienced by each magnetizing coil can be reduced, so that a decrease in the critical current density of the superconducting wire can be suppressed. This makes it possible to reduce the size and weight of the superconducting magnetized coil. FIG. 2A shows the magnetic field distribution applied to the superconducting bulk body when the magnetizing coil is arranged only on the outer peripheral side of the cylindrical superconducting bulk body having the radius a and the inner diameter b, and FIG. 2 shows magnetic field distributions when magnetized coils are arranged on both the inner and outer peripheral sides of a cylindrical superconducting bulk body having an inner diameter b.
[0020]
As shown in FIG. 2A, when the magnetizing coil is arranged only on one side, the applied magnetic field on the magnetizing coil side increases and the critical current density decreases. Then, when a magnetic field is applied to the entire bulk, the bias of the magnetic field applied to the bulk becomes considerably large.
[0021]
On the other hand, if magnetized coils are arranged on both sides of the cylindrical superconducting bulk body as in the present invention, a magnetic field is applied from the magnetized coils on both sides, and therefore, as shown in FIG. The maximum value of the applied magnetic field can be reduced.
[0022]
Furthermore, if the magnetic field applied to the superconducting bulk body is made uniform by the inner and outer magnetized coils, the density of the magnetic flux captured by the superconducting bulk body becomes uniform, making the superconductor more than necessary. Therefore, the critical current density is prevented from being lowered and the density of the magnetic flux that can be captured can be increased.
[0023]
In order to make the magnetic field applied to the superconducting bulk material uniform, the shape, the number of turns, and the magnitude of the current to be applied are adjusted for the inner and outer magnetized coils. Uniformity can be improved by optimally combining the shape, the number of turns, and the magnitude of the energized current.
[0024]
The superconducting bulk magnet of the present invention cools the cylindrical superconducting bulk body to a critical temperature or lower in advance, and then applies a magnetic field to the superconductor with magnetized coils arranged on the inner and outer peripheral sides thereof. Alternatively, the superconducting bulk body is cooled to a critical temperature or lower while applying a magnetic field to the superconductor by the magnetizing coil.
[0025]
As a cooling method of the superconducting bulk body, there are immersion cooling and conduction cooling. In the case of immersion cooling, liquid helium, liquid nitrogen, liquid neon, or the like is used as the refrigerant. In the case of conduction cooling, the superconducting bulk body is surrounded by a heat insulating member, and the heat conducting member is cooled by a refrigerator.
[0026]
Here, if the strength of the external magnetic field applied to the bulk is greater than or equal to the lower critical magnetic field and less than or equal to the upper critical magnetic field, the bulk becomes mixed and the external magnetic field penetrates locally. The entered magnetic flux is trapped at the pinning point of the superconductor, and a vortex-like permanent current is generated around it. Even if the magnetic field applied to the bulk is eliminated, the magnetic flux trapped at the pinning point is preserved. Accordingly, the superconducting bulk body itself is magnetized.
[0027]
When the magnetic field is applied by the magnetizing coil after the superconducting bulk body is cooled below the critical temperature, a pulse current may be passed through the magnetizing coil. The pulse current may be repeatedly passed through the magnetizing coil.
[0028]
Using a superconducting coil as the magnetizing coil is advantageous in maintaining the superconducting state of the superconducting bulk body because heat generation from the magnetizing coil can be suppressed. In this case, however, the magnetized coil (superconducting coil) must also be cooled below the critical temperature. The cooling method is the same as the cooling method of the superconducting bulk body.
[0029]
【Example】
Examples of the present invention will be described below.
FIG. 3 is a schematic cross-sectional view of a superconducting bulk magnet that is an embodiment of the present invention. The superconducting bulk magnet includes a cylindrical superconducting bulk body 1, an inner peripheral side magnetized coil 3 disposed along the inner periphery of the bulk body 1, and an outer peripheral side disposed along the outer periphery of the bulk body 1. It consists of a
[0030]
The superconducting bulk body 1 is prepared by melting a Y-Ba-Cu-O superconducting material into a cylindrical bulk body having an outer diameter of 46 mm and a height of 20 mm by a melting method, and a hole having a diameter of 20 mm is formed in the cylindrical bulk body. It was. Inside the superconducting bulk body 1, an inner peripheral side magnetized coil 3 wound with a copper wire with an outer diameter of 20 mm, an inner diameter of 16 mm and a height of 20 mm is inserted, and further on the outer side of the superconducting bulk body 1 with an outer diameter of 50 mm and an inner diameter of 46 mm. A superconducting bulk magnet was constructed by arranging an outer peripheral magnetizing
[0031]
The magnetic field of the superconducting bulk body portion when a current of 5000 A / cm 2 is applied only to the outer peripheral side magnetized
[0032]
Further, if an electric current is applied only to the inner peripheral side magnetizing coil 3 and a magnetic field of 53 mT or more is applied to the superconducting bulk body 1, it is necessary to pass an electric current of 73810 A / cm 2 to the inner peripheral side magnetizing coil 3. The maximum value of the magnetic field applied to the superconducting bulk body 1 reaches 175 mT.
[0033]
On the other hand, when a current is passed through both the outer peripheral magnetizing
[0034]
Then, after applying the magnetic field to the superconducting bulk body 1 and cooling the superconducting bulk body 1 to a critical temperature or lower, the currents of the inner peripheral side magnetized coil 3 and the outer peripheral side magnetized
[0035]
【The invention's effect】
According to the superconducting magnet of the present invention, both magnetized coils arranged on the inner peripheral side and the outer peripheral side apply a magnetic field to the superconducting bulk body, so that the magnetic field applied by each magnetized coil can be small. Therefore, when the normal conducting magnetized coil is used, the amount of generated heat can be reduced, so that the temperature of the superconducting bulk body is unlikely to rise. When the superconducting magnetized coil is used, deterioration of the critical current density due to the magnetic field can be suppressed. In addition, since the magnetic field applied to the superconducting bulk body can be made substantially uniform, it is advantageous in capturing the magnetic flux in the superconducting bulk body.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a magnetic field generated when currents in opposite directions are applied to both inner and outer magnetized coils.
FIG. 2A is a schematic diagram of a magnetic field distribution when a magnetizing coil is disposed only on the outer peripheral side.
(B) Schematic of magnetic field distribution when magnetized coils are arranged on the inner peripheral side and the outer peripheral side.
FIG. 3 is a schematic cross-sectional view of one embodiment of a superconducting magnet of the present invention.
FIG. 4 is a schematic diagram of a magnetic field distribution of a superconductor bulk body portion in one embodiment of the superconducting magnet of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Superconducting bulk body 3 Inner circumference side magnetized
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26961296A JP3727122B2 (en) | 1996-10-11 | 1996-10-11 | Superconducting bulk magnet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26961296A JP3727122B2 (en) | 1996-10-11 | 1996-10-11 | Superconducting bulk magnet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10116721A JPH10116721A (en) | 1998-05-06 |
| JP3727122B2 true JP3727122B2 (en) | 2005-12-14 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26961296A Expired - Fee Related JP3727122B2 (en) | 1996-10-11 | 1996-10-11 | Superconducting bulk magnet |
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| Country | Link |
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| JP (1) | JP3727122B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3858221B2 (en) * | 2002-06-12 | 2006-12-13 | 財団法人国際超電導産業技術研究センター | Superconducting magnet made of high-temperature superconducting bulk material and method for producing the same |
| JP4799979B2 (en) * | 2005-04-28 | 2011-10-26 | 新日本製鐵株式会社 | Oxide superconductor coil, oxide superconductor coil manufacturing method, oxide superconductor coil excitation method, oxide superconductor coil cooling method, and magnet system |
| WO2007148571A1 (en) * | 2006-06-19 | 2007-12-27 | Kyushu Institute Of Technology | Pulse magnetization method of bulk superconductor |
| JP4895714B2 (en) * | 2006-07-31 | 2012-03-14 | アイシン精機株式会社 | Superconductor, superconducting magnetic field generator, superconducting magnetic field generator, and nuclear magnetic resonance apparatus |
| JP5360638B2 (en) * | 2007-12-27 | 2013-12-04 | 株式会社イムラ材料開発研究所 | Superconducting magnetic field generator, method of magnetizing superconducting magnetic field generator, and nuclear magnetic resonance apparatus |
| JP6393916B2 (en) * | 2014-02-20 | 2018-09-26 | 北田回転機関合同会社 | Electric rotating machine |
| CN115158029B (en) * | 2022-08-03 | 2023-04-14 | 成都理工大学 | Superconducting magnetic levitation train |
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1996
- 1996-10-11 JP JP26961296A patent/JP3727122B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| JPH10116721A (en) | 1998-05-06 |
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