JP4275262B2 - Superconducting coil - Google Patents
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- JP4275262B2 JP4275262B2 JP25155299A JP25155299A JP4275262B2 JP 4275262 B2 JP4275262 B2 JP 4275262B2 JP 25155299 A JP25155299 A JP 25155299A JP 25155299 A JP25155299 A JP 25155299A JP 4275262 B2 JP4275262 B2 JP 4275262B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
Description
【０００１】
【発明の属する技術分野】
本発明は、強制冷却導体の接続構造およびその製造方法、並びに強制冷却型超電導コイルおよび核融合用超電導コイルシステムに関するものである。
【０００２】
【従来の技術】
従来一般に採用されている核融合装置用などの大型超電導コイルは、全体を構成する個々のコイルに分割して製作した後、全体を組み上げてコイル間を接続する方法がとられる場合が多い。ケーブル・イン・コンジット型強制冷却導体を巻線して製作される超電導コイルにおいては、接続端部のステンレス鋼等の金属コンジットを銅管に置き換えて、この銅管間を相互にラップ接続する方法がとられることがある。この接続構造は、銅管が接続部の電流パスを担うとともに、内部を強制循環する超臨界圧ヘリウムの気密構造部材の役割を果たすことが特徴である。
図５には、その従来法によるケーブル・イン・コンジット型強制冷却導体の接続構造の一例が示されている。また、図６には従来法による超電導撚線と銅管の接触界面部の拡大図が示されている。この構造において超電導撚線３を流れる電流は、その外周部を覆う銅管２、銅ブロック６へと分流した後に、他方の導体端部の銅管２から超電導撚線３へと流れる。なお、この種の強制冷却導体の接続構造に関連するものとしては、例えばP.Bruzzone et al. : Design and R&D of the Joint for ITER Conductor IEEE Trans. on Applied Superconductivity Vol.7 No.2 P.461 1997などが挙げられる。
【０００３】
【発明が解決しようとする課題】
このケーブル・イン・コンジット型強制冷却導体の接続部は、電流が超電導撚線から銅管を介して他方の撚線へ流れるため、通電動作時にはジュール発熱を伴う。この発熱が大きい場合には、導体および接続端部の銅管内部を強制循環する超臨界圧ヘリウムの温度が上昇し、冷凍機に大きな熱負荷を与えることになるとともに、場合によっては接続部の超電導状態が常電導に転移する問題が生じる。 すなわち、導体接続部には冷凍機の熱負荷低減および接続部を含めた超電導コイルの超電導安定性の観点から低い電気接続特性が要求される。しかしながら、
超電導撚線から銅管へ電流が流れる領域の電気的な接触形状は、丸型の超電導素線が銅管内壁と点接触している場合が多く、接触面積が小さいことに起因して、両者間の接触電気抵抗は必ずしも低くない。
また、この接触率を大きくするため銅管の内径を小さくするように減面加工すると、撚線と銅管の接触抵抗は低下するが、銅管内部の空隙率が小さくなり、内部を循環する超臨界圧ヘリウムの圧力損失が大きくなるという問題が生じる。すなわち、超電導撚線と銅管の接触抵抗を低減させるには構造上の限界があった。
また、超電導撚線と銅管の接触部は、超電導生成のためのコイル熱処理が施されているため、両者は拡散反応し冶金的に結合しているものの、一般的な熱処理温度である６５０℃〜８００℃の温度範囲では固相反応であり、接合界面の仕上げ荒さや清浄度等の表面状態の影響が大きい。すなわち、接合界面部の電気・機械特性の信頼性が十分でなく、コイル冷却時の熱ひずみや運転時の電磁力で撚線と銅管間の接触電気抵抗が劣化する懸念があった。
本発明はこれに鑑みなされたもので、その目的とするところは、上記従来技術の欠点を排除し、機械強度が高くかつ接続電気抵抗が低く、接続部においてジュール発熱が小さく超電導安定性にすぐれた強制冷却導体の接続構造およびその製造方法を提供することにある。
【０００４】
【課題を解決するための手段】
すなわち本発明は、接続端部の超電導撚線が電気接続部材である銅管で覆われ、電流が超電導撚線から前記銅管を介して他方の電気部材に流れる構造を有し、かつ動作時に前記銅管内部の超電導撚線の間隙に冷媒ヘリウムが循環するＮｂ３ＡｌあるいはＮｂ３Ｓｎ系の化合物超電導素線からなるケーブル・イン・コンジット型強制冷却導体の接続構造において、前記超電導撚線と前記銅管内壁の接触界面部に、厚さが前記銅管の１／５０以下の銅あるいは銀等の低電気抵抗の金属箔を配置し、かつ前記銅管内部の冷媒ヘリウムが循環する空隙率を、接続端部以外の空隙率よりも１０〜１５％小さく形成するようにして初期の目的を達成するようにしたものである。
また本発明は、接続端部の超電導撚線が電気接続部材である銅管で覆われ、電流が超電導撚線から前記銅管を介して他方の電気部材に流れる構造を有し、かつ動作時に銅管内部の超電導撚線の間隙に冷媒ヘリウムが循環するＮｂ３ＡｌあるいはＮｂ３Ｓｎ系の化合物超電導素線からなるケーブル・イン・コンジット型強制冷却導体の接続構造の製造方法において、前記銅管の内壁部に厚さが５０μｍ以下の銀層を形成して超電導生成熱処理前の多重撚線を挿入し、次いで前記銅管を所定の内径まで減面加工した後に、７８０℃以上の超電導生成熱処理を施すことによって、超電導撚線、銀層、銅管の接触界面部に銀と銅の合金相を形成させるようにしたものである。
また、ケーブル・イン・コンジット型強制冷却型超電導コイルに、前記接続構造あるいは前記製造方法にて製造した接続構造を用いるようにしたものである。また、核融合用超電導コイルシステムに前記強制冷却型超電導コイルを用いるようにしたものである。
すなわち、このように構成された強制冷却導体の接続構造であると、超電導撚線と銅管間の接触電気抵抗を大きく低減することができる。これは金属箔の中間材を配置したことにより、超電導撚線と銅管の接触面積が大幅に増加するためである。
この接触面積が増加するメカニズムについて説明すると、超電導撚線に金属箔を巻き付けて銅管に挿入した後に、減面加工して銅管の内径を小さくすると、銅管内部の超電導撚線も圧密化されてその外径も小さくなる。換言すれば銅管の内周長が短くなるために、その撚線外部に巻き付けられた金属箔も外周長が短くなるような変形力を受ける。金属箔は銅管に比べて厚さが非常に薄く剛性も小さいため、金属箔は銅管側に変形することなしに、超電導撚線の表面部のくぼみにシワがよるように容易に変形する。
結果として、金属箔は撚線表面部に位置する素線の丸型に沿うように変形配置され、超電導撚線と銅管の接触領域は従来の点接触ではなく面接触になり、その接触面積が増加する。なお、ケーブル・イン・コンジット型強制冷却導体の金属コンジット内部の空隙率は３５−４０％であるのに対し、接続端部の導体内部の空隙率１０〜１５％小さくすることで接続端部の金属コンジットを除去した超電導撚線の外径は、銅管を被せて減面加工する際にその外径が小さくなるため、金属箔を配置する効果は必ず発揮される。
また、撚線と銅管の界面に銀メッキ層を配置し、７７９℃以上の熱処理を施すことによって、超電導撚線を構成する銅安定化素線の表面の銅と、銀メッキ層、銅管の３者の接触界面部には、冶金的に銅−銀共晶反応による液相が生成する。液相は界面部の凹部を埋め、その拡散を助長するため拡散反応速度は非常に早くなり、従来の銅相互の固相反応による冶金結合より強固な機械結合が得られるのである。
【０００５】
【実施例】
以下図示した実施例に基づいて本発明を詳細に説明する。図１および図２にはその強制冷却導体の接続構造部が断面で示されている。
（実施例１）
超電導生成の反応熱処理を施す前の未熱処理Ｎｂ３Ａｌ素線を１９２本撚線して導体を作製した。Ｎｂ３Ａｌ素線の線径はφ０．８１ｍｍで、導体は素線を３本撚り合わせたものをさらに４本撚り合わせるという工程を繰り返して得られる３×４×４×４の撚線構造を有する多重撚線である。撚線ピッチは各々６５ｍｍ、９０ｍｍ、１５０ｍｍ、２７０ｍｍである。
この導線を長さ３５０ｍｍに切断し、導線外周部に厚さ２０μｍの無酸素銅の箔を長手方向の全域に渡って２回巻き付けた。その後、外径１９．０ｍｍ、内径１６．４ｍｍの銅管内部に挿入して、スエージ装置で外径１５．８８ｍｍ、内径１２．８５ｍｍまで減面加工した。
比較用のサンプルとして、無酸素銅箔を巻き付けない導線のみを銅管に挿入したものを作成した。作製された２種類の反応熱処理前の超電導導体と銅管の複合体を７５０℃で５０時間、真空中で熱処理し、超電導相を生成させるとともに、超電導撚線と銅箔および銅箔と銅管を冶金的に接合させた。これらサンプルにおける銅管内部の空隙率は２２．６％である。
このようにして作成された２種類の接続要素サンプルを液体ヘリウム中で通電試験し、銅管と超電導導体間の接触抵抗を測定した。図３には超電導撚線と銅管の接触抵抗の測定結果が示されている。その結果、ゼロ磁場から４Ｔの全磁場領域において、超電導導体から電気接続部材である銅管への電気接触抵抗が２／３以下に低減できることが明らかとなった。
そこで、この電気抵抗低減の要因を明確にするために測定された接続要素サンプルを切断して、その断面構造を観察した。図４は銅箔を巻き付けたサンプルの断面写真で、その写真から明らかなように、超電導撚線と銅管の界面部に配置された銅箔が減面加工によって導体表面のくぼみに入り込み、結果として導体表面と銅管内面の接触面積を増加させたことが、両者間の電気抵抗の低減に大きく寄与したことがわかった。
これは、銅箔を巻き付ける前の導体は外部からの拘束が無いためにその外径が約１５ｍｍ程度であったが、銅管を被せて減面加工することにより外径が約１２．８ｍｍまで絞られたため、導体外周部に巻き付けられた銅箔の周長が短くなり、結果として導体表面のくぼみに移動したものである。なお、銅箔を巻き付けないサンプルの断面における、超電導導体と銅管の接触部は、丸型の素線が銅管内面に点で接触している状態であった。
（実施例２）
上記実施例１と同様のＮｂ３Ａｌ超電導撚線と銅管を用いて接続サンプルを作製した。ここでは銅管の内壁部に厚さ１０μｍの銀メッキした後に、超電導撚線を挿入し、減面加工と熱処理を施した。熱処理温度は銀−銅の共晶温度である７７９℃以上の８００℃とし、時間は１０ｈとした。超電導撚線と銅管の接触抵抗を測定したところ、４Ｔの外部磁場中での接触抵抗は３５ｎΩであった。その断面構造を観察したところ、銀メッキ層の銀が超電導撚線を構成する素線表面の安定化銅や銅管に拡散しており、十分な拡散反応層が形成されていることが確認できた。
撚線と銅管の接触部の機械強度を評価したところ、銀メッキを施さない従来の撚線と銅管の複合体は接合界面部で破壊したが、銀メッキ処理したものは超電導素線の安定化銅の領域で破壊した。すなわち、銀メッキ処理によって接合界面部の強度は十分に確保できることが確認された。なお、銀メッキ層の厚さを変化させた接続サンプルを種々作製し、その機械強度を評価したところ、８００℃で１０ｈの熱処理条件下では、メッキ厚さが５０μｍ以上のサンプルの場合、界面の部分的に未反応の銀層が残存し、強度の弱い銀層から破壊することがわかった。なお接触電気抵抗に関しては銀層が残存しても、その電気抵抗自身が低いため大きな特性劣化は認められなかった。
【０００６】
【発明の効果】
以上説明してきたように本発明によれば、機械強度が高くかつ接続電気抵抗が低く、接続部においてジュール発熱が小さく超電導安定性にすぐれた強度冷却導体の接続構造を得ることができる。
【図面の簡単な説明】
【図１】本発明の強制冷却導体の接続構造の一実施例を示す要部拡大断面図である。
【図２】銅管内壁の銀メッキ層が超電導撚線と銅管の銅と拡散反応して銅−銀の合金層が形成された部の拡大図である。
【図３】本発明の強制冷却導体の接続構造部における接触抵抗の特性図である。
【図４】本発明の実施例で作製されたサンプルの断面写真を示す図である。
【図５】従来の強制冷却導体の接続構造を示す平面図および要部拡大断面図である。
【図６】従来の強制冷却導体の接続構造を示す要部拡大断面図である。
【符号の説明】
１…純金属中間箔、２…銅管、３超電導撚線、４…銅−銀合金層、５…銀メッキ層、６…銅ブロック。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a forced cooling conductor connection structure and a manufacturing method thereof, and a forced cooling superconducting coil and a superconducting coil system for fusion.
[0002]
[Prior art]
A large superconducting coil generally used for a fusion device or the like conventionally employed is often divided into individual coils constituting the whole and then assembled to connect the coils in many cases. In a superconducting coil manufactured by winding a cable-in-conduit type forced cooling conductor, a metal conduit such as stainless steel at the connection end is replaced with a copper tube, and the copper tubes are lap-connected to each other May be taken. This connection structure is characterized in that the copper tube serves as a current path for the connection part and also serves as a hermetic structure member of supercritical pressure helium forcibly circulating inside.
FIG. 5 shows an example of a connection structure of a cable-in-conduit type forced cooling conductor according to the conventional method. FIG. 6 shows an enlarged view of a contact interface between a superconducting stranded wire and a copper tube according to a conventional method. In this structure, the current flowing through the superconducting stranded
[0003]
[Problems to be solved by the invention]
In the connection portion of the cable-in-conduit type forced cooling conductor, current flows from the superconducting stranded wire to the other stranded wire through the copper tube, and therefore, Joule heat is generated during energization operation. When this heat generation is large, the temperature of the supercritical pressure helium that forcibly circulates inside the copper pipe at the conductor and the connection end rises, giving a large heat load to the refrigerator, and in some cases the connection part There arises a problem that the superconducting state is transferred to normal conduction. In other words, the conductor connection portion is required to have low electrical connection characteristics from the viewpoint of reducing the thermal load of the refrigerator and the superconducting stability of the superconducting coil including the connection portion. However,
The electrical contact shape in the region where current flows from the superconducting stranded wire to the copper tube is often due to the fact that the round superconducting wire is in point contact with the inner wall of the copper tube and the contact area is small. The contact electrical resistance between them is not necessarily low.
In addition, if the surface is reduced so that the inner diameter of the copper tube is reduced in order to increase the contact ratio, the contact resistance between the stranded wire and the copper tube is reduced, but the porosity inside the copper tube is reduced and circulates inside. The problem arises that the pressure loss of supercritical helium increases. That is, there is a structural limit in reducing the contact resistance between the superconducting stranded wire and the copper tube.
Moreover, since the coil heat treatment for superconductivity production | generation is given to the contact part of a superconducting twisted wire and a copper pipe, both are diffusion-reacted and are metallurgically bonded, but 650 degreeC which is a general heat processing temperature. In the temperature range of ˜800 ° C., it is a solid-phase reaction, and the influence of the surface condition such as the finishing roughness and cleanliness of the bonding interface is large. That is, the reliability of the electrical / mechanical characteristics of the joint interface is not sufficient, and there is a concern that the contact electrical resistance between the stranded wire and the copper tube is deteriorated due to thermal strain during coil cooling or electromagnetic force during operation.
The present invention has been made in view of the above, and the object of the present invention is to eliminate the drawbacks of the above-described conventional technology, to have high mechanical strength and low connection electrical resistance, low Joule heat generation at the connection portion, and excellent superconducting stability. Another object is to provide a forced cooling conductor connection structure and a method of manufacturing the same.
[0004]
[Means for Solving the Problems]
That is, the present invention has a structure in which the superconducting stranded wire at the connection end is covered with a copper tube as an electric connecting member, and a current flows from the superconducting stranded wire to the other electric member through the copper tube, and during operation. In the connection structure of a cable-in-conduit type forced cooling conductor made of Nb3Al or Nb3Sn-based compound superconducting wire in which refrigerant helium circulates in the gap between the superconducting stranded wires inside the copper tube, the superconducting stranded wire and the inner wall of the copper tube A metal foil having a low electrical resistance such as copper or silver having a thickness of 1/50 or less of the copper pipe is disposed at the contact interface portion of the copper pipe, and a porosity at which the refrigerant helium circulates inside the copper pipe The initial object is achieved by forming it to be 10 to 15% smaller than the porosity other than the portion.
Further, the present invention has a structure in which the superconducting stranded wire at the connection end is covered with a copper tube as an electric connecting member, and a current flows from the superconducting stranded wire to the other electric member through the copper tube, and during operation. In the manufacturing method of the connection structure of the cable-in-conduit type forced cooling conductor made of Nb3Al or Nb3Sn compound superconducting element wire in which refrigerant helium circulates in the gap between the superconducting stranded wires inside the copper tube, the inner wall portion of the copper tube By forming a silver layer having a thickness of 50 μm or less and inserting a multiple stranded wire before heat treatment for superconductivity generation, then reducing the surface of the copper tube to a predetermined inner diameter, and then performing heat treatment for superconductivity generation at 780 ° C. or higher. An alloy phase of silver and copper is formed at the contact interface between the superconducting stranded wire, the silver layer, and the copper tube.
Further, the cable-in-conduit forced cooling superconducting coil uses the connection structure or the connection structure manufactured by the manufacturing method. Further, the forced cooling superconducting coil is used in a superconducting coil system for nuclear fusion.
In other words, the forced cooling conductor connection structure configured as described above can greatly reduce the contact electrical resistance between the superconducting stranded wire and the copper tube. This is because the contact area between the superconducting stranded wire and the copper tube is greatly increased by arranging the metal foil intermediate material.
Explaining the mechanism by which this contact area increases. After winding a metal foil around a superconducting stranded wire and inserting it into a copper tube, reducing the inner diameter of the copper tube by reducing the surface area will also consolidate the superconducting stranded wire inside the copper tube. As a result, the outer diameter is also reduced. In other words, since the inner peripheral length of the copper tube is shortened, the metal foil wound around the stranded wire is also subjected to a deformation force that shortens the outer peripheral length. Since the metal foil is much thinner and less rigid than the copper tube, the metal foil is easily deformed so that it is wrinkled by the depression on the surface of the superconducting stranded wire without being deformed to the copper tube side. .
As a result, the metal foil is deformed and arranged so as to follow the round shape of the strand located on the surface portion of the stranded wire, and the contact area between the superconducting stranded wire and the copper tube becomes a surface contact instead of the conventional point contact, and its contact area Will increase. In addition, while the porosity in the metal conduit of the cable-in-conduit type forced cooling conductor is 35-40%, the porosity of the connection end is reduced by 10-15% inside the conductor in the connection end. Since the outer diameter of the superconducting stranded wire from which the metal conduit is removed is reduced when the copper tube is covered to reduce the surface, the effect of arranging the metal foil is always exhibited.
Further, by placing a silver plating layer at the interface between the stranded wire and the copper tube and performing a heat treatment at 779 ° C. or higher, the copper on the surface of the copper stabilizing strand constituting the superconducting stranded wire, the silver plating layer, the copper tube A liquid phase is formed metallurgically by a copper-silver eutectic reaction at the three contact interfaces. Since the liquid phase fills the recesses at the interface and promotes its diffusion, the diffusion reaction rate becomes very fast, and a stronger mechanical bond can be obtained than the conventional metallurgical bond by solid phase reaction between copper.
[0005]
【Example】
Hereinafter, the present invention will be described in detail based on the illustrated embodiments. 1 and 2 show the connection structure of the forced cooling conductor in section.
(Example 1)
A conductor was produced by twisting 192 unheated Nb3Al strands before the reaction heat treatment for superconductivity generation. The Nb3Al strand has a wire diameter of φ0.81 mm, and the conductor has a 3 × 4 × 4 × 4 stranded wire structure obtained by repeating the process of twisting four strands of three strands. It is a stranded wire. The twisted wire pitches are 65 mm, 90 mm, 150 mm, and 270 mm, respectively.
The conducting wire was cut into a length of 350 mm, and an oxygen-free copper foil having a thickness of 20 μm was wound around the entire circumference in the longitudinal direction twice. After that, it was inserted into a copper tube having an outer diameter of 19.0 mm and an inner diameter of 16.4 mm, and the surface was reduced to an outer diameter of 15.88 mm and an inner diameter of 12.85 mm with a swage device.
As a sample for comparison, a sample in which only a conductive wire without an oxygen-free copper foil was inserted into a copper tube was prepared. The two kinds of composites of the superconducting conductor and the copper tube before the heat treatment were heat-treated at 750 ° C. for 50 hours in a vacuum to generate a superconducting phase, and a superconducting twisted wire and copper foil and copper foil and copper tube Were metallurgically joined. The porosity inside the copper tube in these samples is 22.6%.
The two types of connection element samples prepared in this manner were subjected to a current test in liquid helium, and the contact resistance between the copper tube and the superconducting conductor was measured. FIG. 3 shows the measurement results of the contact resistance between the superconducting stranded wire and the copper tube. As a result, it has been clarified that the electrical contact resistance from the superconducting conductor to the copper pipe as the electrical connecting member can be reduced to 2/3 or less in the entire magnetic field region from zero magnetic field to 4T.
Then, in order to clarify the factor of this electric resistance reduction, the measured connection element sample was cut | disconnected and the cross-sectional structure was observed. Fig. 4 is a cross-sectional photograph of a sample wound with copper foil. As is clear from the photograph, the copper foil placed at the interface between the superconducting stranded wire and the copper tube enters the recess on the conductor surface by the surface-reducing process. It was found that increasing the contact area between the conductor surface and the inner surface of the copper tube greatly contributed to the reduction in electrical resistance between them.
This is because the outer diameter of the conductor before winding the copper foil is about 15 mm because there is no restriction from the outside, but the outer diameter is reduced to about 12.8 mm by covering the copper tube and reducing the surface. As a result of the reduction, the circumference of the copper foil wound around the outer periphery of the conductor is shortened, and as a result, the copper foil has moved to a recess on the conductor surface. Note that the contact portion between the superconducting conductor and the copper tube in the cross section of the sample where the copper foil was not wound was in a state where the round wire was in contact with the inner surface of the copper tube.
(Example 2)
A connection sample was prepared using the same Nb3Al superconducting stranded wire and copper tube as in Example 1 above. Here, after silver plating of a thickness of 10 μm was applied to the inner wall portion of the copper tube, a superconducting stranded wire was inserted, and surface reduction processing and heat treatment were performed. The heat treatment temperature was set to 800 ° C. of 779 ° C. or higher, which is a silver-copper eutectic temperature, and the time was 10 hours. When the contact resistance between the superconducting stranded wire and the copper tube was measured, the contact resistance in an external magnetic field of 4T was 35 nΩ. When the cross-sectional structure was observed, it was confirmed that the silver in the silver plating layer had diffused into the stabilized copper or copper tube on the surface of the strands constituting the superconducting stranded wire, and that a sufficient diffusion reaction layer was formed. It was.
When the mechanical strength of the contact portion between the stranded wire and the copper tube was evaluated, the composite of the conventional stranded wire and copper tube not subjected to silver plating was destroyed at the joint interface, but the silver-plated composite was a superconducting element wire. It broke down in the area of stabilized copper. That is, it was confirmed that the strength of the joint interface portion can be sufficiently secured by the silver plating process. Various connection samples with different thicknesses of the silver plating layer were prepared and their mechanical strength was evaluated. Under a heat treatment condition of 800 ° C. for 10 hours, the sample having a plating thickness of 50 μm or more It was found that a partially unreacted silver layer remained and destroyed from a weak silver layer. Regarding the contact electrical resistance, even if the silver layer remained, the electrical resistance itself was low, and no significant deterioration in characteristics was observed.
[0006]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a connection structure of a strength cooling conductor having high mechanical strength, low connection electric resistance, low Joule heat generation at the connection portion and excellent superconducting stability.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a main part showing an embodiment of a forced cooling conductor connection structure according to the present invention.
FIG. 2 is an enlarged view of a portion where a silver-plated layer on the inner wall of a copper tube is diffusion-reacted with a superconducting stranded wire and copper in the copper tube to form a copper-silver alloy layer.
FIG. 3 is a characteristic diagram of contact resistance in the connection structure portion of the forced cooling conductor of the present invention.
FIG. 4 is a view showing a cross-sectional photograph of a sample produced in an example of the present invention.
5A and 5B are a plan view and a main part enlarged cross-sectional view showing a conventional forced cooling conductor connection structure, respectively.
FIG. 6 is an enlarged cross-sectional view of a main part showing a connection structure of a conventional forced cooling conductor.
[Explanation of symbols]
DESCRIPTION OF
Claims (6)
接続端部の超電導撚線が電気接続部材である銅管で覆われ、電流が超電導撚線から前記銅管を介して他方の電気部材に流れる構造を有し、かつ動作時に前記銅管内部の超電導撚線の間隙に冷媒ヘリウムが循環するＮｂ３ＡｌあるいはＮｂ３Ｓｎ系の化合物超電導素線からなるケーブル・イン・コンジット型強制冷却導体の接続構造において、前記超電導撚線と前記銅管内壁の接触界面部に、厚さが５０μｍ以下の銅あるいは銀の金属層が配置され、かつ前記接続端部の銅管内部の冷媒ヘリウムが循環する空隙率が、接続端部以外の空隙率よりも１０〜１５％小さく形成されていることを特徴とする強制冷却導体の接続構造。 Manufactured by the method according to claim 1 or 2,
The superconducting stranded wire at the connecting end is covered with a copper tube as an electric connecting member, and a current flows from the superconducting stranded wire to the other electric member through the copper tube, and the copper tube inside the copper tube during operation In a connection structure of a cable-in-conduit type forced cooling conductor composed of a Nb 3 Al or Nb 3 Sn-based compound superconducting wire in which refrigerant helium circulates in the gap between the superconducting stranded wires, the superconducting stranded wire and the inner wall of the copper tube the contact interface portion, the thickness is arranged a metal layer of less copper or silver 50 [mu] m, and porosity refrigerant helium inside the copper tube of the connection end portion is circulated, than the porosity of the non-connecting end portion 10 A forced cooling conductor connection structure characterized in that it is formed to be smaller by 15%.
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| JP25155299A JP4275262B2 (en) | 1999-09-06 | 1999-09-06 | Superconducting coil |
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| JP25155299A JP4275262B2 (en) | 1999-09-06 | 1999-09-06 | Superconducting coil |
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