Abstract
The stabilization of current intensity in superconductor coils, a problem of major importance in the construction of large coils, has been studied both theoretically and experimentally. Investigations, into the dynamics of the transition of a superconductor transporting a current between the superconductor state at zero resistance and the state at normal resistance (blocking) reveal the existence of a characteristic intensity, Im, for which the propagation velocity of the normal region is zero. This intensity is directly dependent on the heat exchanges occurring between the superconductor and the environment and on the resistance of the material in the normal state; Im depends indirectly on the intensity of the magnetic field. If a superconductor Is used at. a current intensity of less than lm, the propagation velocity is negative and the superconductor may be able to effect the opposite transition from the normal state to the superconductor state. It can be shown that, for an intensity Is such that Is = lm/{radical}2 the propagation velocity which is negative becomes infinitely large. The existence of these two characteristic intensities makes it possible to distinguish three types of behaviour differing in the intensity of the current passing through the superconductor. Measurements have been made
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Citation Formats
Donadieu, L., and Maldy, J.
Studies of the Stabilization of Superconductor Coils; Etudes sur la Stabilisation des Bobines Supraconductrices.
IAEA: N. p.,
1966.
Web.
Donadieu, L., & Maldy, J.
Studies of the Stabilization of Superconductor Coils; Etudes sur la Stabilisation des Bobines Supraconductrices.
IAEA.
Donadieu, L., and Maldy, J.
1966.
"Studies of the Stabilization of Superconductor Coils; Etudes sur la Stabilisation des Bobines Supraconductrices."
IAEA.
@misc{etde_22177961,
title = {Studies of the Stabilization of Superconductor Coils; Etudes sur la Stabilisation des Bobines Supraconductrices}
author = {Donadieu, L., and Maldy, J.}
abstractNote = {The stabilization of current intensity in superconductor coils, a problem of major importance in the construction of large coils, has been studied both theoretically and experimentally. Investigations, into the dynamics of the transition of a superconductor transporting a current between the superconductor state at zero resistance and the state at normal resistance (blocking) reveal the existence of a characteristic intensity, Im, for which the propagation velocity of the normal region is zero. This intensity is directly dependent on the heat exchanges occurring between the superconductor and the environment and on the resistance of the material in the normal state; Im depends indirectly on the intensity of the magnetic field. If a superconductor Is used at. a current intensity of less than lm, the propagation velocity is negative and the superconductor may be able to effect the opposite transition from the normal state to the superconductor state. It can be shown that, for an intensity Is such that Is = lm/{radical}2 the propagation velocity which is negative becomes infinitely large. The existence of these two characteristic intensities makes it possible to distinguish three types of behaviour differing in the intensity of the current passing through the superconductor. Measurements have been made of Im for different superconductor materials with intense fields: Nb-Zr, Nb-Ti ami Nb{sub 3}-Sn in file form of wires, cables or tapes. The effects produced by adding a metal with high electrical conductivity such as refined copper have been studied. In this way very intense (1300 A) stable currents have been produced for certain cable configurations. The results obtained in the tests are analysed and discussed. If Ic is used to denote the maximum permissible critical intensity in a coil and Is and Im to denote the stable and metastable intensities of the coil material, it is possible to define the following modes of operation: (a) ic < Im and a fortiori Is, the operation of the coil will be stable and the passage of the I-B characteristic of the material will be reversible; (b) Ic < Im, the operation of the coil is unstable and any sufficiently large disturbances (flux jump, movement of windings, etc. ) can produce blocking. This is inevitably the case with the large coils whose operational limit tends towards Im. Different coils have been constructed with more or leas stabilised materials and the results of tests on them are analysed as a' function of the previous theories. There Is a full discussion of the advantages and disadvantages of coil stabilizations. (author) [French] La stabilisation de l'intensite du courant dans les bobinages supra-conducteurs, qui apparait d'une importance capitale pour la construction de bobinages de grande taille , est etudiee a la fois du point de vue theorique et du point de vue experiment a l. L'etude de la dynamique de la transition d'un supraconducteur transportant du courant, entre l ' e t at supraconducteur a resistance nulle et l ' e tat a resistance normale ( l e blocage), revele l'existence d'une intensite caracteristique, Im, pour laquelle la vitesse de propagation de la region normale est nulle. Cette intensite depend directement des echanges de chaleur entre le supraconducteur et le milieu ambiant, et de la resistance du materiau a l ' e t a t normal; Im depend indirectement de l'intensite du champ magnetique. Si un supraconducteur est utilise avec une intensite de courant inferieure a Im, la vitesse de propagation est negative et le supraconducteur est capable eventuellement de realiser la transition inverse de l ' e t a t normal a l ' e t a t supraconducteur. On peut montrer que pour une intensite Is telle que Is = Im/ Square-Root 2 , la vitesse de propagation qui est negative devient infiniment grande. L'existence de ces 2 intensites caracteristiques permet de distinguer trois cas de comportement differents selon l'intensite du courant qui parcourt le supraconducteur. L'auteur a mesure Im pour differents materiaux supraconducteurs a champs intenses: Nb-Zr, Nb-Ti et Nb3-Sn, sous forme de fils, cables ou rubans. Les effets de l'addition d'un metal a haute conductivite electrique, tel que le cuivre raffine, ont ete etudies. Ainsi, l'auteur a obtenu des courants stables tres intenses (1300 A) pour certaines configurations de cables. U analysera et discutera les differents resultats obtenus au cours des essais. Si on designe par l e l'intensite critique maximale admissible dans un bobinage et par Is et Im les intensites stables et metastables du materiau du bobinage, on peut definir les modes de fonctionnement suivants: a) lc < Im et, a fortiori, Is, le fonctionnement du bobinage sera stable et le passage de la caracteristique I-B du materiau sera reversible, b) lc > Im, le fonctionnement du bobinage est instable et toute perturbation suffisamment importante (saut de flux, mouvement des spires, etc.) peut declencher le blocage. Cela se produit inevitablement pour les gros bobinages dont la limite operationnelle tend vers Im. Differents bobinages ont ete realises avec des materiaux plus ou moins stabilises et les resultats de leurs essais seront analyses en fonction des theories precedentes. Les avantages et les inconvenients de la stabilisation des bobinages seront pleinement discutes. (author)}
place = {IAEA}
year = {1966}
month = {Dec}
}
title = {Studies of the Stabilization of Superconductor Coils; Etudes sur la Stabilisation des Bobines Supraconductrices}
author = {Donadieu, L., and Maldy, J.}
abstractNote = {The stabilization of current intensity in superconductor coils, a problem of major importance in the construction of large coils, has been studied both theoretically and experimentally. Investigations, into the dynamics of the transition of a superconductor transporting a current between the superconductor state at zero resistance and the state at normal resistance (blocking) reveal the existence of a characteristic intensity, Im, for which the propagation velocity of the normal region is zero. This intensity is directly dependent on the heat exchanges occurring between the superconductor and the environment and on the resistance of the material in the normal state; Im depends indirectly on the intensity of the magnetic field. If a superconductor Is used at. a current intensity of less than lm, the propagation velocity is negative and the superconductor may be able to effect the opposite transition from the normal state to the superconductor state. It can be shown that, for an intensity Is such that Is = lm/{radical}2 the propagation velocity which is negative becomes infinitely large. The existence of these two characteristic intensities makes it possible to distinguish three types of behaviour differing in the intensity of the current passing through the superconductor. Measurements have been made of Im for different superconductor materials with intense fields: Nb-Zr, Nb-Ti ami Nb{sub 3}-Sn in file form of wires, cables or tapes. The effects produced by adding a metal with high electrical conductivity such as refined copper have been studied. In this way very intense (1300 A) stable currents have been produced for certain cable configurations. The results obtained in the tests are analysed and discussed. If Ic is used to denote the maximum permissible critical intensity in a coil and Is and Im to denote the stable and metastable intensities of the coil material, it is possible to define the following modes of operation: (a) ic < Im and a fortiori Is, the operation of the coil will be stable and the passage of the I-B characteristic of the material will be reversible; (b) Ic < Im, the operation of the coil is unstable and any sufficiently large disturbances (flux jump, movement of windings, etc. ) can produce blocking. This is inevitably the case with the large coils whose operational limit tends towards Im. Different coils have been constructed with more or leas stabilised materials and the results of tests on them are analysed as a' function of the previous theories. There Is a full discussion of the advantages and disadvantages of coil stabilizations. (author) [French] La stabilisation de l'intensite du courant dans les bobinages supra-conducteurs, qui apparait d'une importance capitale pour la construction de bobinages de grande taille , est etudiee a la fois du point de vue theorique et du point de vue experiment a l. L'etude de la dynamique de la transition d'un supraconducteur transportant du courant, entre l ' e t at supraconducteur a resistance nulle et l ' e tat a resistance normale ( l e blocage), revele l'existence d'une intensite caracteristique, Im, pour laquelle la vitesse de propagation de la region normale est nulle. Cette intensite depend directement des echanges de chaleur entre le supraconducteur et le milieu ambiant, et de la resistance du materiau a l ' e t a t normal; Im depend indirectement de l'intensite du champ magnetique. Si un supraconducteur est utilise avec une intensite de courant inferieure a Im, la vitesse de propagation est negative et le supraconducteur est capable eventuellement de realiser la transition inverse de l ' e t a t normal a l ' e t a t supraconducteur. On peut montrer que pour une intensite Is telle que Is = Im/ Square-Root 2 , la vitesse de propagation qui est negative devient infiniment grande. L'existence de ces 2 intensites caracteristiques permet de distinguer trois cas de comportement differents selon l'intensite du courant qui parcourt le supraconducteur. L'auteur a mesure Im pour differents materiaux supraconducteurs a champs intenses: Nb-Zr, Nb-Ti et Nb3-Sn, sous forme de fils, cables ou rubans. Les effets de l'addition d'un metal a haute conductivite electrique, tel que le cuivre raffine, ont ete etudies. Ainsi, l'auteur a obtenu des courants stables tres intenses (1300 A) pour certaines configurations de cables. U analysera et discutera les differents resultats obtenus au cours des essais. Si on designe par l e l'intensite critique maximale admissible dans un bobinage et par Is et Im les intensites stables et metastables du materiau du bobinage, on peut definir les modes de fonctionnement suivants: a) lc < Im et, a fortiori, Is, le fonctionnement du bobinage sera stable et le passage de la caracteristique I-B du materiau sera reversible, b) lc > Im, le fonctionnement du bobinage est instable et toute perturbation suffisamment importante (saut de flux, mouvement des spires, etc.) peut declencher le blocage. Cela se produit inevitablement pour les gros bobinages dont la limite operationnelle tend vers Im. Differents bobinages ont ete realises avec des materiaux plus ou moins stabilises et les resultats de leurs essais seront analyses en fonction des theories precedentes. Les avantages et les inconvenients de la stabilisation des bobinages seront pleinement discutes. (author)}
place = {IAEA}
year = {1966}
month = {Dec}
}