Upper Critical Field Changes in Electron‐Irradiated Niobium

Ullmaier, H.; Papastaikoudis, C.; Schilling, W.

doi:10.1002/pssb.19700380117

Cited by 15 publications

(2 citation statements)

References 11 publications

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“…Irradiation of conventional superconductors with fast neutrons enhances vortex pinning [21][22][23] but electron irradiation does not [21,30], because the created defects are too small as compared with ξ . In contrast, due to the small value of ξ in HTSC, even the point defects created by electron irradiation result in measurable increase in J c .…”

Section: Irradiation-induced Defectsmentioning

confidence: 99%

Vortex pinning and creep in high-temperature superconductors with columnar defects

Civale

1997

Supercond. Sci. Technol.

209

110

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Columnar defects introduced by irradiation with very energetic heavy ions are the most effective pinning centres for flux lines in high-temperature superconductors. This correlated disorder generates large increases in the critical current densities and expansion of the irreversible regime in and the various Bi- and Tl-based compounds. In single crystals and thin films, the pinning enhancement is strongly angular-dependent, and maximizes when the applied magnetic field is parallel to the amorphous latent tracks. In contrast, in the much more anisotropic Bi- and Tl- based materials this unidirectional anisotropy is very small due to the quasi two-dimensional character of the vortices. Some of the extensive experimental studies on this topic are reviewed. Measurements of the temperature, field and defect density dependence of the persistent currents and their time relaxation in YBCO are presented. The analysis of these results based on recent theoretical models permits the identification of various pinning and creep regimes. Studies in other compounds, including technologically relevant Bi-based tapes, are summarized. The influence of the angular dispersion (splay) of the tracks on vortex pinning and creep is discussed.

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Section: Irradiation-induced Defectsmentioning

confidence: 99%

Vortex pinning and creep in high-temperature superconductors with columnar defects

Civale

1997

Supercond. Sci. Technol.

209

110

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“…t e res1st1v1ty c ange. e cone us1on was t at t e res1st v1ty ue c to self-interstitials was a factor of 50 more effective in effecting T reduce tionsthan was resistivity due to other defectso The response of the upper critical field Hc 2 to damage followed a linear dependence with increasing normal-state resistivity as predicted by theoryo ( 3 ) The behavior of the critical-current density I with radiation, however, c was not so straightforward. Ullmaier et al ( 4 ) demonstrated that low-temperature ~lectron and neutron irradiations to essentially equivalent resistivity increases in niobium produced drastically different results on I • There was c almost no change (a small increase) for the electron case, but for the neutron case a significant I increase (factor of 2).…”

Section: Nbtimentioning

confidence: 96%

Effects of irradiation and mechanical stress on the superconducting properties of candidate magnet conductors

Snead¹,

Luhman²

1980

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The effects of .radiation damage on the superconducting critical properties of candidate magnet materials are reviewed. Neutron, and charged-particle irradiation results• are covered. The discussion is restricted to effects in NbTi and the Al5-compound superconductors. The utility of these conductors in radiation fields is first explored by defining the magnitude of critical-property changes with the fluence of various irradiating particles. The physical mechanisms that couple the irradiation defects to the observed critical-property changes are discussed. Annealing/recovery data on irradiated materials are included where• they pertain to the understanding of the physical mechanisms involved, and thereQy to the desirability of magnet annealing in actual operating circumstances. Although among the Al5 compounds Nb 3 Sn is now the leading candidate for high-field magnet applications, results for other Al5 compounds that appear to be fabricable as conductors will also be covered. The general conclusions to be drawn for AlS's and NbTi operating in a fusion-magnet configuration are that total fluences on the order of a few x10 18 n/cm 2 over the life of the magnet offers no serious. problem to the magnet's properties. Annealing NbTi to room temperature is beneficial, annealing the Al5's is detrimental. The fluence limits are for the entire magnet, spots of higher fluence resulting from lesser shielding being not tolerable. The effects of both tensile and bending stresses on the properties of Nb 3 Sn filamentary conductors are also surveyed. Some new data on the synergism • *Work performed under the auspices of the U.S. Department of Energy.-2between irradiation and stress effects are also presented. The results are discussed in terms of materials limits in application, and also in terms of possible ways new fabrication techniques may extend the range of strain that is both tolerable and beneficial. I.

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Pinning of Flux Lines in Superconducting Niobium due to Point Defects

Ullmaier

Papastaikoudis

Takács

et al. 1970

Physica Status Solidi (b)

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Measurements of pinning forces due to statistically distributed vacancies and interstitials (Frenkel pairs) in niobium are reported. The defects were produced by low temperature 3 MeV electron irradiation. The results indicate that fluctuations in the defect density and not the interaction between a single point defect and a flux line are responsible for the observed pinning effects. Es wird iiber Messung von Verankerungskrgften auf FluSlinien in Niob berichtet. DieVerankerungskriifte werden durch statistisch verteilte Frenkelpaare verursacht, die diirch eine 3 MeV-Elektronenbestrahlung bei tiefer Temperatur erzeugt wurden. Die Resultate zeigen, daB nicht die Wechselwirkung zwischen einem einzelnen Punktdefekt und einer FluBlinie, sondern Fluktoationen in der Defektdichte fur die beobachtete FluBlinienverankernng verantwortlich sind. l) Guest from Electrotechnical Institute, Slovak Academy of Sciences, Bratislava. Czechoslovakia.

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Upper Critical Field Changes in Electron‐Irradiated Niobium

Cited by 15 publications

References 11 publications

Vortex pinning and creep in high-temperature superconductors with columnar defects

Vortex pinning and creep in high-temperature superconductors with columnar defects

Effects of irradiation and mechanical stress on the superconducting properties of candidate magnet conductors

Pinning of Flux Lines in Superconducting Niobium due to Point Defects

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