Effect of flux flow on current distribution and heat generation in composite superconductors during a thermal disturbance

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An analytical investigation of current distribution and heat generation rate in composite superconductors, incorporating the effects of flux flow during disturbances, is carried out. Equations describing current density in the superconductor and the heat generation rate per unit volume of the composite conductor in the current sharing regime are derived. The results show that when the superconductor is in the flux-flow state, the current density and the heat generation rate depend only on a dimensionless parameter {phi}{sub f} = ({rho}{sub n}/{rho}{sub st})[H/H{sub c2(0)}](l-{lambda})/{lambda}. When the thermal disturbance is relatively small and {phi}{sub f} >> 1, the current density in the ... continued below

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43 p.

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Cha, Y.S.; Hull, J.R. & Askew, T.R. September 1, 1994.

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Description

An analytical investigation of current distribution and heat generation rate in composite superconductors, incorporating the effects of flux flow during disturbances, is carried out. Equations describing current density in the superconductor and the heat generation rate per unit volume of the composite conductor in the current sharing regime are derived. The results show that when the superconductor is in the flux-flow state, the current density and the heat generation rate depend only on a dimensionless parameter {phi}{sub f} = ({rho}{sub n}/{rho}{sub st})[H/H{sub c2(0)}](l-{lambda})/{lambda}. When the thermal disturbance is relatively small and {phi}{sub f} >> 1, the current density in the superconductor remains at the critical current density with all the excess transferred to the stabilizer and the heat generation rate is equal to that usually employed for low temperature superconductors. When the thermal disturbance is large and {phi}{sub f} >> 1, the current density in the superconductor can be greater than the critical current density and the heat generation rate equals the critical generation rate, independent of whether the superconductor is in the flux-flow state or the normal state. For moderate and large thermal disturbances and {phi}{sub f} =1, which is applicable to high-temperature superconductors because of high H{sub c2}(0), the heat generation rate is q = q{sub c}/2 if the Superconductor is in the flux-flow state and q = q{sub c} if the superconductor is in the normal state. An argument is provided to indicate when and Linder what circumstances will all the excess current be transferred to the stabilizer while the current in the superconductor remains at the critical current during a thermal disturbance. The differences between hi-h- and low-temperature superconductors and its implication for cryogenic stability are discussed. Data on critical currents and thermal runaway of sintered YBa{sub 2}Cu{sub 3}O{sub 7} with unoriented grains are presented.

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43 p.

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OSTI as DE97002615

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  • Other Information: PBD: Sep 1994

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  • Other: DE97002615
  • Report No.: ANL/ET/PP--84192
  • Grant Number: W-31109-ENG-38
  • DOI: 10.2172/426999 | External Link
  • Office of Scientific & Technical Information Report Number: 426999
  • Archival Resource Key: ark:/67531/metadc678505

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  • September 1, 1994

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • Dec. 16, 2015, 12:22 p.m.

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Cha, Y.S.; Hull, J.R. & Askew, T.R. Effect of flux flow on current distribution and heat generation in composite superconductors during a thermal disturbance, report, September 1, 1994; Illinois. (digital.library.unt.edu/ark:/67531/metadc678505/: accessed October 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.