Quench Developmentat Supercritical Currents in Lown-value Superconductors

Joonas Järvelä, Antti Stenvall and Risto Mikkonen

Abstract—Superconducting magnets consisting of conductor having a low n-value can be operated shortly with overcritical currents without quenching the magnet. This applies also to epoxy-impregnated coils. However, when sufficiently high disturbance occurs at a supercritical current a magnet quenches. Traditional approaches on minimum quench energy (MQE) do not consider the supercritical region. In this study we measured MQE at sub- and super critical currents for MgB₂ and Bi-2223/Ag conductors having low n-values, i.e. below 15. A Finite Element Method model was compared with the measurement results and the differences in MQE between the sub-and supercritical regime were scrutinized.

IndexTerms—MgB₂ , Bi-2223/Ag, HTS, stability, quench, measurements

Manuscript received August 18., 2008.
J. Järvelä, A.Stenvall, and R.Mikkonenare with Tampere University of Technology, Electromagnetics,
P.O. Box 692, FIN-33101Tampere, Finland (phone:+385-3-31154305; fax :+358-3-31152160; e-mail: joonas.jarvela@tut.fi;
www:http://www.tut.fi/smg).

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