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Avalanche-like Quenches in Cable in Conduit Conductors
Kazutaka Seo,Arata Nishimura,Yoshimitsu Hishinuma 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Superconducting conductors carrying large currents of more than several tens of kA are required for magnetic confinement fusion apparatuses. A cable-in-conduit conductor (CICC), which has around a thousand parallel and twisted thin superconducting strands in a stiff conduit, is a promising candidate for such large and high-magnetic-field superconducting systems. We developed a numerical code AQUAPS (Avalanche-like QUench Analysis for Parallel Superconducting strands) simulating electromagnetic and thermal phenomena in a conductor consisting of parallel superconducting strands. A specific phenomenon in the CICC is so-called avalanche-like quench. When one strand becomes resistive due to current saturation or a mechanical disturbance, e.g. frictional heating, it loses the transport current and the current re-distributes into neighboring strands. Neighboring strands are electromagnetically well coupled and electrically contact each other. Therefore, neighboring strands receive supplemental current from the original strand and this results in a following quench. We call this phenomenon ’avalanche-like quench’. With the newly developed numerical code AQUAPS, we have simulated quenches in multi-strand cables with both Nb3Sn and NbTi strands and compared these. For the Nb3Sn cable, the critical temperature (Tc) may be much larger than the liquid-helium bath temperature (T0), in spite of the fact that current sharing temperature (Tcs) is almost equal to T0. This situation is very different from that in the NbTi cable. We analyzed this issue intensively and present some discussion.0chh9mu