Detecting Quench in HTS Magnets With LTS Wires-A Theoretical and Numerical Analysis

Using a co-wound and insulated NbTi low temperature superconducting (LTS) wire to detect quench in coils wound with high temperature superconducting (HTS) tapes has recently been experimentally proved, yet a theoretical study is still needed to further develop this technique and make it prepared to be applied more generally in high field accelerator magnets. In this manuscript, we present some theoretical and numerical analyses, which confirm a few important facts: 1) It is the significant difference in the temperature dependence of critical current between LTS and HTS but not the normal zone propagation velocity (NZPV), that makes LTSs good quench detectors; 2) LTS quench detectors should have low matrix fraction or high matrix resistivity to increase its normal resistivity and therefore enhance its ability as a quench detector; 3) Heat transfer between cable and detector is important, but a poor heat transfer condition is tolerable; 4) At field beyond 15 T, Nb3Sn, Nb3Al and MgB2 all show good potential as quench detectors, and some degradation in wire performance is also acceptable.

Automated summary

This manuscript presents theoretical and numerical analyses on using a co-wound and insulated NbTi low temperature superconducting wire as a quench detector in coils wound with high temperature superconducting tapes. The study confirms the significant difference in temperature dependence of critical current between LTS and HTS, and suggests that LTS quench detectors should have low matrix fraction or high matrix resistivity to enhance their ability. Heat transfer between cable and detector is important, but a poor heat transfer condition is tolerable. The study also shows that Nb3Sn, Nb3Al, and MgB2 have potential as quench detectors at field beyond 15 T, with some degradation in wire performance being acceptable.