Quench Protection Solutions for Magnets Fabricated With Insulated HTS Tape Conductors

Quench protection is the elephant in the room, when it comes to high temperature superconducting (HTS) magnets. For many HTS magnets, quench protection has not been much of a problem, because the stored energies of the magnets have been low compared to low temperature superconducting magnets. The principles of quench protection are the same regardless of the type of superconductor used. In general, a quench is not a problem if the adiabatic hot spot temperature at the end of the quench is less than a temperature that damages the conductor or its insulation and the magnet voltages are low enough not to breach the magnet insulation. It has long been understood that quench propagation along an HTS conductor is much slower than for Nb-Ti. The reason for this is the large enthalpy change that occurs during a quench of an HTS conductor. The magnet quench characteristics are a function of the conductor current density, the local temperature margin, and the ratio of copper to noncopper in the conductor. With an HTS conductor one must add the effect of conductor field orientation that can affect both the critical current and the critical temperature. This paper explores ways for protecting magnets made from insulated rare earth (and Yttrium) barium copper oxide (ReBCO) tape or a similar HTS conductor that can be wound after reaction.