Quench Protection of HTS Magnet Composed of Multiple Pancake-coils by Forming Auxiliary Dump Resistor Loop

The most probable cause of quench damage of HTS magnets is over-heating at the highest temperature spot (hot-spot) in the magnet wire during the quench protection sequence. Therefore, to avoid damage, it is necessary to reduce heat generation in the hot-spot. The authors propose a method to reduce the hot-spot temperature of a magnet composed of multiple sub-pancake-coils by reducing current in a quenching sub-coil. A quench occurs most often in a sub-coil that has critical current Ic lower than that of the other sub-coils. When a quench is detected in the lower Ic sub-coil, the current of the quenching sub-coil is transferred to the other coils with higher Ic ' s resistively shorting the other sub-coils by forming auxiliary dump resistor loop. In this paper, the effectiveness of the method is shown by a case study of a magnet composed of eight pancake sub-coils.