Active Protection of an MgB2 Test Coil

This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with similar to 500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a "hot spot" of a length similar to 10 cm, induced by a "quench heater," a "protection heater" (PH) of similar to 600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil's entire initial stored energy and still keeps the peak temperature within the winding below similar to 260 K.