Stability analysis of the TPX toroidal field coil

摘要

The energy stability margin of the TPX/TF conductor has been calculated as a response to heat pulses with short initial quench zones (IQZ=10, 20 cm for 4, 20, 100 ms), and with long initial quench zones (IQZ=2.28, 4.53 m for 20, 50, 100 ms). The short IQZs approximate ramp-rate induced heating, and the long IQZs approximate heating from a plasma disruption. These IQZs are centered in the bore inner leg of the double pancake, where the operating field and temperature are maximum. Energy margin stability curves are plotted as a function of current. The stability of the 10 cm IQZ differs from that for the 20 cm IQZ by less than 20%. Similarly the stability of the 2.28 m IQZ differs from that for the 4.53 m IQZ by less than 20%. However the stability of the short IQZs (10 and 20 cm) is about twice as high as that of the long IQZs (2.28 and 4.53 m). The friction in the long IQZs prevents the conversion of heat to work by helium expansion during the pulse. At the 33.5 kA design current, the minimum calculated stability margin with short IQZs is 390 mJ/cc. The minimum calculated stability margin with long IQZs is 205 mJ/cc. A comparison of the stability margin with the available enthalpy (short IQZs) and with the available internal energy (long IQZs) shows that the conductor utilizes the available helium energy well.