Analysis of sudden quench of an ITER superconducting NbTi full-size short sample using the THELMA code

The coupled thermal–hydraulic electromagnetic model, implemented in the THELMA code, is applied to the analysis of the sudden quench in the ITER NbTi poloidal field conductor insert full-size joint sample. The computed results are compared with the measured values, showing that the major experimental features, like the premature and sudden voltage take-off, as well as the presence of precursors of the quench in the form of voltage spikes, can be qualitatively reproduced by the code. A self-consistent explanation of the phenomenon is resented, emphasising the effect of current, magnetic field and temperature non-uniformities on the cable cross section, together with the fundamental role played by coupled electromagnetic and thermal–hydraulic dynamics in the current redistribution associated with the voltage spikes.