SIMULATIONS OF TOKAMAK DISRUPTIONS INCLUDING SELF-CONSISTENT TEMPERATURE EVOLUTION
The simulations couple transport effects, which slowly change the equilibrium profiles, and resistive MHD instabilities occurring on shorter timescales. The stability of the MHD modes is determined by the equilibrium profiles; an instability drastically modifies the profiles. Sharply defined disruptive events occur when q (boundary of current channel) is lowered towards 2 and are best described as shocks propagating inward from the q = 2 surface breaking up magnetic surfaces and leaving turbulent plasma behind. The model used is the lowest order reduced MHD system including a self-consistently determined temperature with a highly anisotropic thermal conductivity, Spitzer resistivity eta alpha T**-3/2 and ohmic heating alpha eta x j**2. The boundary at r = a is assumed non-conducting and the magnetic field is notched to a vacuum solution. In the run described here, resistivity at the centre was eta = 6x10**-6 and the heat conductivities were assumed constant k = 1.2 x 10**-5 and k = 100. Numerical integration: 120 radial grid points and 20 to 35 Fourier modes in the theta and z directions. A semi-implicit algorithm for integration over transport timescales, using large time steps for small perturbation levels. To force the simulation into the disruptive regime, the toroidal electric field was adjusted so that the total plasma current was slowly increasing, q-a(t) = q-a(O) exp(-t-tq), tq = 2x10RU5t-A, and qa went from 2.74 to 2.49 in about 19000 Alfven times.
Bibliographic Reference: 13TH EUROPEAN CONFERENCE ON CONTROLLED FUSION AND PLASMA HEATING, SCHLIERSEE (GERMANY), APRIL 14-18, 1986 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32544 ORA
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Record Number: 1989125010400 / Last updated on: 1987-01-01
Available languages: en