Simulation of Burning Plasma Dynamics in ITER

Abstract

The dynamics of burning plasma for various transient situations in International Thermonuclear Experimental Reactor (ITER) plasma have been simulated with the 1½-dimensional up-down asymmetry Tokamak Transport Simulation code. Attention is paid primarily to intrinsic plasma transport processes such as confinement improvement and changes of plasma profiles. A large excursion of fusion power is shown to take place with a small improvement of plasma confinement; e.g., an increase of the global energy confinement by a factor of 1.2 yields a fusion power excursion of ∼30% within a few seconds. Given this short timescale of the fusion power transient, any feedback control of fueling deuterium-tritium gas is difficult. The effect of plasma profile on fusion power excursion is studied by changing the particle transport denoted by the peaking parameter C_v. When the fusion power excursion is mild and slow, the feedback control is quite effective in suppressing the fusion power excursion and in shortening the duration time of the power transient. Changes of the pumping efficacy are also studied, and large excursions of fusion power are not observed because of a decrease of the fuel density itself when the pumping efficacy is increased; and helium ash accumulates in the case of a decrease of the pumping efficacy. Finally, magnetohydrodynamic sawtooth activity leads to a fusion power fluctuation of ±20%, although such activity is helpful for helium ash exhaust.