EFDA-JET-CP(05)02/21
Transport Balance of RF-Heated Impurity Ions
Operation in impurity seeding mode needs a control of seeded impurity behavior to avoid the accumulation of the impurity ions in the plasma core. One of the possible ways to control the puffed impurity is to apply the Radio-Frequency (RF) waves. The purpose of this work is to study the possibility of using ICRH for impurity density control, including impurity exhaust, in impurity seeded fusion discharge. When the absorption of RF power by the selected impurity ionization state is high enough a difference between temperatures of the main and impurity ions becomes essential. Up to now the impurity temperature is disregarded in transport modeling and it is normally assumed to be equal to the temperature of the main ions. We show that to simulate correctly the impurity transport under condition of the strong heating of a selected impurity ionized state the heat balance equations for the impurity should be solved. The numerical simulations of the selected impurity heating have been carried out for typical JET parameters with argon puffed in deuterium plasma. The absorption power profiles were calculated by full wave code TORIC. A direct loss of impurity ions due to scattering into first orbit loss cone is calculated using an ion bounce-averaged Fokker-Planck solver with a nonlinear collisional operator. Finally, ICRF-induced losses are included in the transport code RITM. The three codes are used repeatedly until a self-consistent picture of the impurity transport in reached. The impact of impurity heating on the heat transport and intensity of impurity radiation has been shown. Simulated argon density profiles demonstrate a local reduction of the Ar18+ concentrations during ICRF heating. The results of the quantitative analysis of the transport alteration in the regime of essential ICRF impurity heating are presented.