Numerical tracking of impurities by dust ablation in HT-6M plasma

HT-6M will be officially installed in Thailand in next few years. Some computational studies of possible experiments should be helpful in case of its experiment planning. The authors are interested on the scenario of macro-particle, i.e. dust and droplet, transporting in HT-6M. The study was carried out by the Dust and Droplet Tracking (DDT) code, consisting of basic equations and physical models involving with charging, heating, equation of motion and ablation on macro-particle in a tokamak plasma. DDT implemented a set of HT-6M core plasma profiles from the Transport Analyzing System for tokamaK (TASK) code and a set of HT-6M edge plasma profiles approximated from simple SOL model. We observed that relatively small macro-particles, i.e. initial sizes are less than 10⁻⁶ m, significantly involve with impurity generation near plasma facing components (PFCs). In addition, the 10⁻⁵-m macro-particles mostly ablate in SOL. The 10⁻³-m and 10⁻⁴-m macro-particles completely ablate if they transport towards core plasma, but some with the inclination with respect to the horizontal direction obtain longer lifetimes. Moreover, few of them can achieve abnormal high speed. The mechanism for this is the acceleration by rocket force due to partial ablation near core plasma. (paper)