Simulation study of the fueling pellet trajectory with the new rocket-effect model based on HPI2 code

The asymmetric ablation of the pellets is similar with rocket acceleration, which may change its trajectory. Based on the fundamental theory of the NGS model [Parks P B and Rosenbluth M N 1998 Phys. Plasmas 5 1380-1386], we have proposed a new model to study the rocket-effect for pellet trajectory, upgrading the research on the pellet acceleration process in the HPI2 code. By improving the existing code, we not only consider the radial motion of the pellet but also simultaneously calculate its toroidal direction, thus providing crucial information on pellet acceleration and velocity. To validate the reliability of the new model, we selected the background plasma discharge operating parameters of the typical ohmic heating in the EAST device and compared them with a semi-empirical model. The results show that the new model is a better fit compared to the Szepesi model. The simulation results indicate that when the pellet is injected from the high field side, the rocket acceleration effect increases the penetration depth of the pellet, while the opposite is observed when the pellet is injected from the low field side. Additionally, the trajectory of the pellet is deflected more under the influence of the rocket-effect than without it. Compared to experimental results from Tore Supra, the provided pellet acceleration and velocity information is similarly accurate. Through this study, we can gain a better understanding of the flight characteristics of pellets under different operations on tokamak, including flight distance and trajectory.