Atomic models for description of high-Z impurities dynamics in tokamak plasmas – summary of HARMONIA project

Abstract

Since the year 2019, the project entitled „Study of the mutual dependence between Lower Hybrid current drive and heavy impurity transport in tokamak plasmas ”has been jointly executed by Polish (IFJ PAN) and French (CEA-IRFM) research teams. A particularly crucial topic studied within this project is the influence of not fully ionized high-Z impurities (e.g. tungsten ions) on suprathermal electrons dynamics. The influence can be studied using a Fokker-Planck solver. However, in this case, it is necessary to modify the electron-ion collision operator, in order to incorporate the efect of partially ionized high-Z atoms, arising from uncontrolled influxes of impurities. This, in turn, requires atomic models that are accurate enough but allow preforming fast and efficient calculations for all elements present in the plasma, regardless their local level of ionization. For this purpose, a few simple atomic models for elastic and inelastic collisions of electrons with high-Z ions have been proposed and implemented into a Fokker-Planck solver – LUKE code and DREAM (Disruption and Runaway Electron Analysis Model) code. Those semi-empirical atomic models have been calibrated and optimized using results of Density Functional Theory (DFT) calculations, Dirac-Fock-Slater (DFS) method, relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method or available reference experimental data. This paper introduces to the achievement of the whole project, with a special emphasis placed on eforts to incorporate the physics of partially ionized high-Z elements in kinetic calculations.