Modelling of electron cyclotron energy gain in the tokamak pre-ionization phase

Abstract This work presents a model for predicting electron energy gain from electron cyclotron (EC) wave–particle interactions during the breakdown phase of tokamak pre-ionization. Investigation of this phase to infer the EC requirements inevitably demands high-fidelity simulation study covering gas breakdown physics, plasma dynamics, and EC absorption. Under the significantly low density and temperature, electrons interact nonlinearly with EC wave and gain energy of which picture is distinct from the linear or quasilinear EC heating. For room temperature electrons, analytic estimates of energy gain have been derived using adiabatic nonlinear theory (Farina 2018 Nucl. Fusion 58 066012). However, electrons with large incident perpendicular energy can be generated from the ionization reactions and even be present in the Maxwellian tail during the breakdown. In this work, we refined the th…