A model of multi-pass absorption of external EC radiation at initial stage of discharge in ITER

Abstract

A model is developed for multi-pass absorption of external electron cyclotron radiation (ECR) in tokamaks, which is used at initial stage of discharge to overcome the impurity radiation barrier (burn-through). Model is based on a semi-analytical solution of the ECR transport problem in the case of multiple reflection of radiation from the wall of the vacuum chamber. We estimate the efficiency of absorption of injected radiation for typical values of the electron temperature and density at the initial stage of discharge in ITER.