The effect of charge exchange with neutral deuterium on carbon emissionin JET divertor plasmas

Abstract

High-density, low-temperature divertor plasma operation in tokamaks results inlarge neutral deuterium concentrations in the divertor volume. Under theseconditions, low-energy charge transfer reactions between neutral deuterium andthe impurity ions can, in principle, enhance the impurity radiative losses andthus help to reduce the maximum heat load to the divertor target. Auantitative study of the effect of charge exchange on carbon emission ispresented, and applied to the JET divertor. Total and state-selectiveeffective charge exchange recombination rate coefficients were calculated inthe collisional radiative picture. These coefficients were coupled to divertorand impurity transport models in order to study the effect of charge exchangeon the measured carbon spectral emission in JET divertor discharges. Thesensitivity of the effect of charge exchange to the assumptions in theimpurity transport model was also investigated. A reassessment of fundamentalcharge exchange cross section data in support of this study was made.