MODELING OF THE INTERACTION OF HYDROGEN PLASMA WITH AMORPHOUS-CARBON FILMS REDEPOSITED IN FUSION DEVICES

A model is presented to describe the interaction/retention of hydrogen plasma in redeposited amorphous carbon layers forming in carbon-protected tokamaks. The subject is relevant for quantifying the buildup and the possible mobilisation of tritium to be used in the next generation of devices. The goal of the model is to predict some of the basic features and properties of amorphous hydrogenated carbon films (e.g., H/C codeposition rate, bonded versus unbonded hydrogen ratio, thermal stability and reactivity with air) as a function of some of the key process parameters (e.g., surface temperature, flux, energy, and type of the particle species incident upon the film surface). The examples presented cover: (i) the kinetics of the H/C codeposition process emphasising the hydrogen content of the film; (ii) the removal of the film due to energetic ion bombardment; and (iii) the thermal stability of hydrogen trapped in the codeposited layer in vacuum and in air.