Experimental investigations on hydrocarbon-enhanced MAR processes in low temperature plasma in divertor simulator MAP-II

Plasma recombination phenomena were observed in the interactions of hydrogen or hydrocarbon gasses with low temperature helium plasma stream along the longitudinal magnetic field, which simulated the divertor region. The reduction of the ion saturation current implies the existence of molecular activated/assisted recombination (MAR) processes. The recombination efficiency is much stronger in the methane and ethane than in the hydrogen injection case, namely, He≪H2≪CH4<C2H6. In order to clarify the dominant processes in the hydrocarbon-enhanced MAR phenomena, spectroscopy on the A2Δ–X2Π band of CH radical was conducted. In the electron temperature lower than about 6 eV, the dominant dissociation and emission processes of the CH radicals have qualitatively been revealed to be related to their charge exchange with bulk ions, which can be followed by the dissociative recombination with electrons.