On the application of He I collisional-radiative model to the He–H2 mixture plasmas in MAP-II divertor simulator

Abstract Atomic helium (He I) optical emission spectroscopy was carried out in a MAP-II divertor simulator to investigate the applicability of He I collisional-radiative (CR) model for the measurement of electron temperature ( T e ) and density ( n e ) in He–H 2 mixture plasmas. The result was compared with Langmuir probe measurements. The excited population distribution of the He–H 2 mixture plasma was not reproduced by the He I CR model, although it was reproduced well for pure He and He–Ar mixture plasma. Specifically, the deviation of the population ratio of singlet to triplet states became more evident as the concentration of H 2 increased. This fact implies that the measurement of T e for He–H 2 plasma using the He I CR model could lead to a significant error under a certain condition, such that T e