Optical emission spectroscopy diagnosis of low-pressure microwave discharge helium plasma based on collisional-radiative model

Abstract

Abstract An inverse model based on a low-pressure helium collisional-radiative (CR) model was developed. Parts of the rate coefficients were recalculated from the cross-sections. The dominant processes in the revised model were extracted to simplify the calculation and to develop an inverse model. The model can calculate the electron density and temperature of low-pressure helium plasma by inputting the population densities of levels 3 1 S , 3 3 S , and 3 1 D , which can be measured by optical emission spectroscopy (OES) measurement in the visible wavelength range. The results demonstrate that the electron temperature obtained by the model is extremely close to the original value in the CR model. The output values of the electron density were of the same order and magnitude as the input values. The electron density and temperature measured by OES measurement in the experiment using the developed inverse model are consistent with the results measured by the probe method.