Investigation on enhancing sensitivity method for monitoring trace erosion product concentration in ceramic channel of a Hall thruster

Optical emission spectroscopy (OES) method with a non-invasive measurement capability and none induce disturbance to the discharge, represents an effective method for material monitoring. However, when OES method is employed to monitor trace erosion product within the ceramic channel of a Hall thruster, it becomes challenging to distinguish between signal and noise. In this work, we propose a model filtering method based on the signal characteristics of Hall thruster plume spectrometer. This method integrates the slit imaging and spectral resolution features of the spectrometer. By employing this method, we extract the spectral signals of erosion product and working gas from Hall thruster under different operating conditions. The results indicate that our new method performs comparably to traditional method without model filtering when extracting atom signals from strong xenon working gas. However, for trace amounts of erosion product, our approach significantly enhances the signal-to-noise ratio (SNR), enabling the identification of extremely weak spectral signals even under low mass flow rate and low voltage conditions. We obtain boron atom concentration of 3.91×10-3 kg/m3 at mass flow rate of 4×10-7 kg/s and voltage of 200 V while monitoring a wider range of thruster operating conditions. The new method proposed in this work is suitable for monitoring other low concentration elements, making it valuable in materials processing, environmental monitoring, and space propulsion applications.