Spatial distribution measurement of plasma parameters using spectral image processing

Summary form only given. The plasma-chemical reaction in reactive plasma was strongly influenced by the gas temperature and mean electron energy. To understand the gas temperature in plasma is significantly important for control of plasma-chemical reaction. In addition, the gas heating in discharge plasma causes a degradation of electrodes and a breakdown of insulation gas. Therefore, advanced plasma diagnostic method has been expected for developments of efficient plasma processing and reliable gaseous insulation technology. Previous research concerning the gas temperature measurement in corona discharge using spectroscopic measurement of second positive system bands of nitrogen has shown the gas temperature in positive DC glow corona is approximately 400 to 500 K
¹
. However, this result indicates spatially-averaged gas temperature of measurement area, and not represents the spatial distribution of gas temperature.Spectral image processing has been applied to the study of variety of emission sources, such as electrical arc discharges, inductively coupled plasmas. In this work, the spatial distribution of gas temperature and mean electron energy in positive DC glow corona was two-dimensionally measured using spectral image processing. The positive DC glow corona was generated using a rod-plane electrode in atmospheric air. The gap distance was 30 mm and the diameter of rod electrode was 1.5 mm. In the case of gas temperature measurement, the spectral images of positive DC glow corona were taken by using ICCD camera with ultranarrow bandpass filters correspond to the head and the tail of N2 second positive system band (0-2), respectively. Similarly, in the case of mean electron energy, the spectral images were taken with ultra-narrow bandpass filters correspond to the head of N2 second positive system band (0-2) and the head of N2 1st Negative System Band (0, 0), respectively. The qualitative 2D distribution of gas temperature and mean electron energy was obtained from these emission intensity ratios. As a result, it was revealed that a distinctly high-temperature spot is formed in positive DC glow at the tip of rod electrode just before the sparkover voltage. In addition, the mean electron energy at the tip of rod electrode was indicated as highest spot in the positive DC glow corona. Spectral image processing reproduced spatial distribution of gas temperature and mean electron energy well.