Plasma sensor for monitoring laser-interacting particles in contact with an electrode

Abstract

A particle imaging system adopting digital in-line holography (DIH) was applied to monitor plasma with variations in radio frequency bias power. This work is the first attempt to examine the effect of bias power on DIH-captured particle distributions in contact with an electrode. The bias power was varied from 0 to 100 W by intervals of 10 W. Particle count specific to a grayscale range of 61 to 80 showed an increasing tendency with the bias power. Particle counts in the bulk plasma fluctuated randomly irrespective of the grayscale range. The peak intensity variations measured with optical emission spectroscopy (OES) showed a little variation in the range of 0–40 W and an increase in the range of 50–100 W. Over the entire range of bias power, the particle count strongly correlated with the two intensities peaked at 539.013 and 583.949 nm. The DIH imaging system demonstrated improved detection performance tan OES at low bias powers. The identified position of a sheath was close to the reported one.