Investigation into light emission from droplet spots produced by low-current vacuum are discharge

Some of droplets emitted by vacuum arc cathode spot and surrounded by dense plasma were suggested recently to be referred to as droplet spots. Droplet spot plasma temperature and concentration are close to those of the cathode spot plasma. The goal of this work is study of spectral characteristics of droplet spot light emission. High-speed imaging based on an IMACON 468 camera in combination with narrow-banded interference filter was used for getting spectrum. Droplet spot spectrum was compared with cathode spot one taken in the same experiments. Comparison revealed resemblance in the spectrums. Second part of the work describes light emission dynamics of droplet spots after arc discharge extinction. It has been found that brightness in visible an IR light of some droplets grows in time during tens to hundreds microseconds after discharge extinction, then it decreases gradually. The most intriguing fact is that a cycle of growing brightness is followed sometimes by a repeated cycle (and even a few cycles).