On the nature of radiation of blue and green jets in laboratory discharges initiated by runaway electrons

Spectral and amplitude-temporal parameters of radiation from different regions of discharges initiated by runaway electrons have been studied. The pulse-periodic mode of discharge formation was used. It is shown that the color of a part of jets observed during laboratory discharges is determined by radiation of electrode metal vapors. It is found that blue mini jets from an electrode with a small radius of curvature appear in the cases of stainless steel and aluminum electrodes and are caused by emissions of atomic transitions of these metals. Green mini jets observed near copper electrodes are mainly caused by CuI atomic transitions mainly at wavelengths of 521.8 and 522 nm. It is confirmed that jets of different colors appear during formation of bright spots on electrodes, as well as sparks in the discharge. © 2015, Pleiades Publishing, Ltd.