Miniaturized ultraviolet sources driven by dielectric barrier discharge and runaway electron preionized diffuse discharge

In this work we have studied the energy and spectral characteristics of miniaturized dielectric barrier discharge KrCl-, XeCl-, XeBr-, and Xe2-excilamps of various designs as well as short pulse point-like light sources based on runaway electron preionized diffuse discharge. The maximum ultraviolet power density was 20 mW/cm², which is comparable with the densities of ordinary dielectric barrier discharge excilamps, whereas the maximum efficiencies of the excilamps were not greater than 2.5%. The causes for the low radiation efficiency of the compact dielectric barrier discharge driven excilamps were analyzed. It is found that at an electron concentration of ne > 10¹⁴ cm^-3, the efficiency decreases due to enhanced quenching of excited atoms or molecules in dissociation by electron impact. The spectral characteristics of a runaway electron preionized diffuse discharge formed between two pointed electrodes in atmospheric pressure air in an inhomogeneous electric field at a gap shorter than 8 mm were investigated. It is shown that the radiation spectrum of the discharge consists of bands of the second positive nitrogen system, and as the discharge transforms to a spark, lines of the electrode material appear in the spectrum. At a gap of 0.5 mm, weak X-rays from the discharge gap were detected.