Effects of the Operating Conditions on the UV-B (308 nm) Power and Efficiency of the XeCl* Barrier Discharge Excilamp

Abstract

A dielectric barrier discharge in Xe-Cl2 mixtures has been investigated numerically in a wide range of operating conditions with the purpose to study their effects on the XeCl* excimer radiation by means of a 1-D fluid model. First, a simplified chemical kinetics scheme is proposed and validated by benchmarking with the long chemical kinetics. These results show a limited loss of accuracy of discharge properties, while it is two times faster in computational time as compared with the complete version. The simulated results demonstrate that the discharges are typically Glow-like. During the breakdown, the cathode fall region is contracted to 85 μm. At that instant, the number density of XeCl* molecules in the sheath is maximum, and the principal channel of the XeCl* generation is harpoon reactions. The UV-B radiation dependence on the total gas pressure, voltage amplitude, and frequency of power supply and gap width has been analyzed. It was shown that the maximal radiative efficiency of UV-B emission is obtained at low gas pressure, high alternating voltage frequency, and high gap width. The radiative efficiency slowly depends on amplitude of the source alternating voltage. In addition, the emission power of the B→X band of XeCl* molecules grows when frequency or amplitude of the source voltage increases as well as when pressure decreases, but the emission power depends weakly on the gap width. Furthermore, the most part of the power deposited in the gas goes into heating electrons and lesser part goes into heating ions in the cathode fall.

Keywords

• XeCl* excilamps
• Fluid model
• Simplified scheme
• Excimer and exciplex molecules
• UV-B radiation
• Radiation power and efficiency