Theoretical kinetics with a one-dimensional fluid model and experimental investigation of coaxial XeCl excilamps

Abstract This paper presents a one-dimensional homogenous model of a high power density XeCl excilamp pumped by dielectric barrier discharge (DBD) with a larger discharge gap and lower Cl 2 density in the Xe/Cl 2 mixture in order to research the electrical and chemical discharge characteristics leading to the production of XeCl* molecules for optimal discharge parameters. The peaked wavelength of 308 nm from the emission band of XeCl* exciplex molecules shows great promise for photochemotherapy in biomedicine applications. The temporal evolutions of the plasma voltage, current density, and the species densities are analyzed. The model validity is checked by comparing it with the experimental results. It is shown that the XeCl excilamp has a capacitive discharge during the entire voltage cycle, and the accumulation of charge deposited in the dielectric surfaces plays an extremely important role in promoting the extinction of this discharge and the generation of the next discharge. The ultraviolet (UV) radiant efficiency of the DBD XeCl excilamp depends on the effect of the discharge behavior on the amplitude of the applied voltage, the total gas pressure, and the Cl 2 density. The XeCl excilamp has an optimized pressure of around 150 mbar with a maximum radiant efficiency of 8.5% for 308 nm from XeCl* molecules and 1.3% for 172 nm from Xe 2 * molecules. According to the corrected simulation, the radiant efficiency of the optimum pressure is 5.8% for XeCl*molecules. The Cl 2 density in the DBD-based XeCl excilamp strongly influences the balance of electron production and loss due to the dominant dissociative attachment process of electrons to Cl 2 molecules, which have significant dependence on the UV light output efficiency. It is demonstrated that the highest XeCl* density occurs near the dielectric during the current pulse. Therefore, the electrical and radiant characteristics of XeCl excilamps can be considered as the basis for designing high power density exciplex lamps in practical applications.