The Ultraviolet-B Radiation Characteristics of Planar Excilamps Filled with Gas Mixture of Xenon, Bromine and Chlorine

Ultraviolet B radiation (UVB) is widely used in agricultural plant growth and phototherapy. The traditional light sources have a low UVB radiation efficiency, poor uniformity radiation, high energy consumption, and short service lifetime. The multiband XeBr^* and XeCl^* planar excilamps as high-power UVB sources have not been researched in existing studies and the power density of XeBr^*/XeCl^* excilamps reported in the study are not high. This work presents a high-power density planar excilamp of homogeneous dielectric barrier discharge in a mixture of xenon and molecular bromine and chlorine (Xe/Br₂/Cl₂). The spectrum, electrical parameters, total gas pressure, and gas mixture composition, have been analyzed. For the multiband excilamp filled with Xe/Br₂/Cl₂, it has been demonstrated that the maximum UVB and total radiant efficiency is 7.9% and 9.7% with optimal chlorine ratio of 0.1% and the bromine ratio ranging from 0.1 to 0.2%, with the input power of 138 W at the total pressure of gas mixture of 200 mbar. This work has confirmed that the percentage of bromine molecules must be higher than the percentage of chlorine by a factor of about 2.6 to achieve the same intensities of the XeBr^* 282 nm and XeCl^* 308 nm bands. These results allow to find out the optimum radiation efficiency of multiband excilamps with a large planar geometry to meet the requirement of UVB industrial applications.