Investigation of Emission Characteristics of Dielectric Barrier Discharge-Based Kr/Cl2 Excilamp at Different Operating Conditions

Abstract

A coaxial dielectric barrier discharges based Kr/Cl₂ excilamp featuring a double dielectric barrier has been developed to generate 222 nm Far UV-C radiation. The excilamp is excited by a short unipolar pulse (rise time 800 ns, FWHM: ~2µs) of negative polarity and investigated at different operating conditions to efficiently generate 222 nm radiation. The investigation includes the electrical and optical characterisation of the excilamp under varying Cl₂ proportion (0.1-3%) and total gas pressures (100–300 mbar). The typical V-I characteristics and the corresponding Q-V curve have been analysed to understand the discharge characteristics and determine the electrical parameters, including the capacitance of the excilamp and input power. The optical characterization included emission spectroscopy and absolute radiance measurements, focusing on the 222 nm spectral band, a key emission wavelength of KrCl* excimers. The emission spectra reveal the emission of the 222 nm spectral band, along with relatively weak bands of 235 nm, 258 nm, and 325 nm, particularly at higher pressures. The absolute irradiance at 222 nm was found to increase with Cl₂ concentration up to 1%, reaching a peak value of 2.09 mW/cm² (at 300 mbar) before significantly decreasing at 3%, indicating an optimal Cl₂ content for KrCl^* excimer formation. Similarly, increasing the total gas pressure from 100 mbar to 400 mbar led to a substantial enhancement in 222 nm emission, with irradiance rising from 0.47 mW/cm² to 2.35 mW/cm². This comprehensive analysis provides crucial insights into the development and optimization of Kr/Cl₂ excimer lamps for efficient 222 nm far-ultraviolet (Far-UV) radiation generation.