Compact Microwave Plasma Electrodeless UV Lamps With Low Breakdown Power and High Energy Efficiency

Microwave electrodeless ultraviolet (UV) lamps are employed in a multitude of fields, including healthcare, air sterilization, sewage treatment, resin curing, and others, owing to their long lifespan, robust input power, and high luminous intensity. However, the existing feeder structures are bulky and heavy, restricting handheld use in a narrow and small space. This article presents a new type of compact microwave plasma electrodeless UV lamps based on a coaxial structure that helps cut overall weight remarkably compared to rectangular waveguide and microwave oven lamps. Besides the simple structure design, the proposed microwave plasma UV lamps have significant advantages in breakdown power and microwave energy efficiency. With an ignitor linked to the inner conductor, argon discharge can be easily trigged at an input microwave power of 60 W (4 torr), and the breakdown power can further drop to 50 W with mercury. For the energy efficiency of power coupling from the incident microwave to the discharge, a pure argon lamp has over 90% energy efficiency below 80 W, while an argon-mercury lamp achieves this above 120 W. These lamps thus hold great promise for resin curing, bacteria inactivation, pollutant degradation, and wastewater treatment.