Radiant Efficiency Of Positive Column For T6High Output Low Pressure Mercury Lamp

High output LPM (low pressure mercury) discharge lamps with power density100-200W/m have characteristics of high254nm UV output and radiant efficiency,185nm VUV radiation. The lamps are widely applidy in sterilization, waste water industry, surface activitation and photo-chemical reaction. However, research of the lamps, such as radiant efficiency and optimum parameters is not seen recently. This thesis focused on the optimum discharge parameters for high output LPM lamps. It is vital for improving the manufacture procedure, developing competitive domestic products.UV light sources, especially LPM discharge lamps, and their application for sterilization or photo-chemical activation are firstly introduced in Chapter1. The theoretical research history and experimental studies of LPM are illustrated, including early T12lamps, increasing power load with narrower bore, recent T2tubes for compact fluorescent lamps, color temperature, spectra and electrodes region. This work related to T6lamps with outer diameter19mm, filled with6speices of buffer gas. Dependence of electric field, input power,254nm radiant power and efficiency with buffer gas and cold spot temperature has been studied, and explanation for the results was illustrated.Experimental setup and Keitz formula for254nm radiant power calculation are narrated in Chapter2. Discrepancy between Keitz formula and gonio-radiometry method is below1%under the condition for lamp length L and sensor distance D:2.5L<D<4L. Divided by the input power,254nm radiant power can deduce the radiant efficiency.The dependence of cold spot temperature to the positive column radiation is explained in Chapter3. Maximum254nm radiant power of the T6lamp is with cold spot temperature of40-45℃and maximum254nm radiant efficiency with45-48℃, respectively. For the lamps with2Torr Ne-Ar buffer gas, under the condition of1.6A45℃, positive column input power is above160W/m and254nm radiant efficiency is above40%. The visible spectra radiant efficiency of lamps filled with Ne-Ar buffer gas under different discharge conditions is below10%, generally. Lamps filled with pure Ne have poor starting character due to the higher start-up voltage while those with pure Ar have lower UV output power.The dependence of buffer gas species and pressure to the positive column radiation is given in Chapter4.254nm radiant efficiency is close for various buffer gas species with same pressure. Higher Ne percentage is preferred for high radiant power demand and higher Ar percentage is preferred for energy saving with relatively lower output. Balance between UV radiant power output and electrode protection for long-life operation should be considered when deciding the buffer gas pressure. There is severe electrode sputtering in the lamps filled with very low pressure buffer gas.254nm radiant efficiency for lamps with very high pressure buffer gas is too low. Radiation of other lines of the lamps except254nm can sustain lower than10%with different buffer gas species and pressure.In Chapter5, comparison to previous studies, measurement uncertainty and future research studies are represented briefly.Vital conclusions are listed in Chapter6.