Shanduan Zhang

The efficiency of coaxial KrCl* excilamps

The spectrum, input power and 222 nm radiant efficiency were measured for coaxial KrCl* excilamps based on a dielectric barrier discharge. The inner tubes of the lamps have an inner/outer diameter (ID/OD) of 14/16 mm. The OD of the outer tubes is 40 mm with wall thicknesses of 1.2, 1.5 or 2.0 mm. The lamps were driven by sinusoidal, rectangular and pulsed electronic control gears (ECGs). The 222 nm radiant power is derived from irradiance, according to the Keitz formula. The input electric power is measured with an oscilloscope, combined with a voltage probe and a current probe. The results show that the maximum efficiency of the 222 nm radiation is 9.2% for a KrCl* excilamp with a wall thickness of 1.2 mm, filled with krypton (198 mbar) and chlorine (2 mbar), driven by a pulsed ECG. The effects of waveform, frequency, wall temperature and transmittance of the tube are discussed. We observe that the filament configuration of the micro-discharges changes for different voltage waveforms. The results of gas composition and pressure show an optimum pressure at 200 mbar and an optimum chlorine percentage around 0.4–1.0%.

Photo-dissociation of dimethylamine by KrBr* excilamp

A study of dimethylamine photo-dissociation in the gas phase has been conducted using UV radiation delivered from a KrBr(*) excilamp, driven by a sinusoidal electronic control gear with maximum emission at wavelength of 207 nm. The electrical input power and radiant power of the lamp were measured to determine their effects on the degradation. The influence of flow velocity and initial concentration of dimethylamine were also examined. In order to evaluate the photo-dissociation process comprehensively, several parameters were investigated, including removal efficiency, energy yield, carbon balance and CO₂ selectivity. It is shown that the removal efficiency increases with enhanced input power and decreased gas flow rate. A high removal efficiency of 68% is achieved for lamp power 102W and flow velocity 15 m(3) h(-1). The optimum dimethylamine initial concentration is around 3520 mg m(-3), for which the energy yield reaches up to 442 gk Wh(-1) when the input power is 65W. In addition, two chain compounds (1,3-bis-dimethylamino-2-propanol; 3-penten-2-one, 4-amino) and three ring organic matters (1-azetidinecarboxaldehyde, 2,2,4,4-tetramethyl; N-m-tolyl-succinamic acid; p-acetoacetanisidide), were identified by GC-MS as secondary products, in order to demonstrate the pathways of the dimethylamine degradation.

Dimming properties of medium and small wattage ceramic metal halide lamps

Ceramic metal halide lamps with rated powers of 70 W and 150 W are dimmed by reducing their operating power. Under dimmed conditions, photometric, colorimetric and electric parameters, as well as the temperature distribution of the outer wall of the arc tube have been measured. As the lamp power is reduced, luminous efficacy and colour rendering index decrease while correlated colour temperature rises. For each lamp, at 70% of its rated power, the luminous efficacy is greater than 80 lm/W, colour rendering index is above 74 and correlated colour temperature increases by less than 800 K. Dimming applications of these lamps are validated by these parameters. Furthermore, the complicated variation of lamp parameters as a function of operating power is explained by the variation of metal halide vapour pressure with wall temperature.

Radiation characteristics of coaxial KrBr* excilamps based on a dielectric barrier discharge

The characteristics of the emission spectra of coaxial KrBr* excilamps driven by sinusoidal, rectangular and pulsed electronic control gear (ECGs) are investigated, based on the dielectric barrier discharge (DBD) with an annular gap of 10.5?mm. The radiant power of intense narrow band ultraviolet radiation at 207?nm is derived from the irradiance according to the Keitz formula, while the input power is computed from the integral of the product of voltage and current. The radiant characteristics of the 207?nm spectral line have been studied with regard to total pressure and bromine percentage, demonstrating an optimum pressure at 300?350?mbar as well as an optimum bromine percentage 0.1?0.3%, resulting in (3?4%)???(0.3?0.5%) radiant efficiency at the optimum lamp power density of 360?540?W?m?1. Of the three ECGs, results indicate that the pulsed waveform produces a higher efficiency than rectangular and sinusoidal waveforms.