Egils Bogans

Tomographic diagnostics of high-frequency electrodeless lamps in argon-mercury mixtures

Tomographic reconstruction of spatial profiles of the mercury atom density in the excited state 7 3S1 in high-frequency electrodeless lamps (HFELs) has been performed. The measurements of the Hg 546.1 nm line emission intensity have been made for the HFELs in argon–mercury mixture depending on the operation regime with different cold spot temperatures in the range 31–98 °C. The maximum entropy-based algorithm was applied for the reconstruction of local emission coefficients from the integrated intensities. The emission coefficients are directly related to the local values of the mercury atom density in the excited state 7 3S1, the upper state of the 546.1 nm transition. Such an investigation has been performed first for the HFEL. We have found that the emitting mercury atoms in the state 7 3S1 are concentrated in a thin layer located close to the lamp wall. The radial profiles have demonstrated a strong depletion of the population density in the state 7 3S1 from the lamp centre at high generator currents and low mercury vapour density. The obtained results are analysed theoretically in the context of the radial cataphoresis phenomenon. We found a qualitative agreement between the reconstructed density profiles and theoretical model predictions.

Imaging of Emitting Mercury Atom Spatial Distributions in a Capillary Discharge Lamp by Using Tomography Approach

A tomographic reconstruction of emitting mercury atom spatial profiles in a capillary lamp with an inner diameter of 1 mm has been made for the first time in this work. Measurements of emission intensity have been performed for the capillary lamp in a xenon-mercury mixture in dependence on the operation position. Intensities were measured for the 546.1-nm Hg line for vertically and horizontally operated lamps. We have found that the emitting mercury atoms in the state 73S1 (the upper state of the 546.1-nm transition) are differently distributed within the lamp in the vertical and horizontal lamp positions.

Analysis of Mercury Pollution in Air in Urban Area of Riga Using Atomic Absorption Spectrometry

Toxicity of mercury and its compounds is well known, and they are considered as substances of heightened concern. Though mercury is to some extent released into the environment by natural processes such as volcanic eruptions, additional releases from anthropogenic sources have increased the environmental exposure and deposition significantly. There are many commonly used items containing mercury, for instance, mercury light bulbs, switches, and mercury thermometers, the disposal of which into trashcans can cause an increase of mercury concentration in the air of the local area. The paper reports mercury pollution surveys performed in several districts of Riga (the capital of Latvia). Using an RA 915+ Zeeman atomic absorption spectrometer, the concentration of mercury was measured in the air above objects of interest. The measurements mainly made from driving a car equipped with a GPS receiver have allowed the assignment of Hg concentration to a particular place to provide a digitised pollution database in geographic coordinates at different times. Results of the surveys show the background concentration of atmospheric mercury in Riga generally did not exceed 5 ng/m3 while some places of increased mercury pollution need particular attention and clean-up. Examples of such surveys are shown.