Technical development of UV-C- and VUV-photochemically induced oxidative degradation processes.

Technical development work is presented, where the VUV photochemically induced oxidative degradation is used: (i) for analytic purposes, and (ii) for small to medium scale (< 10 m2/d) waste water treatment processes or ultrapure water production. In the first case, small Xe-excimer radiation sources with an integrated reaction space designed for optimal conditions, as far as incident photon flux density, turbulence and concentration of dissolved molecular oxygen are concerned, have been built and tested. Under conditions of exhaustive oxidation and/or mineralization of pollutants in a continuous regime, they may be used for sample pre-treatment modules prior TOC, TOX and electrochemical trace metal analysis. Under conditions of partial oxidation or mineralization, the same lamp/reactor combination may be used for functionalization purposes prior to e.g. GC or HPLC analyses. In the second case, mass transfer limitations between the non-irradiated bulk volume and the irradiated volume are overcome by the electrochemical generation of molecular oxygen within or close to the irradiated volume and by the design of the photochemical part of the reactor.

Continuous-wave laser pump light sources: new concepts.

The relatively short lifetime of rare-gas discharge pump light sources for high-power cw solid-state lasers is caused mainly by vaporized cathode emitter material reacting with the thermally highly loaded quartz wall. The introduction of new bipolar electrodes without special emitter materials mounted on hot-ended molybdenum-cup seals, together with 60-kHz ac operation, makes possible the application of a tungsten halide cleaning cycle within the lamp bulb. This new type of high-power rare-gas pump light source exhibits 20% better radiation efficiency, 20% lower Nd:YAG laser threshold, and considerably extended lifetime.

Spectroscopic measurements of electron densities and gas temperatures in deuterium lamps.

Plasma diagnostics results of electron densities and gas temperatures in commercial low-pressure deuterium lamps at current densities from 38 A/cm(-2) to 306 A/cm(-2) are presented. These plasma parameters are obtained by comparing measured and calculated Balmer line profiles, taking into account Stark broadening, Doppler broadening, and the influence of fine structure and the apparatus profile. Results for the plasma spot show a steady increase of electron density from 1.6 x 10(13) cm(-3) to 5.0 x 10(13) cm(-3) and of gas temperature from 1800 to 6800 K.