Anders Sunesson

Mobile remote sensing system for atmospheric monitoring

A mobile optical remote sensing system for environmental monitoring is described. The system, housed in a full-size truck with a laboratory floor surface of 6.0 × 2.3 m2, is mainly intended for differential absorption lidar (DIAL) applications but can also be used for laser-induced fluorescence monitoring and for absorption measurements using classical light sources. The system has a 40-cm diam receiving telescope and a fully steerable flat mirror in a transmitting/receiving dome. A Nd:YAG-pumped dye laser with auxiliary nonlinear frequency conversion is the preferred transmitter in DIAL measurements. Measurement examples for atmospheric SO2 and NO2 monitoring with automatic concentration map drawings are given and further uses are discussed.

Atmospheric atomic mercury monitoring using differential absorption lidar techniques

Three-dimensional mapping of atmospheric atomic mercury has been performed with lidar techniques, to our knowledge, for the first time. Industrial pollution monitoring, as well as measurements of background concentrations, is reported. High-efficiency frequency doubling of narrowband pulsed dye laser radiation was employed to generate intense radiation at the mercury UV resonance line. Field measurements were supplemented with extensive laboratory investigations of absorption cross sections and interfering lines of molecular oxygen.

Differential optical absorption spectroscopy system used for atmospheric mercury monitoring.

A high-resolution differential optical absorption spectroscopy (DOAS) system for long-path atmospheric pollution monitoring is described. The system, consisting of a broadband lamp and a dispersive, fast-scanning optical receiver, separated by a few kilometers, was used in measurements of different pollutants, highlighted by the monitoring of the local concentration of atomic mercury. Mercury levels in the ppt (1:10(12)) range were assessed by comparisons with laboratory measurements.

NO plume mapping by laser-radar techniques

Mapping of NO plumes by using laser-radar techniques has been demonstrated with a mobile differential absorption lidar system. The system was equipped with a narrow-linewidth Nd:YAG-pumped dye laser that, with doubling and mixing, generated pulse energies of 3-5 mJ at 226 nm, with a linewidth of 1pm. This permitted range-resolved measurements of NO, with a range of about 500 m. The detection limit was estimated to 3 microg/m(3), with an integration interval of 350 m. Spectroscopic studies on the gamma(0, 0) bandhead near 226.8 nm were performed with 1-pm resolution, and the differential absorption cross section was determined to be (6.6 +/- 0.6) x 10(-22) m(2), with a wavelength difference of 12 pm.

NO2-Mapping using laser-radar techniques

Abstract Laser-radar mapping of NO2 concentration distributions in an urban area close to a motorway is described. The measurements were performed during inversion conditions leading to elevated concentrations. Horizontal mapping of the NO2 concentration was performed and the results were compared with measurements of wind speed, temperature and NO2 concentration at a point measuring station.

Laser-triggered high-voltage plasma switching with diffractive optics.

High-power lasers can be used to induce ionization of gases and thereby enable rapid triggering of electrical discharge devices, potentially faster than any devices based on mechanical or solid-state switching. With diffractive optical elements (DOEs) the laser light can conveniently be directed to positions within the gas so that an electrical discharge between two high-voltage electrodes is triggered reliably and rapidly. Here we report on two different types of DOE used for creating an electrical discharge in pure argon for potential high-voltage applications. One is the diffractive equivalent of a conventional axicon that yields an extended, and continuous, high-intensity focal region between the electrodes. The other is a multiple-focal-distance kinoform--a DOE that is designed to produce a linear array of 20 discrete foci, with high peak intensities, between the electrodes. We show that DOEs enable efficient, rapid switching and may provide increased flexibility in the design of novel electrode configurations.