In-situ analysis of combustion aerosol using a supercontinuum lidar

We report real-time monitoring of coarse aerosol particle distribution in a 9m wide full-scale industrial boiler using a broadband supercontinuum lidar. The technique utilizes the light backscattered from the aerosol to map the extinction profile using the Klett inversion method, with measured extinction values of 0.04 - 0.2m-1 across the furnace. The technique further exploits differential absorption of water molecules in the 1.25 - 1.5 μm region to map the water vapor concentration profile in the furnace up to a distance of 3.9m with a spatial resolution of 30 cm. We also take advantage of the strong reflection from the boiler back-wall to simultaneously measure the average water vapor temperature and concentration in the boiler in good agreement with reference readings from the boiler. Our results open novel perspectives for versatile 3D profiling of flue gas parameters and other industrial process analysis.Peer reviewe

Sequential Collinear Photofragmentation and Atomic Absorption Spectroscopy for Online Laser Monitoring of Triatomic Metal Species

Industrial chemical processes are struggling with adverse effects, such as corrosion and deposition, caused by gaseous alkali and heavy metal species. Mitigation of these problems requires novel monitoring concepts that provide information on gas-phase chemistry. However, selective optical online monitoring of the most problematic diatomic and triatomic species is challenging due to overlapping spectral features. In this work, a selective, all-optical, in situ gas-phase monitoring technique for triatomic molecules containing metallic atoms was developed and demonstrated with detection of PbCl2. Sequential collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) enables determination of the triatomic PbCl2 concentration through detection of released Pb atoms after two consecutive photofragmentation processes. Absorption cross-sections of PbCl2, PbCl, and Pb were determined experimentally in a laboratory-scale reactor to enable calibration-free quantitative determination of the precursor molecule concentration in an arbitrary environment. Limit of detection for PbCl2 in the laboratory reactor was determined to be 0.25 ppm. Furthermore, the method was introduced for in situ monitoring of PbCl2 concentration in a 120 MWth power plant using demolition wood as its main fuel. In addition to industrial applications, the method can provide information on chemical reaction kinetics of the intermediate species that can be utilized in reaction simulations.publishedVersionPeer reviewe

Novel optical technologies for emergency preparedness and response : Mapping contaminations with alpha-emitting radionuclides

Radiological emergencies involving an accidental or deliberate dispersion of alpha-emitting radionuclides in the environment can cause significant damage to humans and societies in general. Currently, there is a metrology gap in managing such emergencies due to the lack of detectors that can measure alpha particles at distances greater than their range in air: most conventional alpha detectors are only effective when placed just a few centimeters above the contaminated area. This paper presents the development and testing of lens based optical detection systems that utilize alpha particle-induced ultraviolet (UV) luminescence of air, known as alpha radioluminescence. Telescopes based on fused silica and Poly(methyl 2-methylpropenoate) (PMMA) Fresnel lenses were investigated for their usability in facilitating emergency management related to alpha-emitting radionuclides. Careful matching of the diameter and focal length of the receiving optics, the response of the photocathode, and the passband of the filter allows detection sensitivities as high as 34s−1MBq−1 at 2m source-to-detector distance and background count rate of about 3s−1 in the UV-C spectral region, and suppression of daylight background count rate down to 16s−1. By flushing the source with nitrogen (N2) containing trace amounts of nitric oxide (NO), a groundbreaking sensitivity of 1.3×105s−1MBq−1 has been achieved, allowing detection limits as low as 100Bq with room lighting on, and 70Bq in a dark environment. In the UV-A spectral region, a detection limit of 4kBq could be achieved in a dark environment. These optical detection systems are aimed to facilitate a rapid, coordinated, and effective response in emergency situations involving the release of alpha-emitting radionuclides by mounting them on a tripod or an unmanned aerial device (UAV).publishedVersionPeer reviewe