Burtscher, Heinz
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Burtscher
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Heinz
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Burtscher, Heinz
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- PublikationDevelopment of an airborne sensor for reliable detection of volcanic ash(IEEE, 2016) Weingartner, Ernest; Jurányi, Zsofia; Egli, Daniel; Steigmeier, Peter; Burtscher, Heinz [in: 3rd IEEE International Workshop on Metrology for Aerospace. Proceedings]This sensor detects volcanic ash particles and distinguishes them from cloud droplets. Operated on an airplane, this detector can quantify the exposure to hazardous refractory ash and the in-situ measurement is not biased by the presence of cloud particles. A volcanic eruption emits a significant amount of hazardous ash particles into the air. If the event is strong enough, the volcanic ash plume can reach high altitudes and can be a serious security risk for airplanes. We have developed a new prototype aerosol sensor for the reliable detection of volcanic ash. The envisaged application is the employment of this new technique on board of passenger aircraft. It allows in-situ monitoring of the airplane's exposure to volcanic ash. The challenge of this development is the requirement that the sensor can distinguish cloud droplets (or ice crystals) from the hazardous refractory ash particles. At aviation altitudes, water droplets and ice crystals are often present in the particle size region of the ash (1-20 micrometer) and their concentrations can reach the levels that are considered as the limits of the different volcanic ash contamination zones. Therefore, it is crucial that the sensor can differentiate between volcanic ash and water or ice particles. The sensor measures the scattered light intensities from individual particles outside of the airplane cabin through a glass window. The desired discrimination is achieved with two lasers operating at different wavelengths. Ash concentrations (in terms of number and mass) are derived, and the exposure of the airplane is recorded and transmitted in real time to the pilot. The volcanic ash detector was tested in the laboratory with various test aerosols and micrometer-sized water droplets. Then, ground-based outdoor measurements were conducted and the instrument response to mineral dust (a surrogate for volcanic ash) and natural cloud droplets (and ice crystals) was investigated. In a next step, this new technique will be tested in summer 2016 on-board of a research aircraft.04B - Beitrag Konferenzschrift
- PublikationDual-wavelength light-scattering technique for selective detection of volcanic ash particles in the presence of water droplets(Copernicus, 2015) Jurányi, Zsófia; Burtscher, Heinz; Loepfe, Markus; Nenkov, Maxim; Weingartner, Ernest [in: Atmospheric Measurement Techniques]A new method is presented in this paper which analyses the scattered light of individual aerosol particles simultaneously at two different wavelengths in order to retrieve information on the particle type. We show that dust-like particles, such as volcanic ash, can be unambiguously discriminated from water droplets on a single-particle level. As a future application of this method, the detection of volcanic ash particles should be possible in a humid atmosphere in the presence of cloud droplets. The characteristic behaviour of pure water's refractive index can be used to separate water droplets and dust-like particles which are commonly found in the micrometre size range in the ambient air. The low real part of the water's refractive index around 2700–2800 nm results in low scattered light intensities compared to e.g. the visible wavelength range, and this feature can be used for the desired particle identification. The two-wavelength measurement set-up was theoretically and experimentally tested and studied. Theoretical calculations were done using Mie theory. Comparing the ratio of the scattered light at the two wavelengths (visible-to-IR (infrared), R value) for water droplets and different dust types (basalt, andesite, African mineral dust, sand, volcanic ash, pumice) showed at least 9-times-higher values (on average 70 times) for water droplets than for the dust types at any diameter within the particle size range of 2–20 μm. The envisaged measurement set-up was built up into a laboratory prototype and was tested with different types of aerosols. We generated aerosols from the following powders, simulating dust-like particles: cement dust, ISO 12103-1 A1 Ultrafine Test Dust and ash from the 2012 eruption of the Etna volcano. Our measurements verified the theoretical considerations; the median experimental R value is 8–21 times higher for water than for the "dust" particles.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationReal-time characterization of ultrafine and accumulation mode particles in ambient combustion aerosols(Elsevier, 08/2002) Bukowiecki, Nicolas; Kittelson, David B.; Watts, Winthrop F.; Burtscher, Heinz; Weingartner, Ernest; Baltensperger, Urs [in: Journal of Aerosol Science]The diffusion charging sensor (DC), photoelectric aerosol sensor (PAS) and condensation particle counter (CPC) are real-time particle instruments that have time resolutions < 10s and are suitable for field use. This paper shows how the relative fraction of nuclei mode particles (D ≤ 50nm) in ambient combustion aerosols can be determined, along with the coverage degree of the respective accumulation mode particles with a modal diameter of ~ 100nm. Main tools for interpretation are the diameter of average surface DAve,S (obtained from CPC and DC measurements) and PAS/DC versus DAve,S scatter plots. Compared to the scanning mobility particle sizer (SMPS), which is a standard instrument for aerosol particle size distribution measurements, the presented method has a limited accuracy, but is substantially faster. Additionally, it is experimentally less demanding than SMPS measurements, especially for field applications.01A - Beitrag in wissenschaftlicher Zeitschrift