Charakterisierung und Validierung eines optischen Kondensationskernzählers TMCPC - Miniaturisierung und Aufbau eines Instrumenten-Prototyps

Kurzfassung

A new instrument measuring aerosol particles in the size Dp < 100 nm has been developed and characterized in the framework of this thesis at the Institut für Physik der Atmosphäre (IPA) of the Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen. Conventional Optical Particle Counters (OPC) are not able to detect particles with diameter Dp < 100 nm. The new developed measurement system is based on growing particles by condensation of a saturated gas phase onto the nuclei. These enlarged droplets are now detectable by the OPC. The basic difference compared to commercial Condensation Particle Counters (CPC), which do show a deficit in efficiency in low pressure and proved in this thesis, is the mixing technique using a turbulent flow (turbulent mixing). This method of condensation on nuclei is already known and well established. The TMCPC prototype was operated for the first time and was characterized and validated by the whole spectrum of chemical and physical experimental aerosol techniques. The main purpose is an efficient measuring device in low pressure detecting particles Dp < 100 nm. The technical innovation consists of development and construction of an improved and miniaturised unit, which should be operated on commercial aircraft as part of the European research project IAGOS (Integration of routine Aircraft measurements into a Global Observing System). The network of a fleet of passenger aircraft (9 - 13 km; upper troposphere) equipped with permanently installed instruments will be the basis for a world-wide in situ observing system as an essential complement for satellite remote sensing of the atmosphere. Further aerosol measurement instrumentation had to be calibrated and characterized to define the TMCPC. Three available OPCs were calibrated for the particle size range between 250 – 1200 nm. The results were compared among each other and to the specifications given by the manufacturer. The channel borders were determined for each OPC using polystyrol-, sodium chloride-, ammoniumsulphate- and diethylhexylsebacat-aerosol as test aerosol. The size of the test aerosol was set by a Differential Mobility Analyzer (DMA) which was calibrated before in the particle size range between 40 – 900 nm with polystyrol-aerosol. A CPC (TSI 3010) was characterized with an Aerosolelectrometer (AE) at ambient and low pressure conditions (≈ 150 mbar) using the test aerosol mentioned above. An expectable inefficiency in low pressure was proved. The concluding characterization of the TMCPC was conducted for different particle diameters Dp at different operational modes and at ambient and low pressure conditions successfully.