TY - JOUR A1 - Weigel, Ralf A1 - Hermann, Markus A1 - Curtius, Joachim A1 - Voigt, Christiane A1 - Walter, Saskia A1 - Böttger, Thomas A1 - Lepukhov, Boris A1 - Belyaev, Gennady A1 - Borrmann, Stephan T1 - Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application T2 - Atmospheric measurement techniques : AMT N2 - A characterization of the ultra-fine aerosol particle counter COPAS (COndensation PArticle counting System) for operation on board the Russian high altitude research aircraft M-55 Geophysika is presented. The COPAS instrument consists of an aerosol inlet and two dual-channel continuous flow Condensation Particle Counters (CPCs) operated with the chlorofluorocarbon FC-43. It operates at pressures between 400 and 50 hPa for aerosol detection in the particle diameter (dp) range from 6 nm up to 1 micro m. The aerosol inlet, designed for the M-55, is characterized with respect to aspiration, transmission, and transport losses. The experimental characterization of counting efficiencies of three CPCs yields dp50 (50% detection particle diameter) of 6 nm, 11 nm, and 15 nm at temperature differences (DeltaT) between saturator and condenser of 17°C, 30°C, and 33°C, respectively. Non-volatile particles are quantified with a fourth CPC, with dp50=11 nm. It includes an aerosol heating line (250°C) to evaporate H2SO4-H2O particles of 11 nm