Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application

Abstract. A characterization of the ultra-fine aerosol particle counter COPAS ( CO ndensation PA rticle counting S ystem) 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 ( d p ) range from 6 nm up to 1 μm. 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 d p 50 (50% detection particle diameter) of 6 nm, 11 nm, and 15 nm at temperature differences (Δ T ) between saturator and condenser of 17°C, 30°C, and 33°C, respectively. Non-volatile particles are quantified with a fourth CPC, with d p 50 =11 nm. It includes an aerosol heating line (250°C) to evaporate H 2 SO 4 -H 2 O particles of 11 nm d p 16 kg −1 fuel burned has been estimated based on measurements of the Geophysika's own exhaust.