Hossein Saghafifard - Planck Institute for Chemistry, Particle Chemistry Group, Mainz, Germany, Physics Group, Faculty of Science, University of Isfahan, Isfahan, Iran
Joachim Curtius - Johannes Gutenberg University, Institute for Atmospheric Physics, Mainz, Germany
Andreas Kurten - Planck Institute for Chemistry, Particle Chemistry Group, Mainz, Germany
Stephan Borrmann - Planck Institute for Chemistry, Particle Chemistry Group, Mainz, Germany, Johannes Gutenberg University, Institute for Atmospheric Physics, Mainz, Germany

The Design and performance of a condensation nucleus counter (CNC) based on fast adiabatic expansion is described. To make the particles large enough to be detected they are brought into a supersaturated environment where they grow due to the uptake of water vapor. The particle number concentration is calculated by Mie theory without the necessity of making any further calibration. It is demonstrated that the lower cut-off size of this counter is in the range of 3 nm or even at smaller diameters and that it can be used for measuring the number concentration of atmospheric particles.

Condensation Nucleus Counter, Mie theory, Nanoparticles