Abstract: An alternative correction method for coincidence counting error in condensation particle counters (CPCs) is presented in this work. Due to the Poisson process can be used to describe the probability of particle occurrence within a certain period of time during particle counting in CPC, the perevent dead time is found to be varying with the sampling particle number concentration. Therefore, the concentration-dependent dead time can be determined experimentally and parameterized by a second-order exponential function, while parameterization also provides a good estimation of the average dead time of CPC. By using Newton's method based on concentration-dependent dead time, the particle number concentration measured by TSI 3788 water-based CPC is corrected, and an average error of less than 0.2% is achieved for particle concentrations ranging from 3000 to 40000 #/cm3. It is shown that Newton's method combined with a concentration-dependent dead time outperforms other methods with fixed dead time, including Lambert W function method and Taylor series expansion method, especially in the low particle concentration range.

Key words: per-event dead time, coincidence correction, Newton's method, condensation particle counter