Particle Size Magnifier for Nano-CN Detection

Abstract

A new particle size magnifier (PSM) for detection of nano-CN as small as ∼1 nm in mobility diameter was developed, calibrated and tested in atmospheric measurements. The working principle of a PSM is to mix turbulently cooled sample flow with heated clean air flow saturated by the working fluid. This provides a high saturation ratio for the working fluid and activates the seed particles and grows them by condensation of the working fluid. In order to reach high saturation ratios, and thus to activate nano-CN without homogeneous nucleation, diethylene glycol was chosen as the working fluid. The PSM was able to grow nano-CN to mean diameter of 90 nm, after which an ordinary condensation particle counter was used to count the grown particles (TSI 3010). The stability of the PSM was found to be good making it suitable for stand-alone field measurements. Calibration results show that the detection efficiency of the prototype PSM + TSI 3010 for charged tetra-alkyl ammonium salt molecules having mobility equivalent diameters of 1.05, 1.47, 1.78, and 2.57 nm are 25, 32, 46, and 70%, respectively. The commercial version of the PSM (Airmodus A09) performed even better in the smallest sizes the detection efficiency being 51% for 1.47 nm and 67% for 1.78 nm.

Operation of the Airmodus A11 nano Condensation Nucleus Counter at various inlet pressures and various operation temperatures, and design of a new inlet system

“…In our study we confirmed the calculation presented in Vanhanen et al (2011), which predicted the peak supersaturation to occur at mixing ratio of 0.1 in the mixing zone. The calibration of the nCNC in the mixing activation mode is presented in Fig.…”

“…The mixing ratio in the PSM is defined as Q saturator /(Q aerosol + Q saturator ), where Q indicates a volume flow rate of a given flow. In our study the observation of Vanhanen et al (2011) is experimentally explained by two different regions of supersaturation inside the PSM.…”

“…The inversion routine for the nCNC is presented by Lehtipalo et al (2014), and the inversion routine has been experimentally verified by Kangasluoma et al (2015). Vanhanen et al (2011) reported a theoretical prediction of the maximum supersaturation in the mixing region at a mixing ratio of 0.1, whereas their experiments showed that supersaturation continued to increase at mixing ratios larger than 0.1. The mixing ratio in the PSM is defined as Q saturator /(Q aerosol + Q saturator ), where Q indicates a volume flow rate of a given flow.…”

“…Some of these newly formed particles can subsequently grow into large enough sizes to affect climate by influencing cloud formation and by scattering sunlight (Kerminen et al, 2012). With the development of new particle counters that are applicable to atmospheric measurements of sub-3 nm particles (Jiang et al, 2011;Sipilä et al, 2009;Vanhanen et al, 2011;Wimmer et al, 2013), measurements of new particle formation have been extended to molecular sizes. Based on laboratory verifications, these new particle counters are able to activate and detect large molecules and molecular clusters.…”

“…The design of the A10 is based on the PSM design of Sgro and Fernández de la Mora (2004), in which the mixing chamber has only one inlet for the aerosol flow, compared to two (Gamero-Castano and Fernández de la Mora, 2000) or even four (Kim et al, 2002) in the previous designs. An in-depth description of the A10 instrument is given by Vanhanen et al (2011), although this study describes the model A09. The A10 is essentially the same instrument as the A09, but with improved electronics, software, flow control and therefore improved operation stability.…”