Construction and Characterisation of a Particle Magnifier Helene Holmgren

Outline Background Condensation Particle Counter – CPC Pulse Height Analysis - PHA Particle Magnifier Future Applications Take Home Messages

Background Particle formation and growth Clusters - particle Nanoparticles Too small to scatter enough light to be detected by optical methods Too small to carry significant charge to be classified according to electrical mobility Diffusion losses

Condensation Particle Counter 2.5 – 1000 nm (TSI) <10,000,000 particles cm-3 (TSI) Measures particle number concentrations, but all information regarding size is lost

Condensation Particle Counter Heated saturator Vaporisation of working medium Cooled condenser Supersaturation Condensation and growth Optical detector Light scattering

Condensation Particle Counter S saturation ratio P actual vapour partial-pressure (Pa) P saturation vapour pressure (Pa) g surface tension (N m-1) M molecular weight (kg mol-1) r density (kg m-3) R universal gas constant (J K-1 mol-1) T absolute temp (K) d Kelvin diameter (m)

Pulse Height Analysis Measures pulse heights produced when particles pass laser beam Particles <15 nm (Saros et. al 1996) Pulse height increases with particle size Particles > 15 nm (Saros et. al 1996) All particles grow to the same size

Particle Magnifier Detect, count AND size nanoparticles Push size detection limit downwards Optimise saturation and cooling systems Find the most favourable working medium Minimise diffusion losses Instrument design

optical detection condenser saturator particles

Particle Magnifier

Particle Magnifier Grimm Dust Monitor IR-laser Light-scattering Pulse Height Analysis

Particle Magnifier

Future Applications Field measurements Laboratory studies SOA formation Terpenes emitted from vegetation Laboratory studies Connect to laminar flow tube (Emanuelsson)

Take Home Messages It is possible to obtain number-size distributions of nanoparticles by combining the principles of CPCs with PHA technique Particles <10 nm are activated at different sites in the condenser, and grow to different sizes Particles >10 nm are activated near the entrance of the condenser, and grow to the same size

References Saros, M., et al., Ultrafine aerosol measurement using a condensation nucleus counter with pulse height analysis. Aerosol Science and Technology, 1996. 25(2): p. 200-213.