AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
A New Laminar-Flow, Water-Based Condensation Particle Counter with near 1-nm Detection
SUSANNE HERING, Gregory Lewis, Steven Spielman, Arantzazu Eiguren Fernandez, Nathan Kreisberg, Chongai Kuang, Michel Attoui, Aerosol Dynamics Inc
Abstract Number: 238 Working Group: Instrumentation and Methods
Abstract A new, water-based, condensation particle counter has been developed that provides particle detection near 1nm at an aerosol flow of 0.3L/min, without use of a sheath. This “nano-WCPC” employs a three-stage, laminar-flow growth tube that moderates the temperature and water content of the output flow without reducing the peak supersaturation, and makes feasible operation at the large temperature differences necessary for high supersaturations. The sample flow passes through a wet-walled growth tube, the first portion of which is cooled to 1°-10°C. The second portion is heated to 90-95°C, and the third is cooled to ~22°C. The optics are held at 40°C. The warmed section, referred to as the “initiator”, is 20% of the overall length, and the temperature difference between the initiator and the first “conditioner” stage creates the super-saturation for particle activation. The final “moderator” section reduces both water vapor content and temperature, while maintaining the supersaturation. The system is implemented using the optics and motherboard from a TSI model 3783.
The nano-WCPC was calibrated using a “half Mini”-type high resolution differential mobility analyzer, with confirmation of sizing using tetraheptyl ammonium bromide mobility standards. When operated at an 88°C temperature differential between the conditioner and initiator, the nano-WCPC detects metal oxide particles generated from a hot nichrome wire with a 50% cut-point at 1.5 nm mobility diameter. However under these conditions the nano-WCPC also detects 10%-20% of the ions generated from either a Po-210 or soft X-ray bipolar ion source. Operation at a smaller temperature differential of 80°C mostly eliminates this detection of charger ions, but increases the 50% cut-point for the metal oxide particles to 1.8 nm mobility diameter. Pulse heights are observed to be very uniform, even though there is no sheath flow, likely due to Stefan flow driving particles towards the centerline.