AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Design and Performance of an Indirect Ionization Soft X-ray Charge Conditioner
DEREK OBERREIT, Siqin He, Kanomax FMT, Inc.
Abstract Number: 406 Working Group: Instrumentation and Methods
Abstract Aerosol measurements using electrical-based instruments such as Faraday cup electrometers and electrical mobility classifiers require corrections to account for charge probability distribution within the population of aerosol particles. Often this is accomplished by exposing the aerosol to ionizing radiation (light, radioactive, x-ray), where gas molecules within the aerosol are ionized and, through collisions with the aerosol particles, achieve a known charge probability distribution. Exposing the aerosol to this ionizing energy can result in new particle formation by the radiolytically excited gas vapors within the aerosol, as well as directly ionization the particles. The radiolytically generated particles may be indistinguishable from the particles within the sampled aerosol, leading to measurement errors. Additionally, using these methods does not allow for controlled chemical ionization, where the ionizing molecule is chosen for its specific properties. Finally, in special cases, it is possible to alter the properties of the particles themselves by exposing them to high levels of electromagnetic radiation (e.g. particle heating from a photoionization process).
A novel indirect ionization device has been developed to allow for controlled chemical ionization of aerosol particles without exposing the aerosol to relevant levels of ionizing energy. The principle of operation and performance of the device are presented, including size-dependent charge distribution measurements for different ionizing gases.