AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
The Transfer Function of a Drift Tube Ion Mobility Spectrometer-Condensation Particle Counter Combination
JIHYEON LEE, David Buckley, Jikku Thomas, Christopher Hogan Jr., University of Minnesota
Abstract Number: 55 Working Group: Instrumentation and Methods
Abstract Our laboratory group has developed an atmospheric pressure drift tube ion mobility spectrometer (DTIMS), which can be coupled to a condensation particle counter (CPC). The DTIMS-CPC combination enables rapid (< 20 seconds) and adaptable size distribution measurements up to ~40 nm in size, with an optimum size range of 4-30 nm. To classify particles the DTIMS utilizes the same particle property as the differential mobility analyzer, i.e. electrical mobility, but instead of spatially filtering particles, it temporally separates them in a linear electric field, such that their arrival time at the CPC detector is inversely proportional to the electrical mobility. The transfer function of the DTIMS is necessary to convert the concentration per arrival time to concentration per unit mobility or to size distribution function. We have determined the transfer function for the most recent version of the DTIMS-CPC system (Kanomax FMT Model 3006), which operates with 10 kV applied across the DTIMS inlet and is coupled with a subsecond response CPC. A Twomey-Markowski algorithm was used to derive the transfer function from differential mobility analyzer-DTIMS-CPC measurements. For the verification of the transfer function, sodium chloride particles generated by a nano-aerosol generator (NAG) were measured by the DTIMS-CPC and the inverted mobility distributions were compared to the results from a commercially available differential mobility analyzer. The comparison results show that the transfer function of DTIMS for particles up to 40 nm is successfully determined to imply the wider application of the device.