Preprints
https://doi.org/10.5194/amt-2021-62
https://doi.org/10.5194/amt-2021-62

  11 Mar 2021

11 Mar 2021

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

The nano-scanning electrical mobility spectrometer (nSEMS) and its application to size distribution measurements of 1.5–25 nm particles

Weimeng Kong1,a, Stavros Amanatidis1, Huajun Mai2, Changhyuk Kim1,b, Benjamin C. Schulze2, Yuanlong Huang2, Gregory S. Lewis3, Susanne V. Hering3, John H. Seinfeld1,2, and Richard C. Flagan1,2 Weimeng Kong et al.
  • 1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
  • 2Department of Environmental Science and Engineering, California Institute of Technology, Pasadena, CA 91125
  • 3Aerosol Dynamics Inc., Berkeley, CA
  • anow at: California Air Resources Board, Sacramento, CA 95814
  • bnow at: Department of Environmental Engineering, Pusan National University, Busan, Republic of Korea

Abstract. Particle size measurement in the low nanometer regime is of great importance to the study of cloud condensation nuclei formation and to better understand aerosol-cloud interaction. Here we present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS consists of a charge conditioner, a novel differential mobility analyzer, and a two-stage condensation particle counter (CPC). The charge conditioner employs a soft x-ray bipolar ion source in a compact housing designed to optimize both nanoparticle charging and transmission efficiency. The mobility analyzer, a radial opposed migration ion and aerosol classifier (ROMIAC), can classify nanometer-sized particles with minimal degradation of its resolution or diffusional losses. The ROMIAC operates on a dual high-voltage supply with fast polarity-switching capability to minimize sensitivity to variations in the chemical nature of the ions used to charge the aerosol. Particles transmitted through the charge conditioner and mobility analyzer are measured using a two-stage CPC. They are first activated in a fast-mixing diethylene glycol (DEG) stage before being counted by a second detection stage, an ADI MAGICTM water-based CPC. The transfer function of the integrated instrument is derived from both finite-element modeling and experimental characterization. The nSEMS performance has been evaluated during measurement of transient nucleation and growth events in the CLOUD atmospheric chamber at CERN. We show that the nSEMS can provide high time and size resolution measurement of nanoparticles, and can capture the critical aerosol dynamics of newly formed atmospheric particles.

Weimeng Kong et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-62', Juan Fernandez de la Mora, 29 Mar 2021
    • AC1: 'Reply on RC1', Weimeng Kong, 03 Jun 2021
  • RC2: 'Comment on amt-2021-62', Anonymous Referee #2, 18 Apr 2021
    • AC2: 'Reply on RC2', Weimeng Kong, 03 Jun 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-62', Juan Fernandez de la Mora, 29 Mar 2021
    • AC1: 'Reply on RC1', Weimeng Kong, 03 Jun 2021
  • RC2: 'Comment on amt-2021-62', Anonymous Referee #2, 18 Apr 2021
    • AC2: 'Reply on RC2', Weimeng Kong, 03 Jun 2021

Weimeng Kong et al.

Weimeng Kong et al.

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Short summary
We present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS has been proved to be extremely powerful in examining atmospheric nucleation and the subsequent growth of nanoparticles in the CERN CLOUD experiment, which provides a valuable asset to study atmospheric nanoparticles and to evaluate their impact on climate.