CAPS PMssa Monitor

The CAPS PMssa monitor provides simultaneous measurement of both particle-based total optical extinction and scattering, producing a direct measurement of the particle single scattering albedo (SSA), the ratio of scattering to total extinction. Based on the CAPS PMex particle extinction monitor, this instrument incorporates an integrating sphere within the optical path, allowing for an accurate and precise measurement of particle scattering with minimal truncation effects. Operation is identical to the PMex monitor except for the need for periodic calibration of the scattering channel. With knowledge of the particle size distribution of the sample, SSA can be measured with an accuracy of better than ±0.03 at high values of SSA (typical of non-urban air masses) and ±0.01 as SSA approaches zero (typical of fresh soot emissions from combustion sources).

Correlation plot of measured scattering versus extinction for 250 nm diameter ammonium sulfate particles at a wavelength of 630 nm.

Allan analysis of the instrument noise in both measurement channels as a function of sample integration time for a monitor operating at 450 nm.

  • Climate change research.
  • Air quality monitoring.
  • Roadside monitoring.
  • Combustion plume analysis.
  • Aircraft engine exhaust monitoring.
  • Inverse nephelometer incorporated into CAPS extinction cell
  • Measurement of optical extinction and scattering at the 1 Mm-1 level (1σ,1s)
  • Fast time response (~1 second)
  • Choice of 1 of 4 Wavelengths:

    Far Red (660 nm)
    Red (630 nm)
    Green (530 nm)
    Blue (450 nm)

  • Autonomous Operation
Sensitivity (S/N =3) 3.0 Mm-1 (1 s), 0.5 Mm-1 (60 s) both channels
SSA ± 0.03 (30 s)
Response Time (10-90%) 1 s
Sample Flow 0.85 l min-1 (volumetric flow), Internal Pump
Operating Pressure Ambient
Materials Exposed to Sample: Conductive Urethane, Glass, Stainless Steel and     Aluminum
Data Output: RS-232 To Provided Netbook –
MS Windows-Based DAQ Software
On-Board Data Storage (6 GB) –
Download through USB Port Front Panel Display
Size/Weight: 24” x 19” x 9” (5U), 35 lbs
[61 cm x 43 cm x 23 cm, 16 kg]
Electric Power: 50 W; 100-250 VAC (50-60 Hz)

Single scattering albedo monitor for airborne particulates, T. Onasch, P. Massoli, P. Kebabian, F. Hills, F. Bacon, A. Freedman, Aerosol Sci.Technol., 49, 267-279, 2015..

Aerosol light extinction measurements by Cavity Attenuated Phase Shift Spectroscopy (CAPS): laboratory validation and field deployment of a compact aerosol extinction monitor, P. Massoli, P. Kebabian, T. Onasch, F. Hills, A. Freedman, Aerosol Sci.Technol., 44, 428–435, 2010.

System and method for precision phase shift measurement,  P. L. Kebabian, U.S. Patent No. 8,364,430 issued Jan. 29, 2013.

System and method for trace species detection using cavity attenuated phase shift spectroscopy, P. L. Kebabian, A. Freedman, U.S. Patent No. 7,301,639 issued November 27, 2007.