White-light optical particle spectrometer for in situ measurements of condensational growth of aerosol particles

Kiselev, Alexei; Wex, Heike; Stratmann, Frank; Nadeev, Alexandre; Karpushenko, Dmitry

doi:10.1364/ao.44.004693

Cited by 31 publications

(35 citation statements)

References 28 publications

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“…The lens focuses the scattered light to a spot that is off-axis from the lens center on the opposite side of the drilled hole, leading to clear physical separation of the laser beam and focused scattered light. Kiselev et al (2005) have reported a similar design. Instead of the modified lens in our design, they used a pair of customdesigned off-axis elliptical mirrors.…”

Section: Basic Design Conceptmentioning

confidence: 71%

A High-Sensitivity Low-Cost Optical Particle Counter Design

Gao

Perring

Thornberry

et al. 2013

Aerosol Science and Technology

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We report the design of a small optical particle counter with high sensitivity and low construction cost for atmospheric aerosol measurements. Particle sensing is based on the detection of the forward scattering of laser light. The separation of the laser beam and scattered light is achieved with a novel yet simple optical system. A laboratory prototype system with a 405-nm laser and photomultiplier tube detector has successfully detected polystyrene latex particles as small as 125 nm in diameter with unit efficiency. Theoretical calculations suggest that a lower detectable size limit of 100 nm can be achieved with reduction of background scattered light. The new counter will be useful in a variety of ground-based as well as small balloon-borne applications such as vertical profiling and in situ measurement of particles from explosive volcanic eruptions.

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Section: Basic Design Conceptmentioning

confidence: 71%

A High-Sensitivity Low-Cost Optical Particle Counter Design

Gao

Perring

Thornberry

et al. 2013

Aerosol Science and Technology

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“…LACIS consists of a laminar flow tube and an white-light optical particle spectrometer (OPS, Kiselev et al, 2005) that measures the size of particles after the passage through the tube. For this study, a flow tube length of 1 m was used for LACIS.…”

Section: Lacismentioning

confidence: 99%

Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol: Part 1 – Evidence from measurements

et al. 2009

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Abstract. Secondary Organic Aerosols (SOA) studied in previous laboratory experiments generally showed only slight hygroscopic growth, but a much better activity as a CCN (Cloud Condensation Nucleus) than indicated by the hygroscopic growth. This discrepancy was examined at LACIS (Leipzig Aerosol Cloud Interaction Simulator), using a portable generator that produced SOA particles from the ozonolysis of α-pinene, and adding butanol or butanol and water vapor during some of the experiments. The light scattering signal of dry SOA-particles was measured by the LACIS optical particle spectrometer and was used to derive a refractive index for SOA of 1.45. LACIS also measured the hygroscopic growth of SOA particles up to 99.6% relative humidity (RH), and a CCN counter was used to measure the particle activation. SOA-particles were CCN active with critical diameters of e.g. 100 nm and 55 nm at super-saturations of 0.4% and 1.1%, respectively. But only slight hygroscopic growth with hygroscopic growth factors ≤1.05 was observed at RH<98% RH. At RH>98%, the hygroscopic growth increased stronger than would be expected if a constant hygroscopicity parameter for the particle/droplet solution was assumed. An increase of the hygroscopicity parameter by a factor of 4-6 was observed in the RH-range from below 90% to 99.6%, and this increase continued for increasingly diluted particle solutions for activating particles. This explains an observation already made in the past: that the relation between critical super-saturation and dry diameter for activaCorrespondence to: H. Wex (wex@tropos.de) tion is steeper than what would be expected for a constant value of the hygroscopicity. Combining measurements of hygroscopic growth and activation, it was found that the surface tension that has to be assumed to interpret the measurements consistently is greater than 55 mN/m, possibly close to that of pure water, depending on the different SOA-types produced, and therefore only in part accounts for the discrepancy between hygroscopic growth and CCN activity observed for SOA particles in the past.

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“…At the outlet of the flow tube, the number concentration and size of the humidified particles was measured with an optical particle spectrometer that has been designed and built especially for LACIS (for details see Kiselev et al, 2005). A xenon-arc lamp provided white light for the measurement.…”

Section: Methodsmentioning

confidence: 99%

“…Figure 2 shows the measured PSL signals, the modeled PSL response curve, and an exemplary response curve for NaCl particles with a dry diameter of 50 nm. Response curves calculated for solutions account for changes in the particle refractive index with changing particle concentration (see Kiselev et al, 2005). For the experiment introduced in this work, the smallest detectable size was about 250 nm when the full intensity of the light source of the optical particle spectrometer was used.…”

Section: Methodsmentioning

confidence: 99%

“…When more than one measurement was available, the values were averaged. The deviations between these separate measurements depend on uncertainties in different parameters, as there are the sizing with the DMA, the dew point temperatures and T wall , and uncertainties of the optical particle spectrometer as discussed in Kiselev et al (2005). However, these deviations between up to 4 separate measurements were found to be below 0.03% (one standard deviation; value given as absolute value in terms of measured critical super-saturation), being smaller for smaller supersaturations.…”

Section: Calibrationmentioning

confidence: 97%

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Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

et al. 2006

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Abstract. A calibration for LACIS (Leipzig Aerosol CloudInteraction Simulator) for its use as a CCN (cloud condensation nuclei) detector has been developed. For this purpose, sodium chloride and ammonium sulfate particles of known sizes were generated and their grown sizes were detected at the LACIS outlet. From these signals, the effective critical super-saturation was derived as a function of the LACIS wall temperature. With this, LACIS is calibrated for its use as a CCN detector. The applicability of LACIS for measurements of the droplet activation, and also of the hygroscopic growth of atmospheric aerosol particles was tested. The activation of the urban aerosol particles used in the measurements was found to occur at a critical super-saturation of 0.46% for particles with a dry diameter of 75 nm, and at 0.42% for 85 nm, respectively. Hygroscopic growth was measured for atmospheric aerosol particles with dry diameters of 150, 300 and 350 nm at relative humidities of 98 and 99%, and it was found that the larger dry particles contained a larger soluble volume fraction of about 0.85, compared to about 0.6 for the 150 nm particles.

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White-light optical particle spectrometer for in situ measurements of condensational growth of aerosol particles

Cited by 31 publications

References 28 publications

A High-Sensitivity Low-Cost Optical Particle Counter Design

A High-Sensitivity Low-Cost Optical Particle Counter Design

Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol: Part 1 – Evidence from measurements

Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

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