Symmetric Inclined Grid Mobility Analyzer for the Measurement of Charged Clusters and Fine Nanoparticles in Atmospheric Air

Tammet, Hannes

doi:10.1080/02786826.2010.546818

Cited by 26 publications

(22 citation statements)

References 27 publications

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“…For many designs, the proper Reynolds number for IGMAs from the perspective of flow stability is that of the separation gas flow, which is a factor of R nd larger than that of the aerosol flow considered here. Although the limits of accessible Re are generally unknown at present, the favorable scaling in κ relative to DMAs nonetheless suggests that OMAC and IGMA designs may even enable DEMCs to peer into the subnanometer range of small molecules, opening the door to an array of new applications ranging from front-end purification of samples going to mass spectrometers to monitoring for dangerous airborne chemicals in the field or use, as demonstrated by Tammet (2011), as an airborne-ion detector.…”

Section: Comparing Dmas To Omacs and Igmasmentioning

confidence: 99%

“…This has recently been applied in an instrument called the symmetric inclined grid mobility analyzer (SIGMA), which enables simultaneous measurement of gas ions or small nanoparticles of both polarities. Employing high volumetric flow rates, the SIGMA can measure ions/particles in the 0.4-7.5 nm size range (Tammet 2011). Flagan (2004) modeled another form of inclined field mobility analyzer called the opposed migration aerosol classifier (OMAC) in which porous electrodes define the classification channel.…”

Section: Introductionmentioning

confidence: 99%

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An Asymptotic Analysis of Differential Electrical Mobility Classifiers

Downard

Dama

Flagan

2011

Aerosol Science and Technology

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An asymptotic analysis of balanced flow operations of differential mobility analyzers (DMAs) and a new class of instruments that includes opposed migration aerosol classifiers (OMACs) and inclined grid mobility analyzers (IGMAs) provides new insights into the similarities and differences between the devices. The characteristic scalings of different instruments found from minimal models are shown to relate the resolving powers, dynamic ranges, and efficiencies of most such devices. The resolving powers of all of the instruments in the nondiffusive regime of high voltage classifications, R nd , is determined by the ratio of the flow rate of the separation gas (sheath or crossflow) to that of the aerosol. At low voltage, when diffusion degrades the classification, the OMAC and the IGMA share an R nd factor advantage in dynamic range of mobilities over the DMA, although the OMAC also suffers greater losses because diffusion immediately deposits particles onto its porous electrodes. On the basis of this analysis, a single master operating diagram is proposed for DMAs, OMACs, and IGMAs. Analysis of this operating diagram and its consequences for the design of differential electrical mobility classifiers suggests that OMACs and IGMAs also have advantages over DMAs in design flexibility and miniaturization. Most importantly, OMACs and IGMAs may outperform DMAs for the currently difficult classification of particles with diameters less than 10 nm. On the other hand, DMAs are more amenable to voltage scanning-mode operation to enable accelerated size distribution measurements, whereas it is most convenient to operate OMACs and IGMAs in voltage stepping-mode operation.

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Section: Comparing Dmas To Omacs and Igmasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Asymptotic Analysis of Differential Electrical Mobility Classifiers

Downard

Dama

Flagan

2011

Aerosol Science and Technology

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“…While the adverse gradient is integral to the design of all commonly used DMAs, Labowsky and de la Mora (2006) described a novel instrument in which particles are introduced and extracted from the grounded side of the classifier; that classifier can, however, only be used with an electrometer or other charged particle detector because neutral particles will be included in the classified-sample outlet flow. Tammet demonstrated a highly modified DMA in which the field is created by applying a potential between a pair of screens that are inclined with respect to the sheath flow (Tammet 2003(Tammet , 2011. This symmetric inclined grid mobility analyzer classifies ions and particles of both polarities (hence "symmetric") in the 0.4-7.5 nm range with R of 2-3.…”

Section: Advancing Nanometer Particle Classificationmentioning

confidence: 99%

“…This method relies on the availability of fastresponse particle detectors that have recently become available. Flagan (2004) proposed and modeled an alternate differential mobility classifier that has some features of that of Tammet (2003Tammet ( , 2011; like the DMA, this opposed migration aerosol classifier (OMAC) can continuously extract particles within a narrow range of mobilities for detection or use in other experiments. In this device, migration between two permeable electrodes that define the classification channel is opposed by a cross-flow (Q cf ) of particle-free gas through those electrodes.…”

Section: Advancing Nanometer Particle Classificationmentioning

confidence: 99%

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

Mui

Mai

Downard

et al. 2017

Aerosol Science and Technology

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We present the design, simulation, and characterization of the radial opposed migration ion and aerosol classifier (ROMIAC), a compact differential electrical mobility classifier. We evaluate the performance of the ROMIAC using a combination of finite element modeling and experimental validation of two nearly identical instruments using tetra-alkyl ammonium halide mass standards and sodium chloride particles. Mobility and efficiency calibrations were performed over a wide range of particle diameters and flow rates to characterize ROMIAC performance under the range of anticipated operating conditions. The ROMIAC performs as designed, though performance deviates from that predicted using simplistic models of the instrument. The underlying causes of this nonideal behavior are found through finite element simulations that predict the performance of the ROMIAC with greater accuracy than the simplistic models. It is concluded that analytical performance models based on idealized geometries, flows, and fields should not be relied on to make accurate a priori predictions about instrumental behavior if the actual geometry or fields deviate from the ideal assumptions. However, if such deviations are accurately captured, finite element simulations have the potential to predict instrumental performance. The present prototype of the ROMIAC maintains its resolution over nearly three orders of magnitude in particle mobility, obtaining sub-20 nm particle size distributions in a compact package with relatively low flow rate operation requirements.

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“…To tackle the low transmission, the University of Tartu developed low-resolution DMAs that have high inlet flow rates. They have successfully used the Air Ion Spectrometer (AIS; Asmi et al, 2009;Gagn'e et al, 2011;Mirme and Mirme, 2013), the Balanced Mobility Scanning Analyzer (BSMA; Tammet, 2006) and the Symmetric Inclined Grid Mobility Analyzer (SIGMA; Tammet, 2011) to measure concentrations and size distributions of ambient ions. These instruments have extremely high inlet flow rates (from 54 to thousands of liters per minute, L min −1 ), which enable high ion transmission efficiencies (greater than 80 %) but limit their resolution to R < 2, where R is defined as the ratio of the mobility of the ion/particle that is transmitted with the greatest efficiency to the range of mobilities for which the transmission efficiency is at least half of that value.…”

Section: Introductionmentioning

confidence: 99%

A new high-transmission inlet for the Caltech nano-RDMA for size distribution measurements of sub-3 nm ions at ambient concentrations

et al. 2016

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Abstract. Reliable and reproducible measurements of atmospheric aerosol particle number size distributions below 10 nm require optimized classification instruments with high particle transmission efficiency. Almost all differential mobility analyzers (DMAs) have an unfavorable potential gradient at the outlet (e.g., long column, Vienna type) or at the inlet (nano-radial DMA), preventing them from achieving a good transmission efficiency for the smallest nanoparticles. We developed a new high-transmission inlet for the Caltech nano-radial DMA (nRDMA) that increases the transmission efficiency to 12 % for ions as small as 1.3 nm in MillikanFuchs mobility equivalent diameter, D p (corresponding to 1.2 × 10 −4 m 2 V −1 s −1 in electrical mobility). We successfully deployed the nRDMA, equipped with the new inlet, in chamber measurements, using a particle size magnifier (PSM) and as a booster a condensation particle counter (CPC). With this setup, we were able to measure size distributions of ions within a mobility range from 1.2 × 10 −4 to 5.8 × 10 −6 m 2 V −1 s −1 . The system was modeled, tested in the laboratory and used to measure negative ions at ambient concentrations in the CLOUD (Cosmics Leaving Outdoor Droplets) 7 measurement campaign at CERN. We achieved a higher size resolution (R = 5.5 at D p = 1.47 nm) than techniques currently used in field measurements (e.g., Neutral cluster and Air Ion Spectrometer (NAIS), which has a R ∼ 2 at largest sizes, and R ∼ 1.8 at D p = 1.5 nm) and maintained a good total transmission efficiency (6.3 % at D p = 1.5 nm) at moderate inlet and sheath airflows (2.5 and 30 L min −1 , respectively). In this paper, by measuring size distributions at high size resolution down to 1.3 nm, we extend the limit of the current technology. The current setup is limited to ion measurements. However, we envision that future research focused on the charging mechanisms could extend the technique to measure neutral aerosol particles as well, so that it will be possible to measure size distributions of ambient aerosols from 1 nm to 1 µm.

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Symmetric Inclined Grid Mobility Analyzer for the Measurement of Charged Clusters and Fine Nanoparticles in Atmospheric Air

Cited by 26 publications

References 27 publications

An Asymptotic Analysis of Differential Electrical Mobility Classifiers

An Asymptotic Analysis of Differential Electrical Mobility Classifiers

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

A new high-transmission inlet for the Caltech nano-RDMA for size distribution measurements of sub-3 nm ions at ambient concentrations

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Symmetric Inclined Grid Mobility Analyzer for the Measurement of Charged Clusters and Fine Nanoparticles in Atmospheric Air

Cited by 26 publications

References 27 publications

An Asymptotic Analysis of Differential Electrical Mobility Classifiers

An Asymptotic Analysis of Differential Electrical Mobility Classifiers

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

A new high-transmission inlet for the Caltech nano-RDMA for size distribution measurements of sub-3 nm ions at ambient concentrations

Contact Info

Product

Resources

About

A new high-transmission inlet for the Caltech nano-RDMA for size distribution measurements of sub-3 nm ions at ambient concentrations