High Speed Particle Beam Generation: A Dynamic Focusing Mechanism for Selecting Ultrafine Particles

Mallina, Ramakrishna; Wexler, Anthony S.; Rhoads, Kevin P.; Johnston, Murray V.

doi:10.1080/027868200410868

Cited by 54 publications

(66 citation statements)

References 18 publications

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“…This has been accomplished primarily by the use of aerodynamic focusing lens systems (Liu et al 1995a, b;Mallina et al 2000;Schreiner et al 1999;Zhang et al 2002), whose transmission efficiency degrades significantly for particle diameters smaller than 20 nm. Recently, new instruments have been introduced that have been designed specifically for the characterization of ultrafine aerosol.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Measurements of Sub-20 nm Diameter Particle Chemical Composition by Thermal Desorption Chemical Ionization Mass Spectrometry

Smith

Moore

McMurry

et al. 2004

Aerosol Science and Technology

178

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We report the first online measurements of the chemical composition of atmospheric aerosol in the 6-20 nm diameter range. These measurements were performed using the recently developed Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS), and were made possible by recent sensitivity enhancements resulting from (a) the development of a unipolar charger optimized for high aerosol flow rates, and (b) an improved flow system in the TDCIMS sample inlet. Measurements of atmospheric aerosol in Boulder, CO revealed large concentration variations in most detected compounds. The most dominant observed compounds in the negative ion TDCIMS spectra were nitrate and sulfate, while in the positive ion spectra ammonium dominated all other observed compounds. Comparison with laboratory data suggests that particles are composed primarily of ammonium sulfate during times of relatively low ambient aerosol concentration.

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Section: Introductionmentioning

confidence: 99%

Atmospheric Measurements of Sub-20 nm Diameter Particle Chemical Composition by Thermal Desorption Chemical Ionization Mass Spectrometry

Smith

Moore

McMurry

et al. 2004

Aerosol Science and Technology

178

View full text Add to dashboard Cite

show abstract

“…Another approach uses aerodynamics to size-selectively transmit particles to the source region (see below). 16,17 In either case, the aerodynamic particle size is obtained without the need for particle detection by light scattering.…”

Section: -14mentioning

confidence: 99%

“…Figure 5 shows a real-time single particle mass spectrometer (RSMS) that is able to characterize particles between about 50 and 1250 nm. 16,17,41 Particles enter the inlet through one of several flow-limiting orifices and the aerosol expands into the vacuum through a critical orifice. The flowlimiting orifice determines the gas pressure immediately upstream of the critical orifice, which in turn determines the particle size range (d va ) transmitted through the differentially pumped stages into the source region.…”

Section: Nanoparticle Mass Spectrometersmentioning

confidence: 99%

Nanoparticle Mass Spectrometry: Pushing the Limit of Single Particle Analysis

2006

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“…The Cunningham correction factor can be expressed to a fairly good degree of accuracy by a linear correlation given by (Mallina et al 2000)…”

Section: Calculation Of the Slot Dimensionsmentioning

confidence: 99%

“…Liu et al (1995) developed an inlet design comprising several orifices in series for producing collimated particle beams that transmit a wide particle size range. However, their approach cannot be used to focus a narrow, selectable size range of particles, which is required for chemical characterization of single particles (Mallina et al 2000). Further, as the lenses operate at low pressures, they are limited in the mass flow that can be transmitted.…”

Section: Introductionmentioning

confidence: 99%

Particle–Focusing Characteristics of Matched Aerodynamic Lenses

Middha

Wexler

2005

Aerosol Science and Technology

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Forming collimated and size-selected particle beams is a necessary component of certain instruments and industrial processes. An ideal aerosol inlet produces particle beams at high efficiency and transmission rate. The particle transmission rate can be maximized by slot geometries to generate a tightly focused particle beam that is confined to a desired volume. Traditionally, orifices and capillaries have been employed to generate focused particle beams where particle inertia is used to separate them from the carrier gas. The goal of this work is to improve the current inlet geometries for enhanced transmission of particles. For this purpose, we propose a novel inlet geometry that comprises a series of matched capped slots upstream of a choked orifice inlet. By adjusting the pressure, the geometry transmits an arbitrary particle size with high efficiency while maintaining a high flow rate. The slot dimensions can be analytically determined by constraining the design such that the slots and choked orifice focus the same particle sizes and have the same mass flow rate. Numerical simulations of the flow and particle trajectories through the inlet are carried out using the CFD code FLUENT. The new geometry is found to enhance the focusing characteristics of the orifice while maintaining the high flow throughput. The geometry is further optimized to maximize the transmission rate.

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High Speed Particle Beam Generation: A Dynamic Focusing Mechanism for Selecting Ultrafine Particles

Cited by 54 publications

References 18 publications

Atmospheric Measurements of Sub-20 nm Diameter Particle Chemical Composition by Thermal Desorption Chemical Ionization Mass Spectrometry

Atmospheric Measurements of Sub-20 nm Diameter Particle Chemical Composition by Thermal Desorption Chemical Ionization Mass Spectrometry

Nanoparticle Mass Spectrometry: Pushing the Limit of Single Particle Analysis

Particle–Focusing Characteristics of Matched Aerodynamic Lenses

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