or or L aser V aporizer -AMS Aerodyne Research, Inc. et al. - - PowerPoint PPT Presentation

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or or L aser V aporizer -AMS Aerodyne Research, Inc. et al. - - PowerPoint PPT Presentation

Dec 05, 2022 308 likes •716 views

S oot P article -AMS or or L aser V aporizer -AMS Aerodyne Research, Inc. et al. Outline SP-AMS technique and hardware Reference material SP-AMS applications Quick highlight a few applications SP-AMS quantification

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SLIDE 1

SootParticle-AMS

  • r
  • r

LaserVaporizer-AMS

Aerodyne Research, Inc. et al.

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SLIDE 2

Outline

  • SP-AMS technique and hardware
  • Reference material
  • SP-AMS applications
  • Quick highlight a few applications
  • SP-AMS quantification
  • Challenges and summary
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SLIDE 3

SP-AMS hardware

SP Module

Second vaporizer in AMS Different ionization chamber configuration Three potential vaporizer configurations

ADQ, ePTOF, BWP (ebox) upgrades

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SLIDE 4

Laser Vaporizer Module

Onasch et al. (AS&T 2012)

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SLIDE 5

Ionizer Configurations

HR-AMS (Tungsten vaporizer)

  • Filaments on sides of ion

chamber

  • Filament position is

mechanically set

  • Filament wire is typically well

positioned with respect to well formed slits in ion chamber walls

  • Narrow or Wide chamber widths

SP-AMS (Laser Vaporizer)

  • Filament is on bottom of ion

chamber

  • Filament position is moveable (vert

& horz)

  • Filament slit width and breadth

may vary due to custom procedure

  • Large holes in sides to

accommodate laser beam

  • Narrow or Wide chamber widths

Need to

  • ptimize

vertical position

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SLIDE 6

Vaporizer Configurations

  • 1. Tungsten Vaporizer (HR-AMS)
  • 2. Laser Vaporizer
  • 3. Laser + Tungsten Vaporizers
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SLIDE 7

SP-AMS Orthogonal Detection Axes

Sampled Particles Ion Extraction and MS detection

  • Characterization of particle-laser interaction region:
  • Vertical Particle Beam Walk
  • Horizontal/Vertical Beam Width Probe
  • Laser Beam Walk
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SLIDE 8

Laser Vaporizer Detection Scheme

The laser is not the vaporizer, the absorbing particles are the vaporizer!!

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Ambient Mass Spectrum

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Nomenclature

Corbin et al., 2014 - ETH

4000 oC

PM = Particulate Matter NR = Non-Refractory R = Refractory L = Light Absorbing (1064 nm) LR-PM:

  • 1. Refractory Black Carbon (rBC)
  • 2. Metals
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SLIDE 11

SP-AMS applications

Ambient rBC measurements (Massoli et al., 2015) Source characterization of laboratory metal nanoparticles (Nilsson et al., 2015) Dual vaporizer measurements including single particle detection (Lee et al., 2015)

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SLIDE 12

CalNex 2010 – Massoli et al., 2014 JGR

Separate instruments operated side-by-side:

  • SP-AMS laser vaporizer
  • HR-AMS tungsten vaporizer
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rBC particle chemical composition and size

  • Increasing Photochemical aging
  • Observations of secondary

condensation

  • Observations of compaction

and growth of rBC particles

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SLIDE 14

Direct comparison between rBC subset of particles and total aerosol loading

Chemical information Mass information

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SLIDE 15

Source characterization of metal nanoparticles – Nilsson et al., 2015 Nano Research

  • Chemical information,

including metal composition, oxide formation, and contaminants

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SLIDE 16

Source characterization of metal nanoparticles – Nilsson et al., 2015 Nano Research

  • Size and effective

density information

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SLIDE 17

Dual vaporizer measurements of ambient rBC particles – Lee et al., 2015 ACP

  • Single particle detection

allows for the measurement

  • f rBC particles even with dual

vaporizer configurations

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SLIDE 18

Average MS comparisons

  • Apparent increased sensitivity to NR-PM vaporized in laser vaporizer!
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SLIDE 19

SP-AMS Quantification

Sensitivities

Refractory black carbon (rBC) [Laser] Non-Refractory PM [Laser and Tungsten]

Collection Efficiencies

Tungsten Vaporizer Laser Vaporizer

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SLIDE 20

mIE calibrations

300 nm AN

NR-PM using tungsten vaporizer rBC using laser vaporizer

  • We need to include a third calibration: NR-PM for laser vaporizer!
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SLIDE 21

mIE NR-PM calibrations using laser vaporizer

  • Difficult, but not impossible
  • Two approaches attempted to date:
  • 1. Coat Regal black with DOS (Willis et al., 2014 AMT)
  • 2. Atomize ammonium nitrate with Regal black (Carbone et al., 2015 AMTD)
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SLIDE 22
  • Coated Regal black particles with

DOS to make spherical

  • With thicker coatings, RIE_rBC

increased as the particle beam narrowed down closer to laser beam width

  • Dual laser/tungsten vaporizer setup
  • Both rBC and Org ion signals

increased

  • NR-PM mIE for DOS appears to be

~2x larger from laser vaporizer than from tungsten vaporizer!

~2x CE ~2x mIE rBC CE determination NR-PM mIE determination

Willis et al., 2014 AMT

DOS coated BC with vaporizer and laser

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SLIDE 23

AN coated BC with vaporizer and laser

Carbone et al., 2015 AMTD; Fortner lab experiments

  • Dual vaporizers
  • Atomize solution of Regal

black and ammonium nitrate

  • Large [AN] likely produce

significant number of particles without Regal black

  • Small [AN] likely produce

Regal black particles with thin coatings of AN

  • Apparent mIE for AN on laser

vaporizer is ~2.3x tungsten vaporizer (laser OFF)

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SLIDE 24

mIE NR-PM calibrations using laser vaporizer

  • Need to further refine mIE calibrations for NR-PM on rBC particles
  • Need to assess the differences between mIE for laser and tungsten

vaporizer PM

  • Need to verify whether the standard suite of RIE’s, determined using

tungsten vaporizer only, hold for the laser vaporizer

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SLIDE 25

Tungsten Vaporizer Collection Efficiency

EL = Aerodynamic Lens transmission EB = Incomplete vaporization due to particle Bounce ES = Particle beam divergence due to particle Shape (and size) EL ~ 1 for dva = 70-700 nm EB ~ 0.5 due to solid/refractory particle bounce ES = 1 as particle beam width < tungsten vaporizer width

Mass concentration of species “s” EB governs the overall CE for Tungsten Vaporizer

CE = EL · EB · ES

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SLIDE 26

Laser Vaporizer Collection Efficiency

Mass concentration of species “s” ES governs the overall CE for rBC and NR-PM (laser only)  Beam width probe measurement EB complicates rBC (RBC) measurements

CELaser = EL · EB · ES

EL = Aerodynamic Lens transmission EB = Incomplete vaporization ** ES = Particle beam divergence due to particle Shape (and size) EL ~ 1 for dva = 70-700 nm EB ≤ 1 due inefficient energy absorption/transfer issues ** ES < 1 as particle beam width < laser vaporizer width

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SLIDE 27

Beam Width Probe (Huffmann et al./Salcedo et al.)

laser wire wire motion Particle beam

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SLIDE 28

BWP Results

  • Two independent measures of narrowing of particle beam with coating
  • Decreasing particle beam width increases particle-laser beam overlap
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SLIDE 29
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SLIDE 30
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SLIDE 31

Incomplete vaporization and laser power

  • Laser Power Drop experiments show a stronger particle-laser beam overlap dependence for rBC

than NR-PM

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SP-AMS CE’s Vaporizer-dependent

Vaporizer Measured Species Tungsten NR-PM * E B Laser (rBC + R-PMǂ + NR-PMǂ) * E S Laser and Tungsten (rBC + R-PMǂ + NR-PMǂ) * E S + (NR-PM - NR-PMǂ * E S ) * E B NR-PM = Nonrefractory Particulate Material measured by a standard AMS [Jimenez et al., 2003 ] R-PM = Refractory Particulate Material measured by the SP-AMS (see text for details) rBC = Refractory black carbon measured by the SP-AMS (and SP2) [Schwarz et al., 2006 ]

ǂ = Particulate Material on rBC particles as mesaured by the SP-AMS (see text for details)

E B = Particle bounce related Collection Efficiency of the AMS E S = Size and shape related Collection Efficiency of the SP-AMS

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SLIDE 33

Laser vaporizer only

Flame 3

Fortner et al., 2015

Regal black

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SLIDE 34

Resistively heated tungsten vaporizer only

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SLIDE 35

Refractory black carbon (rBC)

Tungsten vaporizer only Dual vaporizers Laser vaporizer only PMF deconvolution

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SLIDE 36
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SLIDE 37

Laser ON vs OFF

Government Flats fire (8/21/2013). SP-AMS plume transect with dual vaporizers (left) and tungsten only (right)

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Summary of quantification issues:

# Issue Importance Comments 1 Differences between vaporizer sensitivities

major

mIE sensitivity issue likely due to vaporization temperatures of molecules and subsent velocities in ion formation chamber. Difficult mIE measurements for NR- PM from laser vaporizer. Laser vaporizer RIE's need verification (or determination). Not well characterized to date. 2 Incomplete vaporization

major

Collection efficiency (CE) issue that has not been characterized very well to date and causes over-estimates of [NR-PM]/[rBC] ratios. 3 Particle beam - laser beam overlap

major

Collection efficiency (CE) issue strongly depenent upon alignment and particle

  • morphologies. BWP will help with quantification, though difficult (and slow)

measurements. 4 Laser misalignment

minor

Includes laser beam hitting tungsten vaporizer or ion formation chamber. Can be mitigated through careful alignment procedures. 5 Cn+ ion interference from Org

minor

Problem for dual vaporizer measurements with significant NR-PM Organics. PMF

  • f rBC ion signals appears to effectively distinguish Cn+ ion sources.

6 Large (mid and fullerene) Cn+ ion formation

minor

Apparent laser power issue that has yet to be resolved.

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SLIDE 39

Summary

  • SP-AMS hardware = laser vaporizer inside HR-AMS
  • Provides refractory PM detection (chemical, mass, and size information)
  • Three vaporizer configurations (laser only, tungsten vaporizer only, dual

vaporizers)

  • Single particle detection
  • SP-AMS technique finding applications in ambient measurements,

source (combustion) characterization, laboratory measurements, metal nanoparticles, and single particle detection

  • SP-AMS quantification is challenging, but we are making progress