SootParticle-AMS. LaserVaporizer-AMS. Aerodyne Research, Inc. et al.

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1 SootParticle-AMS or LaserVaporizer-AMS Aerodyne Research, Inc. et al.

2 Outline SP-AMS technique and hardware Reference material SP-AMS applications Quick highlight a few applications SP-AMS quantification Challenges and summary

3 SP-AMS hardware SP Module Second vaporizer in AMS Different ionization chamber configuration Three potential vaporizer configurations ADQ, eptof, BWP (ebox) upgrades

4 Laser Vaporizer Module Onasch et al. (AS&T 2012)

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 optimize vertical position

6 Vaporizer Configurations 1. Tungsten Vaporizer (HR-AMS) 2. Laser Vaporizer 3. Laser + Tungsten Vaporizers

7 SP-AMS Orthogonal Detection Axes Ion Extraction and MS detection Sampled Particles Characterization of particle-laser interaction region: Vertical Particle Beam Walk Horizontal/Vertical Beam Width Probe Laser Beam Walk

8 Laser Vaporizer Detection Scheme The laser is not the vaporizer, the absorbing particles are the vaporizer!!

9 Ambient Mass Spectrum

10 Nomenclature PM = Particulate Matter NR = Non-Refractory R = Refractory L = Light Absorbing (1064 nm) LR-PM: 1. Refractory Black Carbon (rbc) 2. Metals 4000 o C Corbin et al., ETH

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)

12 CalNex 2010 Massoli et al., 2014 JGR Separate instruments operated side-by-side: SP-AMS laser vaporizer HR-AMS tungsten vaporizer

13 rbc particle chemical composition and size Increasing Photochemical aging Observations of secondary condensation Observations of compaction and growth of rbc particles

14 Direct comparison between rbc subset of particles and total aerosol loading Chemical information Mass information

15 Source characterization of metal nanoparticles Nilsson et al., 2015 Nano Research Chemical information, including metal composition, oxide formation, and contaminants

16 Source characterization of metal nanoparticles Nilsson et al., 2015 Nano Research Size and effective density information

17 Dual vaporizer measurements of ambient rbc particles Lee et al., 2015 ACP Single particle detection allows for the measurement of rbc particles even with dual vaporizer configurations

18 Average MS comparisons Apparent increased sensitivity to NR-PM vaporized in laser vaporizer!

19 SP-AMS Quantification Sensitivities Refractory black carbon (rbc) [Laser] Non-Refractory PM [Laser and Tungsten] Collection Efficiencies Tungsten Vaporizer Laser Vaporizer

20 mie calibrations NR-PM using tungsten vaporizer rbc using laser vaporizer 300 nm AN We need to include a third calibration: NR-PM for laser vaporizer!

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)

22 rbc CE determination DOS coated BC with vaporizer and laser NR-PM mie determination ~2x CE ~2x mie 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! Willis et al., 2014 AMT

23 AN coated BC with vaporizer and laser 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) Carbone et al., 2015 AMTD; Fortner lab experiments

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

25 Tungsten Vaporizer Collection Efficiency CE = E L E B E S E L = Aerodynamic Lens transmission E B = Incomplete vaporization due to particle Bounce E S = Particle beam divergence due to particle Shape (and size) E L ~ 1 for d va = nm E B ~ 0.5 due to solid/refractory particle bounce E S = 1 as particle beam width < tungsten vaporizer width E B governs the overall CE for Tungsten Vaporizer Mass concentration of species s

26 Laser Vaporizer Collection Efficiency CE Laser = E L E B E S E L = Aerodynamic Lens transmission E B = Incomplete vaporization ** E S = Particle beam divergence due to particle Shape (and size) E L ~ 1 for d va = nm E B 1 due inefficient energy absorption/transfer issues ** E S < 1 as particle beam width < laser vaporizer width E S governs the overall CE for rbc and NR-PM (laser only) Beam width probe measurement E B complicates rbc (R BC ) measurements Mass concentration of species s

27 Beam Width Probe (Huffmann et al./salcedo et al.) wire motion Particle beam laser wire

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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31 Incomplete vaporization and laser power Laser Power Drop experiments show a stronger particle-laser beam overlap dependence for rbc than NR-PM

32 SP-AMS CE s Vaporizer-dependent Vaporizer Tungsten Laser Measured Species NR-PM * E B (rbc + R-PM ǂ + NR-PM ǂ ) * E S Laser and Tungsten (rbc + R-PM ǂ + NR-PM ǂ ) * E S + (NR-PM - NR-PM ǂ * 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

33 Laser vaporizer only Regal black Flame 3 Fortner et al., 2015

34 Resistively heated tungsten vaporizer only

35 Refractory black carbon (rbc) Laser vaporizer only Tungsten vaporizer only PMF deconvolution Dual vaporizers

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

38 Summary of quantification issues: # Issue Importance Comments 1 Differences between vaporizer sensitivities major 2 Incomplete vaporization major 3 Particle beam - laser beam overlap major 4 Laser misalignment minor 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. Collection efficiency (CE) issue that has not been characterized very well to date and causes over-estimates of [NR-PM]/[rBC] ratios. Collection efficiency (CE) issue strongly depenent upon alignment and particle morphologies. BWP will help with quantification, though difficult (and slow) measurements. 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 of rbc ion signals appears to effectively distinguish Cn+ ion sources. 6 Large (mid and fullerene) Cn+ ion minor formation Apparent laser power issue that has yet to be resolved.

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