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

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 • Challenges and summary

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

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

Ionizer Configurations SP-AMS (Laser Vaporizer) HR-AMS (Tungsten vaporizer) • Filament is on bottom of ion • Filaments on sides of ion chamber chamber • Filament position is moveable (vert • Filament position is & horz) mechanically set • Filament wire is typically well • Filament slit width and breadth may vary due to custom procedure positioned with respect to well formed slits in ion chamber walls • Large holes in sides to • Narrow or Wide chamber widths accommodate laser beam • Narrow or Wide chamber widths Need to optimize vertical position

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

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

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

Ambient Mass Spectrum

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., 2014 - ETH

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)

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

rBC particle chemical composition and size • Increasing Photochemical aging • Observations of secondary condensation • Observations of compaction and growth of rBC particles

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

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

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

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

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

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

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!

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)

rBC CE determination DOS coated BC with vaporizer and laser ~2x CE • 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 NR-PM mIE determination width • Dual laser/tungsten vaporizer setup • Both rBC and Org ion signals increased ~2x mIE • NR-PM mIE for DOS appears to be ~2x larger from laser vaporizer than from tungsten vaporizer! Willis et al., 2014 AMT

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

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

Tungsten Vaporizer Collection Efficiency CE = E L · E B · E S E L = Aerodynamic L ens transmission E B = Incomplete vaporization due to particle B ounce E S = Particle beam divergence due to particle S hape (and size) E L ~ 1 for d va = 70-700 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”

Laser Vaporizer Collection Efficiency CE Laser = E L · E B · E S E L = Aerodynamic L ens transmission E B = Incomplete vaporization ** E S = Particle beam divergence due to particle S hape (and size) E L ~ 1 for d va = 70-700 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”

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

BWP Results • Two independent measures of narrowing of particle beam with coating • Decreasing particle beam width increases particle-laser beam overlap

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

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

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

Resistively heated tungsten vaporizer only

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

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

Summary of quantification issues: Comments # Issue Importance mIE sensitivity issue likely due to vaporization temperatures of molecules and Differences between vaporizer subsent velocities in ion formation chamber. Difficult mIE measurements for NR- 1 major sensitivities 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 2 Incomplete vaporization major 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) 3 Particle beam - laser beam overlap major measurements. Includes laser beam hitting tungsten vaporizer or ion formation chamber. Can be 4 Laser misalignment minor mitigated through careful alignment procedures. 5 Cn+ ion interference from Org Problem for dual vaporizer measurements with significant NR-PM Organics. PMF minor of rBC ion signals appears to effectively distinguish Cn+ ion sources. Large (mid and fullerene) Cn+ ion 6 minor formation Apparent laser power issue that has yet to be resolved.

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