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SP-AMS Soot Particle – Aerosol Mass Spectrometer
Onasch, Timothy1; Trimborn, Achim1,2; Fortner, Edward1; Kok, Greg3; Jayne, John1; and Worsnop, Douglas1
1Aerodyne Research, Inc., 45 Manning Road, 01821, Billerica, USA2AeroMegt GmbH, Verbindungsstraße 27, 42723 Hilden, Germany3Droplet Measurement Technologies, 5710 Flatiron Parkway Suite,
Boulder, USA
Final Optical Component Design for SP-AMS
Final SP-AMS Design
Pictures of the (A) laser mount from the top, (B) laser mount from theside, (C) laser mount from the bottom, and (D) output coupler with CCD cameraused to image intra-cavity laser beam profile.
• Sold # and shipped 2 to date
Schematic of SP-AMS module
0
Coating Evaporating
Coated Soot Particle
Laser Beam
Core Evaporating
10
Transit of Soot Particles Across
Laser Beam5-20 microsecond
evaporation time
Coatings evaporate first at relatively low temperatures (<600oC) potentially dependent upon vapor pressures
Core evaporates last at high temperature (>1000oC) under SP2-like incandescence conditions
Coating and core material ionized and detected with mass spectrometry
20Gao et al. 2007
ConfigurationsLaser Vaporizer
• Sensitive to black carbon containing particles only
• Readily quantify coating materials
• More difficult to calibrate IE and RIE’s
Laser and Tungsten Vaporizers
• Provides measure of nonrefractory PM and black carbon
• Characterize coating material by turning laser on/off
• Readily calibrate IE and RIE’s with ammonium nitrate (etc.)
CHEMICAL AND PHYSICALINFORMATION
MS info4000
3000
2000
1000
0
Ion
rate
(Hz
s-1)
120010008006004002000m/z
small medium Fullerenes
70x103
60
50
40
30
20
10
0
Sig
nal
10080604020m/z
C8m/z=96
C7m/z=84
Air Beam Organics Elemental Carbon
C6m/z=72
C5m/z=60
C3m/z=36
C4m/z=48
C2m/z=24
C1m/z=12
H2Om/z=18
N2m/z=28
Carbon Signals: Fullerene Series4000
3000
2000
1000
0
Ion
rate
(Hz
s-1)
120010008006004002000m/z
C32 C50 C60 C70
small medium large carbon cluster ions
BC2 Exp 104 Fullerene Soot
0.001
0.01
0.1
1
10
100
1000
Nitr
ate
equi
vale
nt m
ass
(µg
m-3
s-1
)
1000900800700600500400300200100m/z
BC2 EXP#104 Fullerene Soot 100 nm
Ionizer ON Ionizer OFF
10-1
100
101
102
103
104
105
106
Ion
rate
(Hz
s-1)
Fullerene Soot
10-1
100
101
102
103
104
105
106
Ion
rate
(Hz
s-1)
Premixed Ethylene Flame Soot
10-1
100
101
102
103
104
105
106
Ion
rate
(Hz
s-1)
3500300025002000150010005000m/z
Cabot Regal Black Pigment
‘Black Carbon’ Chemical Composition
0.0 0.2 0.4 0.6 0.8 1.0
Regal black
Flame soot
Fullerenesoot
Bla
ck c
arbo
n ty
pe
Fraction
FullereneMedium carbon clustersSmall carbon clusters
Coating Signals: DEHS Mass Spectra
Less fragmentation in SP2-AMS than in Q-AMSLarge parent ion signal and fragmentation pattern more similar to
NIST data base spectrumCoating evaporating at temperatures < 600oC
Inte
nsity
(arb
uni
ts)
20015010050m/z
NIST MS for DEHS
SP2-AMS MS for DEHS
QAMS MS for DEHS
Vaporized from laser-heated soot particles
Vaporized from600oC vaporizer
NIST database
AMS organic signal is linear with respect to coating thickness
Organic Signal of DEHS Coatings30
25
20
15
10
5
0
Org
anic
Sig
nal (
arb.
uni
ts)
50403020100DEHS Coating Thickness (nm)
8
4
0
(µg/
m3 ) /
(dlo
gDva
)
2 3 4 5 6 7 8100
2 3 4 5 6 7 81000
Dva (nm)
8
4
0
8
4
0
Size Distributions for uncoated and coated particles
Obtain chemical mass distribution information for both carbon and organic signals
PTOF show size and particle mass signals increasing with particle coatings
Carbon SignalOrganic Signal
225 nm Glassy Carbon Spheres uncoated and coated with DEHS oil
No coating
3 nm coating
50 nm coating Organics / 15
CALIBRATIONS
Size calibrationsLaser Vaporizer
• Done with tungsten vaporizer and PSL prior to removal
• Can detect some absorbing PSL with laser vaporizer only
• Potentially with spherical metal particles
• Light scattering detection of PSL
Laser and Tungsten Vaporizers
• PSL using tungsten vaporizer
IE and RIE calibrationsLaser Vaporizer
• IE potentially done with spherical metal particles
• IE for Black Carbon done with independent measure of BC mass loading (e.g. SP2, PAS, MAAP, etc.)
• IE’s for carbon ion cluster types (small vs fullerene) may vary and may need to be calibrated separately
• RIE’s for nonrefractory material done with coated spherical metal particles or black carbon particles and an independent measure of mass loadings
Laser and Tungsten Vaporizers
• Standard AN IE calibration• RIE for Black Carbon done with
independent measure of BC mass loading (e.g. SP2, PAS, MAAP, etc.)
• RIE’s for carbon ion cluster types (small vs fullerene) may vary and may need to be calibrated separately
• May have different fragmentations/RIE’s for nonrefractory materials vaporizing from laser or tungsten vaporizers
Metal Particle Detection
(7 – 120 nm)
Silver
SilverGold
Fullerene and Regal Black CalibrationsSP-AMS vs SP2
• Calibrations done with toner and high fullerene soot
• Suggests more efficient fullerene detection than small carbon ion cluster detection (i.e. RIE_fullerene > RIE_lowCarbon
Carbon cluster (Cn) distributions
30x103
25
20
15
10
5
0
m/z
24,
36,
48,
or 6
0
20x103151050m/z 12
2.0
1.5
1.0
0.5
0.0
Abun
danc
e re
lativ
e to
12C
6543210Carbon Number (Cn)
225 nm Glassy Carbon Spheres 350 nm Norit SX Activated Carcoal
m/z 24 m/z 36 m/z 48 m/z 60 m/z 72
The ratio of Cn to 12C is observed to be nearly constant for a range of soot particles
The relative abundance of carbon clusters formed (Cn) follows the predicted stability pattern of odd number of carbons in the cluster
Raghavachari and Binkley, 1987
Comparison of low carbon ratios from burn to burn in HR
C1-C7 proportions for calibrations and measurements
C1 C2 C3
C4
C6 C7
C5
AMS Carbon Signal vs MAAP CBC(laser vaporizer)
10x103
8
6
4
2
0
AMS
Car
bon
Sign
al
50403020100MAAP CBC (ug/m3)
NoritSXNoritSXNoritSXNoritSXNoritSXNoritSX
CarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNano
GlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbon
PSLPSL
SP2-AMS vs MAAP V_Pr= 0.962059
a = -23.695 ± 26.7 b = 176.82 ± 8.02
V_Pr= 0.930573 a = -40.253 ± 29.6 b = 194.62 ± 3.01
V_Pr= 0.70619 a = 4.3244 ± 26.2 b = 204.01 ± 7.74
AMS Carbon signal is constant for different monodisperse soot particles
Chemical measure of the amount of elemental carbon in soot particles
SP-AMS mz 36 vs MAAP(laser and tungsten vaporizers)
• SP-AMS operating 1 s MS and 60 s MS/PTOF with laser on/off
• Correlation of mz36 vs MAAP is incredibly tight, working on making quantitative sense of calibrations vs measurements
Diesel Truck PlumesCaldecott Tunnel
Collection Efficiency IssuesLaser Vaporizer
• Laser – Particle beam overlap (will vary with particle shape/focusing and laser mode/quality)
• Large coating, small BC core detection and large BC particle detection issues (laser intensity and duration of particle in laser beam)
Laser and Tungsten Vaporizers
• Particle bounce (partial vaporization) off of tungsten vaporizer
• Laser – Particle beam overlap
• Different CE’s for two methods
Carbon Signal vs Laser Power
6x10-6
5
4
3
2
1
0
Blac
k ca
rbon
sig
nal
1086420
Laser Power
Hyperbolic tangent functionf(x) = b*((exp(a*x)-exp(-a*x))/(exp(a*x)+exp(-a*x))) Coefficient values ± one standard deviation
a =0.32 ± 0.05b =5.4 ± 0.3e-6
SP2 instruments operate at laser powers of ~2
Higher laser powers required in SP-AMS due to faster particle velocities
157 nm Ethylene Flame Soot
Laser Beam Width Calculations
• Laser Beam 1/e2 diameter at Particle Beam is ~20/23*CCD Camera diameter, FWHM ~1.2 mm
• Laser Beam 1/e diameter ~0.5 mm, FWHM ~ 0.56 mmBarry McManus, ARI
Laser Beam Width Determination300 nm Regal Black Particles
IF, the convolution of two Gaussian functions (i.e. laser beam and particle beam) generates a gaussianfunction with c = sigma of c = sqrt(c1^2+c2^2),
Then in the case of the laser beam = c1 (unknown) and particle beam = c2 (0.34 mm from horizontal -i.e. along laser axis - BWP measurements) and the convolution of the two = particle beam walk experiment, c (0.72 mm from particle ).
Thus, laser beam width, c1 = sqrt(c^2-c2^2) = sqrt(0.72^2 - 0.34^2) = 0.63 mm (FWHM = 1.5 mm)
Laser Profile Camera
Vertical
Camera is inverted
AMBIENT RESULTS
Ambient Measurements
SP-AMS versus MAAP
0.4
0.3
0.2
0.1
0.0
SP2A
MS
Car
bon
Sig
nal (
NO
3 E
q. u
g/m
3)
0.60.50.40.30.20.10.0
MAAP BC (ug/m3)
Coefficient values ± one standard deviationa =0.0028837 ± 0.000764b =0.63088 ± 0.0127
Carbon = m/z 12, 24, 36, 48m/z 36 ~ 50% carbon
Size Distributions
Black Carbon Plume
Organic Plume
SP-AMS projects/deployments• 2007 BC/ARI laboratory development• 2007 and 2008 Karlsruhe AIDA campaigns (two)• 2008 BC weekend measurements of ambient• 2008 Boston College Black Carbon (BC2) project• 2009 NYC results• 2009 FLAME 3• UTRC laboratory tests• Po Valley• Aerodyne laboratory investigations of metal nanoparticles• Metals in Finland dynanometer tests• May 2010 CalNex on board R/V Atlantis• May 2010 CalNex at CalTech site• July 2010 Caldecott Tunnel study• September 2010 John Zink Flare project
Summary• SP-AMS successful instrument• Two configurations (laser vaporizer, combo
laser+tungsten vaporizers) that provide two unique measurement capabilities (i.e. BC-containing particles only, or NR PM1 + BC PM1)
• Provides Black Carbon (Elemental Carbon) measurements (chemistry, mass loading, size distributions) as well as metal particle measurements
• EC/OC and Coated-BC measurement capabilities in real-time