PhysicalSize 41"W x 24"D x 53"H

Weight 170 kg

Power 600 Watts. Universal power 110VAC/60Hz or 220VAC/50Hz.

(Shipped in one reusable container. Total shipping weight ~280 kg. Approx. outside dimensions 30”W x 51”L x 63”H)

Q-AMS System

Compact TOF AMS High Resolution TOF AMS

Time-of-Flight AMS Systems

Current Development Activities

• Alternate Soft Ionization schemes-Li+ ion attachment-VUV photo-ionization-low energy electrons/negative ions-Meta stable ion bombardment (MAB)-Glow discharge source

• Aerodynamic lenses-PM2.5 particle lens (~100nm – 3 um)-Nano particle lens (>20 nm)

• ACSM (aerosol chemical speciation monitor)-low cost/lower performance version of the AMS

• ACM (aerosol collector module)• Aerosol collection and thermal desorption • Thermal denuder for volatility studies• Particle detection by light scattering• Black carbon detection module.• Analysis algorithms, Positive matrix factorization (PMF)

Aerosol Mass Spectrometer (AMS)

Particle Inlet (1 atm)

100% transmission (40-600 nm), aerodynamic sizing, linear mass signal.Jayne et al., Aerosol Science and Technology 33:1-2(49-70), 2000.

QuadrupoleMass Spectrometer

Thermal Vaporization

&Electron Impact

Ionization

Aerodynamic Lens

(2 Torr)

Beam Chopper

Pump Pump Pump

TOF Region

Particle Beam Generation

Aerodynamic Sizing

Particle Composition

Separation of Vaporization and Ionization Process

Positive IonMass

Spectrometry

Oven

e-

Electron EmittingFilament

R+

Particle Beam

Flashvaporization

of non-refractory components

600 CElectron Impact Ionization

Vaporization and analysis of most aerosol chemical constituents - with primary exception of crustal oxides and elemental carbon.

Information Obtained with the AMSDual Operating Modes

Spectrometer is Scanned (0-300 amu)

Spectrometer Setting is Fixed (small subset of 0-300 amu)

Alternate between both modes Record time series of size distributions and mass loadings

Size Distribution(limited composition info)

Average Composition(no size info)

Ion

Sig

nal

0.0060.0040.0020.000

Particle TOF (s)

“Beam Chopped” “Beam Open”

Ion

Sig

na

l

100806040200

Mass

Marker Peaks for Aerosol Species Identificationcolor coded to match spectra

Water H2O H2O+ , HO+ , O+ 18, 17, 16

Ammonium NH3 NH3+, NH2

+, NH+ 17, 16, 15

Nitrate HNO3 HNO3+, NO2

+, NO+ 63, 46, 30

Sulfate H2SO4 H2SO4+, HSO3

+, SO3+ 98, 81, 80

SO2+, SO+ 64, 48

Organic CnHmOy CO2+ 44

(Oxygenated) H3C2O+, HCO2+, Cn’Hm

+ 43, 45, ...

Organic CnHm Cn’Hm’+ 27,29,41,43,55,57,69,71...

(hydrocarbon)

Group Molecule/Species Ion Fragments Mass Fragments

e-

e-

e-

e-

e-

e-

Standard electron impact ionization 70 eV

Instrument control and data collection Data analysis and displayIGOR www.wavemetrics.com

Software

AMS Web Page

http://cires.colorado.edu/jimenez-group/QAMSResources/

qamsuser / qamspass

Includes:• Data Acquisition (DAQ) Software Downloads• Manual for DAQ Software• Release Notes • Supplemental Software tools• “To Do” list describing planned DAQ development timeline• Guidelines for making software requests and reporting bugs• Analysis software

Sample Aerosol Mass Spectra

Interpretation of organic fraction is “challenging”.Classes of compounds can often be identified

F. McLafferty/F. Tureček “Interpratation of Mass Spectra (1993)

102

103

104

105

106

Ion

Sig

nal (

Hz)

20018016014012010080604020

AMU

Water Nitrate Sulphate Ammonium Organics

081102_Flight_DC.pxp

Oxygenated Organicmz 43,44,45

Queens, New York PMTACS

F. Drewnick, K. Demerjian ASRC SUNY Albany

Characteristic Urban Bi-modal Size DistributionOrganic fraction dominates small size mode

8

6

4

2

0

dM

/dlo

g(D

p)

(µ

g/m

3)

3 4 5 6 7100

2 3 4 5 6 71000

2 3

Aerodynamic Diameter (nm)

Organic Nitrate Sulfate

Jul. 1-Aug. 5, 2001

Urban Site

Time Series Sulfate IntercomparisonPMTACS Queens New York July 2001

30

25

20

15

10

5

0

Sul

fate

Mas

s (µ

g m

-3)

7/1/2001 7/6/2001 7/11/2001 7/16/2001 7/21/2001 7/26/2001 7/31/2001 8/5/2001

Date/Time

AMS R&P 8400 PILS HSPH

Good correlation between four separate measurement technologies

but AMS uses a correction factor…

F. Drewnick, K. Demerjian ASRC SUNY Albany

Primary Calibrations

• Volumetric flow rate

• Ionization efficiency

• Particle velocity-aerodynamic size

g

m3

mass

volume

From quad (IE calibration)

From volumetric flow rate

Particle Mass Loading

Flow CalibrationA

vol

umet

ric

flow

met

er

Absolute pressure gauge

Ambient temperature and pressure needed to convert to volumetric flow into mass flow

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Flo

w (

cc/s

)

2.52.01.51.00.50.0

Pressure (torr)

U. Tokyo Cal at ARI NOAA Cal at ARI

NOAA Cal at Boulder NOAA Scaled to 760 torr

Particle Mass Calibration

Time

Sig

na

l

Single particle pulses

Particle threshold set above single ion level

Single ions above electronic noise level

Time

Am

ps

(Co

ulo

mb

s/tim

e)

Average single ion pulse

Average single particle pulse= Ions per particle (IPP)

Ionization Efficiency = IPP/Molecules per Particle

EI Ionization Cross Sections

Mass Loading A (MWA/IEA) Ion Signalai

A+e- ----> A+ ----> ai+

Nitrate/Sulfate

Oxygenated1.3 x Nitrate

Hydrocarbons1.9 x Nitrate

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0 20 40 60 80 100 120 140 160 180 200

Molecular Mass

Ele

ctro

n Im

pac

t Io

niz

atio

n C

ross

Sec

tio

n (

A^2

) Hydrocarbons

NO3/SO4

Small Inorganic Gases

Oxygenated

AMS-Oxygenated

AMS-Small Acids/Bases

Linear (Nitrate)

Linear (Oxygenated)

Linear (Hydrocarbons)

1

0.2

0.8

0.6

0.4

0

x 10-5

Ioni

zati

on

Eff

icie

ncy

(IE

)

HydrocarbonsOxygenatesInorganic (& rare gases)

Molecular Mass

Ion

izat

ion

Eff

icie

ncy

(IE

)

EI

Cro

ss S

ecti

on (

Å2 )

Calibration Factor *(MWNO3/IENO3)

12

8

4

0

Sig

na

l (b

its)

0.0060.0050.0040.0030.002

p-TOF (s)

NH4NO3 Dmob 100 nm 250 nm 450 nm 350 nm

d600/ship/U_Tokyo/velocity.pxp

5

6

789

100

2

3

Ve

loci

ty (

m/s

)

101

2 4 6 8

102

2 4 6 8

103

2 4 6 8

104

Aerodynamic Diameter (nm)

PSL, F=1.43 cc/s NO3, F=1.41 cc/s

p_0 = 658 ± 0 fixedp_1 = 4.4553 ± 0.353p_2 = 0.43986 ± 0.00864p_3 = 16.449 ± 2.2

d600/ship/U_Tokyo/velocity.pxp

Particle Velocity calibration

Daero = Dgeo * ρ* Shape Fac

Sample “known” size particles and calculate a velocity…Velocity = flight path / TOF

~-(1.8-3.4) kV

+

Ejection of several electrons at each dynode on impact

Discrete dynode multiplierA high gain/low noise device that works only under vacuum

Gain = (1-3)20 ~1M electrons/incident ion

n electrons out

Resistor network connects each dynode to a lower potential than the one above it.

One ion in

Time

Sig

na

l

electronic noise level 0.3 to 0.6 bits

Single Ion PulsesThreshold

Time

Am

ps

(Co

ulo

mb

s/tim

e)

Average single ion pulse height

Area = Coulombs (charge)Gain = Area/Faraday constant

Pulse Height

Nu

mb

ers

of

Pu

lse

s

Pulse height Distribution

Threshold sets cut-off for smallest pulses

Determination of Electron Multiplier Gain

Ion (s)

Electrons

Voltage

Computer (bits)

Quad mass/charge filterm/z selection with near unit transmission

Electron multiplierGain ~(2-4)x106

Current-to-voltage inverting amplifierGain 106 volts/amp0 to -10 μAmp = 0 to +10V

Computer analog to digital conversion12 bit resolution. 212 = 4096 (-10 to +10V)bit range in acquisition program = 0-2048 (0-10V)

“Signal Train” in QAMS

Electron Impact Ionization Ion productionEfficiency ~(2-4)x10-6

Particle vaporization Vaporization on impact…

Quantification Issues

• Particle transmission into vacuum system • Particle impaction/collision at vaporizer

• Particle detection-vaporization/ionization-particle bounce effects

Particle bounce likely the largest uncertainty for quantificationAs large as a factor of 2…

Particle Transmission versus Collection in Aerodynamic Lens

Aerodynamic Size

CE

/Tra

nsm

issi

on

Target

TransmissionNo Collection

No Transmission or Collection

Large particle losses are controlled by the pin-hole

Small particle losses are controlled by geometry and Brownian diffusion

Figure 10. Experimental results for DEHS (solid circles), NH4NO3 (triangles) and NaNO3 (squares) at an ambient pressure of 585 torr. The solid line is the Fluent modeling result for 585 torr and is re-plotted from Figure 7.

Liu, P.S.K., R. Deng, K.A. Smith, L.R. Williams, J.T. Jayne, M.R. Canagaratna, K. Moore, T.B. Onasch, D.R. Worsnop, and T. Deshler, Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer, Aerosol Science and Technology, 41(8):721-733, 2006.

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Lens

Tra

nsm

issi

on E

ffic

ienc

y E

L

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

Dva (nm)

Mass Method: NH4NO3

DEHS NaNO3

Fluent

Measured and Modeled Transmission for Standard Lens

Figure 1a. Drawing of the lens system which is composed of the pinhole assembly, the valve body and the lens assembly.

Modeling must consider complete systemPinhole assembly + valve body + lens assembly

450mm

3.8mm OD

7”, 178mm6.055”, 154mm

FEDCBA100 m Orifice

15D

1.6mm ID

Figure 1b. Structure used in the Fluent simulations, including the lens system, particle flight chamber and vaporizer. The diameters of the apertures are given in Table 1.

Cross section of chamber showing differentially pumped regions

18 mm

348 mm

301 mm

276 mm

140 mmPivot point

Channel skimmer1 mm ID x 25.4 L

Channel aperture3.8mm ID x 20 mm L

Channel aperture3.8mm ID x 10 mm L

0.15”(3.8mm) OD Heater

Distances and Aperturesfor 215-xxx AMS Chamber

293 mm

178 mm

Chopper

251 mmBeam Probe Jan. 2008

18 m m

450 m m

403 m m

378 m m

140 m mPivo t p o int

C ha nne l skim m e r1 m m ID x 25.4 L

C ha nne l a p e rture3.8m m ID x 20 m m L

C ha nne l a p e rture3.8m m ID x 10 m m L

0.15”(3.8m m ) O D He a te r

Dista nc e s a nd Ap e rture sfo r 255-xxx AM S C ha m b e r

395 m m

178 m m

C ho p p e r

353 m mBe a m Pro b e

Aug . 2003

For 255 series chambers the Projected beam diameter at wire location = 353/450*.8mm = 3.0mm

For 215 series chambers subtract 102 mm from distance downstream of the chopper

Agenda• Get familiar with software(s).• Perform calibrations.

– Flow rate– Particle velocity – Ionization efficiency

• How to determine operational status. – Air beam concept– Electron multiplier gain

• Understanding current state of developments.

Goal: to be able to turn on the instrument, get ion signals and save ‘good’ data.

SW1

SW2

SW3

1 2 3 4 5 6 7 8 9

10

B

A C D E F G

1 2 3 4 5 6 7

9

8

B

A D

B C E F

G H I J K L

Current Calibration and Quantification Issues

Biggest Issue is the factor of 2 or CE=0.5

• Particle focusing/divergence Improved Beam Width Probe

Shortened length of chamber by 10 cm

• Particle BounceLight scattering probe and BWP results Is there a better design for the vaporizer? Can we directly measure a “bounce” event?