Physical Size 41"W x 24"D x 53"H Weight170 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 ( nm), aerodynamic sizing, linear mass signal. Jayne et al., Aerosol Science and Technology 33:1-2(49-70), Quadrupole Mass Spectrometer Thermal Vaporization & Electron Impact Ionization Aerodynamic Lens (2 Torr) Beam Chopper Pump TOF Region Particle Beam Generation Aerodynamic Sizing Particle Composition

Separation of Vaporization and Ionization Process Positive Ion Mass Spectrometry Oven e-e- Electron Emitting Filament R+R+ Particle Beam Flash vaporization of non-refractory components 600 C Electron Impact Ionization Vaporization and analysis of most aerosol chemical constituents - with primary exception of crustal oxides and elemental carbon.

Information Obtained with the AMS Dual Operating Modes Spectrometer is Scanned (0-300 amu) Spectrometer Setting is Fixed (small subset of amu) Alternate between both modes Record time series of size distributions and mass loadings Size Distribution (limited composition info) Average Composition (no size info) “Beam Chopped”“Beam Open”

Marker Peaks for Aerosol Species Identification color coded to match spectra Water H 2 O H 2 O +, HO +, O + 18, 17, 16 AmmoniumNH 3 NH 3 +, NH 2 +, NH + 17, 16, 15 Nitrate HNO 3 HNO 3 +, NO 2 +, NO + 63, 46, 30 SulfateH 2 SO 4 H 2 SO 4 +, HSO 3 +, SO , 81, 80 SO 2 +, SO + 64, 48 Organic C n H m O y CO (Oxygenated) H 3 C 2 O +, HCO 2 +, C n’ H m + 43, 45,... Organic C n H m C n’ H m’ + 27,29, 41,43,55,57,69,71... (hydrocarbon) Group Molecule/SpeciesIon FragmentsMass Fragments e-e- e-e- e-e- e-e- e-e- e-e- Standard electron impact ionization 70 eV

Instrument control and data collectionData analysis and display IGOR Software

AMS Web Page 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) Oxygenated Organic mz 43,44,45

Queens, New York PMTACS F. Drewnick, K. Demerjian ASRC SUNY Albany Characteristic Urban Bi-modal Size Distribution Organic fraction dominates small size mode Jul. 1-Aug. 5, 2001 Urban Site

Time Series Sulfate Intercomparison PMTACS Queens New York July 2001 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g m3m3 mass volume From quad (IE calibration) From volumetric flow rate Particle Mass Loading

Flow Calibration A volumetric flow meter Absolute pressure gauge Ambient temperature and pressure needed to convert to volumetric flow into mass flow

Particle Mass Calibration Time Signal Single particle pulses Particle threshold set above single ion level Single ions above electronic noise level Time Amps (Coulombs/time) 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  (MW A /IE A )  Ion Signal aiai A+e > A > a i + Molecular Mass Ionization Efficiency (IE) EI Cross Section (Å 2 ) Calibration Factor *(MW NO3 /IE NO3 )

Particle Velocity calibration Daero = Dgeo * ρ* Shape Fac Sample “known” size particles and calculate a velocity… Velocity = flight path / TOF

~-( ) kV + Ejection of several electrons at each dynode on impact Discrete dynode multiplier A 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 Signal electronic noise level 0.3 to 0.6 bits Single Ion Pulses Threshold Time Amps (Coulombs/time) Average single ion pulse height Area = Coulombs (charge) Gain = Area/Faraday constant Pulse Height Numbers of Pulses Pulse height Distribution Threshold sets cut-off for smallest pulses Determination of Electron Multiplier Gain

Ion (s) Electrons Voltage Computer (bits) Quad mass/charge filter m/z selection with near unit transmission Electron multiplier Gain ~(2-4)x10 6 Current-to-voltage inverting amplifier Gain 10 6 volts/amp 0 to -10 μAmp = 0 to +10V Computer analog to digital conversion 12 bit resolution = 4096 (-10 to +10V) bit range in acquisition program = (0-10V) “Signal Train” in QAMS Electron Impact Ionization Ion production Efficiency ~(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 quantification As large as a factor of 2…

Particle Transmission versus Collection in Aerodynamic Lens Aerodynamic Size CE/Transmission Target Transmission No 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), NH 4 NO 3 (triangles) and NaNO 3 (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): , 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 system Pinhole assembly + valve body + lens assembly 450mm 3.8mm OD 7”, 178mm6.055”, 154mm FE DCB A 100  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

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

B ACD EFG

B A D BCEF GHIJKL

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