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reelingripebeltUrban and Civil

Nov 15, 2013 (3 years and 8 months ago)

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Physical

Size


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.

Quadrupole

Mass 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 Ion

Mass

Spectrometry

Oven

e
-

Electron Emitting

Filament

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 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 Signal
0.006
0.004
0.002
0.000
Particle TOF (s)
“Beam Chopped”

“Beam Open”

Ion Signal
100
80
60
40
20
0
Mass
Marker Peaks for Aerosol Species Identification

color coded to match spectra

Water


H
2
O



H
2
O
+

, HO
+

, O
+


18,

17
, 16

Ammonium

NH
3



NH
3
+
, NH
2
+
, NH
+


17,
16
, 15

Nitrate


HNO
3




HNO
3
+
, NO
2
+,

NO
+


63,
46, 30


Sulfate


H
2
SO
4



H
2
SO
4
+
, HSO
3
+
, SO
3
+


98, 81, 80





SO
2
+
, SO
+



64, 48

Organic


C
n
H
m
O
y




CO
2
+




44


(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/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 display

IGOR
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)

10
2
10
3
10
4
10
5
10
6
Ion Signal (Hz)
200
180
160
140
120
100
80
60
40
20
AMU
Water
Nitrate
Sulphate
Ammonium
Organics
081102_Flight_DC.pxp
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

8
6
4
2
0
dM/dlog(Dp) (µg/m
3
)
3
4
5
6
7
100
2
3
4
5
6
7
1000
2
3
Aerodynamic Diameter (nm)
Organic
Nitrate
Sulfate
Jul. 1
-
Aug. 5, 2001

Urban Site

Time Series Sulfate Intercomparison

PMTACS
Queens New York

July 2001

30
25
20
15
10
5
0
Sulfate Mass (µg 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


m
g

m
3

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

3.0
2.5
2.0
1.5
1.0
0.5
0.0
Flow (cc/s)
2.5
2.0
1.5
1.0
0.5
0.0
Pressure (torr)
U. Tokyo Cal at ARI
NOAA Cal at ARI

NOAA Cal at Boulder
NOAA Scaled to 760 torr

Particle Mass Calibration

Time

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


a
i

A+e
-

----
> A
+
----
> a
i
+

Nitrate/Sulfate
Oxygenated
1.3 x Nitrate
Hydrocarbons
1.9 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
Electron Impact Ionization Cross Section (A^2)
Hydrocarbons
NO3/SO4
Small I norganic 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
Ionization Efficiency (IE)
Hydrocarbons
Oxygenates
Inorganic
(& rare gases)
Molecular Mass

Ionization Efficiency (IE)


EI Cross Section (Å
2
)


Calibration Factor *(
MW
NO3
/
IE
NO3
)

12
8
4
0
Signal (bits)
0.006
0.005
0.004
0.003
0.002
p-TOF (s)
NH4NO3 Dmob
100 nm
250 nm
450 nm
350 nm
d600/ship/U_Tokyo/velocity.pxp
5
6
7
8
9
100
2
3
Velocity (m/s)
10
1
2
4
6
8
10
2
2
4
6
8
10
3
2
4
6
8
10
4
Aerodynamic Diameter (nm)
PSL, F=1.43 cc/s
NO3, F=1.41 cc/s
p_0
= 658 ± 0 fixed
p_1
= 4.4553 ± 0.353
p_2
= 0.43986 ± 0.00864
p_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 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
μ
Amp = 0 to +10V

Computer analog to digital conversion

12 bit resolution. 2
12

= 4096 (
-
10 to +10V)

bit range in acquisition program = 0
-
2048 (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. De
shl
er,
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 Transmission Efficiency E
L
10
2
3
4
5
6
7
8
9
100
2
3
4
5
6
7
8
9
1000
2
D
va
(nm)
Mass Method:
NH
4
NO
3
DEHS
NaNO
3
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 system

Pinhole assembly + valve body + lens assembly

-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0.05
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
B
B
Y Axis Title
X axis title
450mm

3.8mm
OD

7”, 178mm

6.055”, 154mm

F

E

D

C

B

A

100
m
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 mm
Pivot point
Channel skimmer
1 mm ID x 25.4 L
Channel aperture
3.8mm ID x 20 mm L
Channel aperture
3.8mm ID x 10 mm L
0.15”(3.8mm)
OD Heater
Distances and Apertures
for 215-xxx AMS Chamber
293 mm
178 mm
Chopper
251 mm
Beam Probe
Jan. 2008
18 mm
450 mm
403 mm
378 mm
140 mm
Pivot point
Channel skimmer
1 mm ID x 25.4 L
Channel aperture
3.8mm ID x 20 mm L
Channel aperture
3.8mm ID x 10 mm L
0.15”(3.8mm)
OD Heater
Distances and Apertures
for 255-xxx AMS Chamber
395 mm
178 mm
Chopper
353 mm
Beam Probe
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 Bounce

Light scattering probe and BWP results

Is there a better design for the vaporizer?

Can we directly measure a “bounce” event?