ACSM Topics

System Design

-Lower cost Data acquisition thru Ethernet line and OPC , laptop

Igor interface. Builds off of Squirrel tools

Design Philosophy-fill the matrix-file formats-runtime view and archived data

Performance-IE cal results-Noble gas mixture, ion transmission-EM gain

Design tasks to do-auto inlet valve-auto filter sample-beam block by solenoid, externally mounted

Sample data-2 month time series, unattended-noise analysis-time series comparison to QAMS

Deployment planned in Feb/March 2009 Barcelona, Queens Summer 2009

Outstanding Issues-stream line data collection and analysis-particle bounce-PM2.5 lens

Aerosol Chemical Speciation Monitor

ACSM• Continuous monitoring of aerosol composition.

• Limited sizing information.

• Designed for long term unattended operation.

• Builds on Q and ToF AMS concepts. Same vaporizer and ionizer

• Lower cost, lower sensitivity.Sally Ng, Tim Onasch, Achim Trimborn, Scott Herndon,

Donna Sueper, John Jayne

Size: 18”D x 22”W x 24”H

(46 cm x 56 cm x 61 cm).

Weight: 140 lbs (64kg)

Power: 300W

Aug. 2008

Aerosol Chemical Speciation Monitor

September 10, 1999

Did we already build this?

The ACSM is a product of Q and TOF AMS developments

ACSM Designed Around Pfeiffer Prisma RGA

• Prisma electronics supports:– Ethernet connectivity with OPC1 interface.– A Windows CE computer/OS.– Built-in digital and analog I/O.– 6mm diameter rods with 100, 200 and 300 amu

range heads.– 1 mA/mbar sensitivity to Ar (200 amu head)

1OPC is a standard software interface which enables data communication between applications of different manufacturers. OPC stands for Openness, Productivity, Collaboration (formerly OLE for Process Control).

OPC EngineVB.NET

Igor InterfaceAutomation Server

Data processing -display

PrismaWindows CE OS

OPC Server

ACSM Data Acquisition Software Plan

Acquisition Computer

Raw Data

Ethernet Connectivity

ACSM Software PanelsVB.NET OPC interface Igor User Interface

Raw Data files• Currently, MSOpen and MSClosed files are

saved.• Data files written as *.itx scaled waves.• File names are UTC time stamp, 1 sec

resolution.• Each year is a new folder.• Each day is a new sub folder.• ~2 GB/year data size at 30 min. data rate.

Signal-to-Noise Airbeam Intensity and Position for Quad Settings

20 ms/amu 50 ms/amu 100 ms/amu

12 min12 min 30 min

~ 1 day for each scan speed depictedAllan Variance of the Airbeam intensity for the full time series to quantify noise and signal averaging

Allan Variance of Airbeam Intensity

150x10-9

100

50

0

Sign

al (a

mps

)

29.028.027.026.0

m/z

Resolution 100 80 60 40 20

200x10-9

150

100

50

0S

igna

l (am

ps)

120100806040200Resolution Setting

Prisma Resolution and Signal Intensity

N2

2.5x10-9

2.0

1.5

1.0

0.5

0.0

Sig

nal (

amps

)

302928272625

m/z

Resolution Setting 100 80 60 40 20

50

45

40

35

30

25

20

Res

olut

ion

(M/∆Μ)

120100806040200

Resolution Setting

N2

Prisma Resolution

Ion Transmission1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Nor

mai

lzed

Ion

Inte

nsity

14012010080604020

m/z

16 mm (QAMS) 6 mm (Prisma)

Ne

N2

ArKr

Xe

Compares 16mm (QAMS) to 6mm (ACSM)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Rel

ativ

e Io

n Tr

ansm

issi

on

140120100806040200

m/z

Ion Transmission in Quad

6mm quad has significant decrease in ion transmission. More characterization needed.

Multiplier Gain Estimate

Ratio SEM to Faraday Signal

Gain ~1.1e42000V

MSOpen Signal

N2O2

2.0x10-9

1.5

1.0

0.5

0.0

SEM

Sig

nal (

amps

)

250200150100500

Point Number (amu axis)

2.0x10-13

1.5

1.0

0.5

0.0

Fara

day

Sign

al (a

mps

)

Gain plot

104

2

3

4

5678

105

2

3

4

5678

106

Gai

n

22002100200019001800170016001500SEM_voltage

At 2000V, gain = 5e5

ACSMDMA

CPC

Atomizer

AerosolDiluter

Setup for Mass Based IE Determination

By-pass

Input Mass = ρ x Volume(size) x Number Measured Mass

filter

Plot Measured Mass vs Input Mass

Drier

Must consider lens transmission and multiply charged diameters from DMA

NH4NO3 IE Calibration60x10-12

50

40

30

20

10

0

30+4

6 S

igna

l (am

ps)

20151050

CPC Mass (ug/m3)

slope = 2.61e-012

NH4NO3 Effective Ionization Efficiency

Sig (amps) ions/sec

[µg/m3]

(gain)

(flow) molecules/sec

2.61x10-12 1.1x10-7 ions/molecule

~20 times lower sensitivity compared to QAMS

System Calibration Number

IE/AB = [ug/m3] / amps2

= 3.85x1011 / 1.20x10-9

= 3.2x1020

Long Term Stability

AB decrease ~0.5% per day

4.0x10-8

3.0

2.0

1.0

0.0

AB

(am

ps)

7/25/2008 8/1/2008 8/8/2008 8/15/2008 8/22/2008

Date/Time

28.36

28.35

28.34

m/z

cor

rect

ion

AMU Calibration Issue1.0

0.8

0.6

0.4

0.2

amu

Offs

et

140120100806040200

AUM

Xe

Kr

ArNeN2

Long Term Stability

Analysis based on SQUIRREL frag functions

1.2

0.8

0.4

0.0

µg/m

3

7/21/2008 7/31/2008 8/10/2008 8/20/2008Date and Time

0.30

0.20

0.10

0.00

3.0

2.0

1.0

0.0

cTOF Comparison

ACSM - cTOF Comparison

SO4

NO3

m/z55

14 min ACSM Data Rate

0.30

0.20

0.10

0.00

µg/m

3

12:00 AM8/23/2008

12:00 PM 12:00 AM8/24/2008

12:00 PM 12:00 AM8/25/2008

12:00 PM

Date and Time

0.20

0.15

0.10

0.05

0.00

3.0

2.0

1.0

0.0

Summary• Stable over long periods. • Sensitivity of ~0.1 µg/m3 in 15 min.• Ion transmission corrections? • Data analysis based on SQUIRREL frag

functions. • Sizing by velocity selection to be

demonstrated.• Possible field deployments: Barcelona

March 2009 and Queens, NY Summer 2009.

END

Velocity Selector• Allows for size resolved particle sampling

without the need for fast detection.• Application for Aerosol Chemical

Speciation Monitor (ACSM).

Motor

Two chopper wheels with the slits offset rotating at a known speed

Poldisperse in “monodisperse” out

Variables:Angular velocitySlit offset angleSlit widthDisc separation

Particle Beam

Velocity Selector and Control Electronics

Velocity selector mounts on an NW63 port

Velocity SelectorStandard Chopper

Velocity Selector Measurements with 1% and 2% Duty Cycle Slits

1%

2%

25

20

15

10

5

0

NO

2+ S

igna

l

0.00250.00200.00150.00100.0005

pTOF (s)

2% slits Polydisperse in Chopped Mode

Sig_p46_R10Velocity selector Mode (Hz)

Sig_p46_R3 200 Sig_p46_R4 240 Sig_p46_R6 280 Sig_p46_R12 320 Sig_p46_R14 360 Sig_p46_R16 400 Sig_p46_R18 440 Sig_p46_R21 500

20

15

10

5

0

-5

NO

2+ s

igna

l

0.00250.00200.00150.00100.0005

1% slitsPolydisperse in Chopped Mode

Sig_p46_R37Velocity selector Mode (Hz)

Sig_p46_R45 300 Sig_p46_R44 280 Sig_p46_R43 260 Sig_p46_R42 240 Sig_p46_R41 220 Sig_p46_R40 200 Sig_p46_R39 180