Aerosol Chemical Speciation Monitor ACSM

Transcription

1 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

2 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

3 Aerosol Chemical Speciation Monitor 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

4 Did we already build this? September 10, 1999 The ACSM is a product of Q and TOF AMS developments

5 ACSM Designed Around Pfeiffer Prisma RGA Prisma electronics supports: Ethernet connectivity with OPC 1 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) 1 OPC 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).

6 ACSM Data Acquisition Software Plan Prisma Windows CE OS OPC Server Ethernet Connectivity Acquisition Computer OPC Engine VB.NET Raw Data Igor Interface Automation Server Data processing - display

7 ACSM Software Panels VB.NET OPC interface Igor User Interface

8 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.

9 Signal-to-Noise Airbeam Intensity and Position for Quad Settings 20 ms/amu 50 ms/amu 100 ms/amu 12 min 30 min 12 min ~ 1 day for each scan speed depicted Allan Variance of the Airbeam intensity for the full time series to quantify noise and signal averaging

10 Allan Variance of Airbeam Intensity

11 Prisma Resolution and Signal Intensity 200x x10-9 Signal (amps) Resolution N 2 Signal (amps) m/z Resolution Setting

12 Prisma Resolution Signal (amps) 2.5x N 2 Resolution Setting m/z Resolution (M/ Μ) Resolution Setting

13 Ion Transmission 1.4 Normailzed Ion Intensity Ne N 2 Ar Kr 16 mm (QAMS) 6 mm (Prisma) Xe m/z Compares 16mm (QAMS) to 6mm (ACSM)

14 Ion Transmission in Quad 1.2 Relative Ion Transmission m/z 6mm quad has significant decrease in ion transmission. More characterization needed.

15 Multiplier Gain Estimate 2.0x10-9 SEM Signal (amps) MSOpen Signal Gain ~1.1e4 2000V 0.0 N 2 O 2 2.0x Faraday Signal (amps) Point Number (amu axis) Ratio SEM to Faraday Signal

16 Gain plot Gain At 2000V, gain = 5e SEM_voltage

17 Setup for Mass Based IE Determination Atomizer Drier Must consider lens transmission and multiply charged diameters from DMA By-pass DMA Aerosol Diluter filter ACSM CPC Input Mass = ρ x Volume(size) x Number Measured Mass Plot Measured Mass vs Input Mass

18 NH 4 NO 3 IE Calibration 60x Signal (amps) slope = 2.61e CPC Mass (ug/m3)

19 NH 4 NO 3 Effective Ionization Efficiency Sig (amps) [µg/m 3 ] (gain) (flow) ions/sec molecules/sec 2.61x x10-7 ions/molecule ~20 times lower sensitivity compared to QAMS

20 System Calibration Number IE/AB = [ug/m3] / amps2 = 3.85x10 11 / 1.20x10-9 = 3.2x10 20

21 Long Term Stability m/z correction x10-8 AB (amps) /25/2008 8/1/2008 8/8/2008 8/15/2008 8/22/2008 Date/Time AB decrease ~0.5% per day

22 AMU Calibration Issue Xe amu Offset 0.6 Kr 0.4 Ne N2 Ar AUM

23 Long Term Stability ctof Comparison 1.0 µg/m /21/2008 7/31/2008 8/10/2008 8/20/2008 Date and Time Analysis based on SQUIRREL frag functions

24 ACSM - ctof Comparison 14 min ACSM Data Rate 3.0 m/z µg/m NO SO :00 AM 8/23/ :00 PM 12:00 AM 8/24/ :00 PM 12:00 AM 8/25/ :00 PM Date and Time

25 Summary Stable over long periods. Sensitivity of ~0.1 µg/m 3 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.

26 END

27 Velocity Selector Allows for size resolved particle sampling without the need for fast detection. Application for Aerosol Chemical Speciation Monitor (ACSM). Two chopper wheels with the slits offset rotating at a known speed Poldisperse in Particle Beam Motor monodisperse out Variables: Angular velocity Slit offset angle Slit width Disc separation

28 Velocity Selector and Control Electronics

29 Velocity selector mounts on an NW63 port Standard Chopper Velocity Selector

30 Velocity Selector Measurements with 1% and 2% Duty Cycle Slits NO2+ signal % 1% slits Polydisperse in Chopped Mode Sig_p46_R37 Velocity selector Mode (Hz) Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R NO2+ Signal % % slits Polydisperse in Chopped Mode Sig_p46_R10 Velocity selector Mode (Hz) Sig_p46_R3 200 Sig_p46_R4 240 Sig_p46_R6 280 Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R Sig_p46_R ptof (s)