Calibration Issues. John Jayne 5 th AMS User s Meeting 10/11/04

Transcription

1 Calibration Issues John Jayne 5 th AMS User s Meeting 10/11/04

2 Decrease in multiplier efficiency with ion mass and effect of conversion dynode ETP AF133 SEM 218 (Balzers CD) Jan 2001 SUNY AMS SI, relative to mz Mass usres/jayne/igor/sge_multgain.pxp Collection efficiency (EM/FC) of ions w/cd multiplier is ~3x lower than standard multiplier

3 Calibration Histories How well are we doing Ground based Aircraft based

4 Twin Otter Aircraft Basic AMS calibration/diagnostic parameters Full ICARTT campaign Opened Quad HB EM KVolts AB(32) IE IE/AB(32) 2.5x x x Changed Multiplier 8/1/2004 8/6/2004 8/11/2004 8/16/2004 8/21/2004 Date

5 Twin Otter Aircraft Basic AMS calibration/diagnostic parameters Full CSTRIPE campaign Roya/Shane HB EM KVolts AB(32) IE IE/AB(32) x x x High tuning frequency 7/6/2003 7/11/2003 7/16/2003 7/21/2003 7/26/2003 Date

6 P3 Aircraft Polydisperse calibrations Basic AMS calibration/diagnostic parameters NOAA AL for ITCT-NEAQS 2004 Ann/Brendan Heater Bias EM Volts 4.0x10-6 IE /24 6/29 7/4 7/9 7/14 7/19 7/24 7/29 8/3 8/8 8/13 ITCT-NEAQS x EM Gain 2.4x AB 2.0x IE/AB

7 17/07/ /07/ /07/ /07/2004 Date HB KV Gain x Pre Flight Post Flight IE/AB IE Airbeam 800x x x

8 Multiplier Voltage Heater Bias x10 6 James and Eben Nova Scotia AB x IE x10-12 IE/AB Good AB/IE ratio 11/07/ /07/ /07/ /07/ /07/ /08/ /08/2004 dat

9 AMS calibration/diagnostic parameters - Nobu x Multiplier Voltage (KV) Multiplier Gain Heater Bias (v) 1.57x10-6 Ionization eff. Multiplier dropped, AB increased, no change to mult Volt x x Duty Cycle (%) Flowrate (cc/sec) TOF Air Beam Strength (Hz) MS Air Beam Strength (Hz) 0: /05/10 12:00 0: /05/11 12:00 0: /05/12 Date and time 12:00 0: /05/13 12:00

10 ARI/CU Ratio Using best calibrations 1.4x10-12 IE/AB Ratio Ratio ARI/CU Mass Ratio /1/2003 4/3/2003 4/5/2003 4/7/2003 4/9/2003 4/11/2003 4/13/2003 4/15/2003 4/17/2003 4/19/2003 4/21/2003 4/23/2003 4/25/2003 4/27/2003 4/29/2003 5/1/2003 5/3/2003 IE/AB Green = ARI IE/AB Black = CU Date and Time Ratio lines = AMS colors Better practice not to fiddle too much?

11 ARI/CU vs (IE/AB)cu/(IE/AB)ari 4 total_ratio fit_total_ratio Colored by Time ARI/CU Mass Concentration (IE/AB)cu / (IE/AB)ari

12 IGOR Procedure under development to analyze single particles to get a multi-point calibration for ionization efficiency TOF (s) Single particles M46_Part M30_Part M17_Part M16_Part M15_Part Thres

13 10 4 IPP - bin average m15avgipp m16avgipp m17avgipp m30avgipp m46avgipp 3:1 line 10 0 NO3 = 2.4e-6 NH4 = 3.1e Molecules - bin average

14 Flow calibration U. Tokyo Cal at ARI NOAA Cal at ARI A volumetric flow meter Flow (cc/s) Tokyo Fit a = ± b = ± NOAA Fit a = ± b = ± Pressure (torr) Absolute pressure gauge

15 Flow calibration 3.0 A volumetric flow meter Flow (cc/s) U. Tokyo Cal at ARI NOAA Cal at ARI NOAA Cal at Boulder NOAA Scaled to 760 torr fit_cc_s1 Tokyo Fit a = ± b = ± NOAA Fit a = ± b = ± NOAA Boulder ccs fit a = ± b = ± estimated sccs flow = 0.823*ccs flow NOAA Boulder sccs fit a = ± b = ± Pressure (torr) Absolute pressure gauge

16 Particle Mass Loading From quad (IE calibration) µg m 3 mass volume From volumetric flow rate Should the air volume we sample be referenced to STP?

17 If the ambient pressure changes: The value for the flow rate in the data file will also change via the flow-pressure calibration curve. However the volumetric flow has not changed Should not let this fold into the AB correction since the sensitivity of the quad system has not actually changed. James, is this what we are doing?

18 Should we routinely measure T and P Absolute pressure and temperature so we can determine the mass flow into instrument?

19 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 a bounce event?

20 Particle Transmission versus Collection in Aerodynamic Lens Small particle losses are controlled by geometry and Brownian diffusion CE/Transmission Large particle losses are controlled by the pin-hole Aerodynamic Size Transmission No Collection Target No Transmission or Collection

21 Can we measure and verify the predicted lens transmission? Fluent Model Prediction Current Measurements CE/Transmission Aerodynamic Size Peter Decarlo s model vs Peter Liu s measurements

22 Lens Transmission/Collection Dilemma Pittsburgh AMS/SMPS data set suggests that AMS transmission is as good as the predicted value. Laboratory measurements by Peter Liu (UW) and ARI have been unsuccessful to match predicted transmission.

23 Collection Efficiency results for 1/2OD lens and 100 um pin hole Peter Liu, U. Wyoming 1.2 AMS Lens Collection Efficiency CE Fluent Result NH 4 NO 3 _A NH 4 NO 3 _B NH 4 NO 3 _C CE_dehs D va Lens press = torr at Wyoming 780 mbars = 585. Variation of flow changes velocity calibration and transmission

24 Collection Efficiency results for 1/2OD lens and 100 um pin hole Peter Liu, U. Wyoming 1.2 AMS Lens Collection Efficiency CE NH 4 NO 3 _A_integrating NH 4 NO 3 _B_integrating NH 4 NO 3 _C_integrating NH 4 NO 3 _A_count NH 4 NO 3 _B_count NH 4 NO 3 _C_count DEHS (spherical particles) Pittsburgh Nucleation Event Sept 12, pm D va Lens press = torr at Wyoming 780 mbars = 585. Variation of flow changes velocity calibration and transmission AMS Organic

25 Calculated mass as a function of aerosol concentration for several particle sizes Detection limit is based on DC704 aerosol m/z197 July 21, 2003 data AMS/CPC ~100% for 200 nm Mass Loading, ug/m^ Aerosol Concentration, #/cc Diameter, nm AMS detection limit SNR~2 This figure suggests that if 30 nm particles at ~1000/cc were transmitted at ~60% as predicted by Fluent we should have no problem detecting them as far as sensitivity is concerned

26 Particle Velocity Scales Equally well in D va or D a Space D aero =D mob *1.0*sqrt(density) D aero =D mob *0.8*density 2 2 PSL, F=1.42cc/s NO3, F=1.41 cc/s using shape factor = 1.0 and Sqrt(Density) PSL, F=1.42cc/s NO3, F=1.41 cc/s using shape factor = 0.8 linear density Velocity (m/s) Coefficient values ± one standard deviation Vg = p_0 = ± 1.78e+03 D* = p_1 = ± 25.5 b = p_2 = ± Vlens = p_3 = ± 44.7 Velocity (m/s) Coefficient values ± one standard deviation Vg = p_0 = ± 1.81e+03 D* = p_1 = ± 32.1 b = p_2 = ± Vlens = p_3 = ± 49.6 G1_2004_VelCalib.pxp G1_2004_VelCalib.pxp Aerodynamic Diameter (nm) Aerodynamic Diameter (nm) What is the impact on D mob vs D AMS comparison Need to carefully consider comparison to SMPS.

27 Particle velocity influenced by collisions with gas molecules inside channel aperture 3 Velocity (m/s) um Orifice NH4NO3 Gas Skimmer Channel Skimmer PSLs Channel Skimmer Daero (nm) Gas Skimmer How does this influence focusing of small particles? Does this impact our thinking on D va vs D a?

28 Beam Width Probe Stepper Motor Design Servo Motor Design New unit Old unit

29 Position Resolution of BWP Servo Stepper Distance Between Stops, mm Wire Diameter, mm 1 1 Number of steps Dist/step, um Hysterisis 3 2 Actual position resolution, um

30 The BWP can be stepped by an externally supplied TTL pulse

31 Schematic of DMA-less calibration setup Atomizer Electrically driven Impactor/ Drier D<2um Dilution AMS 10 4 Particle Diameter (µm) Ions/Particle Ion Signal DOP_TOF.itx Molecules/Particle Velocity Size calibration Time of Flight, sec Sample all single particles Determine IE and linearity in one measurement Check particle transmission