TOF-AMS Data Analysis. Silke Hings MPI Mainz

Size: px

Start display at page:

Download "TOF-AMS Data Analysis. Silke Hings MPI Mainz"

Ralph Rose
6 years ago
Views:

1 TOF-AMS Data Analysis Silke Hings MPI Mainz I-TOF CALIBRATION In TOF-MS: sqrt of is proportional to ion time-of-flight m z t f Signal / Hz Ion Time-of-Flight / ns 640 peak position of = ion time-of-flight default in analysis software: N + ( ); N 2+ ( ); O 2+ ( ); Ar + ( ) 1

2 STICK INTEGRATION Signal at = peak area of Raw Spectra Signal / bits MS Open MS Closed MS Diff MSS Diff 1.4x Stick Spectrum Signal / Hz x Peak integration within fixed borders subtract baseline (average of baseline before and after peak) from each point sum all points between -0.3 and +0.2 around nominal mass of DUTY CYCLE CORRECTION Duty cycle of mass spectrometer: limited by overfilling of ions in extractor ions are lost during time between two pulses D overfill xe = T pulse mion q 1 2U ion duty cycle / % Total duty cycle of ToF MS x e : extraction length; T pulse : time between two pulses; q: charge of the ion (q = z. e); m ion : ion mass; U ion : ion chamber voltage (gives the primary ion beam energy) D ( ) = const TOF AMS. Duty cycle correction: Normalize to one D TOF-AMS ( norm ) 1 signal corr 1 ( ) = signal( ) = signal( ) D( ) norm 2

DC MARKERS Baseline subtraction from P-TOF size distributions 6.4 6.2 6.0 5.

3 DC MARKERS Baseline subtraction from P-TOF size distributions DC markers hardcoded in software: front: points back: points from end of size distribution set DC markers for baseline calculation subtract average of baselines before and behind size distribution x BEFORE LOADING I-TOF Calibration run: 0 every MS calibrated with start parameters from related info file -1 manual calibration parameters are used for all MS N calibration parameters from I-TOF calibration of run N are used for all MS Use_exactmass: 1 use MSDiff for calibration -1 use MSClosed for calibration 0 do not use for calibration 3

4 BEFORE LOADING If you need to change DC markers: Go to function... Get_Parameters Change DC markers... IMPORTANT: Do this BEFORE loading data! LOADING Parameter Control - parameters read from first info file - possibility to change all the parameters - some can also be changed later 4

possibility to set negatives to zero for display FEATURES Time Series of Mass Concentrations possible

5 FEATURES Average Mass Spectra sticks and raw mass spectra sticks colored according to species; stacked on top of each other displayed in Hz or converted into µg/m³ mass concentrations of species added to legend possibility to set negatives to zero for display FEATURES Time Series of Mass Concentrations possible species: nitrate, sulfate, chloride, ammonium, organics, water and individual colored according to AMS colors 5

6 FEATURES Diurnal Patterns calculated and displayed for species chosen in the Time Series box choose between 5-95 % or % whiskers FEATURES Average Size Distributions possible species: nitrate, sulfate, chloride, ammonium, organics and individual smoothing of size distributions normalize size distributions to MS time series 6

FEATURES Size-dependent Mass Spectra average mass spectra for chosen size ranges (> 20

7 FEATURES Time Series of Size Distributions possible species: nitrate, sulfate, chloride, ammonium, organics and individual smoothing in t and d normalize to MS time series FEATURES Size-dependent Mass Spectra average mass spectra for chosen size ranges (> 20 nm) average mass spectrum for whole size range > 20 nm normalized to MS mode average mass spectrum 7

FEATURES Corrections airbeam correction choose reference run or insert values manually smooth airbeam wave rebinning of size distributions (average and time series) selected number of size bins,

8 FEATURES Corrections airbeam correction choose reference run or insert values manually smooth airbeam wave rebinning of size distributions (average and time series) selected number of size bins, evenly spaced in logarithmic space external size bin wave set negatives to zero in average and size-dependent MS display only for display PROBLEMS What s going wrong I-TOF calibration breaks down at about 150 add more exact masses at higher stick integration method: producing e.g. negative organic signal at 29 better integration method will be implemented frag list not user-accessible (at least not easily) James ;-) size-dependent mass spectra there is lots to do and many more I m not aware of 8

9 THE BOTTOM LINE The software works but is far from being perfect! If you find any bugs or have any suggestions please do not hesitate to contact me! 9

ToF-AMS DAQ. Joel Kimmel Univ. of Colorado at Boulder & Aerodyne Research, Inc AMS Users Meeting 2007

ToF-AMS DAQ. Joel Kimmel Univ. of Colorado at Boulder & Aerodyne Research, Inc AMS Users Meeting 2007 ToF-AMS DAQ Joel Kimmel Univ. of Colorado at Boulder & Aerodyne Research, Inc AMS Users Meeting 2007 1 Web Resources http://cires.colorado.edu/jimenez-group/tofamsresources/tofsoftware/ Downloads Release