Instrumentation for insitu determination of chemical composition of fine particles Finnish Meteorolo

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Instrumentation for in-situ determination of
chemical composition of fine particles
Finnish Meteorological Institute Heikki
Lihavainen and Yrjö Viisanen University
of Helsinki, Department of Chemistry Kari
Hartonen, Timo Kivi, Totti Laitinen, Markku
Rasilainen and Marja-Liisa Riekkola University
of Helsinki, Department of Physical Sciences
Kari Kuuspalo, Pasi Aalto and Markku Kulmala
Funded by National Technology Agency of Finland
(TEKES)
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CONTENT

• Introduction
• Aims of the project
• Description of the project (instrumentation to be
  constructed)
• Results and current status of the project
• Conclusions

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Introduction

• Analysis of chemical composition of aerosol
  particles is an important aspect in aerosol
  science. It is known that these particles have
  major impact to worlds climate.
• An instrument that could measure composition of
  nucleation mode particles would shed light on the
  problem of how new particles are formed and which
  substances are involved in the formation process.

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From prof. Jose-Luis Jimenez, University of
Colorado at Boulder, http//cires.colorado.edu/jj
ose/Jimenez_Aerosol_MS_Intro.pdf
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Aims of the project

• The main objective of the project is to develop a
  portable aerosol mass spectrometer that gives
  real time information of chemical composition of
  aerosol particles from nucleation mode to
  accumulation mode
• Gain technical experience
• Instrument for other application as well
• In addition of atmospheric aerosols, instrument
  can be used to monitor, for example, indoor and
  outdoor air quality, chemical and biological
  weapons, narcotics and industrial sources
  (semiconductor and nanoparticle manufacturing)

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From prof. Jose-Luis Jimenez, University of
Colorado at Boulder, http//cires.colorado.edu/jj
ose/Jimenez_Aerosol_MS_Intro.pdf
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Chematic of the Aerosol Time of Flight Mass
Spectrometer
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Front view of the ATOFMS instrument
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Detailed view of the vacuum pumping system and
high voltage supplies under the top table level
above the excimer laser
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Top view of the ATOFMS instrument
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(No Transcript)
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Results 1
First signal obtained by shooting with ionisation
laser (UV 193 nm) onto a small piece of paper
inserted into a ion source (10.8.2004)
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Results 2

• Clear that MS instrument is somehow working but
  not repeatable
• - Ion optics (acceleration lens system) was
  improved
• - Data acquisition with PC was made working
• - Some extra electronics were built for
  detector plus laser triggering and timing
• - Safety features were added for detector and
  high voltage supplies in case of pressure
  increase
• At the same time, particle charger tested with 7
  and 10 nm particles and it is working (but can
  still be further improved)
• Sampling valve most critical point (how it holds
  vacuum when turning) not causing problems (tested
  and working)

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Ion flight paths in the TOF-MS system simulated
by the Simion 7.0 program (by Alexey Adamov)
Detector
repeller
3rd lens
Flight tube
2nd lens
1st lens
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Background noise measured with data acquisition
system using proper preamplifier after the MCP
detector
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Current view of the instrument when building and
testing the electronic setup for laser
triggering and timing
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Current project status

• MS instrumentation (first version) construction
  ready and should be working
• Unipolar particle charger, detector, data
  collection, lasers, HV supplies and vacuum system
  including sampling valve all tested and working
  well
• Computer control of HV-supplies, vacuum system
  (safety cut-off for HV supplies) and lasers
  (timing when triggering) operational

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CONCLUSIONS

• Technically very educating and challenging
  project
• Project will be accomplished (but delayed)
• Instrument now ready for first measurements with
  aerosols generated from pure substances

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Future plans of the GATOFMS Project
In addition to MS-MS possibility, more compact
version of the instrument will be built in the
future as well as option for analysing gas phase
components with the same system