HP-SSA-GCMS-3-FCO-DESCENT

Content: Data Set Overview Science Objectives Mission Phase Definition Data and Data Processing Quality of Stage 2 Archived Data Creating Meaningful GCMS Archive Data File Names Structure of the DATA Directory & Comments Document Subdirectory Extras Subdirectory Dataset Review Data Set Overview Gas Chromatograph Mass Spectrometer (GCMS) Instrument The GCMS uses a quadrupole mass filter with a secondary electron multiplier detection system and a gas sampling system providing continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic columns. The mass spectrometer used five electron impact ion sources with available electron energies of either 70 or 25 eV. Three ion sources served as detectors for the gas chromatographic columns and two were dedicated to direct atmosphere sampling and Aerosol Collector Pyrolyser (ACP) gas sampling, respectively. The multiple ion source approach allowed rapid switching between sample systems and prevented crosscontamination. The instrument was also equipped with a chemical scrubber cell for noblegas analysis and a sampleenrichment cell for selective measurement of highboilingpoint carboncontaining constituents. The mass filter produced flattop mass peaks that allowed rapid scanning in 5ms steps of unit values of mass to charge (m/z) ratios over a range from 2 to 141. The nominal detection threshold was at a mixing ratio of 10^8. Pressure reduction from the ambient pressure, ~3 to ~1,500 hPa (~1.5 bar), during the probes descent to the vacuum level of <10^4 hPa was achieved with micrometresized glass capillary arrays. A choice of two capillary arrays of different gas conductance was used for the direct atmosphere ion source to cover the wide pressure range during the descent. Gases were removed from the ion sources by conductance limited getter and sputter i truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]