Atmospheric Measurement Techniques www.atmos-meas-tech.net 1867-1381 1867-8548 3 2 2010 10.5194/amt-3-507-2010 http://www.atmos-meas-tech.net/3/507/2010/ http://www.atmos-meas-tech.net/3/507/2010/amt-3-507-2010.html http://www.atmos-meas-tech.net/3/507/2010/amt-3-507-2010.pdf 507 521 2010-04-29 μDirac: an autonomous instrument for halocarbon measurements B. Gostlow A. D. Robinson N. R. P. Harris Neil.Harris@ozone-sec.ch.cam.ac.uk L. M. O'Brien D. E. Oram G. P. Mills H. M. Newton S. E. Yong J. A Pyle Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK Malaysian Meteorological Department, Ketua Stesen GAW Lembah Danum, Malaysia National Centre for Atmospheric Science, NCAS-Climate, UK We describe a new instrument (μDirac) capable of measuring halocarbons in the atmosphere. Portability, power efficiency and autonomy were critical design requirements and the resulting instrument can be readily deployed unattended on a range of platforms: long duration balloon, aircraft, ship and ground-based stations. The instrument is a temperature programmed gas chromatograph with electron capture detector (GC-ECD). The design requirements led to μDirac being built in-house with several novel features. It currently measures a range of halocarbons (including short-lived tracers having biogenic and anthropogenic sources) with measurement precision relative standard deviations ranging from ± 1% (CCl4) to ± 9% (CH3I). The prototype instrument was first tested in 2005 and the instrument has been proved in the field on technically challenging aircraft and ground-based campaigns. Results from an aircraft and a ground-based deployment are described. Bassford, M. R., Simmonds, P. 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