Spectrum analysis of organic and inorganic dust particles measured by ert634


									 Spectrum analysis of organic and inorganic dust particles measured
         by an impact ionization mass analyzer instrument

       J. G. Salter1, Z. Sternovsky2, 3, R. Srama4, F. Postberg4, S Kempf4, S. P. Armes5,
                       E Gruen2, 4, M Horanyi2, 3, K. Drake2, 3, A. Westphal6

                    1. Physics, University of Colorado, Boulder, CO, USA.
                     2. LASP, University of Colorado, Boulder, CO, USA.
 3. Colorado Center for Lunar Dust and Atmospheric Studies, University of Colorado, Boulder.
              4. Max Planck Institute for Nuclear Physics, Heidelberg, Germany.
                  5. The University of Sheffield, Sheffield, United Kingdom.
          6. Space Science Laboratory, University of California, Berkeley, CA, USA.

The composition of individual cosmic dust particles can be measured in-situ using existing
techniques and instrumentations. A dust particle impacting on a solid surface with hypervelocity
(> 1 km/s) is vaporized and partially ionized. The generated ions can then be extracted and
analyzed using time-of-flight methods, from which a mass spectrum is built. Observing the
relative mass percent composition of the constituents, over a range of velocities, yields further
insight into the nature of these projectile species. Laboratory calibration measurements are
possible at the dust accelerator facility in Heidelberg, Germany. The accelerator is limited to
using conductive dust that was limited in the past to Fe, Al or graphite samples. In the recent
years, however, dust samples of organic materials and inorganic minerals of cosmic interest were
developed that are suitable for application in the accelerator. This is achieved by coating micron
and submicron sized dust particles by conductive polymers. Here we present the comparison of
spectra measured using organic and inorganic dust samples (polystyrene, poly-[bis(4-
vinylthiophenyl)sulphide], Phyrotite). The particles were accelerated to speeds between 3 and 35
km/s. Depending on the projectile type and the impact speed aliphatic and aromatic molecular
ions and cluster species were identified in the mass spectra with masses up to 400 Daltons.
Clusters resulting from the target material (silver) and mixed clusters of target and projectile
species were also observed. These fundamental studies are expected to enhance our
understanding of cometary, interplanetary and interstellar dust grains, which travel at similar
hyper-velocities and are known to contain both aliphatic and aromatic organic compounds.

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