Teaching and old dog new tricks: Pushing the flowing afterglow to new frontiers in plasma chemistry kinetics

August 29, 2014

Nicholas S. Shuman

It is of interest to measure the kinetics of plasma processes (i.e. ion-molecule reactions, electron attachment, dissociative recombination, mutual neutralization) over a broad range of temperatures and pressures with the aim of predictively modeling environments such as the ambient or modified atmosphere, vehicle reenty, or combustion.  For four decades that effort has been advanced by the use of flow tube apparatuses, first the flowing afterglow and later the selected ion flow tube.  After so many years, much of the experimental space accessible through these versatile machines appeared to be covered.  Recently we have expanded that space by employing a novel technique using a flowing afterglow – Langmuir probe (FALP) apparatus.  The technique, variable electron and neutral density attachment mass spectrometry (VENDAMS) has allowed for study of categories of processes for which little or no prior data existed in the literature.  This includes reactions of radicals with both electrons and ions, and numerous aspects of mutual neutralization.  These efforts are summarized along with details of statistical models used to better understand these processes and to extrapolate the observations to temperature and pressure regimes inaccessible by the experiment.

Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, NM