Simulations of Thermionic Emission, Collisions and Ion Trapping in Multidimensional Plasma Systems, and Illustration of a Technique to Identify the Sheath Regime Around Emissive Probes

Using a recently developed 2D-2V kinetic continuum code designed to study effects of strongly emitting surfaces on plasmas with collisions, we have shown that multiple dimensions introduce new sheath effects that are not captured in previous 1D simulations of emitting surfaces. Analysis of the sheath physics, current flow and potential distributions in various 2D configurations including floating and biased emissive probes, filament discharges, and surfaces with nonuniform emission have demonstrated multidimensional extensions of inverse and space-charge limited sheath regimes. Using emissive probe simulations, we introduce a methodology that one could use in experiments to differentiate classical, space-charge limited and inverse regimes by the probe's current response.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07NA27344. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231.