Numerical Simulation of Probe Measurements in a Non- equilibrium Plasma, Using a Detailed Model Electron Fluid

This study investigates the axisymmetric plasma flow field near a Faraday probe. A hybrid fluid PIC computational code simulates heavy particles with a Particle In Cell (PIC) model, and electrons with a detailed model derived from conservation of mass, momentum, and energy. These simulations show significant departures from the planar Bohm sheath solution and from previous simulations using the Boltzmann model electron fluid. In the current work, the sheaths extend three to six Debye lengths from the probe depending on the properties of the ion distribution. This is significantly more compact than seen in the Bohm sheath solution and previous simulations, which show sheaths that extend twice as far from the probe. Simulated measurements of ion current at the probe surface do not change as much, only increasing by 1% over Bohm sheath solution values. Variation in the conductivity of the plasma is believed to be the main source of the discrepancies.