Modeling of a Langmuir Probe Sheath in a Fast Air Flow

Summary form only given. To investigate the influence of the "J cross B" force on the boundary layer of an airfoil, a plasma is generated in a wind tunnel and convected downstream to a test body. A Langmuir probe is used to characterize the flowing plasma, however the effects of flow on the probe sheath at pressures less than 5 torr are unknown. To investigate the probe sheath in a fast air flow, a particle-in-cell (PIC) and fluid approach are employed for low (<1.0 torr) and moderate pressure (>1.0 torr) regimes respectively. Comparison\´s between the PIC and fluid model methods at 0.01 and 1.0 torr are made. Probe sheath length alteration due to flow velocities between 500 and 1000 m/s and pressures of 0.01 to 5.0 torr are examined and the validity of a Langmuir probe as a diagnostics tool for a plasma in a fast, low pressure air flow is discussed.