Evaluation of Para-Perp Type Mach Probe by Using a Fast Flowing Plasma

Abstract

Mach probe with two collecting tips facing to the direction parallel and perpendicular to the plasma flow, named para-perp type one, is evaluated by using a directional Langmuir probe (DLP) in a fast owing plasma produced by an MPD (Magneto-Plasma-Dynamic) arcjet. We present simple formulas to determine an ion acoustic Mach number M_i from the ratio of collected ion saturation currents. The formulas and experimentally-obtained data are compared with Hutchinson’s simulation results which are calculated using a particle-in-cell(PIC) code in an unmagnetized plasma condition. [I.H. Hutchinson, Plasma Phys. Control. Fusion, 44 1953 (2002).] Good agreements are obtained among these data in both subsonic and supersonic plasma flows. Correction factor κ to determine M_i is presented under various conditions of T_i/T_e and the specific heat ratio for ions γ_i.