Experiments on cylindrical electrostatic probes in a slightly ionized hypersonic flow.

Abstract

The behavior of biased electrostatic probes in ionized media is of substantial interest to those concerned with space flight environment, re-entry, and laboratory simulation, among others. The effect of finite cylindrical probe length, probe diameter, ratio of probe radius to debye shielding distance, angle of attack in the case of a flowing plasma, and length-to-diameter ratio on the current collection ability of a probe is experimentally investigated in a slightly ionized, frozen, hypersonic shock-tunnel flow. The results are linked to the detailed analysis of Laframboise for probe operation in a free-molecular collisionless plasma. It was found experimentally that for RP/\D < 3 the results of the experiments deviate from those of the idealized collisionless free-molecular theory, that the current density increases with the decrease of length-to-diameter ratio, and that the angle-of-at tack trends deviate considerably from the aligned probe behavior.