EXPERIMENTS ON CYLINDRICAL ELECTROSTATIC PROBES IN SLIGHTLY IONIZED HYPERSONIC FLOW

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.