Electrostatic Probe Measurements in a Collisionless Plasma Sheath

Experimental data are presented on electrostatic probe measurements in the collisionless plasma sheath of a 3.2-cm-diam conducting plate. The plate was immersed in a glow discharge-produced argon plasma in which the pressure was varied from 0.2 to 0.8 μ. A movable probe of 0.0064 cm diam, 0.64 cm length, tungsten wire was used as a Langmuir probe, emissive probe, and floating emissive probe. The data explicitly shows that experimental measurements to determine the local sheath potential based on Langmiur probe theory are meaningless. However, it is explicitly shown that the experimentally measured floating potential distributions of the emissive probe and the floating emissive probe in the sheath of a positive plate do follow the expected trend of the local potential of the plasma sheath.