Electrostatic Probe Measurements in Flowing NaK-Seeded Argon

摘要

This experimental study was motivated by the need to examine the applicability of existing theories for electrostatic probes in environments characteristic of closed-cycle MHD generators. Numerous probe theories for collision-dominated plasmas have been proposed but few, if any, experimental results have been reported for probes in alkali-metal-seeded inert gases. Experimental studies of probes in atmospheric argon and in seeded combustion gases have been reported. Current-voltage characteristics have been obtained using a cooled cylindrical probe in a low-velocity atmospheric-pressure argon flow seeded with NaK (90% K by weight). The gas temperature was approximately 2300K. The current collected by the probe depended strongly on the probe temperature which ranged from 350 to 1000K. Above 450K, collected currents were considerably larger than those predicted either by present probe theory or by thermionic emission. Results obtained when the probe was cooled below 450K agree approximately with theoretical predictions. (Author)