COMPUTER-CONTROLLED PROBE DIAGNOSTIC SYSTEM AND APPLICATIONS IN A MAGNETIZED LABORATORY PLASMA

A computer controlled acquisition and evaluation system for electrostatic probes is presented. Fully automatic evaluation of the probe characteristics yields electron temperature, plasma potential, and density during the recording. Two-dimensional probe positioning is accomplished with stepping motors. The system is characterized by 12-bit probe current resolution and extremely wide probe voltage range (+/-130 V). It is tested in a collisionless argon magnetoplasma and compared to standard wave diagnostic techniques for magnetized plasmas, i.e., the resonance cone technique. The influence of the probe radius on the electron current in a magnetized plasma is studied experimentally. The two techniques yield identical density and temperature values within 20% accuracy and therefore show the reliable applicability of the automatic evaluation system.