LANGMUIR PROBE MEASUREMENTS IN AN EXPANDING MAGNETIZED PLASMA

Langmuir probe measurements are performed in magnetized expanding plas mas of different compositions. The influence of the magnetic field on the currents collected by the probe in an argon plasma is investigated at two different flows and for two different probe sizes. The experim ental results are compared to existing theories. A decrease in the rat io of electron to ion saturation currents is found both in theory and experimentally. However, the theoretically predicted dependence of the ratio of electron to ion saturation current on probe diameter is not observed. An empirically derived function is fitted to the data. Under the assumption that the function fitted to the results in argon is va lid in other plasmas, it is possible to determine relative ion densiti es in magnetized nitrogen and hydrogen plasmas. It is found that the d ominant ionic species in both plasmas is the atomic ion (N+ and H+, re spectively).