Anomalous electron mobility in a coaxial Hall discharge plasma - art. no. 026410

A comprehensive analysis of measurements supporting the presence of anomalo us cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and i onized xenon velocities, and various electrostatic probe diagnostic measure ments are used to locally determine the effective electron Hall parameter i nside the accelerator channel. These values are then compared to the classi cal (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find tha t in the vicinity of the discharge channel exit, where the magnetic field i s the strongest and where there are intense fluctuations in the plasma prop erties, the inferred Hall parameter departs from the classical value, and i s close to the Bohm value of (omega (ce)tau)(eff)approximate to 16. These r esults are used to support a simple model for the Hall parameter that is ba sed on the scalar addition of the electron collision frequencies (elastic c ollision induced plus fluctuation induced), as proposed by Boeuf and Garrig ues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to th e possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.