On the electron energy distribution function in a Hall-type thruster

The electron energy distribution function measured at the channel exit of a small Hall-type thruster is interpreted as a beam-plasma electron distribu tion function with electron beam energy of several tens of electronvolts. T hough unstable, the distribution function does not correspond to the comple tely quasilinear relaxed beam function. Comparison with the measured functi on in the vicinity of the channel exit shows that the electron beam energy is about 30 eV for the total voltage applied similar to 200 V. The contribu tion of the electron beam is shown to be essential in the ionization of the working gas, even when only the single ionization processes are considered . (C) 1999 American Institute of Physics. [S1070-664X(99)00211-6].