Laser-induced fluorescence measurements of velocity within a Hall discharge

The results of a study of laser-induced fluorescence velocimetry of neutral and singly ionized xenon in the plume and interior portions of the acceler ation channel of a Hall thruster plasma discharge operating at powers rangi ng from 250 to 725 W are described. Axial ion and neutral velocity profiles for four discharge voltage conditions (100 V, 160 V, 200 V, 250 V) are mea sured as are radial ion velocity profiles in the near-field plume. Ion velo city measurements of axial velocity both inside and outside the thruster as well as radial velocity measurements outside the thruster are performed us ing laser-induced fluorescence with nonresonant signal detection on the xen on ion 5d[4](7/2)- 6p[3](5/2) excitation transition while monitoring the si gnal from the 6s[2](3/2)-6p[3](5/2) transition. Neutral axial velocity meas urements are similarly performed in the interior of the Hall thruster using the 6s[3/2](2)(0)-6p[3/2](2) transition with resonance fluorescence collec tion. Optical access to the interior of the Hall thruster is provided by a l-mm-wide axial slot in the insulator outer wall. While the majority of the ion velocity measurements used partially saturated fluorescence to improve the signal-to-noise ratio, one radial trace of the ion transition was take n in the linear fluorescence region and yields a xenon ion translational te mperature between 400 and 800 K at a location 13 mm into the plume.