Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy

Near exit plane non-resonant light induced fluorescence spectroscopy is performed in a Hall effect low-power Xenon thruster at discharge voltage of 250 V and anode flow rate of 0.7 mg/s. Measurements of the axial and radial velocity components are performed, exciting the \documentclass[12pt]{minimal}\begin{document}$6s ^2[3/2]^o_2\rightarrow 6p ^2[3/2]_2$\end{document}6s2[3/2]2o→6p2[3/2]2 transition at 823.16 nm in XeI and the \documentclass[12pt]{minimal}\begin{document}$5d [4]_{7/2}\rightarrow 6p [3]^o_{5/2}$\end{document}5d[4]7/2→6p[3]5/2o transition at 834.724 nm in XeII. No significant deviation from the thermal velocity is observed for XeI. Two most probable ion velocities are registered at a given position with respect to the thruster axis, which are mainly attributed to different areas of creation of ions inside the acceleration channel. The spatial resolution of the set-up is limited by the laser beam size (radius of the order of 0.5 mm) and the fluorescence collection optics, which have a view spot diameter of 8 mm.