The dynamics of xenon atoms and ions expanding in the magnetic nozzle of a Helicon plasma thruster is studied by means of near-infrared laser-induced fluorescence spectroscopy on resonant and metastable states. Fluorescence spectra are measured for several operating conditions inside and outside the thruster discharge chamber. In the near-field plume, the relatively intense magnetic field induces Zeeman effect on the probed optical transitions. Hence, modeling of the atomic lineshapes is addressed to accurately compute the Doppler shift and infer the velocity. The first direct measurements of the neutral flow in a magnetic nozzle reveal that atoms are accelerated to supersonic velocities behind the thruster exit. The ions acceleration region extends several centimeters downstream the exit plane. Larger axial ion speeds are attained when the thruster operates at lower mass flow rates and higher levels of input power.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Measurements are taken using a helicon plasma device to analyze the spatial distribution of plasma properties as the throat of the magnetic nozzle is axially shifted with respect to the antenna center. Krypton plasma is generated in the sub-kilowatt range and probed using a suite of diagnostics including a rf-compensated Langmuir probe, a planar probe, and laser-induced fluorescence. It is found that larger ion currents and increased plasma confinement are achieved when the throat of the magnetic nozzle is located downstream the antenna center, at a distance that equals or exceeds two times the antenna length. The ions, although being accelerated, retain subsonic velocities even beyond the magnetic throat.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.