Experimental investigations of radial physics in Hall thrusters*

Hall plasma thrusters and other devices with crossed electric and magnetic field geometries feature complex three-dimensional physics. The development of instabilities in such geometries is the subject of active study. In recent years, results from numerical simulations have provided some insight regarding radial features (observed parallel to the magnetic field), such as the complex coupling between wall emission and drift driven instabilities [1, 2]. However, few direct measurements of plasma properties and dynamics in the radial direction are available. In this work, radial investigations of electron properties in the exit plane of a Hall thruster have been performed using incoherent Thomson scattering. For the conditions investigated, large electron temperature gradients are measured between the inner and outer walls of the annular discharge, while a radial density gradient consistent with non-uniform ionization is observed. These measurements of electron properties (non-invasive and highly spatially-resolved) provide a means to develop an understanding of the radial features of Hall thrusters and contribute to the ongoing development of 3D codes.

[1] A. Héron and J-C. Adam. Phys Plasmas 20, 082313 (2013)

[2] A. Tavant et al., Plasma Sources Sci. Technol. 27, 124001 (2018)