Magnetic Nozzle and RPA Simulatons vs. Experiments for a Helicon Plasma Thruster Plume Articles uri icon

publication date

  • April 2022

start page

  • 1

end page

  • 15

volume

  • 10

International Standard Serial Number (ISSN)

  • 2296-424X

abstract

  • The experimental characterization of electrodeless plasma thrusters with a magnetic
    nozzle is fundamental in the process of increasing their maturity to reach the
    industrialization level. Moreover, it offers the unique opportunity of validating existing
    numerical models for the expansion of a magnetized plasma plume, and for the synthetic
    simulation of diagnostics measurements, like those of a retarding potential analyzer, which
    provides essential information regarding the ion beam energy distribution function.
    Simulations to experiments comparison ultimately enables a better understanding of
    the physical processes behind the observed experimental curves. In this work, input
    experimental data of a Helicon plasma plume is used to simulate both a magnetic nozzle
    expansion in the divergent field region, and the corresponding measurements of a
    retarding potential analyzer, through dedicated small-scale simulations of this
    diagnostics tool. Magnetic nozzle simulation and experimental results agree well in
    terms of the angular distribution of the ion current at 40 cm distance from the source,
    and also in the prediction of the energies of the two main peaks of the ion energy
    distribution function: a first one at 45 eV due to source ions, and a second one, at
    15–20 eV, due to ions from charge-exchange and ionization collisions in the plume. Finally,
    the small-scale simulation of the retarding potential analyzer permits to assess the parasitic
    effects caused by the ion current collected by the different analyzer grids. The inclusion of
    the retarding and electron suppression grids currents in the overall I-V characteristic is
    shown to correct almost entirely these effects on the obtained ion velocity distribution.

keywords

  • helicon, plasma plumes, retarding potential analyzer (rpa), particle in cell (pic), fluid models, hybrid; models, magnetic nozzle (mn)