Publication: Magnetic Nozzle and RPA Simulatons vs. Experiments for a Helicon Plasma Thruster Plume
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2022-04-14
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Frontiers
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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.
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Keywords
Helicon, Plasma plumes, Retarding potential analyzer (RPA), Particle in cell (PIC), Fluid models, Hybrid models, Magnetic nozzle (MN)
Bibliographic citation
Cichocki, F., Navarro-Cavallé, J., Modesti, A., & Ramírez Vázquez, G. (2022). Magnetic Nozzle and RPA Simulations vs. Experiments for a Helicon Plasma Thruster Plume. Frontiers in Physics, 10.