Analysis of a cusped helicon plasma thruster discharge

TL;DR

This paper investigates a cusp-enhanced helicon plasma thruster using experiments and simulations, revealing how the cusp influences plasma losses and suggesting design optimizations to improve efficiency.

Contribution

It combines experimental measurements with advanced simulations to analyze the effects of a magnetic cusp on plasma behavior and thruster performance, providing new insights into loss mechanisms.

Findings

Cusp reduces rear wall losses but increases lateral wall losses.

Electron temperature peaks downstream in the magnetic nozzle.

Performance limited by low production efficiency and wall losses.

Abstract

A compact helicon plasma thruster that features a cusp in its internal magnetic field is analyzed with experiments and simulations. A compensated Langmuir probe and a Faraday cup are used in the former, while a hybrid PIC/fluid transport model combined with a frequency-domain electromagnetic field model are used in the latter. Measurements serve to tune the anomalous transport parameters of the model and overall show the same trends as the numerical results, including a secondary peak of electron temperature downstream in the magnetic nozzle, where electron cyclotron resonance conditions for the 13.56 MHz excitation frequency are met. The cusp plays a central role in determining the plasma losses to the walls and the profile of electron temperature, which in turn defines the excitation and ionization losses. While losses to the rear wall are reduced, losses to the lateral wall are increased, which, together with the low production efficiency, limit the performance of the device. Shorter chamber lengths and optimization of antenna and cusp location are suggested as potential ways to improve performance.