First Helicon Plasma Physics and Applications Workshop

The First Helicon Plasma Physics and Applications Workshop was held on September 23−24, 2021, through Zoom Cloud Meeting, instead of in an on-site gathering, due to the COVID-19 pandemic. It was convened by Rod Boswell (IOC) and Guangnan Luo (LOC), and organised by Lei Chang’s group. The workshop attracted 110 registrations and ∼100 online audiences from ∼30 affiliations. There were 33 presentations covering the various fundamental physics of helicon plasma and its applications to space electric propulsion, material processing, and magnetic confinement fusion. This paper highlights the presentations, discussions, and perspectives given in the workshop, serving as reference for the helicon community.

Development of a Plasma Chemistry Model for Helicon Plasma Thruster analysis

The present work is part of a wider project aimed at improving the description of the plasma dynamics during the production phase of a Helicon Plasma Thruster. In particular, the work was focused on the development of a chemical model for Argon- and Xenon-based plasma. The developed model consists of a collisional radiative model suitable to describe the dynamics of the 1s and 2p excited levels. The model is meant to be complementary to 3D-VIRTUS, a numerical tool which enforces a fluid description of plasma, developed by the University of Padova to analyse helicon discharges. Once identified, the significant reactions for both propellants, the reaction rate coefficients, have been integrated exploiting cross sections from literature and assuming a Maxwellian velocity distribution function for all the species. These coefficients have been validated against experimental measurements of an Argon Inductively Coupled Plasma and compared with a well-established code. For Argon, the selected reactions have been reduced through a proposed lumping methodology. In this way, it was possible to reduce the number of equations of the system to solve, and implement them into 3D-VIRTUS. A validation against an experimental case taken from literature was performed, showing good agreement of the results. Regarding the Xenon model, only a verification has been performed against the results of another collisional-radiative model in literature. Finally, a predictive analysis of the propulsive performances of a Helicon Plasma Thruster for both Argon and Xenon is presented.

Measurement of Plasma Potential, Ion Saturation Current and Mach number using Retarding Field Energy Analyzer

This article deals about the experimental measurement of plasma potential, ion saturation current and Mach number obtained with the variation of power, operating gas pressure and radial position using retarding field energy analyzer. We employed a retarding field energy analyzer by rotating with different angles such as 0° (facing toward source), 90° (facing side walls) and 180° (facing opposite the source). The coil current is varied from 0 to 15 A to produce the magnetic field which is used to confine the plasma. The flow of plasma has been characterized which was found to be subsonic. The low-temperature plasma is produced by means of a 13.56 MHz helicon plasma source at 300-1000 kW radio frequency power. The plasma is expanding from 13.8 cm diameter source into a 150 cm long diffusion chamber of 60 cm diameter.