Characterisation of a thermionic plasma source apparatus for high-density gaseous plasma antenna applications

Abstract

A thermionic plasma source apparatus has been developed and characterised for high-density gaseous plasma antenna (GPA) applications. The system produces a cylindrical plasma column which is 100 mm long with a diameter of 8 mm and operates with a total plasma power consumption of 70 to 200 W, depending mainly on the DC discharge current. The plasma column electron density and temperature is measured via microwave interferometry and optical emission spectroscopy. The plasma properties are investigated for Ar, Kr and Xe at pressures from 1 to 4 mbar. The system has demonstrated higher electron densities (>1019 m−3) at low pressures (<2 mbar) than has been experimentally achieved before for GPA applications. This could allow for high gain GPA operation comparable to that of conventional metallic antennas. Additionally, the source has demonstrated operation over a wide range of electron densities, from 2 × 1018 to 1 × 1019 m−3, which can allow for frequency hopping. The plasma columns electron temperature remains around 1.5 eV for argon, largely uninfluenced by the pressure or discharge current. These plasma column measurements obtained are used to analyse the plasma properties influence on GPA performance. This analysis indicates that at high density operation, a gain is achieved which is only 22% lower than that of the conventional metallic antenna. Furthermore, the density ranges demonstrated could enable wide-range frequency hopping of over 100 MHz, with a gain greater than 1.3 dBi.

Design and In-orbit Demonstration of REGULUS, an Iodine electric propulsion system

“…Moreover, the selection of COTS can be tailored to different customers' needs by means of a dedicated risk analysis. The electronics rely on a flexible architecture and they have been designed for operating REG-ULUS with an input power from 30 up to 60 W, although the nominal value is 50 W. Moreover, a simplified laboratory version of the electronics subsystem has been used in a completely different application field, namely plasma antennas [45][46][47][48]. The schematic of the electronics of REGULUS is depicted in Fig.…”

Plasma monopole antenna array

“…Taking into account the plasma source’s rigid structure and by electromagnetically shielding most of its metallic parts through an additional metallic cover, the current plasma source is considered to approximate a quarter-wave monopole antenna that is placed perpendicular against a conducting ground plane. In fact, this plasma antenna exhibits electromagnetic characteristics and operation rather close to that of a conventional metallic quarter-wave monopole antenna of similar dimensions (Daykin-Iliopoulos et al , 2020).…”

“…A single element of the antenna under consideration is based on the hollow cathode thermionic plasma source described in Daykin-Iliopoulos et al (2020) and shown in Figure 1. Its function relies on the high-density gaseous plasma column that has the substantial advantage of being able to rapidly and effectively turn ON, meaning high-density plasma with electromagnetic parameters close to that of metals, and OFF, meaning complete absence of conductive materials along the main column.…”

“…The plasma properties are measured across various positions of the gaseous plasma column (see Table 1) (Daykin-Iliopoulos et al , 2020). Based on the plasma measurements of Table 1 and the mathematical formula (1), the electromagnetic parameters are computed at different positions of the plasma column.…”

“…In this paper, we examine the function of plasma monopole antenna arrays based on the thermionic plasma sources developed in Daykin-Iliopoulos et al (2020). More specifically, we investigate different configurations of these plasma antenna arrays and multiple combinations based on whether the plasma dischargers are set ON or OFF.…”