Impact of Plasma Dynamics on Electrodynamic-Tether Current Collection: Experimental Analysis and Comparative Study

Abstract

This study conducts an experimental investigation to analyze and compare the electron current collection of a cylindrical electrodynamic tether under various simulated plasma conditions. The current-voltage (I-V) characteristics of electron current collected by a cylindrical tether sample were examined for different tether materials, plasma densities and composition, and tether biasing levels. Three plasma gases—hydrogen, oxygen, and ambient air were used to simulate plasma conditions within a plasma chamber at ANU, SP3 group measuring 50 cm by 40 cm. Plasma densities range from 1014- 1015 particles m, with plasma temperatures between 2.5 and 4.3 eV, are simulated. The current collected for different tether materials - Aluminum, Tungsten, and Aracon biased from -80V to 80V peak to peak, enabling a detailed examination of current collection under positive and negatively charged tether. The comparison between experimental data and theoretical Orbital-Motion-Limited (OML) models showed that tethers exposed to air and oxygen plasma displayed values more consistent with theoretical predictions, particularly at higher applied voltages. The exper-imental results showed discharges in all tether samples at high positive biasing, with Aracon sample collecting higher currents in oxygen and air plasma than other samples despite having the lowest current collection area. Among the tether materials tested, the Aracon sample performed a superior performance for the simulated plasma, indicating the e iciency of the braided tether. Results unveiled discharges in all tether samples, with tungsten exhibiting the most dis-charges at peak positive voltages, particularly excelling in Oxygen and Air plasma compared to Hydrogen plasma. The study additionally found secondary plasma formation, indicating the complicated interaction between tether material and the surrounding plasma environment.