Investigating the impact of different ion species and materials on Electrodynamic Tether current collection efficiency

This paper describes the analysis and comparison of the electron current collection of a cylindrical tether for different variables like plasma density and temperature, plasma ion species, tether material, and applied bias. The plasma is generated by ionizing hydrogen, oxygen, and ambient air in a 50 cm × 40 cm plasma chamber. Multiple plasma densities were generated in the range 10¹⁴–10¹⁵ particles per m³ with corresponding plasma temperatures 2.5–4.3 eV. EDT materials — aluminum, tungsten, and aracon were used in the experiment to examine the material performance in the generated plasma environment and evaluate the impact on the current collected. Several observations have been made from the data collected. The I-V curves vary due to each ionized plasma, indicating the impact of ion species on the electron current. The OML model overestimates the current for each experiment run analyzed. Aracon sample exhibited superior performance when placed in oxygen and air plasma, whereas aluminium demonstrated higher I-V curves in hydrogen plasma. Plasma bubbles and secondary plasma were observed during the experiment for both positively and negatively biased tether samples. In the positively biased regime, anomalous electron current occurred for certain plasma densities. In the negatively biased regime, the ion current for hydrogen plasma was recorded to be higher than the oxygen and air plasma. It was concluded that the OML does not accurately estimate the collected current, as more complex interactions are involved.