Klar, Peter J.Leiter, HansReitemeyer, Malina KatrinMalina KatrinReitemeyer2024-09-092024-09-092024https://jlupub.ub.uni-giessen.de/handle/jlupub/19356https://doi.org/10.22029/jlupub-18716A key component for many electric propulsion systems is the cathode or neutraliser. By combining the thermionic emission of a low work function material with a plasma environment, the device provides electrons for the thruster’s plasma and beam neutralisation. The electride material C12A7:2e- offers a low work function and good ambient stability, making it a promising candidate as a cathode insert material. In this work, Hall effect measurements, weight gain by oxidation, EPR and Raman spectroscopy are applied to electride material over a wide range of electron concentrations. In particular, the carrier densities obtained by Hall effect measurements and the reduction degree obtained from weight gain by oxidation technique correlate with features in the Raman spectrum, to be specific with the intensity ratio of the phonon band at 521 cm−1 with respect to the double band at 566 cm−1 and 610 cm−1. This allows a simple and non-intrusive assessment of sample quality based on the Raman spectrum of a sample. In addition, two cathode design concepts using disk-shaped C12A7:2e- electride inserts were tested. The first design, a thermionic plasma cathode, is successfully operated for several hours and achieves currents up to 1.4 A (1 A keeper, 0.4 A anode). Furthermore, reasons for voltage drifts and instabilities due to changes in the insert material are analysed and possible solutions identified. The second design uses a magnet to enhance gas ionisation and can be ignited at room temperature. Currents up to 70 mA are achieved. Various alternative propellants are studied, including iodine. In particular, several hundred hours of operation are performed with krypton as propellant. Insert degradation and device performance are closely monitored throughout the test.enAttribution-NonCommercial-NoDerivatives 4.0 InternationalRaumfahrtKathodenC12A7Raman Spektroskopieddc:530