10th Russian-German Conference on Electric Propulsion; Kaliningrad, April 2021

  • Compatibility of C12A7:e- electride with alternative propellants for electric propulsion.

    Malina Reitemeyer, Daniel Zschätzsch, F Michel, L Chen, S Benz, Kristof Holste, Peter J. Klar

    Abstract: A neutralizer’s performance is, among others, judged by its lifetime and the total electron current emitted from its insert. Since the extracted current mostly increases with operating temperature while the lifetime decreases, a mission-based compromise must be made. C12A7:e- is a crystalline anionic material, which allows electron emission at lower temperatures than state of the art materials due to its low work function of 2.4 eV. Following the trend towards alternative propellants, also the insert material should be compatible with as many propellant candidates as possible. In this paper we present results on the compatibility of C12A7:e- with the alternative propellants indium, iodine, bismuth, and krypton. Structural and compositional changes of the materials are studied by XPS, Raman spectroscopy and SEM imaging. Furthermore, the possible effect of surface contamination by the propellant on the work function was analyzed. The results demonstrated that the overall structural integrity of the electride was not affected by the contamination. Only the material’s surface roughness was altered by iodine and indium. No signifcant impact of alternative propellant contamination on the work function and on the electron emission properties was found.
  • Investigation of C12A7:e- under harsh conditions in relation to hollow cathode neutralizers

    Daniel Zschätzsch, Malina Reitemeyer, Limei Chen, J. Fabián Plaza, Angel Post, Peter J. Klar

    Abstract: The electride C12A7:e􀀀 is the oxygen deprived form of mayenite C12A7. The material is stable (does not oxidize) under ambient conditions, which is likely due to a thin oxidized surface layer serving as protection of the bulk of the material. When the electride is exposed to oxygen at elevated temperatures, the material starts to incorporate oxygen and loses its remarkable properties. In our experiments, the electride started to oxidize at a temperature of about 200  C. The level of oxidation was estimated by the weight gain of the samples. The rate of weight gain increased exponentially with annealing temperature in air. No oxidation was observed at an oxygen partial pressure of 9e-4mbar. Raman spectra revealed characteristic changes, which may help to estimate the free-electron concentration of the sample non-invasively.
  • Electron emissions from NACES high performance cathode based on C12A7:e- electride material for in-space electric propulsion applications

    J.F. Plaza, A. Post , J. Toledo, L. Conde

Abstract: The physical properties and characteristics of C12A7:e- material will be reviewed in the context of electric propulsion applications. The NACES cathode design incorporates this promising ceramic to produce a substantial electron flow for ion beam neutralization. Its electron emission performance has been studied in the laboratory by electrically biasing the cathode with respect to a metallic electrode. The observed dependence of these current-voltage (I-V) emission curves with the electride sample temperature will be discussed as well as future improvements in NACES cathode design in the perspective of its space applications.

Spanish-Russian Congress. November 2020

  • Plasma thrusters for in-space propulsion of satellites.

    D. Dyubo, J. González, O. Tsybin, M.A. Castillo, J. Casado and L.Conde

EPIC Workshop 2019; ESA/ESTEC, 12-23 October 2019

  • NACES cathode: High performance cathode for electric propulsion devices based on C12A7:e- electride novel material

    Fabián Plaza, Angel Post.