Mario Panelli (CIRA)
The development plan of CIRA Electric Propulsion Program financed by PRORA, called IMP-EP1, is structured in three main lines and will develop according to: I. design and realization of the facilities (MSVC, LSVC) including the improvement of test definition and competences; II. development and improvement of basic and advanced diagnostics methodologies; III. development of design methodologies and technologies for electrical thrusters, including the set-up of a preliminary design tool, improvement of numerical modeling and post-test analyses and laboratory models manufacturing. In the frame of line III the development of a low power Hall thruster to be tested in the MSVC facility is currently ongoing. In order to design the cathode for this thruster, a preliminary numerical design tool describing the physics of orificed Hollow Cathode devices with low work function insert has been developed, combining relevant literature models2-6 with some different customized relations. A time-independent, volume-averaged model has been developed to determine plasma properties in the emitter, orifice regions. The model includes a current density equation, an ion flux balance, a plasma power balance and a plasma pressure equation. The systems of equations are solved to compute self-consistently the plasma number density, the electron temperature, the cathode voltage fall and the neutral number density. The code employs the fsolve MATLAB routine with dedicated Graphical User Interface (Figure 1) and a convergence check is performed at each iteration by comparing the evolution of the relative error until the stop condition is met. Simulated parameters have been compared with the available experimental data and trends found in the literature on existing devices2-7, showing good agreement. This parametric study of the cathode performance has assessed the dependence of the average plasma parameter on discharge current and mass flow rate, as well as on the geometry. References 1 M. Invigorito, D. Ricci, F. Battista, V. Salvatore \CIRA Roadmap for the Development of Electric Propulsion Test Facilities,” 4th SP2016, Rome, IT, 2016. 2 Domonkos, M. T., \Evaluation of Low-Current Orificed Hollow Cathodes," PhD dissertation, Dept. Aerosp. Eng., Univ. Michigan, Ann Arbor, MI, USA 1999. 3 Siegfried, D. E., \A Phenomenological Model for Orificed Hollow Cathodes," PhD dissertation, Dept.Mech. Eng., Colorado State Univ., Fort Collins, CO, USA, 1992. 4 Capacci, M., Minucci, M., and Severi, A., \Simple Numerical Model Describing Discharge Parameters in Orificed Hollow Cathode Devices," AIAA 1997-2791, 33rd JPC, Seattle, WA, 1997. 5 Albertoni, R., Pedrini D., Paganucci, F., and Andrenucci, M., “A Reduced-Order Model for Thermionic Hollow Cathodes," IEEE Trans. Plasma Sci., Vol. 41, No. 7, pp. 1731-1745, 2013. 6 Korkmaz O. and Celik M., \ Global Numerical Model for the Assessment of the Effect of Geometry and Operation Conditions on Insert and Orifice Region Plasmas of a Thermionic Hollow Cathode Electron Source,“ Contrib. Plasma Phys. Vol 54, No. 10,pp. 838 – 850, 2014. 7 D. M. Goebel, R. M. Watkins, and K. K. Jameson, \LaB6 Hollow Cathodes for Ion and Hall Thrusters,” Journal of Propulsion and Power, vol. 23, no. 3, pp.552–558, 2007.