Topic/Type: 1.6 Plasma-based devices, Poster

Self consistent kinetic simulations of SPT and HEMP thrusters including the near-field plume region

K. Matyash1, R. Schneider1, A. Mutzke1, O. Kalentev1, F. Taccogna2, N. Koch3, M. Schirra3

1 Max-Planck-Institut f?r Plasmaphysik, EURATOM Association, Greifswald, Germany
2 Istituto di Metodologie Inorganiche e di Plasmi IMIP-CNR, Sect. Bari, Bari, Italy
3 THALES Electron Devices GmbH, Ulm, Germany

SPT (Stationary Plasma Thruster) and HEMP (High Efficiency Multistage Plasma) [1] thrusters are both relying on the creation of propulsive ion beams by ionization of propellant atoms. The specific shape of the magnetic fields in both concepts is used to optimize efficiency and ion acceleration.
In this work Particle-in-Cell simulations with Monte Carlo collisions (PIC-MCC) are used to compare the two different thruster concepts. The computational model resolves 2 spatial (rz) and 3 velocity components (2d3v). It includes the relevant collisional processes: electron-neutral elastic, ionization and excitation collisions, ion neutral momentum- transfer and charge exchange collisions. The secondary electron emission (SEE) module included into the simulations enables us to self-consistently resolve the anomalous electron transport due to near wall conductivity. For both thrusters the computational domain is extended beyond the discharge channel and includes the near-field plume region.
The two thruster concepts result in quite different plasma-wall interaction characteristics. The SPT thruster relies on the strong secondary electron emission from the dielectric walls of the thruster channel, which causes a large ion flux over the whole channel surface and consequently high erosion rate [2]. In contrast, in the HEMP thruster the plasma contact to the wall is limited only to very small areas of the magnetic field cusps, which results in much smaller ion flux to the thruster channel surface as compared to SPT. Consequently, experimental studies of HEMP gave no evidence of erosion [3].
In order to study the wall erosion for both thrusters, the binary collision approximation (BCA) based Monte-Carlo code SDTrimSP [4] is applied, taking as input the ion flux spatial-energy-angle resolved distributions self-consistently calculated with PIC MCC.

[1] N. Koch, H.-P. Harmann, G. Kornfeld , Status of the THALES High Efficiency Multi Stage Plasma Thruster Development for HEMP-T 3050 and HEMP-T 30250, Proceedings of the 30th IEPC, 17-20 Septemper, 2007, Florence, Italy.

[2] C. E. Garner, J. E. Polk, K. D. Goodfellow, and J. R. Brophy, Performance Evaluation and Life Testing of the SPT-100, IEPC-93-091, Proceedings of 23rd International Electric Propulsion Conference, Seattle, WA, 1993 (Electric Rocket Propulsion Society, Worthington, OH, 1993).

[3] N. Koch, H.P. Harmann, G. Kornfeld, ?Development and Test Status of the Thales High Efficiency Multistage Plasma (HEMP) Thruster Family?, Proceedings of the 29th International Electric Propulsion Conference, Princeton, 2005, IEPC-2005-297.

[4] W. Eckstein, R. Dohmen, A. Mutzke, R. Schneider. SDTrimSP: A Monte-Carlo Code for Calculating Collision Phenomena in Randomized Targets, IPP 12/3, 2007.