Approaches to modeling the process of erosion products deposition on the gas discharge chamber walls of an ion engine

DOI: 10.34759/trd-2022-124-08

Аuthors

Cherkasova M. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: maria-post@mail.ru

Abstract

Currently, many tasks of space exploration use ion engines, including high-frequency ion thrusters. At the same time, special attention is paid to the terms of active engine operation. In the design of a ion thruster, the ion beam is extracted from the discharge plasma and accelerated using an electrode system operating on the principle of electrostatic lenses. The accelerating electrode of such system is subject to erosion due to bombardment with exchange ions. Electrode damage results in engine performance change for two reasons. Changing the electrode configuration worsens the characteristics of the ion beam and also the sprayed electrode material penetrates the discharge chamber and settles on its walls, changing the discharge characteristics. Extensive theoretical and experimental studies have been devoted to the erosion of the accelerating electrode itself, while the problem of deposition of sprayed material on the walls of the gas discharge chamber has not been practically investigated.

This paper proposes a physical and mathematical model for depositing sputtered atoms of accelerating electrode material on the walls of a gas discharge chamber of a high-frequency ion engine. Two-dimensional model of spatial sputtering of accelerating electrode surface by exchange ions and interaction of sputtered material atoms with primary beam ions is considered. Possible ranges of emission angles of sprayed atoms penetrating inside the discharge chamber through the holes of the emission electrode are estimated.

Based on the created model, calculation of the accelerating electrode erosion of the two-electrode ion-optical system with the accelerating electrode from molybdenum was carried out. In the first approximation, the penetration of sprayed molybdenum atoms into the plasma of the discharge chamber was simulated. An estimate of the distribution of polluting atoms over the conditional model surface was obtained. Quantitative estimates of surface contamination rate have been made.

The developed physical and mathematical model of processes will allow in the future to create an engineering methodology for calculating the dynamics of deposition of sprayed material on the walls of the gas discharge chamber of a high-frequency ion engine. The use of such a technique will reduce the time of life tests and better predict the change in engine performance for long service life.

Keywords:

high frequency ion thruster, accelerating electrode, erosion, sputtering indicatrix, threshold energy, impurity deposition, gas discharge chamber contamination

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