Objective
The aim of the proposed project is to develop a methodical approach for new ceramic selection for Hall Plasma Thrusters (HPT), aimed at guaranteeing the increasing of thrusters lifetime. The new approach will take into account not only the ionisation efficiency of the ceramic material, but also its resistance to sputtering and some of its functional properties such as the secondary electron emission.
Ceramic erosion is one of the main wearing mechanisms of Hall thrusters, limiting at a significant extent their lifetime. In this frame, the development of new ceramic materials with improved characteristics of resistance to sputtering is one of the main scientific challenges for Hall thrusters. Moreover, physical surface properties, such as secondary electron emission, have a strong functional impact on Hall thrusters operation. Thus, a new selection method for ceramic materials has to take into account not only the ionisation efficiency and the resistance to sputtering but also the secondary electron emission properties.
It is intended to examine a wide number of problems concerning: new ceramic composition selection, measurement of erosion performances, accelerated tests of ceramic samples, analysis of surface layers condition.
Specific tasks to be fulfilled will be:
- To develop a procedure of accelerated test, permitting to measure the ceramic erosion resistance under realistic operation conditions;
- To measure ceramic samples sputtering rate under realistic operation conditions;
- To measure ceramic samples erosion resistance ability under realistic operation conditions.
The goal of the investigation is to select a material with the higher erosion resistance against ion sputtering under HPT operation conditions. In this framework it is intended to investigate ceramic material of x*BN - y*Si3N4 type with different content of components.
Based on the analysis of preliminary test results, it is here proposed to select two ceramic types that seem more promising from the erosion resistance point of view and test them under realistic operation conditions. Ceramic samples to be extensively tested will be selected on the basis of sputtering rate and emission performances. The criterion of selection will be a trade off between the best erosion resistance ability in combination with sufficiently intense secondary electron emission.
A number of ceramic samples will be subjected to simulation testing and real-environment testing: the results of these tests, in particular the analysis of the impact of real operation condition on the surface layer composition and structure will allow to better understand mechanisms of plasma flow interaction with ceramic materials. The results of the test campaign will allow defining a procedure of accelerated tests permitting to select proper ceramic materials for ion-plasma devices.
Topic(s)
Call for proposal
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PISA
Italy