In-Situ Diagnostic of Channel Erosion in Hall Thrusters

In this work, we introduce a design of a high-resolution optical diagnostic system for in situ monitoring and measurements of wall erosion in electric propulsion devices. Focused on addressing erosion in Hall thrusters, we explore a recently proposed strategy of the accelerated erosion test which exploits the angular dependence of the ion-induced sputtering yield to enhance erosion of micropatterned channel walls. The developed erosion diagnostic incorporates a Long-Distance Microscope (LDM), positioned outside the vacuum chamber to simplify operation. It achieves a narrow in-focus range over distances greater than 1 meter, enabling the use of a shape-from-focus algorithm for 3D object geometry reconstruction with resolutions in the tens of micrometers. Initial tests utilized a boron nitride target with wall pattern optimized for maximum erosion rates. The target was exposed a 600 eV ion beam generated by a gridded ion source. The LDM setup was validated by comparing measurements of the uneroded target with the 3D computer design model data. In this initial test, a resolution of about 70μm was achieved.