What physical process causes erosion in ion thruster electrostatic accelerator grids?

Answer

Sputtering from bombardment by high-velocity ions

A critical factor limiting the lifespan of ion thrusters operating over multi-year missions is component wear caused by the very process that creates thrust. The electrostatic accelerator grids, which are perforated metal plates, are subjected to constant bombardment by the charged ions that are being accelerated out of the engine. This high-velocity ion bombardment causes a process known as sputtering, where material is gradually eroded from the grid surface. Over time, this sputtering changes the precise geometry of the grid holes, which negatively impacts the shape and direction of the ion beam, leading to reduced efficiency and, potentially, short-circuiting if the erosion becomes uneven between the plates.

What physical process causes erosion in ion thruster electrostatic accelerator grids?

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