ATOMIC OXYGEN BEAM SOURCE FOR ORBITAL ENVIRONMENT EXPERIMENTS

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Abstract
We describe a new system for the production of high flux neutral beams of low energy (5-10 eV) atoms, for use in beam-surface interaction and surface modification studies. This source can recreate the flux of superthermal atomic oxygen and other neutral species to which spacecraft surfaces are exposed in low Earth orbit. The system is based upon a magnetically confined (3-4 kG) co-axial plasma source driven by 1 kW RF at 2.45 GHz. The beam is. produced by the acceleration of plasma ions onto a negatively biased plate of high-Z metal (Mo or Pt); the ions are neutralized and reflected by the surface, retaining a large fraction of their incident kinetic energy, forming a beam of superthermal atoms. The source can provide neutral flux > 5 × 10 16 /cm2 s and fluence > 1020 cm2 in a five hour exposure. Such a high fluence source can provide accelerated simulation testing of materials and coatings for space applications. To date, samples of carbon film, carbon-based paint (Z-302), Kapton, mylar, teflon, and photoresist have been exposed to atomic O beams. These samples show effects quite similar to those observed after exposure in orbit on the Space Shuttle.

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