Radio frequency oxygen plasma Asher is a simulation facility widely used for many years as materials screening tool for LEO applications.
The complex plasma environment, which contains, in addition to the neutral oxygen atoms, excited species, electrons, and ions as well as vacuum ultraviolet (VUV) radiation, might lead to some deviations or uncertainties in determination of materials reactivity with respect to LEO.
However, it was shown numerous times that this test is more severe than the fast atomic oxygen (FAO) beam testing, and this was fully confirmed by a study at ITL for 67 worldwide selected space-flown materials in plasma Asher and fast atomic oxygen facilities.
A plasma Asher that is used for creating atomic oxygen environment. A set of samples that are being exposed in the Asher are shown in the right image.
The materials that withstand O-plasma Asher testing survived FAO beam testing, but the wise versa is not always the case. Providing O-plasma testing at ITL is done with special care, like avoiding plasma under-cutting, using pure oxygen plasma instead of air plasma, used widely, the temperature control can be offered by using special temperature sensor strips placed under the materials samples, etc. Examples of surface morphology of some space materials after O-plasma Asher testing are shown below.
Images of the surface of a Kapton 500HN sample after an exposure to atomic oxygen plasma to a fluence of 1.26E21 at/cm2
Images of the surface of a Polyamide (Nomex®) fiber lacing tape sample shown in the insert) before and after exposure to atomic oxygen plasma to a fluence of 1.1E20 at/cm2