OXYGEN DEPLETION OF MYLAR UNDER BOMBARDMENT BY 1.0 AND 1.6 MeV PROTONS

Abstract

Oxygen losses in polyethylene terephthalate (PET, Mylar, (C10H8O4)n) samples under proton bombardment in vacuum were studied with proton energies 1.0 and 1.6 MeV, in the fluence range from 5·1012 to 2.6·1016 cm-2 at the current density 1 μA/cm2. The oxygen depletion was ivestigated in situ by proton backscattering spectrometry. The relation between oxygen content n and the fluence φ was studied for the nearsurface layer of a sample (up to 0.9 μm for 1.0 MeV proton energy, and 1.9 μm for 1.6 MeV energy). Approximation n=n0exp(-σφ) was used at the initial section of the n(φ) dependence (up to 20% oxygen content decreasing). Here σ is the oxygen depletion cross section. The measured cross section values equal 1.1·10-17 cm2 (±12%) for 1.0 MeV proton energy, and 4.2·10-18 cm2 (±15%) for 1.6 MeV energy.