| In this paper, damage mechanism of electron and proton exposures on ZnO powders was studied by anlyzing the change of spectral reflectance. In proton irradiation tests, the flux was chosen as 5×1011cm-2·s-1, the energy was 90keV and the fluence was varied in the range of 1×1015cm-2 2×1016cm-2. In electron irradiation tests , the flux was 1×1012cm-2·s-1, the energy was 70keV110keV, and the fluence was varied in the range of 1×1015cm-22×1016cm-2. In simultaneous irradiation tests, the electron flux was 1×1012cm-2·s-1, the electron energy 90keV, the electron fluence 3×1015cm-2; the proton flux 5×1011cm-2·s-1, the proton energy 90keV and proton fluence 3×1015cm-2 .Experimental results shows that spectral reflectance decreases with the increase of fluence for ZnO powders under proton exposure. The optical degradation is dependent upon proton fluence. Under the proton exposure, the optical degradation occurs mainly in the visible region. Surface morphology analysis shows that after the proton exposure, the surface colour becomes yellow obviously. With the increase of the proton fluence, the yellow colour becomes deeper. Photoluminescence spectrum analysis shows that after proton exposure, a large amount of point defects is generated in the ZnO samples, which is the main cause of the obvious optical degradation in the visible region.Under the electron exposure, the color of the sample did not change a lot. But photoluminescence spectrum results shows that a great number of VZn and Zni are generated. It is the reason for the decline of spectral reflectance.Under the simultaneous exposure of electron and proton, the ZnO powders becomes yellow. Experimental results shows that the optical degradation is mainly induced by the proton exposures. A synergistic effect is presented in the simultaneous exposure. The synergistic effect reduces the tendency of optical degradation. There is a difference between the simultaneous exposure and the consecutive exposure.
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