The microstructures of pure aluminium foil and filters, irradiated with photons to various doses were investigated. The vacancy defect clusters induced by proton irradiation in both samples were characterized by transmission electron microscopy, and the density and the size distribution of vacancy defect clusters were determined. Their transmittances were measured before and after irradiating the samples by protons with energy E = 100 keV and dose of 6 x 1011/mm2. The experimental results show that the density and the size of vacancy defect clusters increase with the increase of irradiation doses in the irradiated pure aluminium foils. As irradiation dose increases, vacancies incline to form larger defect clusters. In the irradiated filter, a large number of banded void defects were observed at the agglomerate boundary, which results in the degradation of the optical and mechanical performances of the filter after proton irradiation.

Effect of Vacancy Defect Clusters on the Optical Property of the Aluminium Filter Used for the Space Solar Telescope. X.W.Cheng, Q.F.Guan, X.H.Fan, B.Chen: Chinese Physics B, 2010, 19[1], 016103