Study Of The Irradiation Effects On Sapphire Optical Window Growth By SAPMAC

The optical window of sapphire will be irradiated by rays and ion beam during it's service, such asγ-ray and electron flow. The optical capability will be reduced. We choose the typicalγ-ray and electron flow to irradiate optical window of sapphire grown by SAPMAC method and changes in optical and structural properties were investigated in this paper.The PIXE result indicates that the sapphire grown by SAPMAC method has low impurity content. AFM showsγ-ray has a little impact on the surface roughness of sapphire, however electron flow damage the surface roughness of sapphire more greatly. The absorption spectra and fluorescence spectra of large sapphire irradiated byγ-ray and electron flow was measured. The experimental results show there are some absorption peaks of 206 nm, 238 nm and 256 nm; the fluorescence spectra correspond to these peaks are 410nm, 480nm and 506nm. Further study suggests the color centers are cause by the presence of oxygen vacancy (F and F+). The EPR display that there are F+ color centers in sapphire after irradiated byγ-ray and electron flow. Because of the concentration of F3+ in sapphire is low, so there isn't any signal in the EPR spectra. And Fe3+ and Cr3+ signal was also not detected in EPR spectra. The results of TL reveal that there are new peaks at 216℃,219℃and 223℃induced byγ-ray and new peaks at 223℃and 242℃are induced by electron flow. The peaks at these temperatures are due to F color centers in sapphire and the intensity of these peaks is high and stabilized. The analysis of PAT announces that after irradiated byγ-ray and electron flow the positron life ofτ1 changes a little, whereas after irradiated by electron flow the positron life ofτ1 changes greatly. Along with the increase of the dose ofγ-ray and electron flow, the concentration of defects in sapphire also increased.Measures to bring down the concentration of color centers in sapphire are also proposed. After 3h of annealing in air, there is no obvious signal detected in the absorption spectra.