Control of defect generation in pure quartz

The effects of the manufacturing method and the effects of Cl and OH was studied on the defects of pure quartz fiber, resulted that the cause of the induced loss in OHC, and OHC is lowest in quartz manufactured by VAD method. The control of defect generation in VAD method was investigated experimentally. The purposes were to find out relations between i) defects and oxygen content ii) defects and dehydration process, and iii) defects and sintering condition. In experiment i) 3 kind of soot were prepared by changing oxygen content in synthesizing atmosphere, but no significant difference was recognized. In experiment ii), the effects of Cl in drying process were tested, but no differences were observed in specimens irradiated in room temperature by ESR spectrum. In experiment iii), it was found that the higher the sintering temperature, the more remarkable the structural dispersion. The generation of H0 by γ-ray irradiation is depressed with no regard to OH content. The ESR intensities of E'-center and OHC by γ-ray irradiation decrease following the rise of sintering temperature. The relation between induced loss and temperature agree with the changes of OHC and H0. Based on these experiment, investigations on mechanism of defect generation, and the control of defect generation relating to sintering condition including atmosphere, temperature and cooling rate, are scheduled. (Ishimitsu, A.)