The Effect Of Total Dose And Dose Rate On The Radiation Defects And Optical Properties Of Silica Glass

In this paper,1MeV electron andγ-ray irradiation experiment was carried out with JGS1 quartz glass,using DD1.2 high-frequency high-voltage electron accelerator and⁶⁰Co radiation source.The regulation of the spectral transmittance of quartz glass with radiation dose under different irradiation was summarized.Analyzing the types of the color centers and their accumulation procedure,the influence rule and mechanism of the dose rate on the coloring effect were discussed,and the equivalence principle and the calculation method of the electron andγ-ray irradiation were put forward.The test result shows that under the irradiation of 1MeV electrons andγ-rays,the spectral transmittance of JGS1 quartz glass changes in the ultraviolet light band less than350 nm,and the transmittance decreases monotonously with the increase of the radiation dose.Irradiation-colored quartz glass has obvious annealing effect,and the spectral transmittance gradually recovers with the extension of annealing time and temperature.The analysis of the experimental data by the absorption spectrum analysis method shows that four color center defects,oxygen deficient center（ODC）,E_γ’center,E_β’center and non-bridging oxygen hole center（NBOHC）are generated in the quartz glass after irradiation,and the absorption peak positions correspond to 6.8eV,5.8eV,5.4eV and4.8eV,respectively.the concentration of these color centers accumulates with the increase of the radiation dose,which leads to an increase in the light absorption of the quartz glass.These color centers are unstable defects and recover under annealing conditions.Among them,the E_β’center is the most unstable.While annealing at 200℃,the color center disappears quickly.The three color centers of ODC（6.8eV）,E_γ’center（5.8eV）,and NBOHC（4.8eV）have relatively higher stability.They will still maintain a certain light absorption after annealing below 300℃.But keeping enough at 400℃,The spectrum basically returned to the level before the irradiation.The irradiation dose rate has a certain influence on the coloring effect of quartz glass.Within the electron fluence rate range of 1×10¹⁰e/cm²·s～2×10¹²e/cm²·s and theγ-ray dose rate range of 4.34rad（Si）/s～500rad（Si）/s,the lower the radiation dose rate,the greater the spectral change.The generation of E_β’centers is almost not affected by the irradiation dose rate,but only related to the irradiation dose.The greater the irradiation dose,the higher the generation of E_β’centers inside the quartz glass.The concentration of NBOHC,E_γ’center and ODC is greatly affected by the irradiation dose rate.The lower the radiation dose rate,the greater the concentration of the three color centers.