脉冲γ射线对光纤的辐射效应

Effects of pulse Gamma-ray radiation on optical fibers

介绍了光纤的损耗机制和γ射线对光纤的辐射效应,设计了针对脉冲γ射线作用于光纤而产生辐射感生损耗的实验测量系统。利用平均光子能量为0.3 MeV、脉冲宽度25 ns、剂量率2.03×107Gy.s^-1,和平均光子能量为1.0 MeV、脉冲宽度25 ns、剂量率5.32×109Gy.s^-1的2种脉冲γ射线分别作用于多模和单模光纤,分别采用波长为405,660,850,1 310和1 550 nm的激光光纤传输系统对辐射感生损耗进行了测量。获得了光纤辐射感生损耗和辐射剂量的关系,并对实验结果进行分析。从实验结果可以看出：在近红外到可见光范围内,脉冲γ射线对光纤作用产生的辐射感生损耗随探测波长减小而增大;在0.1-3.5 Gy剂量范围内,多模光纤辐射感生损耗和辐射剂量呈线性关系。分析辐射对光纤的作用机制和实验结果后得出：光纤基质原子的电子能级对传输光子的共振吸收而造成吸收损耗增加;光纤折射率分布的改变从而导致波导损耗增加。

The general mechanism of light transmission loss in optical fiber and the effects of optical fiber under γ-ray radia- tion environment are introduced. In order to measure the pulse γ-ray radiation-induced loss, an experimental measurement system is developed. Two kinds of pulse γ-ray devices with an average photon energy of 0.3 MeV, a pulse width of 25 ns, a dose rate of 2.03×10^7 Gy · s^-1 and an average photon energy of 1.0 MeV, a pulse width of 25 ns, a dose rate of 5.32×10^9 Gy · s^-1 are em- ployed as irradiation sources in the experiment. The transient radiation-induced loss of pulsed y-ray effecting on single-mode and multi-mode optical fibers has been measured. Optical fiber transmission systems with several diHerent wavelength lasers such as 405,660,850,1 310 and 1 550 nm are involved in the experimental measurement system. The results are analyzed subsequently and show that the transient radiation-induced loss will increase as the laser wavelength shifts from near-infrared to visible regions of the optical spectrum. Within dose range of 0.1-3.5 Gy transient multi mode fiber radiation-induced loss displays a near linear dependence upon the total dose. The conclusion can be deduced that the radiation induced loss results from two comprehensive effects： It causes additional absorption loss that atomic electron energy levels resonantly absorb propagation photons in the intrinsic material, and changes of refractive index distribution lead to additional waveguide loss also.