脉冲γ射线对光纤辐射效应研究

Optical fibers have many advantages over metallic lines such as broad bandwidth, low-loss, immunity from interference due to electromagnetic induction, etc. They can be used to implement ultra-fast pulse signal transmission over a long distance under the circumstance with sophisticated electromagnetic radiations. However, while optical fibers are exposed in nuclear radiation environments, changes in their optical properties will occur thus resulting in deterioration of system performance eventually. It is very significant to study the effects of radiation on optical fibers for the design and anti-radiation reinforcement of optical fiber signal transmission systems and radiation detecting systems. In this project the effort will be focused on the calculation of the effect sections of Compton, photoelectric, electron pairs and scattering, the distribution of resulting electronic energy and intensity, the changes of refractive index in optical fibers with free elections in the core, the design of transient optical fiber transmission system and the experimental measurements of additional radiation-induced absorption and waveguide losses. An attempt to explore the mechanism of additional loss and luminescence will be processed by comparing the theoretical results with the experimental data. The research results would be used to evaluate the deterioration degree of optical fiber system performance and their working lives under nuclear circumstance, and to search methods for reducing radiation-induced loss such as the development of anti-radiation optical fibers. In addition, nuclear radiation detecting systems based on optical fiber properties changes would be established to monitor the ambient radiation doses of underground nuclear exploders, space-aircrafts, radiation reactors and other nuclear facilities.

光纤与同轴电缆相比具有传输频带宽、损耗低、抗电磁干扰能力强等优点，适用于复杂电磁环境中的超快信号传输，然而在核辐射环境下光纤性能的变化必将影响系统的信号传输能力。开展核辐射对光纤的效应研究，对于光纤系统的设计和抗辐射加固、利用光纤开展核辐射探测研究具有重要的意义。本项目开展脉冲γ射线对光纤的辐射效应研究，分析计算γ射线对光纤的康普顿、光电、散射和电子对效应随光子能量的变化，次级电子密度及角度分布，辐射感生吸收损耗、波导损耗的产生机理以及与辐射剂量的关系，辐射致光纤发光的产生机理及光谱随辐射剂量的变化。研制可用于脉冲辐射感生损耗以及荧光的测量系统，利用大型辐射模拟装置开展辐射感生损耗和辐射致发光测量实验，并将实验结果与理论计算结果进行对比分析。为预估脉冲辐射对光纤系统性能影响、寻求减小辐射对光纤影响的方法提供理论分析和实验数据；同时为开展利用光纤探测核辐射研究提供技术准备。

光纤与同轴电缆相比具有传输频带宽、损耗低、抗电磁干扰能力强等优点，适用于复杂电磁环境中的超快信号传输，然而在核辐射环境下光纤性能的变化必将影响系统的信号传输能力。开展核辐射对光纤的效应研究，对于光纤系统的设计和抗辐射加固、利用光纤开展核辐射探测研究具有重要的意义。本项目开展脉冲γ射线对光纤的辐射效应研究，分析计算γ射线对光纤的康普顿、光电、散射和电子对效应随光子能量的变化，次级电子密度及角度分布，辐射感生吸收损耗、波导损耗的产生机理以及与辐射剂量的关系，辐射致光纤发光的产生机理及光谱随辐射剂量的变化。研制可用于脉冲辐射感生损耗以及荧光的测量系统，利用大型辐射模拟装置开展辐射感生损耗和辐射致发光测量实验，并将实验结果与理论计算结果进行对比分析。. 项目组完成了光纤辐射感生吸收损耗相关理论分析及模拟计算；开展了光纤波导中的电磁场传输理论分析；完成了脉冲γ辐射光纤的瞬态感生损耗测量系统设计；建立了块状融石英材料在Co60γ辐射作用下折射率变化的测量系统；开展了光纤波导中的电磁场传输理论分析及γ射线对块状融石英材料及光纤光栅折射率的影响实验；模拟并验证了光纤色散系数随辐射剂量变化规律；建立传输系统并开展脉冲γ辐射对光纤的感生损耗测量；完成了经受脉冲γ辐射的光纤永久性损耗及折射率变化测量；开展了掺杂光纤的γ辐射性能测量。. 通过以上工作，项目组建立完善了相应的理论模型，解决了一系列科学问题，得到了测量系统关键参数，为预估脉冲辐射对光纤系统性能影响、寻求减小辐射对光纤影响的方法提供理论分析和实验数据，同时为开展利用光纤探测核辐射研究提供技术准备。