亚皮秒精度定时系统研究

Recently, a hot spot in synchrotron radiation research is to take advantage of pump-probe experiment to make the time-resolved movies of material structure in atom-level spatial resolution. A key technology in pump-probe experiment is synchronization and adjustment of the temporal delay between pump pulse of laser and probe pulse of synchrotron radiation. Relying on the platform of Shanghai Synchrotron Radiation Facility, the applicants aim to research and design a hybrid timing system of sub-picosecond precision, moderate cost and high scalability, which takes advantage of fiber laser technology and electronics, and productize it. After expansion, the system would cover most timing requirements of large accelerator facilities, including RF signal transmission, multiple clocks distribution and pulse trigger generation. Furthermore, hopefully the timing system would be implemented in newly constructed synchrotron radiation facilities, free electron lasers and spallation neutron sources both at home and abroad. The modulated RF signal is processed by small fiber laser modules and is transmitted by network of fiber optics. Techniques of microwave radio frequency and software-defined radio are utilized to compensate the drift and jitter in RF signal with high precision. The applicants study long-term synchronized transmission of both of RF clock and timing triggers in sub-picosecond level to realize high-resolution and low-jitter synchronization and high-precision delay control with both beam and equipments in large accelerator facilities.

在原子尺度上通过泵浦-探测实验研究物质结构的动态影像，是目前同步辐射光源的研究热点。泵浦-探测实验中的一个关键技术就是泵浦激光脉冲和探针光脉冲在亚皮秒精度进行同步，并精确调整两者间的延迟。 本项目以上海光源为平台，研究和开发一套能够达到亚皮秒精度、成本适中、可扩展性强、适用于大科学装置的光纤激光与电子学混合定时系统，并将其产品化。经过扩展，这套系统可以覆盖大型加速器装置的所有定时需求，包括高频信号传输、多种时钟分配与定时脉冲触发等等，并希望在国内外新建的同步辐射光源、自由电子激光与散裂中子源等项目的得到实施和应用。 本项目通过小型激光器件和光纤网络来传输调制过的高频时钟，利用微波射频和软件无线电技术进行精确相位补偿，研究高频时钟和定时信号在亚皮秒级别精度的长时间同步传输，实现大型加速器装置中束流与设备的高分辨率、低晃动的同步和高精度的延迟控制。

随着同步辐射装置束线实验方法学的发展、以及新一代光源——自由电子激光装置的出现，皮秒级别的精度已经无法满足科学家们对定时同步的要求。在国际上各先进加速器实验室中，使用光学而非电子学方法来传递亚皮秒级别精度的定时信息。本项目在调研国际上各先进实验室相关技术的基础上，设计了一套新的亚皮秒定时系统，把高频时钟与定时事件在同一根光纤传输。此系统使用迈克尔逊干涉仪的原理实现亚皮秒级别的相位检测，并通过光学方式对相位漂移进行补偿。传统的事件定时系统集成到新的亚皮秒定时系统中，以降低定时触发的晃动。.本项目已完成高频时钟在光纤光学系统中的调制传输设计，并检测到迈克尔逊干涉的拍频信号；事件定时系统的事件流可在同一根光纤中同步传输，并且与高频时钟同步。目前，完成了系统的物理设计、模拟仿真、样机搭建与在实验室的初步测试。此系统可以应用于需要高稳定度定时信息的大型加速器装置，如同步辐射光源、自由电子激光装置与粒子对撞机等。