太赫兹驱动飞秒条纹相机的关键技术研究

The time resolution of the streak camera generally marks the ultra-fast diagnose state of the art of a country. It has not been improved to lower than 100fs until now. In the analysis of free-electron lasers or study of time resolved x-ray diffraction, a streak camera with better than 100fs temporal resolution is required. This project is dedicated to study on the terahertz-driven electrons in order to make a breakthrough on the temporal resolution of the streak camera. The electrons in the streak camera will be accelerated and swept by the terahertz fields instead of the DC accelerating and waveguide deflecting with the purpose of decreasing the physical time spread and technical time spread respectively. The beam dynamics will also be employed to minimize and compensate the electrons time spread during drifting. As a result, the electron-optics design of the terahertz-driven streak tube with better than 50fs resolution will be provided. The idea of driving electrons by terahertz fields broadens the horizon for development of high performance streak cameras. It also lays the foundation for satisfying the requirements in the large scientific facilities such as the free-electron lasers and high energy photon source which are being built in china , as well as fill the requirements in other frontier sciences. In addition, combining terahertz technology with a streak camera also extends the application of terahertz technology, which will benefits from each other.

条纹相机的时间分辨往往是一个国家超快诊断技术发展水平的重要标志。到目前为止，条纹相机的时间分辨率始终没有突破100fs。基于自由电子激光、时间分辨X射线衍射等领域对百飞秒以下超快诊断技术的需求，本项目开展利用太赫兹驱动电子来提高条纹相机时间分辨的关键技术理论研究。采用太赫兹场代替传统直流加速场来降低条纹相机的物理时间弥散；采用太赫兹扫描系统代替行波偏转板来降低其技术时间弥散；同时开展条纹相机的束流动力学分析，寻找电子在漂移过程产生的时间弥散的补偿方法。完成时间分辨率优于50fs的太赫兹驱动的飞秒条纹变像管电子光学设计。利用太赫兹驱动电子为研制高时空分辨条纹相机提供了新思路，也为满足我正在建设的自由电子激光、高能同步辐射光源等大科学装置以及前沿科学领域对高时空分辨条纹相机的需求奠定基础。另外，将太赫兹技术与条纹相机相结合也拓展了太赫兹技术的应用范围，二者相得益彰。

条纹相机的时间分辨往往是一个国家超快诊断技术发展水平的重要标志。到目前为止，条纹相机的时间分辨率始终没有突破100fs。基于自由电子激光、时间分辨X射线衍射等领域对百飞秒以下超快诊断技术的需求，本项目开展了利用太赫兹驱动电子来提高条纹相机时间分辨的关键技术研究。采用太赫兹场代替传统直流加速场来降低条纹相机的物理时间弥散；采用太赫兹扫描系统代替行波偏转板来提高其技术时间分辨；同时开展条纹相机的束流动力学分析，寻找电子在漂移过程产生的时间弥散的补偿方法。基于此设计了一种全太赫兹场驱动的条纹变像管，时间分辨率优于40fs，静态空间分辨率优于159lp/mm，动态空间分辨率优于28lp/mm。并从理论上深入分析了加速区的时间弥散与电子脉冲发射时刻以及初始时间弥散的关系，精确调控太赫兹场与电子束的相位匹配，有效抑制了时间畸变。详细讨论了空间电荷效应对时间弥散的影响。设计优化了加速区和偏转区的太赫兹脉冲耦合增强装置，太赫兹脉冲电场在该装置中的增强系数最高可达9.39，将加速场、扫描场的场强比传统条纹相机的驱动电场分别提高了接近一个数量级。该技术可用于飞秒时间尺度超快动力学、自由电子激光、时间分辨X射线衍射等领域的研究，也有潜力应用于发展阿秒超快诊断技术，使得人类能够不断向微观超快极限世界探索。