太赫兹电磁波是当前国内外研究的热点，太赫兹辐射源是太赫兹技术发展的关键。作为重要的真空电子学辐射源，线性注器件在太赫兹频段的一个主要障碍是起振电流密度过大。为降低起振电流，本项目提出在原来器件慢波结构的前端增加一段低频工作的慢波结构对电子注进行预群聚，经过预群聚的电子注中包含丰富的高次谐波分量，若第二段慢波结构的工作频率处在某次谐波附近，其起振电流将显著降低。本项目拟采用理论分析，计算机仿真，以及实验验证的方法，对该类器件的工作机理（包括注波互作用机制，辐射条件）以及其中的关键物理问题（包括电子注过群聚，模式竞争等）进行深入研究，揭示其辐射强度、工作稳定性随谐波分量、工作电流及结构尺寸等参数的变化规律。项目将构思并建立一种紧凑实用的两段慢波结构辐射源实验模型，搭建实验平台并开展原理验证性实验，为发展该类新型太赫兹源提供理论指导和实验基础。

Terahertz (THz) wave radiation is one of the most attractive topics to researchers from all over the world, and THz radiation source is the key for THz science and technology. The main obstacle for the linear beam device, an important vacuum electronic radiation source, to be as THz source is the requirement of intense starting current density (SCD). In order to reduce SCD, this program propose to add another slow-wave structure, section-I, to pre-modulate the electron beam, which will contains lots of high harmonics after pre-modulation. And SCD in the second section (section-II) will be significantly reduced provided that its operation frequency is one of the harmonics. By means of theoretical analyses, numerical simulations, and experimental verification, this program will research the mechanism of the beam-wave interactions and the key problems, such as over-bunching and mode competition, of this kind of device. The correlations that the radiation power and stability depend on the harmonics, beam current and structural parameters will be uncovered. The program will also propose a compact device mode and perform experimental verification. The studies in this program will put a solid theoretical and experimental base for the development of this kind of THz radiation source.