第四代光源——相干光源

物理学是自然科学的基础,物理学的发展是许多新兴学科、交叉学科、新技术的基础和前导。光子科学是物理学的一个蓬勃发展的热门分支,它的应用已经远远超过了物理学本身,延伸到天文学、化学、生物学、医学、地质学等。     

超长波荡器系统相位匹配的理论研究

波荡器是自由电子激光装置的核心部件, 如何实现超长波荡器段间相位的匹配是实现高增益X射线自由电子激光饱和输出的必要条件. 本文以北京大学973项目红外SASE自由电子激光实验装置波荡器的研制为模型, 给出了比较完整的相位匹配理论的描述, 进行了实现相位匹配的理论计算, 给出了实现段间相位匹配的具体端部结构和参数, 通过模拟计算表明, 当磁极调节范围为±0.5mm时可获得±100°的相位调整量. 该理论工作为今后高增益X射线自由电子激光超长波荡器系统总体方案的确立奠定了基础.     

Towards one machine, two purposes: using a common SC linac for XFEL and ERL simultaneously

The linac based XFEL and ERL are advanced （or, say, 4th generation） light sources, with different electron beam parameters and different advantages. However, the linac used for XFEL and ERL should provide very advanced beams with high energy, high peak and/or average current, very low emittance and low energy spread, thus making the linac very complicated and expensive. To share the XFEL and ERL advantages and save the construction-operation budget, a proposal of using a common superconducting electron linac for hard X-ray XFEL and ERL is described in this paper. The interactions between the XFEL and ERL beams via the accelerating structure are studied and the result is positive.     

Electro-optical sampling non-synchronous delay scanning measurement of electron beam bunch length at BFEL

The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser （BFEL）, the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.     

BEPC储存环磁聚焦结构的改进

本文叙述了BEPC储存环磁聚焦结构改进的原则及主要结果. 减小β_y为0.08m, 设计亮度达到2×10³¹cm^－2﹒s^－1; 提高β_x/β_y以减小插入节Q铁孔径并使储存环水平方向色差效应减小; 采用较多Q_F铁强度变量的基体, 得到了较好的消色散和较小的β函数调制, 束流稳定区达到12σ_x×12σ_y×12σ_E; 改善了主冲击磁铁之间的相位, 使之接近180°, 简化了注入凸轨系统; 在色散较大的位置上提供了四个安放发射度控制扭摆磁铁的长直线节, 在消色散区附近提供了安放同步辐射扭摆磁铁. 改进后的方案, 有利于提高低能对撞时的亮度及寄生模式和专用模式下的同步辐射应用, 以满足一机两用的要求.     

Study on the characteristics of linac based THz light source

There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation： coherent synchrotron radiation （CSR）, synchrotron radiation （SR）, low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.     

Design studies on the ERL-FEL test facility at IHEP, Beijing

A proposed compact ERL test facility at IHEP, Beijing, is presented in this paper, and includes the design parameters, the essential lattice, and the key components features, such as the photocathode DC gun and the CW superconducting accelerating structures. Some important beam physics issues such as the space charge effect, the coherent synchrotron radiation (CSR) effect and the beam break-up (BBU) effect are briefly described with the simulation results.