基于CT算法的束团横向相空间测量

精确测量束团的发射度和横向相空间, 在高亮度电子束的产生和应用中具有重要意义. 传统测量方法在测量发射度时需要对束团在相空间内分布进行初始假设, 且只能给出相椭圆的twiss参数;基于CT(computerized tomography)算法的束团横向相空间测量方法无需先验假设, 能给出粒子在相空间内的真实分布, 测量结果更为精确. 介绍了基于CT算法的束团横向相空间测量的原理和初步实验结果, 并与四极透镜扫描法测量的结果进行了比较.     

衍射辐射及其在电子束诊断中的应用

衍射辐射是由于运动的带电粒子遇到随空间变化的电介质而由感应电流产生的一种辐射. 衍射辐射由于其非阻拦性, 多参数性, 可在线性, 非常适合下一代对撞机和第四代光源的电子束诊断. 简要介绍了其物理机制, 系统的讨论了其在电子束诊断中的应用.     

First experimental research of the bunch compressor at CAEP

Magnetic bunch compressor is one of the key technologies on the path to next generation accelerator driven facilities. In this paper we report the design principles and the first experimental research of the bunch compressor developed at Chinese Academy of Engineering Physics （CAEP）. The length of the bunch after compressor is found to be about 0.7 ps （rms） and the peak current exceeds 500 A when operated in the optimized condition. The sensitivity of the bunch length on the phase of the acceleration field and magnetic field of the bunch compressor was also measured and analyzed.     

清华大学汤姆逊散射超短脉冲X射线源研究

 介绍了清华大学加速器实验室近年来关于汤姆逊散射超短X射线源的研究工作;研究了在任意散射角度下电子束参数和激光束参数对散射光子参数的影响,给出了散射光子的参数如光子产额、脉冲长度、时间抖动等与电子束参数、激光束参数和散射角度的关系;利用实验室已有的16 MeV反波行波加速器与中国工程物理研究院激光聚变研究中心提供的ns调Q激光搭建了汤姆逊散射初步实验平台并开展了实验研究;加工了1.6-cell光阴极微波电子枪,搭建了高功率实验平台,对产生的电子束参数进行了初步测量;对汤姆逊散射超短X射线源进行了设计并开展了相关的平台建设工作,对产生的X射线脉冲参数进行了模拟。     

A simulation study of Tsinghua Thomson scattering X-ray source

Thomson scattering X-ray sources are compact and affordable facilities that produce short duration, high brightness X-ray pulses enabling new experimental capacities in ultra-fast science studies, and also medical and industrial applications. Such a facility has been built at the Accelerator Laboratory of Tsinghua University, and upgrade is in progress. In this paper, we present a proposed layout of the upgrade with design parameters by simulation, aiming at high X-ray pulses flux and brightness, and also enabling advanced dynamics studies and applications of the electron beam. Design and construction status of main subsystems are also presented.     

A multi-length bunch design for electron storage ringswith odd buckets

A scheme with two superconducting RF cavities is designed to upgrade electron storage rings with odd buckets to multi-length bunches. In this paper, the Hefei Light Source Ⅱ (HLS Ⅱ) is given as an example for odd buckets. As it is designed for 45 buckets, which is a multiple of 3, simultaneous generation of three different lengths of bunches is proposed with the presently applied user optics. The final result, without low-α optics, is to fill HLS Ⅱ with long bunches of length 50 ps, medium bunches of 23 ps and short bunches of 6 ps. Every third bucket can be filled with short bunches, of which the current limit is up to 6.6 mA, more than 60 times the limit for low-α mode. Moreover, particle tracking simulations to examine the beam dynamics, performed by ELEGANT, and calculations of the beam instabilities are presented in this paper.     

First Beam Measurements of the S-Band photocathode Radio-Frequency Gun at Tsinghua University

During the last decades, photocathode rf gun has been proven to be successful in generating the high brightness electron beam （-lnC,-lπ mmmrad,-l ps） which is required by the ILC, XFEL, Thomson scattering x-ra y source, etc. A photocathode rf gun system is built to develop electron source for the Thomson scattering x-ray source at Accelerator Laboratory of Tsinghua University. The system consists of a BNL/ATF-type 1.6 cell S-band rf cavity, a solenoid for emittance compensation, a laser system and some simple equipments for beam diagnosis. The first beam measurements of the photocathode rf gun, including the dark current, transverse beam profile, charge and quantum efficiency, are reported.     

A simulation study of Tsinghua Thomson scattering X-ray source

Thomson scattering X-ray sources are compact and a?ordable facilities that produce short duration, high brightness X-ray pulses enabling new experimental capacities in ultra-fast science studies, and also medical and industrial applications. Such a facility has been built at the Accelerator Laboratory of Tsinghua University, and upgrade is in progress. In this paper, we present a proposed layout of the upgrade with design parameters by simulation, aiming at high X-ray pulses flux and brightness, and also enabling advanced dynamics studies and applications of the electron beam. Design and construction status of main subsystems are also presented.     

超快电子衍射装置的束流能量反馈控制

上海交通大学的超快电子衍射(UED)装置由一台电子直线加速器作为驱动,电子枪为一台光阴极微波电子枪。加速器在运行中电子枪会偶尔打火,腔体失谐,造成束流损失,束流能量产生变化,束流需要很长时间才能恢复到初始状态,影响了用户的使用。为此,对低电平控制器(LLRF)的幅度相位控制环路进行了改进,增加了能量反馈,代替了幅度反馈,通过对束流的中心位置进行实时的反馈以控制低电平控制器输出信号的幅度,保证了电子束流的能量稳定和电子枪加速场强的稳定。长时间的稳定性测试表明,电子枪在打火产生时,束流能量可以很快恢复,能量抖动由4.2933×10^-4(RMS)提高到2.8557×10^-4(RMS),实现了束流能量的长期稳定。     

Time-Resolved Visualization of Laser-Induced Heating of Gold with MeV Ultrafast Electron Diffraction

Time-resolved electron diffraction employing MeV electron beams is demonstrated experimentally at the center for ultrafast diffraction and microscopy of Shanghai Jiao Tong University. A high-quality diffraction pattern is recorded by a single shot of electron pulse. Synchronization between the pump laser and the probe electron beam is achieved through measurement of electron deflection caused by the laser-induced plasmas in a metal tip. We study the ultrafast structural dynamics of the gold lattice excited by a femtosecond laser through tracing the change of Bragg peaks intensity at different time delays. It is expected that the combination of MeV ultrashort electron beams and femtoseeond laser pulses will open many new opportunities in the ultrafast and ultrasmall world.