Longitudinal electron bunch length plays a significant role in single-pass free-electron lasers(FEL), as the high-gain FEL process depends strongly on the high peak current of electron bunches. Longitudinal electron b...Longitudinal electron bunch length plays a significant role in single-pass free-electron lasers(FEL), as the high-gain FEL process depends strongly on the high peak current of electron bunches. Longitudinal electron bunch length was measured by detecting the interferogram of coherent transition radiation generated by electron bunches using a THz interferometer and a Golay cell(spectral range0.02-20 THz) at Shanghai X-ray free-electron laser. The detailed process of measurement and data analysis are discussed herein. Furthermore, the electron bunch length was estimated based on the dispersive strength R_(56) of the bunch compressor and the energy spread δ of electron bunches, which were obtained via experiments. The comparison showed that the measured bunch length was consistent with the estimated bunch length.展开更多
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 pres...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.展开更多
RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment...RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment. Detailed discussion and calculation for measuring the 3.5 MeV bunch and another with further acceleration to 50 MeV, which is under development, are presented. A standing-wave deflecting cavity working at 2856 MHz is designed and the power feeding system has been planned.展开更多
We consider a scheme to generate a sub-picosecond electron bunch in the photocathode rf gun by im-proving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleratio...We consider a scheme to generate a sub-picosecond electron bunch in the photocathode rf gun by im-proving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric.展开更多
An RF deffecting cavity used for bunch length measurement has been designed and fabricated at Tsinghua University for the Thomson Scattering X-Ray Source. The cavity is a 2856 MHz, π-mode, 3-cell standing-wave cavity...An RF deffecting cavity used for bunch length measurement has been designed and fabricated at Tsinghua University for the Thomson Scattering X-Ray Source. The cavity is a 2856 MHz, π-mode, 3-cell standing-wave cavity, to diagnose the 3.5 MeV beam produced by photocathode electron gun. With a larger power source, the same cavity will again be used to measure the accelerated beam with energy of 50 MeV before colliding with the laser pulse. The RF design using MAFIA for both the cavity shape and the power coupler is reviewed, followed by presenting the fabrication procedure and bench measurement results of two cavities.展开更多
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 com...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.展开更多
电子束团长度是束流诊断中的重要参数,基于相干渡越辐射(Coherent Transition Radiation,CTR)的测量方法是一种简单易行的高时间分辨率测量方法。本文调研并分析了不同电子束团长度测量方法的优缺点,选择基于CTR方法作为主要研究方向,...电子束团长度是束流诊断中的重要参数,基于相干渡越辐射(Coherent Transition Radiation,CTR)的测量方法是一种简单易行的高时间分辨率测量方法。本文调研并分析了不同电子束团长度测量方法的优缺点,选择基于CTR方法作为主要研究方向,主要针对上海深紫外自由电子激光实验装置(Shanghai Deep Ultra-Violet Free Electron Laser,SDUV-FEL)和X射线自由电子激光试验装置(Shanghai X-ray Free Electron Laser,SXFEL)进行了实验方案设计和模拟分析。结果表明,通过合理的参数选择和方案优化,用该方法可对飞秒至皮秒范围内的束团长度进行测量,时间分辨率能到达飞秒量级,满足SDUV-FEL的实验需求和SXFEL的工程需求。展开更多
红外波段自由电子激光的小信号增益大小以及饱和功率对束流的能散非常敏感。为满足远红外自由电子激光对能散的要求,在合肥光源栅控直流高压电子枪的基础上,模拟了一种热阴极微波栅控直流高压电子枪。微波栅控直流高压电子枪采用微波栅...红外波段自由电子激光的小信号增益大小以及饱和功率对束流的能散非常敏感。为满足远红外自由电子激光对能散的要求,在合肥光源栅控直流高压电子枪的基础上,模拟了一种热阴极微波栅控直流高压电子枪。微波栅控直流高压电子枪采用微波栅控的方法,控制和压缩阴极引出电子束团的长度。再通过直流高压对电子加速后,在电子枪的出口可以得到量级为几十皮秒的束团。本文使用SUPERFISH、POISSON分别进行栅控微波场与高压电场优化计算,PARMELA(Phase And Radial Motion in Electron Linear Accelerators)进行束流跟踪与分析,得到一组能满足红外自由电子激光需求的电子枪参数。展开更多
基金supported by the National Program on Key Basic Research Project(No.2016YFA0401900)the Ministry of Science and Technology of China
文摘Longitudinal electron bunch length plays a significant role in single-pass free-electron lasers(FEL), as the high-gain FEL process depends strongly on the high peak current of electron bunches. Longitudinal electron bunch length was measured by detecting the interferogram of coherent transition radiation generated by electron bunches using a THz interferometer and a Golay cell(spectral range0.02-20 THz) at Shanghai X-ray free-electron laser. The detailed process of measurement and data analysis are discussed herein. Furthermore, the electron bunch length was estimated based on the dispersive strength R_(56) of the bunch compressor and the energy spread δ of electron bunches, which were obtained via experiments. The comparison showed that the measured bunch length was consistent with the estimated bunch length.
基金Supported by National Natural Science Foundation of China (10575116)
文摘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.
基金National Natural Science Foundation of China (10775080)
文摘RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment. Detailed discussion and calculation for measuring the 3.5 MeV bunch and another with further acceleration to 50 MeV, which is under development, are presented. A standing-wave deflecting cavity working at 2856 MHz is designed and the power feeding system has been planned.
基金Supported by National Natural Science Foundation of China(11205152)Science Foundation of Ministry of Education of China("985 project":173123200402002)
文摘We consider a scheme to generate a sub-picosecond electron bunch in the photocathode rf gun by im-proving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric.
基金Supported by National Natural Science Foundation of China (10775080)
文摘An RF deffecting cavity used for bunch length measurement has been designed and fabricated at Tsinghua University for the Thomson Scattering X-Ray Source. The cavity is a 2856 MHz, π-mode, 3-cell standing-wave cavity, to diagnose the 3.5 MeV beam produced by photocathode electron gun. With a larger power source, the same cavity will again be used to measure the accelerated beam with energy of 50 MeV before colliding with the laser pulse. The RF design using MAFIA for both the cavity shape and the power coupler is reviewed, followed by presenting the fabrication procedure and bench measurement results of two cavities.
文摘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.
文摘电子束团长度是束流诊断中的重要参数,基于相干渡越辐射(Coherent Transition Radiation,CTR)的测量方法是一种简单易行的高时间分辨率测量方法。本文调研并分析了不同电子束团长度测量方法的优缺点,选择基于CTR方法作为主要研究方向,主要针对上海深紫外自由电子激光实验装置(Shanghai Deep Ultra-Violet Free Electron Laser,SDUV-FEL)和X射线自由电子激光试验装置(Shanghai X-ray Free Electron Laser,SXFEL)进行了实验方案设计和模拟分析。结果表明,通过合理的参数选择和方案优化,用该方法可对飞秒至皮秒范围内的束团长度进行测量,时间分辨率能到达飞秒量级,满足SDUV-FEL的实验需求和SXFEL的工程需求。
文摘红外波段自由电子激光的小信号增益大小以及饱和功率对束流的能散非常敏感。为满足远红外自由电子激光对能散的要求,在合肥光源栅控直流高压电子枪的基础上,模拟了一种热阴极微波栅控直流高压电子枪。微波栅控直流高压电子枪采用微波栅控的方法,控制和压缩阴极引出电子束团的长度。再通过直流高压对电子加速后,在电子枪的出口可以得到量级为几十皮秒的束团。本文使用SUPERFISH、POISSON分别进行栅控微波场与高压电场优化计算,PARMELA(Phase And Radial Motion in Electron Linear Accelerators)进行束流跟踪与分析,得到一组能满足红外自由电子激光需求的电子枪参数。