激光驱动高亮度电子束源

采用激光驱动光阴极和１００ｋＶ直流加速间隙可产生宽度为５０～１００ｐｓ的高亮度脉冲电子束，该装置主要由光阴极制备室和直流加速间隙组成，可以用化学气相沉积，离子注入和离子束增强沉积等方法制备光阴极，通过用ＥＧＵＮ和ＰＯＩＳＳＯＮ程序模拟，给出了直流间隙的物理设计，光源采用一台主被动双锁的Ｎｄ：ＹＡＧ激光器，可工作在１０６４、５３２和２６６ｎｍ三个波长，重复频率为１０Ｈｚ，此外，也论述了光阴极制备室与     

激光驱动光阴极高亮度电子束源以及新型光阴极的研究

介绍了北京大学激光驱动光阴极高亮度电子束源,给出了其物理设计.该装置采用激光照射光阴极,通过100kV直流加速结构,产生35—100ps的高亮度电子束.给出了新型离子注入型光阴极和碲化铯光阴极的实验研究结果.     

高亮度1（1／2）超导腔光阴极注入器的腔形设计

对高亮度1 1/2超导腔光阴极注入器进行了腔形的概念研究设计。通过计算比较发现,重入腔的轴电场分布特性,使它很适合做超导光阴极注入器的首腔。我们还通过模拟计算,研究了电子束动力学各种参数的相互依赖关系,最后我们给出1 1/2腔的一组腔及束动力学参数。     

激光驱动的光阴极研究

论述激光驱动的光阴极实验研究。包括直流高压真空试验系统,测试装置和实验结果及其分析讨论。LaB6、纯金属铜(Cu）和钐（Sm）以及半导体碲化铯(Cs2Te）三类有代表性光阴极的量子效率分别是6×10-4、3.8×10-4、11.6×10-4和(2~6)×10-4。利用KrF激光,18kV极间电压下饱和电流密度分别为70A/cm2、50 A/cm2、102A/cm2和57A/cm2。用多孔板法测得的归一化发射度约10pmm· mrad,相应的归一化亮度约1010A/m2· rad2。     

双脉冲电子束源实验研究

 利用现有2MeV直线感应注入器，通过改造，将其次级功率源和8个感应腔分成2组，使之交替工作，建立了一台双脉冲电子束源。二极管电压脉冲幅度达到1MeV，电子束脉冲持续时间为120ns，脉冲间隔可以根据需要在100~500ns间进行调节。实验结果表明：该双脉冲电子束源可以产生双脉冲电子束，其电压幅度差值小于2%，束流可达3kA，并且工作稳定，利用该装置可以进行多脉冲二极管物理和天鹅绒多脉冲发射特性实验研究。     

双脉冲电子束源实验研究

利用现有2MeV直线感应注入器,通过改造,将其次级功率源和8个感应腔分成2组,使之交替工作,建立了一台双脉冲电子束源。二极管电压脉冲幅度达到1MeV,电子束脉冲持续时间为120ns,脉冲间隔可以根据需要在100~500ns间进行调节。实验结果表明：该双脉冲电子束源可以产生双脉冲电子束,其电压幅度差值小于2%,束流可达3kA,并且工作稳定,利用该装置可以进行多脉冲二极管物理和天鹅绒多脉冲发射特性实验研究。     

基于相对论电子束的太赫兹源

太赫兹辐射在基础科学和产业应用中具有重要的应用前景,但传统的电子学和光学方法难以在1～10 THz产生相干的高功率、窄带且连续可调的太赫兹辐射。基于相对论性超短电子束和预调制电子束序列的加速器太赫兹源将能在上述范围内产生可调的高能谱强度窄带太赫兹辐射。综述了清华大学加速器实验室近年来在基于相对论电子束的加速器太赫兹源方面的理论和实验进展,以及与加速器太赫兹源一起发展起来的太赫兹辐射测量、束流诊断和先进加速技术。     

紧凑型高平均流强光阴极注入器

根据北京大学1+1/2单元超导腔直流--超导(DC-SC)光阴极注入器的实验研究结果, 证明了这种新型光阴极注入器的可行性, 在此基础上对这种新型注入器进行了升级设计, 使之成为实用的紧凑型高平均流强的光阴极注入器, 为北京大学自由电子激光装置提供品质良好的电子束流. 给出了升级的3+1/2单元超导腔注入器的详细设计, 包括注入器核心结构的电磁场设计、束流动力学模拟、机械设计. 并对整个注入器的恒温器进行了初步设计.     

光阴极RF腔注入器中激光脉冲的时间抖动

介绍光阴极RF腔注入器中的驱动激光器,采用二极管泵浦的自锁模激光器,通过锁相,使输出激光脉冲的时间抖动小于2ps,实现激光脉冲同微波相位之间的严格同步,在实验上获得流强70A、能量2MeV、亮度4.4×1011A/(m2.rad2)的电子束。     

光阴极RF腔注入器中激光脉冲的时间抖动

 介绍光阴极RF腔注入器中的驱动激光器,采用二极管泵浦的自锁模激光器,通过锁相,使输出激光脉冲的时间抖动小于2ps,实现激光脉冲同微波相位之间的严格同步,在实验上获得流强70A、能量2MeV、亮度4.4×10¹¹A/(m².rad²)的电子束。     

超强激光作用下相对论电子振荡所导致的谐波辐射

研究发现，在超强激光作用下电子运动的相对论效应可导致高次谐波辐射，采用单电子模型计算分析了不同偏振微光作用下的高次谐波发射，表明圆偏振激光较线偏振激光更有利于高次谐波产生。     

Studies on a Laser Driven Photoemissive High-Brightness Electron Source and Novel Photocathodes

A laser driven photoemissive high-brightness electron source at Peking University is reported.Through a DC accelerating gap of 100kV voltage,the device is capable of delivering high-brightness electron beam of 35—100ps pulse duration when irradiated with a mode-locked YAG laser.The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON.The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given.The proposed laser driven superconducting RF gun is also discussed.     

An X-ray Free Electron Laser Driven by an Ultimate Storage Ring

There is a worldwide interest in developing so-called ultimate storage ring (USR) light sources having electron emittances near the X-ray diffraction limit that would provide spectral brightness one or two orders of magnitude higher than present-day, third-generation sources and very large coherent flux in the multi-keV photon energy range [1 Hettel, R. and Qin, Q. 2013. Report on the Workshop on Accelerator R&D for Ultimate Storage Rings, Oct. 30–Nov. 1, 2012, Beijing, China, SLAC-PUB-15379, February [Google Scholar]]. At the same time, there is a growing scientific interest in X-ray FEL sources that can provide a continuous train of evenly spaced, low peak power, coherent photon pulses at repetition rates of above 1 kHz, unlike the bursts of much higher frequency pulses that can be provided by linac-based FELs pulsed with repetition rates of order 100 Hz or less. These CW sources would enable dynamic imaging of materials undergoing transitions in millisecond or less time scales and would open up the development of new non-line spectroscopic techniques that could lead to a better understanding of electronic and nuclear dynamics in materials.     

Investigation of Far Infrared Waveguide Free Electron Laser Driven by RF Linac

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射频远红外波导自由电子激光器的新特性

提出了用波导本征模展开的方法计算射频调制的短脉冲电子束在矩形波导中的自发辐射。模展开系数决定了辐射进入TE0n模的功率。将短脉冲理想化为时间上的d函数,可以发现当辐射频率正好等于用来调制电子束的射频的整数倍时,辐射模式表现为“纯”的波导本征模,此时辐射功率最强。用此方法估算了设计中的上海远红外波导自由电子激光器的辐射功率。     

射频远红外波导自由电子激光器的新特性

 提出了用波导本征模展开的方法计算射频调制的短脉冲电子束在矩形波导中的自发辐射。模展开系数决定了辐射进入TE_0n模的功率。将短脉冲理想化为时间上的d函数,可以发现当辐射频率正好等于用来调制电子束的射频的整数倍时,辐射模式表现为“纯”的波导本征模,此时辐射功率最强。用此方法估算了设计中的上海远红外波导自由电子激光器的辐射功率。     

上海激光电子γ源

激光具有高强度、 高极化度等优异的性能。 用激光束轰击高能电子束就可以产生高强度、 高极化度的γ射线束。 上海激光电子γ源就是上海同步辐射装置上的这样一条束线站。 预计可以获得能量范围为1—22 MeV的准单色、 高强度（109—1011 s-1）和高极化度（线极化或圆极化）的γ射线束。 介绍了这条束线站目前的进展情况。 Shanghai Laser Electron Gamma Source (SLEGS) is a high intensity,short pulse and compact γ ray source which is based on inverse Compton scattering via interaction between pulsed high power laser beams and picosecond relativistic electron bunches. One of the attractive features of the laser Compton scattering is the easy control of polarization of the produced high energy photons that duplicates polarization of the applied laser beam. The γ ray with energy up to 22 MeV and intensity of 109—1011s 1 are expected to be produced by Compton backscattering of CO2 laser photons on the 3.5 GeV electrons bunches in the Shanghai Synchrotron Radiation Facility (SSRF). In this communication, we report same simulation results and the progressing status of SLEGS.     

Electron Acceleration in the Bubble Regime with Dense-Plasma Wall Driven by an Ultraintense Laser Pulse

An optimizing scheme for electron acceleration in the wake bubble with dense-plasma wall driven by an ultraintense laser pulse is presented and investigated by particle-in-cell simulation. The wall has an inner diameter matching the expected lateral bubble size. The bubble shape can be transversely controlled and longitudinally shrunk. The accelerated electrons as a bunch have a high quality because the electrons almost stay close to the bottom of the bubble and are accelerated to much high energy with narrow energy spread.     

相对论电子的逆韧致吸收

在激光强度大于１０＾１８Ｗ／ｃｍ＾２的条件下，利用强激光场中完全相对论的电子运动轨迹，得到了稀薄等离子体中的韧致吸收系数计算公式，并与原有的逆韧致吸收系数的计算公式进行了比较。     

Laser Driven Fusion

Laser-driven fusion, although requiring the use of an unusual source of pulsed energy, depends in its main features on well known and verified results of hydrodynamics and nuclear physics. Under optimized conditions these allow energy breakeven by the fusion process to occur under conditions which appear to be well within the range of present technology. Achieving the energy multiplication required for practical application is expected to be more difficult but not infeasible within short-range projections of the development of laser technology. The feasibility of laser-driven fusion power plants appears to rest more on pellet and laser ecomonics than on reactor technology. The study of these problems is underway and will certainly be greatly intensified as the prediction of the basic processes is experimentally confirmed.