高平均功率FEL的标度律

讨论了设计高平均功率康普顿型自由电子激光（FEL）装置的基本思路与相关的标度律。强调了除电子束平均流强外,能量抽取率是装置实现高平均功率的决定性因素。这个量的标度律基本上由摇摆器参数（周期数）单独确定,与摇摆器周期长度和强度无关,与激光波长无关。指出如无能量回收系统,按目前光阴极电子枪+超导射频加速结构装置可预期的电子束团100 pC/bunch,平均电流为mA情况下,15MeV电子束能给出的激光平均输出功率为百瓦量级。     

用于高平均功率FEL的DC-SC光阴极注入器

为获得用于高平均功率自由电子激光（FEL）的高平均流强电子束,设计了一种新型的DC-SC光阴极注入器。该注入器由皮尔斯直流引出结构、1+1/2超导腔和同轴功率耦合系统组成,可以提供高品质、CW模式或高占空比的电子束。对DC-SC光阴极注入器进行了优化设计和束流动力学研究。模拟和优化结果表明DC-SC光阴极注入器完全可以用于高平均功率自由电子激光。模型腔实验验证了理论模拟的可靠性。     

用于高平均功率FEL的DC-SC光阴极注入器

 为获得用于高平均功率自由电子激光（FEL）的高平均流强电子束，设计了一种新型的DC-SC光阴极注入器。该注入器由皮尔斯直流引出结构、1+1/2超导腔和同轴功率耦合系统组成，可以提供高品质、CW模式或高占空比的电子束。对DC-SC光阴极注入器进行了优化设计和束流动力学研究。模拟和优化结果表明DC-SC光阴极注入器完全可以用于高平均功率自由电子激光。模型腔实验验证了理论模拟的可靠性。     

超临界圆映象的混沌测度及其标度律

本文研究了圆映象中的参数k>1与k》1情况的混沌运动的行为,用在Ω轴的等分点上计算李雅普诺夫指数及转数的办法,给出混沌运动的测度及其标度律。 关键词：     

高平均功率自由电子激光太赫兹源波荡器物理设计

讨论了高平均功率自由电子激光太赫兹源波荡器的物理设计,在确定了波荡器周期、周期数、峰值磁场强度范围和调制参数范围等总体参数后,选用混合型Halbach结构为波荡器的基本结构,永磁块长宽高为8 cm1.3 cm6 cm,磁极长宽高为5 cm0.6 cm4.8 cm。波荡器工作在变间隙模式下,间隙为1.81~3.05 cm时,波荡器峰值磁场为0.529~0.184 T,好场区为3.02~2.13 cm。同时,考虑到波荡器磁场误差对自由电子激光的影响,提出了波荡器各参数误差,并对波荡器端部设计进行了重点讨论。     

石墨烯量子霍尔平台与平台之间转变的标度律关系

在2到50 K温度范围内测量了单层石墨烯量子霍尔平台与平台之间转变的标度律关系. 发现石墨烯的标度律指数κ不是普适的,在低温段的κ大约是0.13,在高温段的κ大约是0.33. 这一结果进一步验证了石墨烯中长程散射的主导地位. 关键词： 石墨烯 量子霍尔效应 标度律     

Levy-Kolmogorov湍流标度律

Kolmogorov的5／3次方律E（k）=Cε^2/3k^-5/3矿乃是20世纪湍流研究最重要的理论研究成果。这里E代表湍流能谱，占为湍流能量耗散率，k为波数，C为一常量。在极高雷诺数流动中-5／3次方律被很多实测数据验证。但是对于有限雷诺数问题，湍流能谱具有-5／3次方律的波数范围一般很窄；湍流实验证实，瞬时湍动能耗散存在时空分布极不均匀的情况，即所谓的间歇性现象，湍流物理量呈明显的非高斯分布，     

SG－1FEL放大器实验中的频率和功率测量

介绍了曙光一号自由电子激光（ＳＧ－１ＦＥＬ）放大器实验中对输出微波功率高达１４０ＭＷ的信号的频率和功率的测量。分析了ｘ射线和微波器件（定向耦合器、衰减器）的窄脉冲响应对测试结果的影响。     

V型阵发李雅普诺夫指数标度律的验证

报道在一个张弛振荡电路中获得的V型阵发李雅普诺夫指数标度律的实验证据.对这个电路的理论模型进行了数值计算，所得结果与实验一致. 关键词：     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

Gain of harmonic generation in high gain free electron laser

In a planar undulator employed free electron laser (FEL), each harmonic radiation starts from linear amplification and ends with nonlinear harmonic interactions of the lower nonlinear harmonics and the fundamental radiation. In this paper, we investigate the harmonic generation based on the dispersion relation driven from the coupled Maxwell-Vlasov equations, taking into account the effects due to energy spread, emittance, betatron oscillation of electron beam as well as diffraction guiding of the radiation field. A 3D universal scaling function for gain of the linear harmonic generation and a 1D universal scaling function for gain of the nonlinear harmonic generation are presented, which promise rapid computation in FEL design and optimization. The analytical approaches have been validated by 3D simulation results in large range.     

处理自由电子激光器强信号的一种简单方法

基于自由电子激光器的能量模型,在具有螺旋磁场自由电子激光器中,本文采用一种简单的方法处理了强信号条件下能量转换过程.讨论了饱和产生的过程和初始能量色散对饱和影响的机制.这种处理方法也适用于自由电子激光器的谐波辐射.     

Design of cascading two stages of high gain harmonic generation scheme based on Shanghai deep ultraviolet free electron laser

Cascading stages of high gain harmonic generation free electron laser (FEL) seem to be a feasible way to generate short wavelength radiation. With help of the analytical estimates, we design a two-stage cascading scheme to achieve 131nm DUV radiation on the basis of the Shanghai deep ultraviolet free electron laser test facility. Detailed studies on the FEL performance, the stability and the sensitivity of the output power to parameter variation have been achieved by GENESIS1.3, and design of the lattice structure is presented.     

Ultra-high order harmonic generation via a free electron laser mechanism

In this paper,by using the"frequency up-conversion"principle with a high gain harmonic generation free electron laser and an external seed laser,we consider the possibility of modulating a relativistic electron beam on the attosecond scale,so that it can produce coherent spontaneous radiation from the deep ultraviolet to the hard X-ray spectral region with a very short radiator.Analytical estimation and three-dimensional numerical modeling show the great potential to reach ultra-high harmonics up to several thousand.For an electron bunch with the typical quality as in the free electron laser scheme and a seed laser with 800 nm wavelength,0.8 nm attosecond trains with alterable duration and GW scale peak power are modeled.The output radiation exhibits good shot-to-shot stability,full coherence and perfect tuning ability between the discrete harmonics of the seed frequency.     

Ultra-high order harmonic generation via a free electron laser mechamsm

In this paper, by using the ＂frequency up-conversion＂ principle with a high gain harmonic generation free electron laser and an external seed laser, we consider the possibility of modulating a relativistic electron beam on the attosecond scale, so that it can produce coherent spontaneous radiation from the deep ultraviolet to the hard X-ray spectral region with a very short radiator. Analytical estimation and three-dimensional numerical modeling show the great potential to reach ultra-high harmonics up to several thousand. For an electron bunch with the typical quality as in the free electron laser scheme and a seed laser with 800 nm wave- length, 0.8 nm attosecond trains with alterable duration and GW scale peak power are modeled. The output radiation exhibits good shot-to-shot stability, full coherence and perfect tuning ability between the discrete harmonics of the seed frequency.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

具有幂率度分布的因特网平均最短路径长度估计

针对具有幂律度分布的复杂网络的平均最短路径长度进行了研究.给出了一个计算因特网平 均最短路径长度的公式.提出因特网的整体构造实质是以最小代价换取最大收益，从此出 发通过对因特网这类复杂网络平均最短路径长度影响因素分析，推断出网络最短路径长度分 布P(l)的基本性质，进而构造了一个只含参数α的P(l)的简洁形式，直接打通了拓扑具有幂 律度分布的因特网的度分布P(k)与网络最短路径长度分布P(l)之间的关系.然后说明了导出 的公式的物理意义，即参数α代表网络节点连接方式和网络的总边数对平均最短路径长 度的影响.此公式意味着只要掌握幂律P(k)～k-α中α值，就可以直接计算相应网 络的平均最短路径长度.通过对已知数据的计算，验证了公式的有效性.阐明了参数 α对网络设计的重要性和对网络功能的影响. 关键词： 复杂网络 幂律 度分布 平均最短路径长度