自由电子激光器中的电子阻尼运动

建立了有阻尼项的摆方程,在小信号情况下,对方程进行了迭代求解.由解得的结果得到了增益函数的表达式.特别对弱阻尼和过阻尼情况进行了计算,分别得到了相应的增益函数简化公式.对阻尼项的来源和物理意义进行了详细的讨论. 关键词：     

拉曼型自由电子激光器中相对论电子运动稳定性的比较研究

拉曼型自由电子激光器作为一种兆瓦级高功率毫米波、太赫兹波辐射源, 其电子的运动稳定性对整体器件的性能至关重要.本文采用科尔莫戈罗夫熵方法, 以典型的麻省理工学院公布的实验数据为例, 比较研究拉曼型正向导引磁场和反向导引磁场两类自由电子激光器中相对论电子的运动稳定性. 结果表明:摇摆器绝热压缩磁场对电子运动的稳定性无实质性影响, 但对电子运动影响大; 电子束自身场在拉曼型正向导引磁场自由电子激光器中使电子运动稳定性变差, 而在拉曼型反向导引磁场自由电子激光器中则可改善电子运动稳定性. 关键词： 拉曼型自由电子激光器 相对论电子运动稳定性 科尔莫戈罗夫熵 电子束自身场     

曙光一号自由电子激光器束调节研究

简单介绍了曙光一号自由电子激光器实验布局．着重就束调节方案进行了数值模拟和实验研究，给出了束流调试结果,并进行了分析；当进入摇摆器的束流为950A，摇摆器磁场为0.31T，在摇摆器长度为2．4m的位置,获得了50MW的饱和功率，经变参数实验后输出功率提高到140MW．     

带轴向引导磁场自由电子激光器中的电子轨迹与稳定性

在对中国工程物理研究院电子学研究所和中国科学院上海光学精密机械研究所所做带引导磁场喇曼型自由电子激光实验进行数值模拟的基础上,本文研究了轴向引导磁场和摇摆磁场联合作用的单电子轨迹,对电子的平衡轨道和一阶微扰轨道进行了仔细分析,揭示了在引导磁场存在的情况下,摇摆磁场横向变化引起的电子感应回旋运动的重要性,推导了带引导磁场情况下的电子感应回旋运动方程,给出了电子感应回旋运动的周期,X方向、Y方向之间的关系。同时,用数值模拟方法研究了电子的运动,两者结果符合很好。 关键词：     

X射线激光器——新兴的短波长相干光源

Ｘ射线激光器是运行在电磁辐射波谱中Ｘ射线波段的短波长相干光源，通常，Ｘ射线激光器都采用高功率激光器作为泵浦源，强激光与靶相互使用形成的高温等离子体作为工作介质，并采用单程（或双程）行波放大的运行方式，近１０年来，Ｘ射线激光器的研制工作取得了重大进展，并开始了Ｘ射线激光应用的初步研究，现在正朝着提供高亮度，有较好相干性并且价格便宜的小型短波长Ｘ光光源的目标努力。     

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。     

自由电子激光器的小信号时域研究

本文推导了自由电子激光器中光脉冲的时间进展方程,数值研究了它的定态解。给出了不同调谐参数和峰值增益参数时的本征值和同步失配的关系,以及不同耦合参数时的光脉冲形状。计算结果与Dattoli的超模理论结果作了比较。     

微型自由电子激光电子运动特性分析

作者曾首次提出以铁电单晶表面势代替摇摆器磁场的自由电子激光新机制.本文从单电子的洛仑兹方程出发,对电子的单摆方程,共振行为进行了研究,获得了第j个表面势共振态的增益公式.单摆方程和文献[1]中从能量方程得到的一致,本文的研究充实了文献[1]的论据。     

短波长激光超热电子产生与抑制机理的研究

介绍了在“神光Ⅰ”和“星光Ⅱ”上分别进行的二倍频、三倍频激光照射金盘靶、腔靶、碳氢有机膜平面靶的实验.通过测量硬X射线谱推断超热电子特性,结合受激Raman散射光和双等离子体衰变产生的(3/2)ω0谐波的观测,分析各种靶超热电子产生和抑制的机理,并探讨了抑制超热电子的有效途径. 关键词：     

Three-dimensional motion of electrons in combined realistic helical wiggler with axial guide field for free-electron laser

3-D motion of electrons with on-axis and off-axis guiding centers in realistic helical wiggler and axial guide field is analysed. It is found that purely helical orbits couldnot exist for the electrons with off-axis guiding centers, except for those with on-axis guiding centers. Perturbation solutions of the electron's velocity and orbit averaged over the cyclotron angle are derived. Our calculations indicate the divergence of the electron orbits near resonance.     

小周期波荡器自由电子激光器：数值模拟与实用化设计

采用三维自洽非线性理论计算方法,针对小周期波荡器自由电子激光器进行了数值模拟计算研究.结果表明,在我所现有脉冲线加速器基础上,采用周期为10mm的波荡器,可获得输出功率为20MW,波长为1.7mm的自由电子激光.最后给出实用化总体实验设计方案.     

波荡器入口区绝热压缩磁场分布对自由电子激光输出功率和效率的影响

本文对波荡器(Wiggler)入口区绝热压缩磁场分布对自由电子激光输出功率、增益、效率的影响,进行了非线性计算机模拟.结果表明:磁场幅值沿轴向接立方函数分布,比通常采用的正弦平方函数和平方函数这两种分布更好,更接近实验值.     

Dispersion relation and growth rate for a corrugated channel free-electron laser with a helical wiggler pump

The effects of corrugated ion channels on electron trajectories and spatial growth rate for a free-electron laser with a one-dimensional helical wiggler have been investigated. Analysis of the steady-state electron trajectories is performed by solving the equations of motion. Our results show that the presence of a corrugated channel shifts the resonance frequency to smaller values of ion channel frequency. The sixth-order dispersion equation describing the coupling between the electrostatic beam mode and the electromagnetic mode has also been derived. The dispersion relation characteristic is analyzed in detail by numerical solution. Results show that the growth rate of instability in the presence of corrugated ion channels can be greatly enhanced relative to the case of an uniform ion channel.     

Effect of normalized plasma frequency on electron phase-space orbits in a free-electron laser

Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser （FEL）. In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron- beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.     

Gain calculation of a free-electron laser operating with a non-uniform ion-channel guide

Amplification of an electromagnetic wave by a free electron laser (FEL) with a helical wiggler and an ion channel with a periodically varying ion density is examined. The relativistic equation of motion for a single electron in the combined wiggler and the periodic ion-channel fields is solved and the classes of possible trajectories in this configuration are discussed. The gain equation for the FEL in the low-gain-per-pass limit is obtained by adding the effect of the periodic ion channel. Numerical calculation is employed to analyse the gain induced by the effects of the non-uniform ion density. The variation of gain with ion-channel density is demonstrated. It is shown that there is a gain enhancement for group I orbits in the presence of a non-uniform ion-channel but not in a uniform one. It is also shown that periodic ion-channel guiding is used to reach the maximum peak gain in a low ion-channel frequency (low ion density).     

Interaction of a relativistic dense electron beam with a laser wiggler in a vacuum: self‐field effects on the electron orbits and free‐electron laser gain

Employing laser wigglers and accelerators provides the potential to dramatically cut the size and cost of X‐ray light sources. Owing to recent technological developments in the production of high‐brilliance electron beams and high‐power laser pulses, it is now conceivable to make steps toward the practical realisation of laser‐pumped X‐ray free‐electron lasers (FELs). In this regard, here the head‐on collision of a relativistic dense electron beam with a linearly polarized laser pulse as a wiggler is studied, in which the laser wiggler can be realised using a conventional quantum laser. In addition, an external guide magnetic field is employed to confine the electron beam against self‐fields, therefore improving the FEL operation. Conditions allowing such an operating regime are presented and its relevant validity checked using a set of general scaling formulae. Rigorous analytical solutions of the dynamic equations are provided. These solutions are verified by performing calculations using the derived solutions and well known Runge–Kutta procedure to simulate the electron trajectories. The effects of self‐fields on the FEL gain in this configuration are estimated. Numerical calculations indicate that in the presence of self‐fields the sensitivity of the gain increases in the vicinity of resonance regions. Besides, diamagnetic and paramagnetic effects of the wiggler‐induced self‐magnetic field cause gain decrement and enhancement for different electron orbits, while these diamagnetic and paramagnetic effects increase with increasing beam density. The results are compared with findings of planar magnetostatic wiggler FELs.     

Three-dimensional simulation of long-wavelength free-electron lasers with helical wiggler and ion-channel guiding

A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser (FEL) with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear differential equations for electron orbits and fields of TE 11 mode in a cylindrical waveguide are solved numerically by the Runge-Kutta algorithm with averages calculated by the Gaussian quadrature technique. Self-fields and space-charge effects are neglected, and the electron beam is assumed to be cold and slippage is ignored. The parameters correspond to the Compton regime. Evolution of the radiation power and growth rate along the wiggler is studied. Ion-channel density is chosen to obtain optimum efficiency. Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV, respectively. The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.     

喇曼自由电子激光器实验的数值模拟

本文采用基于单粒子理论的CAGFEL程序,对中国科学院上海光学精密机械研究所(简称上海光机所)喇曼自由电子激光器的近期实验结果进行了数值模拟,计算表明,当电子能量E_e=0.5MeV,能散度△γ/γ=6％和发射度ξ=0.06(π)rad·cm时,器件的峰值功率高达24MW,对应的辐射增长率为120dB/m,效率为6.1％。