周期磁场中的相对论电子与光辐射的能量交换

基于相对论电子在周期磁场和光辐射场作用下的运动方程,讨论了相对论电子与光辐射之间的有效的能量交换。结果表明,相对论电子与光辐射只有在满足共振条件的频率上发生能量交换。光辐射是被相对论电子放大还是成为加速电子运动的动力,取决于两者的位相关系。     

基于高能电子束曝光的相对论卢瑟福公式研究

高能电子运动速度较大,相对论效应很明显。传统的卢瑟福弹性散射公式是由非相对论的薛定谔波动方程得出的,在预言高能电子束曝光时,需要对其进行相对论修正。采用Born近似解相对论的Dirac方程,得到相对论修正的卢瑟福公式。计算元素Si、O、C、H的弹性散射截面和散射角,与修正前的计算结果进行比较,结果表明,当电子能量达到100keV时,其相对论效应已经很明显。     

梯度周期场自由电子激光器

本文在单电子模型的基础上逐阶求解相对论电子的洛伦兹方程和能量方程,得到了梯度周期场自由电子激光器的增益表达式.计算表明当周期磁场的振幅沿z方向变化时,增益可获得提高.     

掺杂超晶格与超相对论粒子同步辐射的稳定性

指出了对周期介质加上周期变化的电场,可望获得时空周期变化的周期场;在这种场中运动的带电粒子表现出人们预期的行为。讨论了超相对论情况下带电粒子的同步辐射,并以掺杂超晶格为例进行具体分析。在经典力学框架内和偶极近似下,把粒子的相位运动方程化为广义摆方程;讨论了带电粒子的同步辐射能量和系统的稳定性。结果表明,适当选择系统参数就可以保证系统的稳定性,如果选择势阱深度为1eV,周期为100nm,相对论因子为10^4时,电子的辐射频率可达1．25×10^20HZ,辐射进入X-能区。     

圆偏振周期量级激光脉冲作用下电子辐射的空间分布

在电子汤普孙散射的经典理论的基础上,通过理论分析和计算机模拟,研究圆偏振周期量级激光脉冲作用下电子辐射的空间分布特性,提出可能的应用方向。研究发现,在相对论光强下,随着激光强度的增强,电子辐射逐渐增强,能量不断的向辐射中心集中,辐射能量分布的方向性逐渐突出;当改变激光的初相位时,电子辐射的总体方向发生偏移,表现为辐射分布图形的对称平面发生旋转,且旋转角度与激光初相位角改变大小相同。本文所进行的相关探讨基于电子辐射的三维空间立体图,所得到的有关电子谐波辐射的结论,可以为实验和工程上对电子辐射和激光参数测量的相关应用提供参考。     

振幅螺旋变化的周期wiggler场自由电子激光器增益研究

本文用逐阶近似法分析了相对论电子洛仑兹力方程和能量方程,获得了振幅螺旋变化的周期wiggler场自由电子激光器的增益表达式。结果表明,这种激光器的增益比采用恒定振幅周期wiggler场自由电子激光器有较明显的提高。     

回旋自谐振脉塞中束波互作用关系

从状态方程出发,通过四度空间的Maxwell方程协变形式、电磁张量、能量-动量张量在电子注坐标上进行相对论变换,研究了回旋自谐振脉塞的互作用过程,导出了新的互作用状态方程。理论上证明了CARM中工作在TEmn模无纵向电场分量情况下电子注交换纵向能量的机制是存在的。     

迴旋佩尼管束波互作用的理论和模拟

本文从电子的相对论运动方程和能量方程出发,详细分析了迴旋佩尼管内的束波互作用,提出了适用于任意TEmn模和任何次迴旋谐波工作的大信号理论。计算机模拟表明,这种器件具有电子效率高、工作磁场低的突出优点。从而开拓了毫米波迴旋脉塞器件的更广泛的应用前景。     

螺旋泵浦场自由电子激光理论

从相对论电子的经典动力学方程出发,导知了一种有效的求解程序,其所得增益曲线与以前结论有显著不同.此外,还发现激光饱和场正比于电子初始能量平方而反比于泵浦场模,这是本文新结果.     

相对论电子在高斯激光场中的加速

为了研究激光电磁场对真空中电子的作用,从洛伦兹方程出发,得出了电子运动轨迹,实现了激光场对电子的加速。继而由运动电子产生的流密度,得到了电子的辐射能量谱,分析了相对论电子的辐射特点。结果表明,高斯激光场对真空中电子有很好的加速效果,最大轴向速度可达0.9c。     

The Linear and Self-Consistent Nonlinear Theory of the Electron Cyclotron Maser Instability

In this paper the linear and nonlinear theory of the electron cyclotron maser instability is considered. The configuration used to study the maser instability consists of relativistic electrons gyrating about and drifting along a uniform magnetic field within a parallel plate waveguide. Relativistic effects associated with the gyrating electrons are responsible for excitation of the transverse electric mode in the waveguide. Linear theory shows that the growth rate maximizes when the axial beam velocity coincides with the axial wave group velocity of the excited electromagnetic wave. This allows us to perform the nonlinear analysis in a frame where both the axial wave number and axial beam velocity vanish. We have found that the maser instability exists only if the perpendicular beam energy exceeds a threshold value. Our analysis also describes the temporal nonlinear evolution of the field amplitude and frequency of a single excited wave. The nonlinear wave dynamics are self-consistently determined from the nonlinear particle orbits through the force and wave equations. The nonlinear analysis shows that there are two possible mechanisms for the saturation of the unstable wave: 1) depletion of the available free energy associated with the rotating particles and 2) phase trapping of the gyrating electrons in the wave. The initial beam parameters determine which of the two mechanisms is responsible for saturation. Competition between the two saturation mechanisms leads to a peaking in the energy conversion efficiency as a function of beam energy. Numerical results of the nonlinear formalism show that energy conversion efficiencies from the particles to the wave can be as high as 60 percent in the beam frame. Furthermore, by appropriately contouring the external magnetic field, among other things, efficiencies as high as 70 percent can be realized.     

正交场E0×B0飘移电子的自发辐射

根据经典的单粒子运动方程和加速电子产生辐射的规律,计算得到了静态均匀正交场 E0×B0飘移电子时产生自发辐射的谱函数．结果对具有任意速度量值的电子均适用．作为特殊 情况,讨论了非相对论(γ0=1)和强相对论(γ0》1)电子注入时自发辐射情况．     

Equilibrium solutions for partially immersed relativistic electron beams

The equations relating the beam radius and axial electron velocity to easily measurable external beam parameters are developed for solid, relativistic beams. The beam parameters are tunnel voltage, beam current, axial magnetic field, cathode magnetic field, tunnel radius, and cathode radius. The equations are sufficiently complex to warrant the use of a digital computer if many cases are to be evaluated. Error indicators are formulated to prevent use of the relations beyond their range of validity. The equilibrium solutions for relativistic electron beams from unshielded cathodes show that the required magnetic focusing field is lower than that computed from nonrelativistic formulas. The angular magnetic field produced by the beam itself aids in focusing the electrons. The potential depression due to space charge is analyzed. Correction curves are given which allow the use of nonrelativistic equations in predicting equilibrium behavior. The maximum possible microperveance of relativistic beams is shown to be lower than the classical value of 25.4.     

Evolution of Electron Phase Orbits of Multi-photon Nonlinear Compton Scattering in High Power Laser-plasma

The evolution of the electron phase orbits based on the multi-photon nonlinear Compton scattering with the high power laser-plasma is discussed by using Kroll-Morton-Rosenbluth theory. The random evolution of the un-captured electron phase orbits from periodicity to non-periodicity is found after the energy has been exchanged between the electron and photons. With the increase of the absorbed photon number n by an electron,this evolution will be more and more intense, while which is rapidly decreased with the enhancement of the collision non-flexibility ξ and their initial speeds of the electrons and photons, but this evolution is lower than that in the high power laser field. When the electrons are captured by the laser field, the evolution is finished, and the electrons will stably transport, and the photons don‘t provide the energy for these electrons any more.     

激光脉冲初始相位对电子辐射的影响

为了研究超短超强椭圆偏振激光初始相位对于高能电子辐射特性的影响, 采用了Lorentz方程与电子能量方程构造高能电子与强激光场的对撞模型的方法, 并使用MATLAB进行数值模拟, 获得了电子的运动轨迹以及激光场空间辐射的功率与能量分布的数据与图像, 对不同的激光初始相位所对应的3维空间辐射特性进行了研究。结果表明, 当激光脉冲撞击电子时, 电子产生辐射, 且辐射功率呈现出双峰形; 高能电子的辐射功率图像在初始相位为0°, 180°和360°时表现为对称型双峰, 而在其它相位下则呈现出非对称型双峰。该结论为超短超强椭圆偏振激光的初始相位3维反探测研究提供了一定的基础。     

Free-electron interactions with light using the inverse Cerenkov effect

An analysis and experimental verification of momentum modulation of relativistic electrons by laser light using the inverse Cerenkov effect is presented. As an alternative to the free-electron laser for achieving energy exchange between particles and photons, the inverse Cerenkov effect uses the index of refraction of a gaseous medium to retard the phase velocity of an electromagnetic wave, enabling the electrons to remain in a field of constant phase. The momentum modulation converts to charge-density modulation by allowing the electrons to drift, thus forming electron bunches separated by optical wavelengths. An analysis is presented for the maximum amount of energy exchange, the energy exchange distribution, and the optimum bunching distance. A computer simulation of the interaction process is also given. These results are compared with the observed momentum modulation of a 102 MeV electron beam by a 30 MW Nd:YAG 1.06 μm laser in both hydrogen and methane gases. Initial observation of coherent optical radiation from a 57 MeV electron beam using the same laser system is also presented. Laser-driven particle accelerators and optical klystrons are possible applications of this interaction.     

超强激光等离子体中的相对论性朗缪尔孤子

为了研究相对论性朗缪尔孤子的特性,对从动力论出发所获得的超强等离子体中相对论性强朗缪尔湍动控制方程组进行了理论分析。结果表明,随着电子的平均洛伦兹因子以及场的湍动参量增加,朗缪尔孤子的波包半宽变窄,孤子总能量和总动量相应地增大,且电子的相对论效应对孤子总能量和动量的非线性部分的影响远大于线性部分。该研究可为超强激光等离子体中相关的非线性现象提供新的理论参考。     

Phase variation in free-electron laser amplifiers

The evolution of the phase of the output radiation of free-electron laser amplifiers is investigated by means of a three-dimensional simulation code. The configuration employed consists of the propagation of a relativistic electron beam through a loss-free cylindrical waveguide in the presence of a helically symmetric wiggler and a uniform axial guide magnetic field. The analysis is fully three dimensional, and a set of model equations is discussed which describes the coupling between an ensemble of electrons and the radiation field of either the TE or TM modes. The model equations are solved numerically, and the output phase is studied with respect to variations in either frequency or electron beam energy. The output phase is found to depend sensitively on the wave frequency within the unstable bandwidth. In addition, the phase stability of the output radiation is discussed as a function of beam energy. Finally, the evolution of the phase for tapered wiggler free-electron lasers is studied.