喇曼型自由电子激光光导效应数值模拟与分析

本文对喇曼型自由电子激光光导效应进行了理论研究和数值模拟，我们编写了轴对称的二维计算机程序，用来研究无波导和有波导情况下的光导效应，对光场分布，光场半径，填充因子及等效折射率进行了模拟，根据实验参数进行的模拟结果与实验结果符合很好，并对影响光导效应的因素进行了分析。     

自由电子激光光导效应数值研究

本文对喇曼型自由电子激光光导效应进行了理论研究和数值模拟。我们编写了轴对称的二维计算机程序(FELOG),用来研究无波导和有波导情况下的光导效应。对光场分布、光场半径、填充因子及等效折射率等进行了模拟。根据实验参数进行的模拟结果与实验结果进行比较,它们符合很好。并对影响光导效应的因素进行了分析。     

SASE自由电子激光不同带宽统计特性的数值模拟

对自放大自发辐射自由电子激光不同带宽光场统计特性进行了数值模拟。分析了一定频带宽度内光场随机特性的统计规律，模拟结果表明，在较宽的谱线宽度内光脉冲分布规律基本符合Г函数分布，在较窄的谱线宽度内其分布规律服从负指数分布。数值模拟结果与理论结果和实验结果符合较好。     

自由电子激光的色散关系分析

对自由电子激光的色散关系进行理论分析。通过自由电子激光摆方程推导出线性增长区增益系数和折射率（复折射率的虚实部），并证明增益系数Ｉｍ（ｎ）和折射率Ｒｅ（ｎ）－１之间的关系即色散关系满足Ｈｉｌｂｅｒｔ变换对，亦即Ｋｒａｍｅｒｓ－Ｋｒｏｎｉｇ关系，并进行了物理分析。     

返波型自由电子激光的非线性模拟

本文利用自由电子激光的加速器理论,建立了单粒子非线性运动方程及其非自洽数值模拟模型。根据这一数值计算模型进行了非线性模拟,得到了返波自由电子激光在其非线性区的行为特征。数值计算结果证实了线性理论的预言:返波型自由电子激光适宜于作为二级自由也子激光的一级。     

纵向均匀磁场二阶自由电子激光动力学分析

本文的目的是对纵向均匀磁场二阶自由电子激光进行简要的动力学分析。证明了在纵向均匀磁场一阶自由电子激光基础上能够实现二阶自由电子激光的能量补偿。指出在补偿过程中电子束团的能谱将被压缩、束团中的电子数密度分布将被调制,从而能够实现二阶自由电子激光振荡,并且可以大大提高实际单程增益。     

纵向均匀磁场一阶自由电子激光动力学分析

本文的目的是对纵向均匀磁场一阶自由电子激光进行简要的动力学分析。证明可以采用同步旋进准静电磁场对纵向均匀磁场自由电子激光进行能量补偿,而使电子束品质、激光转换效率和单程增益大大改善。     

分布反馈谐振腔拉曼自由电子激光振荡器获得成功

中国科学院上海光机所王明常副研究员的自由电子激光器课题组,首次研制出具有分布反馈谐振腔的拉曼自由电子激光振荡器。该谐振腔满足布拉格条件成为分布反馈腔,取代传统的激光器反射镜,解决了反射镜阻挡电子束同轴通过和大功率激光损伤两个关键技术问题。     

大气湍流对舰载激光通信中光能量分布的影响

针对激光在洋面上大气湍流中传输时,光能量分布发生变化,影响激光通信质量。本文基于大气光通信信道模型,对激光在大气湍流中的传输进行模拟,分析大气折射率结构常数、传输激光的波长,传输距离对光能量分布的影响,并用MATLAB对其影响进行了数值模拟。结果表明：在仅考虑大气湍流对激光传输影响的条件下,传输激光的波长对光能量分布具有重要影响。     

二维摆动磁场自由电子激光自发辐射的频谱特性

本文对二维摆动磁场自由电子激光的自发辐射频谱进行了理论分析，并对分析结果进行了数值计算。计算结果表明，采用ｌ（ｌｋ２＝ｋｙ）值不同的二维摆动磁场，可以增强第ｌ次谐波的自发辐射强度，从而能够有选择地实现自由电子激光的高次谐波运转。     

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.     

Nonlinear Analysis of Relativistic Motion of Electrons in Self-Amplified Spontaneous Emission Free-Electron Laser in Ultraviolet and X-Ray Spectral Regions

The free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) is an effective candidate of the coherent optical sources at wavelengths in ultraviolet and x-rays. It requires a relativistic electron beam with extremely high quality and extremely stable transmission. In this paper we analyze the dynamic behavior of the relativistic electron in that device by calculating the entropy-like quantity. Results show that if there is no adiabatic field of the wiggler, the electron beam may have great fluctuation in velocity space and diverge in configuration space.     

A submillimeter free-electron laser experiment

A free-electron laser (FEL) Raman-backscattering oscillator, using afrac{1}{2}-1MeV, 20 kA electron beam pumped with a weak (∼ 250g) periodic (8 mm) transverse magnetic field, is operated as a source of high power millimeter and submillimeter radiation, with lasing developing during the 150 ns beam pulse. Measurements of lasing operation are described at 1.0 and 0.6 mm. The temporal behavior of cavity radiation is considered and effective gain is measured and compared with theory.     

Mode analysis of a dielectric-loaded Raman-type free-electron laser

The Raman-type free-electron laser consists of a relativistic electron beam contained in a dielectric-induced parallel plate waveguide and an array of permanent magnets for the wiggler. Under the influence of the periodic magnetostatic field, the coupling between the scattered electromagnetic wave of the TE mode (positive-energy wave) and the electron plasma wave of the TM mode (negative-energy wave) is investigated in detail. The following results are obtained. First, when a dielectric sheet is loaded on the waveguide, the maximum growth rate and the oscillation frequency can be greater than those for the vacuum Raman-type free-electron laser. Second, by choosing proper values for the relative permittivity of the dielectric sheet and the ratio of the beam guide, the beam energy can be greatly lowered without degrading the oscillation characteristics. Third, the growth rate decays exponentially with the oscillation frequency kept almost constant as the beam-dielectric gap increases     

Analysis of the uniform magnetic field free-electron laser with scalarized photons in the microwave-spectral region

The recently developed concept of scalarized photons (formally photons of any polarization) is used to analyze the spontaneous and stimulated emission in the uniform magnetic field free-electron laser in the microwave spectral region. In fact, this free-electron laser is the simplest of many other, wiggler and wiggler-free free-electron lasers whose analyses could be done with scalarized photons in the small signal regime and whose physical parameters can be conveniently chosen for radiation to be generated in the microwave spectral region. As to the uniform magnetic field free-electron laser, which is treated here in some detail, with the electron beam energy of up to 10 MeV and the uniform magnetic field of up to 4 Tesla, the radiation (occurring with the fundamental and higher harmonic frequencies) can cover easily a 10 to 10,000 GHz spectral region.     

Gas-loaded free-electron laser experiments on the Stanfordsuperconducting accelerator

The modification of the free-electron laser (FEL) on the Stanford superconducting accelerator to operate as a gas-loaded FEL (GFEL) is described. The addition of a gas to the wiggler chamber of a FEL changes the phase velocity of the electromagnetic wave, and so provides a simple method for wavelength tuning without changing beam energy or wiggler parameters. A wavelength shift of over 950 Å has been achieved from a vacuum wavelength of 1.6 μm by using 15 torr of hydrogen gas, in agreement with the GFEL synchronism condition incorporating the index of refraction of the gas     

关于自由电子激光器电子束的注入问题

非寝渐注入可导致电子束纵向速度随位置的摆动,因此采用寝渐注入为好。对于具有轴向磁场的情形,使电子束初始横向温度冷却和适当选择系统的参数可降低纵向速度的摆动幅度。     

Characteristics of the dispersive free-electron laser

The dispersive free-electron laser (DFEL) was previously introduced as an optical klystron (OK) superimposed upon a free-electron laser (FEL). In this paper it is shown that with proper design this device provides a gain increase of the order of 4 over the gain of the OK (for equal lengths) with a gain-energy acceptance product approaching that of the FEL. Even when the transverse excursion of the electron beam exceeds the optical beam dimension, there is only a slight reduction in gain from the above value.     

Energy-loss calculation of gain in a plane sinusoidal free-electron laser

The gain of a free-electron laser (FEL) made with a plane sinusoidal undulator is calculated by the electron beam energy loss.     

Simulations of a ring resonator free-electron laser

A relatively high gain (≈25 to 40%) free-electron laser (FEL) with an optical ring resonator is simulated using the code FELEX. The laser system corresponds to the `burst mode' FEL. The ring consists of paraboloids, grazing incidence hyperboloids, and a grating rhomb. The wiggler is 5 m in length and has an adjustable taper, while the electron beam is produced by an RF linac. The optical elements of the ring together with the FEL interaction in the wiggler are modeled in three spatial dimensions to investigate the system from start-up to saturation. Both single-frequency and finite-pulse simulations are performed