曙光一号自由电子激光器的理论计算

系统总结曙光一号自由电子激光器理论计算的主要结果:包括曙光一号装置主要参数的选取和理解;磁场失谐曲线的计算;常参数摇摆器和变参数摇摆器的主要结果;高阶波导模的贡献;电子束参数扰动对激光性能的影响;空间电荷效应等。计算结果表明,常参数摇摆器激光输出功率可达80MW,效率约50％;变参数摇摆器激光输出功率可达250MW左右,效率约16％。     

曙光一号自由电子激光自发辐射放大的理论计算

曙光一号自由电子激光装置用自发辐射放大(ASE)机理,在毫米波波段测得了数百毫瓦的光信号输出。利用三维WAGFEL程序,结合曙光一号直线感应加速器型自由电子激光放大器参数,详细地分析了自发辐射放大的增益、输出功率随电子束的质量(包括束流能散度、流强、发射度等因素)的变化情况,给出了相应的定标关系;并且考察了摇摆场随机误差对自发辐射放大功率的影响。最后对自发辐射放大的实验结果进行了分析。     

光学速调管的研究

用毫米波段的光学速调管结构改进自由电子激光器的增益和效率.编制计算机模拟的程序,用来设计光学速调管装置.对于采用小周期摆动磁场的特定情况,片状电子束电压300keV,电流17A,摆动磁场周期3.7mm,工作频率300GHz,光学速调管的增益和效率分别计算为27.9dB和0.5%.若电子束电压为450keV,电流为25A,磁场周期为1cm,工作频率为160GHz,计算结果增益和效率分别为32dB和2.7%.     

Three dimensional gain analysis of free electron laser with focusing permanent magnet wiggler

A three dimensional simulation software system developed to estimate a free electron laser (FEL) gain has been applied to FEL using a standard plane polarized wiggler and an alternately shifted magnet wiggler. It is seen for the latter wiggler that a large filling factor could be selected and each maximum gain corresponding to each orbit of electron beam concentrates at a certain frequency region of FEL radiation. It is, therefore, implied that a proper shift between the adjacent magnets in the wiggler produces the improvement of the FEL gain.     

曙光一号自由电子激光装置的设计研究

曙光一号自由电子激光装置(SG-1 FEL)是一台高功率毫米波段自由电子激光放大器,它由3.5MeV直线感应加速器、电子束调制系统、变参数摇摆器和微波种子源等部件组成。本文扼要叙述了SG-1 FEL的物理设计和主要技术参数,并重点分析了各主要部件的实验研究、计算模拟,以及物理设计和结构的特点。     

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．     

CAEP远红外100 μm FEL自发辐射谱的实验研究

在FEL实验中,电子束通过摇摆器,一方面由于周期性磁场作用,电子束轨迹要周期性的摆动,另一方面还要辐射同FEL辐射波长一致的自发辐射,该辐射谱反映电子束、摇摆器集成后的参数。在CAEP(Institute of China Academic Engineering Physics)远红外100 μm FEL实验中,自发辐射谱通过Ge∶Ga低温探头和远红外100 μm光栅谱仪测量。文章侧重从实际摇摆器磁场分析了远红外100 μm FEL的自发辐射谱。     

Measurements of microwave power and frequency in a pulsed freeelectron laser amplifier

We report output power and frequency measurements of a pulsed free electron laser (FEL) operating as an amplifier at 35 GHz, without guiding field. The experiment used an induction linac, which delivers an 800-A relativistic electron beam (2.2 MeV) with a flat-top of 40 ns into the helical wiggler. The input signal furnished by a 35-GHz magnetron source is amplified to power levels of the order of 80 MW. The experimental results are in good agreement with our simulations. Frequency chirping is observed, and its behavior as a function of the basic FEL parameters is discussed     

Study on a W-band modified V-shaped microstrip meander-line traveling-wave tube

The study on a miniaturized,low-voltage,wide-bandwidth,high-efficiency modified V-shaped microstrip meanderline slow-wave structure is presented.This structure is evolved from the original U-shaped microstrip meander-line slowwave structure,combining the advantages of a traditional microstrip and a rectangular helix.In this paper,simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out.Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA,respectively,this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.     

中物院高功率THz FEL装置的理论分析和优化设计

在1~3 THz频段内设计了11个分点频率,对每一频率的对应的场强和电子束能量进行了选取和计算。模拟结果表明:采用目前参数基本能够达到设计要求;辐射频段在2.6 THz附近时装置输出功率和增益都比较高,可以先锁定这个频段附近进行实验的调试;在长波段即1 THz左右时,滑移效应显著,腔增益和输出功率较低,实验实现比较困难,因此在1 THz频段附近必须积极想办法来提高输出功率。     

Experimental studies of microwave amplification in the ion-focusedregime

Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed     

Ka波段带状注相对论扩展互作用速调管放大器的分析与设计

带状注相对论扩展互作用速调管放大器是一种高功率、高频率的微波毫米波放大型器件, 具有广阔的应用前景. 本文分析了扩展互作用结构多间隙谐振腔的渡越时间效应, 推导了2π模场情况下谐振腔的能量交换系数和电子负载电导, 且通过计算表明工作在2π模式三间隙腔的电子负载电导是单间隙腔的9倍左右, 多间隙结构有利于提高器件效率. 利用三维粒子仿真软件, 对工作在Ka波段的带状注相对论扩展互作用速调管放大器进行了模拟研究, 采用宽高比为30:1的带状电子束以降低空间电荷效应, 在电子束电压为500 kV, 束流为1 kA, 轴向引导磁感应强度为0.8 T的情况下, 器件输出微波功率为190 MW, 频率为40 GHz, 器件效率为38%, 器件增益为69 dB.     

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.     

A long-pulse millimeter-wave free electron maser

An experimental free electron maser (FEM) facility is described which operates in the millimeter-wave regime. The experiment demonstrates that high gain and beam extraction efficiency can be obtained with low-current but high-quality electron beams. In the oscillator configuration, microwave powers of 110 kW were achieved with a 300-kV, 4-A beam, corresponding to a beam extraction efficiency of 9.2%. At low beam currents, with the system operating in the linear regime, the FEM gain curve was measured. The experiment uses a Pierce-type gun with a calculated beam emittance of 10.7-mm mrad at 300 kV and 4 A. The wiggler is of the iron permanent magnet hybrid design. The experiment is intended as a first step towards the development of continuous-wave (CW) devices that use beam energy recovery to make use of low-current, high-voltage power supplies     

Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

The theory for a two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Gain enhancement in two-stream free electron laser with planar wiggler and axial guide magnetic field

The theory for the two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Measurement of the temporal and spatial phase variations of apulsed free electron laser amplifier

We report temporal and spatial phase measurements of a pulsed free electron laser amplifier (FEL) operating in combined wiggler and axial guide magnetic fields. The system uses a mildly relativistic electron beam (750 kV, 90-300 A, 30 ns), and is excited by a high power 33.39 GHz magnetron source. The phase during the voltage pulse is measured by an interferometric technique from which frequency chirping is determined     

磁场逐渐增强的摇摆器

研究了用磁场增强摇摆器来提高自由电子激光器效率的机制．采用KMR方程，考虑空间电荷效应，模拟计算发现自由电子激光器的效率有了很大的提高，而且电子束能散度越大，对提高自由电子激光器效率越有帮助．因此采用磁场增强摇摆器能充分利用加速器的能量来莸得更高的自由电子激光器能量 关键词：     

Amplification and superradiant emission from a 33.3 GHz freeelectron laser with a reversed axial guide magnetic field

A new regime of free-electron laser (FEL) operation using a helical wiggler field and a reversed axial guide magnetic field is reported. The orientation of the axial field is such as to oppose the electron rotation imparted by the helical field. The 33.3-GHz FEL amplifier is driven by a mildly relativistic electron beam (750 kV 300 A, 30 ns) and generates 61 MW of radiation with a 27% conversion efficiency. The results are compared with those obtained when the axial guide field is in its conventional orientation, where considerable loss of power and efficiency is observed