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.     

行波场Wiggler自由电子激光器

分析了辐射行波场Wiggler自由电子激光器的工作状态,计算了激光器的增益,分析了获得正增益的条件。     

驻波场Wiggler自由电子激光器

本文分析了以驻波辐射场作Wiggler的自由电子激光器的工作条件,计算了激光器的增益。     

英国赞助研制自由电子激光器

英国科学和工程研究理事会最近把一笔100万美元的款子赠给苏格兰各大学，赞助他们合作努力，设计、建造和运转一台自由电子激光器。这台激光器将建立在格拉斯哥大学开耳芬实验室的直线电子加速器附近。该项计划由Heriot-Watt大学的D. 史密斯教授领导，他说这笔赠金代表着英国最大的一项高等学府激光计划。     

轴向场自由电子激光器的辐射谱

本文用平均阻尼效应等效于辐射场对相对论电子的反馈作用,用阻尼振于模型来描述自由电子在轴向磁场中的辐射过程。导出了轴向场自由电子激光器的辐射频率和谱线宽度的解析表达式,讨论了影响谱线宽度的因素。     

带轴向场自由电子激光器的增益

给出了带轴向场自由电子激光器的增益,并讨论了轴向场的效应。     

自由电子激光器

一 自由电子激光器的特点 自由电子激光器是一种新型的激光器,问世以来,爱到很大的重视,它的基本特点是:它不需要气体、液体、或固体作为工作物质,而是由高能电子注的能量转变为激光的能量。也可以说,自由电子激光器的工作物质就是自由电子,它和已有的激光器比较起来,具有一系列优点如下:     

自由电子激光器

本文从理论和实验方面评述了自由电子激光器。首先讨论高速电子束穿过螺线摆动器时发射的光谱。当光脉冲与电子一起穿过螺线摆动器时，电子受迫发出同样频率的光。计算了由这种感应辐射而获得的增益。然后介绍了斯坦福关于感应辐射自由电子激光器实验的一些具体细节。最后讨论有关自由电子激光器的一些问题。     

自由电子激光器的位相条件

基于相对论电子在光场和静态磁场作用下的能量方程和洛仑兹方程,分析了自由电子激光器运转的位相条件。结果表明,入射光波相对于相对论电子束的初位相ψ在第1和第4象限,相对论电子的能量将主要表现为能量减低,初位相ψ在第2和第3象限主要表现为使相对论电子进一步被加速。     

Hole coupling in free electron lasers

Numerical simulations of the performance of a far-infrared free electron laser with an aperture in the upstream cavity mirror are presented. Two different applications of mirror apertures are studied: broadband extraction of radiation and injection of the electron beam. The emphasis is on the effect of the aperture on the amplitude of the higher-order transverse modes. It is shown that the mode distribution at saturation can be greatly influenced by variation of the mirror radius of curvature. A simple formula which is quite useful for predicting the dominant higher-order modes is derived. This permits optimization of the cavity with respect to the application in question     

Orbit stability in free electron lasers

Helical magnetic wigglers for free electron lasers can produce non-helical electron trajectories if a uniform axial guide magnetic field is imposed. Friedland's necessary criterion for the existence of helical orbits is reviewed and shown to apply for non-relativistic electron energies. An experiment designed to test this criterion is described and results are compared with theory.     

A 70-period high-precision microwiggler for free electron lasers

We have designed, constructed, and operated a 70-period microwiggler for free electrons lasers (FEL's). The device is a pulsed ferromagnetic-core electromagnet with a period of 8.8 mm, which generates an on-axis peak magnetic field of 4.2 kG. The pulses, of 0.5 ms duration, are generated at a rate of 0.5 Hz. Each field peak is independently tunable. We employed a novel tuning regimen to reduce the RMS spread in the peak amplitudes to 0.12%, the lowest value thus far attained in a sub-cm-period periodic magnetic field     

e-Guns and depressed collectors for two-stage free electron lasers

Ane-gun, depressed collector, and guide-field solenoid have been designed and tested for operation at a maximum of 400 kV and 38 A in order to simulate key components of a typical low-voltage free electron laser (FEL). Detailed beam-energy-spread analyses and computer simulations are presented for thee-gun and the drift regions. The results of experiments with the depressed collector show beam-current-recovery efficiencies of over 90 percent fore-beam voltages from 160 to 400 keV. We have also set up and confirmed computer-code predictions that a space-charge depression in the collector (which is essential for efficient collection) forms at a collector-voltage setting of 1 percent of the beam voltage. These results demonstrate the validity of substantially increasing the efficiency of systems by using depressed collectors to recover the bulk of the energy which is left in thee-beam after it leaves the laser resonator. The recovery-efficiency parameter (recovered current/cathode-emission current) is shown to be a function of the relativistic-orbit parameter (B/betagamma) and reaches a maximum of 94 percent. These results imply that FEL system efficiencies can be achieved which are an order of magnitude higher per stage than would be possible without the use of depressed collection.     

平面形自由电子激光器中的边带不稳定性

本文对平面形自由电子激光器中的边带不稳定性进行了动力学研究。提供了一种处理平面形和螺旋形自由电子激光边带不稳定性的方法,同时解释了平面形自由电子激光边带不稳定性的特点。     

Beam wave interactions in free electron lasers

This paper presents a direct and simple ballistic approach to the analysis of interactions taking place in free electron lasers. By keeping the analysis quite simple and general, including self fields and space charge, it is found that five different interactions can occur in these devices, and that they can be classified in three groups with pertinent characteristics. The ‘synchronous’ interaction, in which the beam electrons remain (approximately) in a fixed phase of the rf-wave, is characterized by a bunching effect which occurs along the DC trajectories with no radial displacements, and results in a gain usually proportional to the cube root of the beam current. Under certain conditions, however, this gain can be proportional to the fifth root of the current. The two other classes of interactions are ‘resonant’ and non-relativistic, and are characterized by large radial displacements. No bunching can occur and the gain is usually found to be proportional to the square root of the current. However, under well defined conditions, the gain is found to be proportional to the cube root of the current. The analysis results in dispersion relations involving coupling and beam impedances which are determined for TE modes in cylindrical waveguides, neglecting space charge     

康普顿型自由电子激光器的实验研究

这里介绍我国第一台康普顿型自由电子激光器的实验研究情况。这是一台以30 MeV直线加速器为基础,配置上电子束输运系统、常周期磁摆动器(Undulator)和光学系统构成的器件。辐射输出波长在9～11μm。1986年11月,在这台器件上获得了平均功率1.4W的10μm辐射输出。下面我们介绍一下康普顿型自由电子激光器的实验装置,如     

变参数自由电子激光器的研究

在单粒子模型基础上用一种简便的能量模型计算了变参数Wiggler自由电子激光器的增益。结果表明,周期磁场振幅沿z方向增加,或空间周期长度沿z变化都可以提高增益。但前者比后者的效果更明显。