振幅螺旋变化周期Wiggler场自由电子激光器增益的研究

本文研究了振幅螺旋变化周期Wiggler场自由电子激光器的增益特性。利用逐阶近似分析法解析了相对论电子在这种Wiggler场中运动的洛仑兹力方程和能量方程,获得了这种激光器的增益表达式。在给定其物理参数情况下,计算了这种激光器的增益。结果表明,激光器增益比同等物理参数下振幅恒定周期Wiggler场自由电子激光器有较明显提高;恒定振幅     

永磁Wiggler磁场的设计和小周期数装置的实验

Wiggler磁场是自由电子激光器的重要组成部分。根据计算分析和自由电子激光器的总体设计要求,提出了Wiggler磁场的设计考虑。研制出小周期数装置,在改变磁隙、周期、磁块尺寸以及材料的情况下进行了测量,同时测量了磁场的正弦分布。结果表明,设计并研制的小周期数Wiggler磁场满足总体要求,可用于自由电子激光器。     

辐射泵浦的自由电子激光器工作条件

分析研究了利用微波束或者光束泵浦自由电子激光器的工作条件。结果表明,辐射的相干时间是重要参数。只有时间足够长的辐射束,才能做自由电子激光器的 Wiggler。     

变参量Wiggler FEL的三维非线性理论

本文建立了变参量Wiggler自由电子激光放大器的三维自洽非线性理论。考虑电磁波、电子注和Wiggler场三者均在三维空间中变化,忽略电子注的自身场和空间电荷效应,导出了带有变参量双绕螺旋Wiggler场和轴向导引磁场的矩形波导,轴对称电子注自由电子激光器的非线性互作用微分方程组。数值模拟表明:在适当位置逐渐减小Wiggler场的幅值或周期均能有效地提高电子注的能量转换效率。     

工作在可见和紫外波段的自由电子激光器

当前,人们非常关心自由电子激光器向短波长发展的问题。Madey论证了用直线加速器可能得到的自由电子激光短波极限为1μm。我们提出利用自由电子激光器的谐波辐射,在直线加速器上,可望得到可见光和紫外波段的短波长激光。实现自由电子激光器谐波输出的关键是建立高K值的Wiggler磁场。我们从理论上分析了自由电子激光器辐射谱和增益的非线     

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。     

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。     

自由电子激光器中Cherenkov相干辐射机理研究

由于普通的Compton—Raman型自由电子激光器是一类利用被Wiggler磁场驱动的相对论电子束横向动能转换成辐射能的装置,在这种系统辐射机理中,大部分电子束的纵向动能没有被利用。为进一步提高能量转换效率,我们根据一种系统可形成二种不同辐射机理的原则,以及现有的相对论电子束Cherenkov辐射理论和实验基础,研究了一种把普通自由电子激光器中相干辐射机理和相对论电子束在慢波器件所形成的Cherenkov辐射机理统一于一体的新辐射机理—Cherenkov相干辐射机理。利用推迟势公式研究了这     

采用静电聚束的环形自由电子激光器

本文用线性理论研究了一种采用静电聚束系统和角向摆动场(Wiggler)的环形自由电子激光器,导出了自由电子激光不稳定性色散方程,并从此方程求得了最大自由电子激光不稳定性增长率。文中还就有关问题进行了讨论。     

自由电子激光模式的波导传输

自由电子激光器通常希望Wiggler磁场间隙小,以提高中心场强。希望Wiggle长度长,以提高相互作用的增益。考虑辐射波长λ=1μ,漂移管半径a=5.0mm及漂移管管长L=30m的例子。在这种情况下,费涅尔数a~2/λL=0.83<1,Wiggler中间的细长波导参与了对辐射的限制,而引起传输损耗。这不同于传统的费涅尔数大于1的自由电子激光器腔,而和近年来发展起来的波导激光器谐振腔情况类似。     

电子在磁场与纵向坐标无关的摆动器中的辐射谱分布

应用Ｍａｄｅｙ定理计算了电子在ＳｈｏｌｍｏＰｉｎｈａｓ提出的一种磁场与纵向坐标无关的摆动器中自发辐射谱分布，并将所得到的结果与利用线性摆动器时产生的辐射谱进行了比较，发现它们有相同的形式。初步论证了利用该摆动器产生高次谐波相干辐射的可能性。     

A solenoid-derived wiggler

A novel wiggler design for use in free-electron lasers (FELs) is proposed, consisting of a staggered array of magnetic poles situated inside the bore of a solenoid. The resultant field pattern consists of a periodic transverse magnetic field on axis, as well as a longitudinal guide field. Such a wiggler has several advantages: the longitudinal field acts to confine the electrons near the FEL axis, high fields can be attained at short wiggler periods, the field strength is easily varied, and fabrication and testing of the wiggler are relatively easy. It is planned to use this wiggler design in a far infrared FEL to be built at Stanford University     

A staggered-array wiggler for far-infrared, free-electron laseroperation

A staggered-array wiggler for a far-infrared free-electron laser (FEL) has been built at Stanford, and its magnetic properties have been tested. This type of wiggler has several desirable features: high wiggler field at short wiggler periods, wavelength tuning by a solenoid current, electron beam confinement by a solenoid field, and looser machining tolerances. A 10.8-kilogauss peak wiggler field has been measured at a 7.0-kilogauss solenoid field for a 1.0-cm wiggler period and a 2.0-mm gap. The small-signal gain has been calculated analytically and by computer simulation for a 0.5-m long wiggler. For an 8-A, 9-ps current pulse and a 3.3-MeV electron beam, 5-dB gain is predicted. Twenty- to thirty-percent wavelength tuning can be achieved by adjusting the solenoid field and still maintain reasonable small-signal gain. The pulsed-wire technique was employed to test the field uniformity of this novel wiggler, and the measured field variation was about 1%     

Design of a compact, optically guided, pinched, megawatt class free-electron laser

A conceptual design for a compact megawatt class free-electron laser (FEL) operating at 1 /spl mu/m is presented. The proposed FEL consists of an optically guided, pinched amplifier configuration driven by a RF linac. The gain length, efficiency, electron pulse slippage, and the distance between the wiggler and first relay mirror are determined for a megawatt class design. Of particular concern in the design is the overall length of the optical system, i.e., the wiggler length and distance to the first relay mirror. In the present design, the wiggler length is /spl sim/1 m and the distance between the first relay mirror and the wiggler is determined by the average intensity damage threshold on the mirror. By focusing the electron beam, the optical beam can be pinched upon exiting the wiggler. The pinched optical beam has a reduced Rayleigh length which permits the first relay mirror to be relatively close to the wiggler. By pinching the optical beam and employing grazing incidence the first relay mirror can be located within /spl sim/3 m of the wiggler. It is shown that frequency detuning can more than double the FEL efficiency. In the present design with frequency detuning and uniform wiggler the efficiency is /spl sim/1.8%. In addition, electron-pulse slippage is shown to be substantially reduced in a high-gain amplifier.     

A microwave FEL design with waveguide and wiggler tapering

We discuss a new design of a very high efficiency FEL amplifier in the microwave band, based on the waveguide and wiggler tapering technique. Up to 75% efficiency is reported, even in a relatively relaxed wiggler design     

Novel approaches to FEL operation: The gas-loaded FEL and a high efficiency FEL design

Two novel methods for improving free-electron laser (FEL) oscillator performance are discussed: (a) The gas-loaded FEL (GFEL) allows operation at snorter wavelengths for a given accelerator energy and wiggler. Experimental results of laser operation with a gas retention foil in the electron beam line and with the introduction of gas to the wiggler cavity are presented, (b) An FEL design utilizing a time-ramped microwave field to accelerate electrons as they lose energy to radiation allows for high conversion efficiencies. Parameter constraints for such an FEL are discussed, leading to a structure that integrates a wiggler with a linac. It is shown that conversion efficiencies of 50% at λ = 10 μm with a 2m wiggler length can be achieved for typical FEL parameter values without sacrificing small-signal gain     

Free-electron lasers with electromagnetic standing wave wigglers

A detailed analysis of the electromagnetic standing wave wiggler for free-electron lasers (FEL's) is conducted for both circular and linear wiggler polarizations, following a single-particle approach. After determination of the unperturbed electron orbits in the wiggler field, the single-particle spontaneous emission spectrum and subsequently the gain in the low gain Compton regime (using the Einstein coefficient method) are explicitly calculated. This analysis results in a clear understanding of the resonance conditions and the coupling strength associated with each resonance of this type of FEL. In particular, a striking feature obtained from this investigation is that the electromagnetic standing wave wiggler FEL, under certain circumstances, exhibits a rich harmonic content. This harmonic content is caused by the presence of both the forward and backward wave components of the standing wave wiggler field. In addition, the nonlinear self-consistent equations for this type of FEL are also presented, permitting further investigation of it by the theoretical techniques and numerical codes developed for conventional FEL's.     

行波磁场摆动器产生自由电子激光的初步研究

在一定放置的线圈中通以正弦交流电时,其附近空间就会产生一个正弦行波磁场,磁场的极距和行波的速度都可以通过输入的频率加以调节。相对论性电子在这种摆动器中的散射波长比较短,而能量因子值可以变,这既有利于向短波长方向发展,又有助于自由电子激光器的小型化。     

等离子体尾波场摇摆器自由电子激光

自由电子激光的小型化和实现激光短波长一直是自由电子激光领域的研究热点,而短周期、强场摇摆器是解决此问题的行之有效的途径。文章分析了利用等离子体尾波场作为自由电子激光摇摆器的机制,推得自由电子的自发辐射谱,利用麦迪定在线阵列理论求得电子的受激辐射公式,得到小信号增益。