拉曼自由电子激光器

文章介绍了拉曼自由电子激光器的应用，概述了我们在拉曼自由电子激光器调谐、新型小周期波荡器、具有分布反馈谐振腔的拉曼自由电子激光振荡器和虚火花放电等方面的研究进展。     

拉曼型自由电子激光器中相对论电子运动稳定性的比较研究

拉曼型自由电子激光器作为一种兆瓦级高功率毫米波、太赫兹波辐射源, 其电子的运动稳定性对整体器件的性能至关重要.本文采用科尔莫戈罗夫熵方法, 以典型的麻省理工学院公布的实验数据为例, 比较研究拉曼型正向导引磁场和反向导引磁场两类自由电子激光器中相对论电子的运动稳定性. 结果表明:摇摆器绝热压缩磁场对电子运动的稳定性无实质性影响, 但对电子运动影响大; 电子束自身场在拉曼型正向导引磁场自由电子激光器中使电子运动稳定性变差, 而在拉曼型反向导引磁场自由电子激光器中则可改善电子运动稳定性. 关键词： 拉曼型自由电子激光器 相对论电子运动稳定性 科尔莫戈罗夫熵 电子束自身场     

渐变摇摆场拉曼自由电子激光实验

采用渐变摇摆场技术进行了拉曼型自由电子激光实验,获得了最大辐射功率31MW、波长8～10.4mm的微波辐射输出,电子能量转换效率达9.68％。实验表明,对强流低能(0.45MeV)电子束拉曼自由电子激光器,渐变摇摆场比恒定摇摆场的自由电子激光器能量转换效率高2.6倍。     

不用导引磁场的虚火花束源拉曼自由电子激光器的数值计算

采用非线笥模型对拉曼自由电子激光器进行数值模拟,发现虚火花束源自由电子激光器苛以去掉导引磁场,用小周期摇摆器,实现器件的小型化和高功率。     

利用拉曼自由电子激光测量目标毫米波散射特性的初步研究

介绍拉曼自由电子激光器应用于目标的毫米波散射特性研究所做的一些探索性工作。自由电子激光器是七十年代中期出现的一种新型强相干辐射源。拉曼自由电子激光输出在毫米波段具有高功率、可调谐等优点。利用自由电子激光辐射高能量和宽频带的特点，研究及材料的毫米波散射特性，开创了新的研究方向和研究途径，具有重大的应用前景。本文在这方面进行了探索性研究，得到了一些初步结果。     

自由电子激光器

<正> 一、自由电子激光器的特点自由电子激光器是一种新型激光器。它的基本特点是:不需要气体、液体或固体作为工作物质,而是由高能电子束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,具有如下优点。     

自由电子迴旋谐振激光器

本文提出了一种新型的自由电子激光器—自由电子迴旋谐振激光器。文中给出了这种激光器的电子效率和起振电流表达式。     

改型摆动器光学速调管谐波自由电子激光器

提出了一种光学速调管自由电子激光器的新方案，并用Ｍａｄｅｙ定理这种新型的谐波自由电子激光器进行了分析和计算。结果表明，这种新型结构的自由电子激光器可以增大高次谐波的辐强度和增益，从而可望使自由电子激光工作在高次谐波上，提供短波长的光输出。     

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：     

自由电子迴旋谐振激光器

本文提出了一种新型的自由电子激光器—自由电子迴旋谐振激光器。文中给出了这种激光器的电子效率和起振电流表达式。 关键词：     

Pump-free crossed-field free-electron laser

Starting from basic concepts, we propose a new kind of free-electron laser (FEL): the pump-free crossed-field FEL in which the condition E_o+V_o×B_o=0 is not satisfied, and the electron orbit without radition fields and undulator or wiggler fields is not straight line (in planar configuration) or cycloid (in magnetron-like configuration). This paper presents a fluid dynamical analysis of the pump-free crossed-field FEL, in which the space charge effect is not taken into consideration. FEL instability is found near resonance . While no FEL instability is found near resonance      

A 1-MW, 1-mm continuous-wave FELtron for toroidal plasma heating

A powerful, continuous-wave millimeter radiation source is presented. An electrostatic Cockcroft-Walton accelerator (2.5 MV) drives an FEL (free-electron laser) of 1 MW power. The accelerator has a new design in order to obtain a very powerful (50 MW) electron beam and very small ripple. A recovery system is used to increase RF power and efficiency. The FEL oscillator is 1.5-m long, with a permanent magnet helical wiggler. The cavity is equipped with Bragg mirrors. The FEL is set at the high voltage terminal     

New method for energy compensation of free electron laser

In this paper the theory of FEL operation in a longitudinal uniform magnetic field integrated with a synchronous precessing electro-magnetic field is expounded in view of the main problems in FEL development. A new energy compensation method is suggested as a new way and basis for the development of FEL research.     

High-gain lasing and polarization switch with a distributed optical-klystron free-electron laser

This Letter reports the first experimental results from the world's first distributed optical-klystron (DOK) free-electron laser (FEL), the DOK-1 FEL, at Duke University. The DOK-1 FEL is a hybrid system, comprised of four wigglers: two horizontal and two helical. With the DOK-1 FEL, we have obtained the highest FEL gain among all storage ring based FELs at 47.8% (+/-2.7%) per pass. We have also demonstrated that the FEL gain can be enhanced by increasing electron bunching using wigglers with a different polarization. Furthermore, we have realized controlled polarization switches of the FEL beam by a nonoptical means through the manipulation of a buncher magnet.     

Possible application of X-ray optical elements for reducing the spectral bandwidth of an X-ray SASE FEL

A new design for a single pass X-ray Self-Amplified Spontaneous Emission (SASE) FEL is proposed. The scheme consists of two undulators and an X-ray monochromator located between them. The first stage of the FEL amplifier operates in the SASE linear regime. After the exit of the first undulator the electron bunch is guided through a non-isochronous bypass and the X-ray beam enters the monochromator. The main function of the bypass is to suppress the modulation of the electron beam induced in the first undulator. This is possible because of the finite value of the natural energy spread in the beam. At the entrance to the second undulator the radiation power from the monochromator dominates significantly over the shot noise and the residual electron bunching. As a result the second stage of the FEL amplifier operates in the steady-state regime when the input signal bandwidth is small with respect to that of the FEL amplifier. Integral losses of the radiation power in the monochromator are relatively small because grazing incidence optics can be used. The proposed scheme is illustrated for the example of the 6 nm option SASE FEL at the TESLA Test Facility under construction at DESY. As shown in this paper the spectral bandwidth of such a two-stage SASE FEL (Δλ/λ 5 × 10⁻⁵) is close to the limit defined by the finite duration of the radiation pulse. The average brilliance is equal to 7 × 10²⁴ photons/(s × mrad² × mm² × 0.1% bandw.) which is by two orders of magnitude higher than the value which could be reached by the conventional SASE FEL. The monochromatization of the radiation is performed at a low level of radiation power (about 500 times less than the saturation level) which allows one to use conventional X-ray optical elements (grazing incidence grating and mirrors) for the monochromator design.     

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。     

稳定波长反馈引起的失谐对自由电子激光的影响

 利用修改的一维非定态程序,基于美国杰弗逊实验室（JLab）Demo自由电子激光装置的参数,对高功率自由电子激光振荡器稳定波长的反馈系统进行了数值模拟。电子微脉冲为高斯型分布,每个纵向网格中取16个模拟宏电子,不考虑电子束的能散度。结果表明：当无反馈时,腔内光功率和波长都可以在一定范围内稳定;加入反馈后,由于电子束能量的变化所引起的等效失谐对整个系统有着重要的影响,甚至可能导致电子和光场失去相互作用,从而使得装置不能工作。提出应该在光场达到饱和以后再启动稳定波长反馈系统。模拟结果证明,该实施方案是合理有效的,可以避免其对FEL运行的严重影响。     

X射线自由电子激光试验装置

X射线自由电子激光试验装置(以下简称"SXFEL试验装置")是中国第一台X射线相干光源,其输出波长小于9 nm.这台基于0.84 GeV直线加速器、以掌握装置相关技术和实验演示种子型自由电子激光(FEL)级联与短波长回声型FEL为主要目标的自由电子激光装置,于2020年11月通过国家验收.本文将介绍SXFEL试验装置的...     

Undulator beamline optimization with integrated chicanes for X‐ray free‐electron‐laser facilities

An optimization of the undulator layout of X‐ray free‐electron‐laser (FEL) facilities based on placing small chicanes between the undulator modules is presented. The installation of magnetic chicanes offers the following benefits with respect to state‐of‐the‐art FEL facilities: reduction of the required undulator length to achieve FEL saturation, improvement of the longitudinal coherence of the FEL pulses, and the ability to produce shorter FEL pulses with higher power levels. Numerical simulations performed for the soft X‐ray beamline of the SwissFEL facility show that optimizing the advantages of the layout requires shorter undulator modules than the standard ones. This proposal allows a very compact undulator beamline that produces fully coherent FEL pulses and it makes possible new kinds of experiments that require very short and high‐power FEL pulses.