喇曼自由电子激光器辐射谱的测量

本文报道了利用微波栅摄谱仪测量在超辐射工作条件下的喇曼自由电子激光器辐射谱的初步结果。观察到了毫米波自由电子激光器的调谐特性。实验结果表明,辐射谱的中心频率随波荡场强度的增加而减小,这与考虑波导模影响的集体制式自由电子激光的有关理论预言相符。     

连续可调的喇曼自由电子激光器

麻省理工学院已经证明了自由电子激光器在7~18 GHz频率之间的连续调谐作用。在该学院物理研究生J.法简斯及其同事合作进行的实验中，对单波导模和集合喇曼方式工作的自由电子激光器的调谐特性进行了演示。     

喇曼自由电子激光器的实验研究

我们研制了一台基于受激喇曼散射的自由电子激光器。精心设计的无箔二极管发射出柱状或空心柱状电子束。电子束打靶实验表明它是高度准直的;利用Lamor运动实验测试出电子束的归一化发射度为23π·mrad-cm,完全满足受激喇曼散射模式判据。该电子束在抽空为5×10~(-5)Torr、内径φ20mm的漂移管中传输,受到右旋圆偏极双绕电磁波荡器或轴对称铁环波荡器(周期分别为2.2cm及2.25cm)的泵浦,均获得超辐射模式的自由电子激光辐射。测     

由厚靶轫致辐射确定喇曼自由电子激光器电子束的分布

本文采用测量电子轰击厚靶所产生的轫致辐射的方法来确定喇曼自由电子激光器中电子束的运动和分布规律.介绍了基本原理.给出了在激光器运转时所测得的电子束在二极管和漂移管内的运动规律和分布情况.实验结果和理论预言基本相符.     

喇曼自由电子激光器参量测量用法拉弟杯

喇曼自由电子激光器装置所使用的激光工作物质是准直度好、能散度小的脉冲强流电子束,其动能0.5Mev,电流密度几 KA/cm~2。因此测量脉冲强流电子束的参量以及在引导磁场作用下电子束在真空金属漂移管内的传输特性成为建立喇曼自由电子激光装置的重要环节。本文的法拉弟杯正是为了适应实验提出的测量高电流密度脉冲电子束的要求。     

喇曼自由电子激光器二极管的实验研究

文章给出了用于一台喇曼自由电子激光器磁场浸没型无箔二极管工作特性的实验研究。比较了不同结构、不同电极参量、不同电极材料和不同磁场下的典型结果。分析了不同的束输出条件下所遵循的规律。     

渐变Wiggler技术在低能电子束喇曼型自由电子激光器中的应用

本文利用有质动力势导出了自由电子激光器效率提取表达式,分析了渐变Wlggler技术对提高激光器效率的作用,并利用这一技术进行了渐变Wiggler场强自由电子激光器实验。结果表明其效率是相应恒定Wiggler自由电子激光器的2.6倍。     

三毫米波喇曼自由电子激光器实验研究

研制出新型小周期波荡器，报道三毫米波拉曼自由电子激光器实验。采用Ｉｃｍ周期双绕螺旋线波荡器，在相同加速器能量下，自由电子激光输出波长由８ｍｍ缩短到３ｍｍ。输出功率为１ＭＷ，效率为０．６６％。     

喇曼自由电子激光器中辐射的输出及测试

获得了喇曼自由电子激光器的激光辐射输出。给出了漂移管、出射及接收喇叭、滤波器等主要元件的设计方法及激光器实验中辐射测试的结果。     

纤维喇曼激光器

用掺钕钇铝石榴石激光器和石英丝谐振腔，五位学者除了1.06微米的受激发射外，还观察到1.12微米和1.18微米的强烈的喇曼辐射。类似的工作已由贝尔电话实验室R. H. Stolen, Ravi Κ. Jain和他们的同事作了演示。     

Effect of velocity spread on finite-length free electron laser gain

A theory of general stimulated backscattering by a hot, relativistic electron beam propagating through a spatially periodic, transverse magnetostatic field is presented. The electrons are chosen to have a Lorentzian distribution in velocity space. Though energy spread acts to diminish gain, its effect is negligible if Δγ/γ < < N_-1, where N is the number of undulator periods. The analysis is linear and applicable to both the single-particle and collective regimes.     

Degradation in gain for a free electron laser amplifier due to electron momentum spread

A finite spread in axial momentum for the electron beam in a free electron laser amplifier is shown to decrease the small-signal gain. For millimeter and sub-millimeter wave amplifiers, where exponential growth dominates the gain, it is shown that the gain is approximately 3 db below that for a cold beam if the relative momentum spread (Δu/u)_1/2 = (G_o/248)^1/2 (λ_o/L), where G_o?1 is the gain in db for the cold-beam case, λ_o is the magnetic wiggler period, and L is the amplifier length. Exact numerical examples are given for representative FEL amplifiers at 35 and 550 GHz.     

Measurement of stimulated transverse mode mixing in a free electron laser

We report the first measurement of the off-diagonal terms in the transverse gain matrix in a free electron laser. We show that the higher order transverse modes stimulated in the FEL interaction diminish in amplitude as the electron beam size is increased, that the far field and the near field effects of the excited modes are not equivalent, and that in this low divergence case, the mode mixing is insensitive to the resonance parameter. Remarkably close agreement is demonstrated with the theory [1]. The effects of a multiple mode input beam are also observed, and the theoretical expression is derived.     

Experimental study of velocity spread in a cycloiding electron beam

The paper describes briefly the effect of electron velocity spread on the principal operating parameters of a gyrotron. A method of reducing velocity spread is discussed, and a new method of measuring electron velocity spread in a cycloiding electron beam is presented. By use of a high precision radial-gauge and multilobe collector, the distribution of the beam transverse velocity of a gyrotron is accurately measured. Compared with other methods conventionally used in this country and abroad such as those using retarding-field, pin-hole collector, this method is characterized by the fact that the space charge effect would not modify the experimental results, and the beam velocity spread of a gyrotron under real operating conditions can be measured. In order to characterize the beam in an overall manner, a new concept of relative density velocity spread is introduced in this paper. The experimental work has been performed on a special electron beam analyser with advanced design.     

Effect of electron velocity spread on gyro-peniotron efficiency

The paper describes the influence of the velocity spread of the electrons on the interaction efficiency and on other operational characteristics in the gyro-peniotron oscillator. Numerical simulation shows a drastic efficiency reduction from more than 45% to less than 30% with an electron velocity spread of 10% for a 35GHz, TE₀₃ mode gyro-peniotron operating at the third harmonic. The operation ranges of the device parameters at a defined efficiency level are also decreased when the velocity spread of the electrons increases.     

CHAOTIC ELECTRON TRAJECTORIES IN A CIRCULAR FREE ELECTRON LASER

The motion of a relativistic electron is analyzed in the field configuration consisting of a circular wiggler magnetic field, an axial magnetic field, and the equilibrium self-electric and self-magnetic fields produced by the non-neutral electron ring. By generating Poincare surface-of-section maps, it is shown that when the equilibrium self-fields is strong enough, the electron motions become chaotic. Although the realistic circular wiggler magnetic field destroys the inte-grability of the electron motion as the equilibrium self-fields do, the role the latter plays to make the motions become chaotic is stronger than the former does. In addition, the axial magnetic field can restrain the occurrence of the chaoticity.     

Chaotic electron trajectories in a circular free electron laser

The motion of a relativistic electron is analyzed in the field configuration consisting of a circular wiggler magnetic field, an axial magnetic field, and the equilibrium self-electric and self-magnetic fields produced by the non-neutral electron ring. By generating Poincare surface-of-section maps, it is shown that when the equilibrium self-fields is strong enough, the electron motions become chaotic. Although the realistic circular wiggler magnetic field destroys the integrability of the electron motion as the equilibrium self-fields do, the role the latter plays to make the motions become chaotic is stronger than the former. In addition, the axial magnetic field can restrain the occurrence of the chaoticity.     

电子束纵向泵浦准分子激光器装置参数的测量

本文描述了电子束纵向泵浦准分子激光器装置中磁场的测量,它是用标准电阻法或带有积分器的探测线圈完成的,而电子束的总能量是用一个石墨量热计测量的。用重氮化铬膜监视激光腔内电子束的位置,我们得到了电子束的FWHM值为～2.7cm。用带有50Ω阻抗的同轴导体构成的法拉弟探头,诊断电子束脉冲的时间特性。     

A prebunched free electron laser

The narrow width of an rf-accelerated electron micropulse can be exploited to yield gain significantly higher than in the conventional FEL. If the micropulses are much shorter than the wavelength of the generated wave and the electrons are resonant with the FEL beat wave, then a low order prebunched FEL interaction results. All electrons lose energy to the wave