共查询到20条相似文献,搜索用时 296 毫秒
1.
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。 相似文献
2.
D. Li K. Imasaki S. Miyamoto S. Amano T. Mochizuki 《International Journal of Infrared and Millimeter Waves》2006,27(2):165-171
The conventional cavity for a free-electron laser (FEL) oscillator usually forms an optical beam of Gaussian mode, which undergoes
transverse spread along the interaction region. The transverse divergence of an optical beam will induce reduction of the
FEL gain from three aspects: degenerating filling factor, causing diffraction loss and limiting the effective interaction
distance. Bessel optical beam has been experimentally demonstrated diffraction-free characteristics in its propagation, which
provides a possibility of improvement of FEL gain. In this paper, we present a conceptual design of a Bessel beam cavity for
the free-electron laser oscillator. This cavity generates nondiffracting optical beam in the wiggler, resulting in improving
the filling factor, decreasing the diffraction loss and elongating the effective interaction distance. 相似文献
3.
Efficiency enhancement of a two-beam free-electron laser using a nonlinearly tapered wiggler 下载免费PDF全文
A nonlinear and non-averaged model of a two-beam free-electron laser (FEL) wiggler that is tapered nonlinearly in the absence of slippage is presented. The two beams are assumed to have different energies, and the fundamental resonance of the higher energy beam is at the third harmonic of the lower energy beam. By using Maxwell's equations and the full Lorentz force equation of motion for the electron beams, coupled differential equations are derived and solved numerically by the fourth-order Runge-Kutta method. The amplitude of the wiggler field is assumed to decrease nonlinearly when the saturation of the third harmonic occurs. By simulation, the optimum starting point of the tapering and the slopes for reducing the wiggler amplitude are found. This technique can be applied to substantially improve the efficiency of the two-beam FEL in the XUV and X-ray regions. The effect of tapering on the dynamical stability of the fast electron beam is also studied. 相似文献
4.
Lalita Tripathi V.K. Agarwal P.C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(1):9-11
The radiation guiding of a plasma wave wiggler free-electron laser (FEL) in the Compton regime was examined. It was found that a Langmuir wave supported by a plasma cylinder acts as a wiggler for the generation of high-frequency coherent radiation when an annular relativistic electron beam passes through it. The radiation mode in the Compton regime tends to be localized close to the radius of the beam. A normal-mode analysis of this process revealed that the growth rate of the instability increases as the square root of the beam current. The treatment presented is restricted to the case where the radial width of the FEL radiation mode is larger than the beam radius, but smaller than the waveguide radius 相似文献
5.
Efficiency enhancement of a two-beam free-electron laser using a nonlinearly tapered wiggler 下载免费PDF全文
A nonlinear and non-averaged model of a two-beam free-electron laser(FEL) wiggler that is tapered nonlinearly in the absence of slippage is presented.The two beams are assumed to have different energies,and the fundamental resonance of the higher energy beam is at the third harmonic of the lower energy beam.By using Maxwell’s equations and the full Lorentz force equation of motion for the electron beams,coupled differential equations are derived and solved numerically by the fourth-order Runge-Kutta method.The amplitude of the wiggler field is assumed to decrease nonlinearly when the saturation of the third harmonic occurs.By simulation,the optimum starting point of the tapering and the slopes for reducing the wiggler amplitude are found.This technique can be applied to substantially improve the efficiency of the two-beam FEL in the XUV and X-ray regions.The effect of tapering on the dynamical stability of the fast electron beam is also studied. 相似文献
6.
Wang C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(5):649-653
We have simulated a 3 cm wavelength free-electron laser afterburner (FEL Afterburner) using two sets of parameters: one is for a 3-cm period wiggler and the other is for a 5.4 cm period wiggler. For the 3 cm period wiggler, the input beam energy is 112.5 keV, and for the 5.3 cm period wiggler the beam energy is increased to 290 keV to make the FEL Afterburner operate at the same frequency. It is found, from the simulations, that the FEL Afterburner with a longer period wiggler has a higher power conversion efficiency: larger than 16% $ for the 5.4 cm wiggler while only about 9% for the 3 cm wiggler. It is also shown that to enhance the interaction efficiency in the slow wave cavity, the slow wave number should be a little larger than the sum of the fast wave number and the wiggler wave number 相似文献
7.
8.
Yoshiaki Tsunawaki Nobuhisa Ohigashi Kunioki Mima Shin-ichiro Kurama Kazuo Imasaki Masayuki Fujita Chiyoe Yamanaka Sadao Nakai 《International Journal of Infrared and Millimeter Waves》1995,16(1):317-325
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. 相似文献
9.
短波长自由电子激光器的电子束在摇摆器中的传输通道长而狭窄, 须得电子具有良好的运动特性, 避免在传输过程中产生横向发散. 本文研究短波长自由电子激光器中超相对论电子在磁场具有横向分布的平面摇摆器中的三维运动特性, 用逐次逼近法推导相对论运动方程的解析表达式, 非线性数值计算模拟传输过程, 采用科尔莫 戈罗夫熵 方法分析运动的稳定性. 结果表明: 摇摆器磁场除使电子做周期性摇摆运动外, 还迭加了偏离轴线的横向漂移运动, 在没有外置的磁场聚焦系统情况下, 电子将偏离轴线横向发散; 但是, 恰当选取电子的横向初始速度, 可有效地防止电子运动的横向发散, 即使没有外置的磁场聚焦系统, 也能在长达10 m 的摇摆器中顺利传输, 横向位移范围不超过0.09 mm, 而且其运动是稳定的.
关键词:
短波长自由电子激光器
平面摇摆器
超相对论电子运动
运动稳定性 相似文献
10.
Shiqiu Cheng Destler W.W. Granatstein V.L. Antonsen T.M. Jr. Levush B. Rodgers J. Zhang Z.X. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(3):750-757
The results of experiments with a short period (9.6 mm) wiggler sheet electron beam (1.0 mm×2.0 cm) millimeter-wave free electron laser (FEL) amplifier are presented. This FEL amplifier utilized a strong wiggler field for sheet beam confinement in the narrow beam dimension and an offset-pole side-focusing technique for the wide dimension beam confinement. The beam analysis herein includes finite emittance and space-charge effects. High-current beam propagation was achieved as a result of extensive analytical studies and experimental optimization. A design optimization resulted in a low sensitivity to structure errors and beam velocity spread, as well as a low required beam energy. A maximum gain of 24 dB was achieved with a 1-kW injected signal power at 86 GHz, a 450-kV beam voltage, 17-A beam current, 3.8-kG wiggler magnetic field, and a 74-period wiggler length. The maximum gain with a one-watt injected millimeter-wave power was observed to be over 30 dB. The lower gain at higher injection power level indicates that the device has approached saturation. The device was studied over a broad range or experimental parameters. The experimental results have a good agreement with expectations from a one-dimensional simulation code. The successful operation of this device has proven the feasibility of the original concept and demonstrated the advantages of the sheet beam FEL amplifier. The results of the studies will provide guidelines for the future development of sheet beam FELs and/or other kinds of sheet beam devices 相似文献
11.
Mishra G. Maheshwari K.P. Praburam G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(1):181-186
Linearized Vlasov-Maxwell equations are solved to obtain the growth rate of free electron laser instability from a tenuous relativistic electron beam propagating in a partially dielectric loaded waveguide immersed in combined axial and longitudinal wiggler magnetic fields. The instability appears via cyclotron resonance interactions for wave perturbations very close to w -kV z-w c=nk 0V Z where n is the general harmonic number. For n =0, the gain is similar to a slow wave cyclotron amplifier. For n ⩾1, the growth rate is substantially larger than the standard slow wave free electron laser scheme utilizing a transverse wiggler field 相似文献
12.
13.
Summary The Hamiltonian for an electron travelling through a large-amplitude backward electromagnetic wave, an axial guide magnetic
field and radiation field is formulated. Poincaré surface-of-section plots show that this Hamiltonian is non-integrable, and
leads to chaotic trajectories. Equilibrium conditions are derived in the limit where the radiation field approaches zero.
Compared to conventional FEL, the total energy of the system at pondermotive resonanceE
c is large, while the electron's critical energy γc is low for electromagnetic wiggler FEL. Moreover, the threshold wave amplitude (A
r=A
c) of beam chaoticity is found at lower values of the radiation field amplitude compared to magnetostatic wiggler FEL. Previous
features confirmed that electromagnetic wiggler FEL can operate more coherently and more efficiently at moderated particle's
energy compared to magnetostatic wiggler FEL. 相似文献
14.
15.
R. El-Bahi M. N. Rhimi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(3):365-374
An analytic linear theory of the electron dynamics in a three-dimensional helical wiggler free electron laser (FEL) with
axial magnetic field is presented. Orbits are obtained by perturbing the steady state-trajectories in order to determine the
characteristic frequencies Ω± of the FEL. The effect of the self-fields on electron dynamics is studied and modified
steady-state orbits and their stabilities have been analysed considering variation of electron energy and density. Among the
features
encountered is that in both group-I and group-II, one of the characteristic frequencies may have either signs affecting then
the
stability of the motion, while in group-II operation a repulsion of the frequencies at a pseudocrossing leads to highly perturbed
trajectories when the wiggler frequency is approximately half the cyclotron frequency. Self-fields effects can significantly
impair
the stability of the electron orbits. For group-I orbits, they are more important for higher wiggler frequencies and lower
beam energies.
For group-II orbits, they remain less important for higher wiggler frequencies and lower beam energies before reaching the
inversion
zone, then they behave as for group-I orbits. It should be remarked that self-fields shift the inversion zone towards higher
cyclotron
frequencies the thing that is obtained by either decreasing the wiggler frequency or increasing the beam energy. It is shown
that the
axial velocity-induced self-magnetic field has a diamagnetic effect for both groups orbits, while the wiggler-induced self-magnetic
field has a diamagnetic effect for group-I orbits and a paramagnetic effect for group-II orbits. The paramagnetic and diamagnetic
effects are more important for higher beam energies and densities. 相似文献
16.
曙光一号自由电子激光装置的设计研究 总被引:1,自引:0,他引:1
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。 相似文献
17.
曙光一号自由电子激光器的理论计算 总被引:1,自引:0,他引:1
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%。 相似文献
18.
A free-electron laser (FEL) operating in the quantum regime can provide a compact and monochromatic x-ray source. Here we present the complete quantum model for a FEL with a laser wiggler in three spatial dimensions, based on a discrete Wigner-function formalism taking into account the longitudinal momentum quantization. The model describes the complete spatial and temporal evolution of the electron and radiation beams, including diffraction, propagation, laser wiggler profile and emittance effects. The transverse motion is described in a suitable classical limit, since the typical beam emittance values are much larger than the Compton wavelength quantum limit. In this approximation we derive an equation for the Wigner function which reduces to the three-dimensional Vlasov equation in the complete classical limit. Preliminary numerical results are presented together with parameters for a possible experiment. 相似文献
19.
Three-dimensional simulation of long-wavelength free-electron lasers with helical wiggler and ion-channel guiding 下载免费PDF全文
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. 相似文献