合肥储存环相干谐波自由电子激光研究方法的改进

 根据简单的计算模型,导出辐射能量谱形状因子和相干谐波辐射表达式,用此表达式讨论了不对称光学速调管的相干谐波辐射;对于合肥储存环相干谐波自由电子激光,提出了一个不对称光学速调管相干谐波辐射的研究方案,并且作了详细的计算,结果表明在较高的电子束能量下,调整光学速调管和外激光参数,使辐射段波荡器的辐射基波与外激光的二次谐波共振,进行相干谐波产生实验,能获得10⁹量级相干加强因子。     

纯永磁波荡器基波与谐波磁场的三维计算与测试

 对标淮的纯永磁波荡器进行了三维磁场的有限元计算,给出了纯永磁波荡器的基波与谐波磁场的幅值与相位,并与测试结果进行对比,结果表明,标准的纯永磁波荡器谐波磁场幅值比基波幅值低两个数量级。     

有轴向磁场的平面摆动器自由电子激光的自发辐射

研究了电子在有轴向磁场的平面摆动器中的辐射，得到了一个较普遍的自发辐射谱表达式，谱线的形状也是由函数ｓｉｎｃ（ｕ）决定，当电子的能量较高或者没摆动器轴线观察时，辐射是满圆极化的，数值分析表明，在平面摆动器中附加适当的轴向磁场，可以提高各次谐波辐射的强度，对于基波和较低次谐波，提高更明显。     

CAEPXFEL波荡器束线初步物理设计

中国工程物理研究院计划开展XFEL光源的研制,主要通过电子束在波荡器中的辐射特性产生硬X射线。根据理论分析和数值模拟,在电子束最高能量可达12GeV的实际条件下,初步设计了一条间隙可调的真空外波荡器束线,波荡器分为25段,每段长3.86m,间隙7~10mm,周期长度25.4mm,磁场0.636~1.03T,束线总长120m左右,辐射光子能量为3~25keV。     

自生磁场对相对论谐波辐射的影响

分析了自生磁场对相对论谐波辐射的影响，得出结论，自生磁场对强激光在欠稠密等离子 产生的相对论相干波辐射有重要作用，自生磁场激发偶次谐波辐射，并对奇次谐波辐射产生影响，对二次，三次谐波作了详细分析，发现，自生磁场激发二次谐波辐射，而对三次谐波辐射有削弱作用，并且它还使谐波的失相时间延长。     

光学速调管相干辐射的数值模拟

 利用实测磁场值对光学速调管的相干辐射进行了数值模拟，计算了基波、三次谐波的谱宽和相干增强因子，提出了优化的激光功率和光学速调管特征参数Nd值。     

相干谐波辐射的测量方法和系统

 研究了光学速调管自发辐射谱,其调制率已达0.80,即将进行相干谐波辐射实验。介绍了相干谐波辐射实验的主要考虑因素、相干增强因子的测量方法和测量系统以及种子激光与电子束的准直和同步。     

上海深紫外自由电子激光的非线性谐波辐射研究

 自由电子激光中的非线性谐波辐射能达到较高的谐波功率，可以用来得到短波长辐射或者降低第4代先进光源对电子束团品质的严厉要求。基于3维自由电子激光软件，深入详细地研究了上海深紫外自由电子激光装置的非线性谐波辐射，并且提出了谐波辐射实验和测量建议。研究表明上海深紫外自由电子激光装置3次非线性谐波辐射的功率可以达到基波功率的2%水平。     

W波段同轴静磁波荡器自由电子激光优化设计

基于同轴静磁波荡器的自由电子激光主要利用环形电子束与同轴TE模式的相互作用产生电磁辐射,是一种重要的毫米波辐射源。分析了同轴结构作用区内外半径、工作模式、电子束电压、波荡器周期等参数对辐射频率的影响规律,研究了电子束平均半径的选取原则和束波互作用腔的设计方法,设计了辐射频率在W波段的基于同轴静磁波荡器的自由电子激光,并进行了粒子模拟,在电子束电压为720 kV,电子束流为1 kA的情况下,获得了频率107 GHz、辐射功率35 MW的TE01模,束波转换效率为4.9%,束波作用腔总长度小于200 mm,同轴静磁波荡器的磁场幅度0.34 T。     

用于THz源的混合型波荡器数值模拟

波荡器是基于自由电子激光的小型THz源关键器件,其可调节的周期性磁场结构与两端的光腔配合,使得穿越的电子束产生带增益的相干辐射,最终达到THz源所需要的功率.同纯永磁结构相比,混合型波荡器通过软铁材料调节由永磁块磁化方向性差异导致的磁场分布误差,同时可提供更高的场强.本文针对小型THz源需求,对混合型波荡器进行了相关物理设计.在解析方法分析的基础上,采用0PERA3/TOSCA有限元分析软件,对波荡器进行了三维磁场数值模拟和积分场优化.通过对波荡器端部结构的调整,优化后模型的一次场积分(导向误差)小于0.0lGs.m,电子轨迹偏移小于0.02mm.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

关于wiggler长波自发辐射的理论分析与数值计算

电子通过wiggler产生的辐射，除了短波辐射在轴线附近也有较强的长波辐射，在与轴线夹 角1/γ处达到最大.推导出wiggler长波辐射公式，理论分析了这种辐射的特点，并且将 理论分析的结果与数值计算的结果进行了比较.对在红外波长范围内电子束通过弯转磁铁和wiggler时产生的辐射强度和光通量作了计算，结果表明wiggler下的辐射强度和光通量均强 于弯转磁铁.比较了弯转磁铁的边沿辐射、波荡器的渡越辐射和wiggler长波辐射，表明wigg ler在红外波长范围辐射的性能最优. 关键词： wiggler 波荡器 弯转磁铁 长波辐射     

High‐efficiency coherence‐preserving harmonic rejection with crystal optics

This work reports a harmonic‐rejection scheme based on the combination of Si(111) monochromator and Si(220) harmonic‐rejection crystal optics. This approach is of importance to a wide range of X‐ray applications in all three major branches of modern X‐ray science (scattering, spectroscopy, imaging) based at major facilities, and especially relevant to the capabilities offered by the new diffraction‐limited storage rings. It was demonstrated both theoretically and experimentally that, when used with a synchrotron undulator source over a broad range of X‐ray energies of interest, the harmonic‐rejection crystals transmit the incident harmonic X‐rays on the order of 10^?6. Considering the flux ratio of fundamental and harmonic X‐rays in the incident beam, this scheme achieves a total flux ratio of harmonic radiation to fundamental radiation on the order of 10^?10. The spatial coherence of the undulator beam is preserved in the transmitted fundamental radiation while the harmonic radiation is suppressed, making this scheme suitable not only for current third‐generation synchrotron sources but also for the new diffraction‐limited storage rings where coherence preservation is an even higher priority. Compared with conventional harmonic‐rejection mirrors, where coherence is poorly preserved and harmonic rejection is less effective, this scheme has the added advantage of lower cost and footprint. This approach has been successfully utilized at the ultra‐small‐angle X‐ray scattering instrument at the Advanced Photon Source for scattering, imaging and coherent X‐ray photon correlation spectroscopy experiments. With minor modification, the harmonic rejection can be improved by a further five orders of magnitude, enabling even more performance capabilities.     

Observation of an optical vortex beam from a helical undulator in the XUV region

The observation of an optical vortex beam at 60 nm wavelength, produced as the second‐harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam. The experimental results were well reproduced by simulation.     

用于THz源的混合型波荡器数值模拟

波荡器是基于自由电子激光的小型THz源关键器件, 其可调节的周期性磁场结构与两端的光腔配合, 使得穿越的电子束产生带增益的相干辐射, 最终达到THz源所需要的功率. 同纯永磁结构相比, 混合型波荡器通过软铁材料调节由永磁块磁化方向性差异导致的磁场分布误差, 同时可提供更高的场强. 本文针对小型THz源需求, 对混合型波荡器进行了相关物理设计. 在解析方法分析的基础上, 采用OPERA3D/TOSCA有限元分析软件, 对波荡器进行了三维磁场数值模拟和积分场优化. 通过对波荡器端部结构的调整, 优化后模型的一次场积分(导向误差)小于0.01Gs﹒m, 电子轨迹偏移小于0.02mm.     

BBO晶体中飞秒脉冲的二次和三次谐波振荡产生

同时考察了群速色散失配、最低阶群速色散和二阶群速色散。研究了在ＢＢＯ晶体中飞秒激光脉冲的谐产生，计算了ＢＢＯ晶体的作为波长函数的晶体的最低阶和二谐群速色散，借助求解改进的耦合波方程的数值计算，得到了飞秒脉冲的二次及三次谐波辐射，分析了最低工阶及二阶ＧＶＤ对于基波脉冲和谐波脉的影响，最后考虑了三次谐波产生中群速失配的补偿。     

Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair

Generation of deep ultraviolet radiation at 210 nm by Type-I third harmonic generation is achieved in a pair of BBO crystals with conversion efficiency as high as 36%. The fundamental source is the dye laser radiation pumped by the second harmonic of a Q-switched Nd: YAG laser. A walk-off compensated configuration with the BBO crystal pair has enabled us to realize such a high conversion efficiency in the interaction.