标题： 波导中的波荡器辐射 显示英文标题

标题： Undulator Radiation in a Waveguide

摘要： 我们提出了一种分析方法来表征接近共振时的波荡器辐射，此时真空管道的存在会显著影响辐射特性。 汉堡自由电子激光（FEL）装置（FLASH）的远红外波荡器光束线便是这种情况，该装置能够提供太赫兹（THz）范围内的脉冲。 这种波荡器允许泵浦-探测实验，其中太赫兹脉冲自然与来自FEL的真空紫外（VUV）脉冲同步，同时还能开发新型电子束诊断技术。 由于太赫兹辐射的衍射尺寸超过了真空室的尺寸，因此在表征红外辐射时必须考虑波导的存在。 我们基于傍轴近似和共振近似，发展了波荡器辐射在波导中的理论。 我们使用张量格林函数技术求解场方程，并提取描述真空管道对辐射脉冲影响的优值参数，这些参数以简单的方式表示为问题参数的函数。 我们的理论充分利用了无量纲分析，允许处理和物理理解参数空间的许多渐近情况及其适用区域。 显示英文摘要

摘要： We propose an analytical approach to characterize undulator radiation near resonance, when the presence of the vacuum-pipe considerably affects radiation properties. This is the case of the far-infrared undulator beamline at the Free-electron LASer (FEL) in Hamburg (FLASH), that will be capable of delivering pulses in the TeraHertz (THz) range. This undulator will allow pump-probe experiments where THz pulses are naturally synchronized to the VUV pulse from the FEL, as well as the development of novel electron-beam diagnostics techniques. Since the THz radiation diffraction-size exceeds the vacuum-chamber dimensions, characterization of infrared radiation must be performed accounting for the presence of a waveguide. We developed a theory of undulator radiation in a waveguide based on paraxial and resonance approximation. We solved the field equation with a tensor Green's function technique, and extracted figure of merits describing in a simple way the influence of the vacuum-pipe on the radiation pulse as a function of the problem parameters. Our theory, that makes consistent use of dimensionless analysis, allows treatment and physical understanding of many asymptotes of the parameter space, together with their region of applicability.