Measurement of an electron bunch and establishment of the intense mm wave light source with the coherent radiation

高能短电子束的相干辐射在亚毫米到毫米波长范围内具有连续的光谱。本工作利用相干辐射建立了一种新型的高亮度毫米波光源，并用干涉仪和远红外光探测器、硅测辐射热计测量了ISIR电子直线加速器强束的相干跃迁辐射光谱。根据计算结果对电子束的形状进行了评价。建立了电子束形状精细结构的监测系统。对直线加速器的工作条件进行了优化，以获得稳定而强烈的辐射。相干跃迁辐射已经从加速器室内传输出去。这是第一个用光栅式光谱仪建立的吸收光谱系统，其辐射峰值和平均功率分别比其他光源高5个数量级以上和1个数量级以上。该强光源可用于吸收较强物质的吸收光谱和研究非线性效应。对远红外光谱的标准物质N_2O气体进行了吸收光谱。还对具有强吸收的水样进行了测量，并研究了其温度依赖性。波长分辨率为1%。这是使用光栅式光谱仪获得的第一批结果。还进行了脉冲辐解实验。该光源具有广阔的应用前景。

The coherent radiation from high-energy short electron bunches has a continuous spectrum in a submillimeter to millimeter wavelength range. In this work a new high-brightness millimeter wave light source has been established by using the coherent radiation.The spectra of the coherent transition radiation from the intense beam of the ISIR electron linac have been measured with an interferometer and far-infrared light detectors, silicon bolometers. The electron bunch shape has been evaluated from the results. The monitoring system for the fine structure of the electron bunch shape has been established. The operational conditions of the linac have been optimized so as to obtain stable and intense radiation. The coherent transition radiation has been transported out from the accelerator room. This is the first system established for the absorption spectroscopy with a grating spectrometer.The peak and the averaged power of the radiation are more than five and more than one order of magnitude higher than those of the other light sources, respectively. The intense light source can be applied to the absorption spectroscopy of matters with relatively strong absorption and to investigating nonlinear effects.Absorption spectroscopy has been performed for N_2O gas, which is a standard material for the far-infrared spectroscopy. Measurements have been also carried out for water samples having strong absorption and the temperature dependence has been investigated. The wavelength resolution is 1%. These are the first results which have been obtained by using a grating spectrometer. Pulse radiolysis experiments have been also performed. The future wide-range applications of the light source are expected.