【作者】 杜应超；

【导师】 林郁正； 唐传祥；

【作者基本信息】 清华大学 ， 核科学与技术， 2006， 博士

【摘要】 基于汤姆逊散射的X射线源是在上世纪末随着加速器技术和激光技术的发展而提出的一种新型X射线源。它利用超短脉冲激光与高亮度的相对论电子束相互作用,在电子束前进方向产生方向性好、高亮度、短时间结构和能量可调的准单能X射线,在超快物理过程研究和医学物理研究中具有广泛的应用前景。清华大学加速器实验室正在积极筹建基于汤姆逊散射的X射线源实验平台,要对汤姆逊散射X射线源的理论和关键技术进行研究,并根据现有实验条件开展初步实验研究。据此,本论文的工作将围绕汤姆逊散射X射线源的理论研究和初步实验研究展开论文首先从单电子线性散射模型出发,对在任意作用角度下的X射线脉冲分布情况和脉冲光子产额与电子束参数和激光参数的关系进行了研究,并分析了非理想因素如作用点位置偏差、激光和电子束时间同步偏差等因素对X射线脉冲参数的影响。在此基础上对光源亮度与电子束和激光束参数的关系也进行了解析求解。本论文的另外一个主要内容是采用16 MeV返波行波加速器与纳秒调Q激光器进行汤姆逊散射X射线源的初步实验研究。我们根据加速器束流和激光器参数和特点,设计了177度角对撞的初步实验方案。根据实验要求,对加速器和激光器进行了改造,设计了实验用的束流传输系统、真空系统、束流测量系统、同步系统,并根据产生的X射线特点设计了X射线的探测方案。在实验中对电子束和激光束参数进行了测量。在采取措施解决加速器运行时的电磁干扰和部分屏蔽电子束产生的轫致辐射本底后,我们测量到了产生的散射X射线脉冲信号,在探测器上探测到的散射光子脉冲宽度约为6 ns,在探测器上探测到的脉冲光子数约为410,推算出6ns内脉冲光子总产额为1.77×10~4。高亮度电子束的产生和诊断是建设汤姆逊散射X射线源的一个重要环节,而对电子束发射度的准确测量对研究电子束在产生、加速、传输和压缩等过程中的发射度变化具有重要意义。基于CT算法的束团发射度测量方法与传统测量束团发射度的四极透镜扫描法不同,应用该方法测量束团发射度不需要预先假设电子束在相空间内的分布情况,可以真实的给出束团在相空间内的分布情况。在实验过程中我们对该方法也进行了实验研究。更多还原

【Abstract】 Thomson scattering based X-ray radiation source, in which a laser beam is scatteredoff a relativistic electron beam resulting in the generation of a high-energy X-ray beam, is anew kind of X-ray source that has been developed with the advancements of the acceleratorand laser technology since 1990’s. It can provide ultra-short pulse duration, high-peakbrightness, tunable and monochromatic X-ray , and is useful in a number of fields includingmedical imaging, solid state physics, material science, chemical, biological and industrialapplications. Tsinghua University Accelerator laboratory is planning to built a Thomsonscattering X-ray source. Study on the Thomson scattering X-ray source is being carried out.This dissertation inculdes theoretical research and preliminary experiment of the thomsonscattering X-ray source.First, the relations of the beam parameters between the X-ray and electron and laserat interaction point based on the linear Thomson scattering model are studied. The formu-las for the pulse length and yield of X-ray photons at arbitrary interaction angles betweenelectron and laser are deduced. The in?uences of some nonideal factors, such as laser band-width, electron energy spread and emittance, interaction point and synchronization errorson the X-ray parameters are studied.The second part of this dissertation is concentrated on the Thomson scattering X-raymeasurement by means of the 16MeV backward traveling wave electron linac and the Q-switched YAG nanosecond laser system. A 177 degree interaction angles between the elec-tron and laser is selected.Also the beam transport system, vacuum chamber, beam measure-ment system, synchronization system and detector system are designed and fabricated. Theparameters of both laser system and linac are measured. In the measurement, some deli-cated methods are taken to eliminate the linac’s radiation background and the EMI(electromagnetic interference) from the modulator and klystron. The X-ray photons created byThomson scattering has been successfully measured by MCP as exppected. The full widthhalf maximun(FWHM) of X-ray pulse duration is about 6 ns, and the total generated pho-tons is about 1.7×10~4 per pulse.The measurement of transvers phase space of the electron beam based on CT(Computed tomography) is studied and the preliminary measure result is presented inthis dissertation, which is in good agreement with that obtain from quadrupole scan.更多还原