【作者】 钱文枢；

【导师】 唐传祥；

【作者基本信息】 清华大学 ， 核科学与技术， 2008， 硕士

【摘要】 加速器产生的高能电子束打靶产生的X射线是辐照加工领域一种应用广泛的辐照源,但由于X射线转换效率较低,辐照功率高时靶中沉积的大量热对转换靶的设计提出了特殊的要求。本文从韧致辐射理论出发,应用蒙特卡罗方法和相关程序研究了关于加速器X射线转换靶的设计问题。论文主要包括三部分内容。第一部分介绍了辐照技术的应用背景、辐照加速器的基本特点和应用以及国内外研究现状。并论述了论文工作的相关理论基础,包括转换靶理论以及韧致辐射角分布的理论分析等。文中还对论文工作中采用的蒙特卡罗方法及程序以及ANSYS程序做了简要的介绍。第二部分研究了大功率辐照加速器的束流传输系统设计,包括总体的光路设计、四极透镜设计等。根据设计的四极透镜机械参数、电参数等,四极透镜已加工完成并安装于该加速器的束流传输系统上。第三部分着重研究了应用于大功率辐照加速器的X射线转换靶。由于电子束功率较高,转换靶内沉积能量多,对靶的冷却要求比较高。文中应用蒙特卡罗方法选择了转换靶的靶材与靶厚,并通过模拟计算确定优化了两种复合靶的结构,即分别采用1.7 mm厚的Ta靶和1.5 mm厚的W靶加上6 mm厚的3水道结构冷却并以2 mm厚的不锈钢作为基底支撑。其中以W作为主靶的转换靶已加工完成。对设计方案进行的复合靶水冷计算和热分布的验证计算确保了转换靶长时间进行辐照工作的稳定性和可靠性。通过模拟各个束团打靶产生的韧致辐射角分布,研究了转换靶的X射线平面均匀性,并初步研究了空间辐照均匀性。更多还原

【Abstract】 X-ray produced by high energy electron beam targeting is a widely-used kind of irradiation sources in irradiation processing field. Irradiation by X-ray has good forward intensity distribution and penetration ablity. Meanwhile, because the conversion efficiency is quite low, the vast quantity of heat deposited in the target, especially when the power is high, requires particular design of the converter.This article starts from the Bremsstrahlung theories, based on the derivation, Monte-Carlo method and related codes are used in research about the X-ray conventer of linacs, including three parts:The principle, application, research and developing status of irradiation linacs home and abroad are given. The related fundamental theories used in the article work are introduced, including the theoretical analysis of X-ray converter and angle-distribution of Bremsstrahlung. After that, methods and software, such as Monte Carlo Method, MCNP and ANSYS, used in this article are briefly introduced.Next, the whole beam route of the linac is investigated and designed. The quadrupole lenses are manufactured and arranged to the right position on the linac, according to the designed mechanical and electrical parameters.The X-ray converter of high-power irradiation linacs is discussed as the main part of this article. Because the beam power of the irradiation linac is quite high, the deposited energy in the convertor will begreat, which brings forward high demands on the converter design. Based on the simulation of MCNP, the target materials and thicknesses are selected, and the multi-layer structures of two design schemes are optimized. Two specific converters are developed with 1.7mm tantalum and 1.5mm tungsten (has been produced) as main targets. The stainless steel board with the 3 channels for cooling water is used as the base of the converter and filter for low energy part of bremsstrahlung spectrum. The study of the cooling effect and thermal distribution shows that the design can meet the actual requirements for long-time irradiation. The dose distribution results are stimulated for the research on the X-ray planar and spatial uniformity.更多还原