非层流无碰撞模型计算LIA焦斑尺寸

 在束流轨迹方程基础上，建立了非层流无碰撞数值模拟模型，并在模型中考虑了束流空间电荷效应、发射度、能散、束心Corkscrew运动、束流横截面分布不均匀等诸多因素，编制数值模拟程序对强流相对论电子束经过磁透镜的轨迹进行了计算。计算结果表明：子束流层数一定时，焦斑直径波动在0.03 mm范围内；随子束流划分层数的不同，计算所得焦斑直径的最大不确定度为±0.05 mm，而焦距几乎不变化，其波动在0.08 cm范围内；随子束流划分层数的增加，焦斑直径计算结果是收敛的，最终收敛值约为1.03 mm。实验得到的焦距为23.2 mm，焦斑直径1.3 mm，实验结果表明焦距绝对误差在3.5 cm范围内，焦斑直径绝对误差在0.4 mm范围内。

Calculation of X-ray spot size in linear induction accelerator

In this article,a non-laminar and non-collision numerical simulation model based on a third order trajectory equation is presented.In this model,the injection angles of beamlets are assumed as a random distribution.Simulation result shows that X-ray spot size is almost certainly convergent when the number of beamlets increases gradually,and the convergent size is about 1.03 mm.The calculated uncertainty is in range of ±0.05 mm with different numbers of beamlets.In the experiment,X-ray spot size being 1.3 mm and focusing length 23.2 mm are obtained,which indicates that the maximum absolute error of the X-ray spot size is 0.4 mm and that of focusing length is 3.5 cm.