中文摘要：

基于Geant4蒙特卡罗程序包建立了低真空条件下高能电子束的输运模型，并用该模型详细研究了电子束在低真空条件的传输特性。结果表明，低真空条件下电子束传输特性与高真空下的有较大差异，环境气体对电子束有散射作用，而磁场可有效约束高能电子的传输轨迹，最终轨迹是磁场约束作用与环境气体散射作用竞争的结果。对于确定的磁场分布，电子束能量存在一个最佳范围，从而保证电子束的传输特性。

英文摘要：

Based on Geant4 Monte Carlo toolkit, a numerical model is established to simulate the electron beam transportation characteristics trader low-vacuum condition. The results indicate that the low-vacuum transportation characteristics differ greatly from the high-vacuum case. The residual gas affects the beam trajectory greatly, but the magnetic field can focus the beam effectively. The final trajectory is determined by both effects. For a given magnetic field, in order to get the desired beam, the beam energy should be in a reasonable range.