介质壁加速腔加速结构优化

Optimization of accelerating structure in dielectric wall accelerator

为了在介质壁加速器中增大轴向加速电场,提高加速梯度的同时抑制径向电场对束包络的扩张,提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真,分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构,轴向加速电场强度提高20%,同时径向电场得到有效抑制;栅网结构下,被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H+3粒子,栅网结构得到的能量增益提高了一倍。

In the dielectric wall accelerator(DWA),the intensity and the distribution of the axial and radial electric fields generated by the electrode structure are obviously different.In order to enhance the axial accelerating field,improve the accelerating gradient and suppress the beam profile expansion caused by the radial electric field,metal grids are embedded in between each accelerating unit.Electromagnetic simulation software based on particle-in-cell method is used to numerically simulate structures with and without metal grids,and to analyze the distribution of electric field as well as the change of the beam profile under different structures.The experimental results agree well with the simulation outcome,which demonstrate that the DWA with the metal grid structure has stronger and more uniform axial accelerating field than the DWA without metal grids.Furthermore,for the metal grid structure,the radial electric field is suppressed efficiently and the radial divergence of the accelerated particle beam in free drift space is improved.