利用偏置磁极周期会切磁铁产生边聚焦场

Side focusing fields generated by offset-pole periodic cusped magnets

利用理论分析和数值计算的方法,研究了偏置磁极周期会切磁铁产生的、可用于带状电子束宽边聚焦的边聚焦场。结果表明:增加偏置长度,减小电子束通道宽度,增大磁极轴向长度可以在基本不改变边聚焦场在x方向上分布特性的前提下提高幅值;增大电子束通道的高度,增大磁极厚度均可以减小边聚焦场在x方向上分布曲线的曲率,但同时其幅值也会降低,该降低可利用前述方法予以补偿。在对带状电子束宽边聚焦进行束匹配时,可以先进行曲率匹配,再进行幅值匹配。在进行参数选择时,应合理选择束通道高度和磁极厚度的取值,以避免束通道内的边聚焦场在x方向上的分布出现曲率反向。

Side focusing fields generated by offset-pole periodic cusped magnets for the propagation of sheet electron beams have been investigated theoretically and numerically.Increasing the offset length,decreasing the width of beam channel,or increasing the axial length of magnet poles will increase the strength of the side focusing fields,without changing their transverse gradient.Increasing the height of beam channel or the thickness of magnet poles will make the side focusing fields weaker,but of a better linearity.It is recommended that gradient match between the focusing force and the defocusing force acting on the sheet electron beam be made before the amplitude match between them for simplicity.The height of beam channel and the axial length of magnet poles should be chosen carefully to prevent the gradient of the side focusing fields in transverse directions from being reversed in the region of the sheet electron beam.