强流脉冲束在螺旋管透镜中的非线性传输计算

Nonlinear transport calculation of intense pulsed beam in solenoidal lenses

为计算强流脉冲束在螺旋管透镜6维相空间中的非线性传输,用Visual Fortran 6.5语言设计了一个计算程序,计算由漂浮空间、螺旋管透镜等元件组成的束流光学系统。程序在计算非强流脉冲束流的线性传输时,粒子的轨迹通过矩阵的直接相乘计算得出;程序在计算强流脉冲束流的非线性传输时,需要考虑束流中的空间电荷效应对束流传输的影响,在束流运动过程中,空间电荷场也在不断地变化,而且粒子运动的轨迹与空间电荷势又是相互依赖的,因此需要求得一个自洽的解,先把元件分成若干均等的区间,把电流分成若干等份,后采用束流电流迭代与元件区间迭代的计算方法。程序运行结束时,横向和纵向相图以及束流光学系统的束流包络线可以在微机屏幕上直观地显示出来。

Abstract：To calculate nonlinear transport of pulsed beams in the six-dimensional phase space of solenoid lens accurately, a beam dynamics program has been designed using Visual Fortran 6.5 to calculate the beam optical system consisting of drift spaces and solenoid lenses. For non-intense beams, particle trajectory can be obtained by multiplying linear transport matrices. For nonlinear transport of intense beams, the influence of space-charge effect on beam transport needs to be taken into account, and self-consistent solution should be derived because of the interaction between charged particle distribution and space charge field. In the program, components and currents are divided into equal intervals, respectively, and each interval is treated as a uniform solenoid field. Then beam current iteration and component interval iteration are conducted to get selfconsistent solutions. When program running is finished, horizontal and vertical phase diagrams of the system, as well as beam envelopes can be visually displayed on the computer screen.