基于PIC方法的二维束流动力学模拟程序及其初步应用

为了深入研究强流负氢束在强流质子回旋加速器CYCIAE-100轴向注入线中的传输, 利用split-operator方法分解外场和束流自身的空间电荷场的作用. 对外 场利用单粒子跟踪技术, 采用一阶线性近似; 对空间电荷场采用PIC方法, 利用 快速傅里叶变换求解Poisson方程. 用FORTRAN95语言开发了一个基于面向对象技术的二维宏粒子传输计算程序CYCPIC2D, 本程序可以计算任意分布的强流束在输运线上的传输.最后给出了对CYCIAE-100注入线的模拟计算结果, 并和程序ORBIT, TRACE 3-D的结果进行比对验证, 结果表明: 空间电荷效应在此注入线上有较大的影响, 而且3个程序计算的不同中性化的结果基本上一致; 束流强度达到几十毫安时, 基于PIC方法的两个程序CYCPIC2D和ORBIT的计算结果完全吻合, 而线性近似程序TRACE 3-D有明显差异.

A Two-Dimension Beam Dynamics Simulation Code Base on PIC Method

In order to carry out an in-depth study on the negative hydrogen DC beam transport in the axial injection line of CYCIAE-100,a high intensity cyclotron under design at CIAE,the split-operator method is adopted in this paper for macro-particle dynamics simulation.In this method,the Hamiltonian is divided into two parts:external applied field and space-charge field.The former is dealt with single particle tracking and adopts first order approximation;the latter is dealt with PIC method,and FFT technique is used to solve the Poisson equation.Moreover,we developed an object-oriented code of two-dimension macro particle dynamics (CYCPIC2D) using FORTRON 95 language.This code can be applied to the transport line calculation of arbitrarily distributed beam.The simulation result for CYCIAE-100 injection line is presented,and validated by ORBIT and TRACE-3D.It indicates that the space charge effects have significant impact on the injection line,and the results given by three codes are basically accordant with each other. When the beam intensity reaches several ten milliamperes,the two PIC-based codes CYCPIC2D and ORBIT still give consistent results,while the result given by TRACE-3D shows evident difference with the other two.