用于质子治疗输运线的二极磁铁设计与优化

Design and optimization of a dipole magnet applied to the beamline of a proton therapy facility

本文介绍了一套质子治疗输运线上的60°平行边二极磁铁的设计与优化过程。为了提高磁铁磁场质量,其横向场均匀度以及沿积分路径上的积分磁场均匀度均需要优化。根据70~250MeV的质子能量范围和1 500mm的偏转半径,二极磁铁的工作场强为0.80~1.62T。采用OPERA-2D/3D等软件进行设计与仿真计算,磁铁端部采用罗高斯基曲线进行切削以避免铁芯局部饱和,同时进行谐波削斜以减少积分场的四极、六极等高阶误差分量,保证积分场品质,最终在高、低场条件下,横向场相对误差≤±5×10^(-4),积分场相对误差≤±1×10^(-3),高阶谐波分量相对误差≤±5×10^(-4)。磁铁可以达到较高的中心磁场,满足结构紧凑的要求,适合应用于质子治疗的束线系统。

In this paper,a 60 degree dipole prototype magnet in the beamline applied to a proton therapy system is designed and the optimization process is discussed in detail.The transverse field and integral field should be optimized to improve the magnetic field quality.The operating field range is 0.80-1.62 Taccording to the proton energy of 70-250 MeV with the bending radius of 1 500 mm.The simulation and optimization process are performed with OPERA-2D/3D.The Rogowski curve chamfering is adopted at the pole end to avoid iron saturation and the pole end chamfering is optimized to compensate the quadrupole and sextupole field components,finally to meet the integrated field quality specifications.Finally,the relative error of the cross-section field is controlled ≤±5×10^（-4）,the allowed integral field homogeneities can be controlled ≤±1×10^（-3） and the harmonic errors are minimized ≤±5×10^（-4）.The magnet design can meet the requirements of high central magnetic field and compactness of the structure.It is suitable for the application in the beam line system for proton therapy facility.