消色散90°磁偏转系统  

A 90° MAGNETIC DEFLECTION SYSTEM FOR NYZ-18 MEDICAL LINEAR ELECTRON ACCELERATOR

作　　者：王厚稳[1] 朱以漳[1] 惠炳炎 丁小平[1] 

机构地区：[1]南京大学物理系,南京市天加速器实业有限公司

出　　处：《南京大学学报（自然科学版）》1995年第4期552-555,共4页Journal of Nanjing University（Natural Science）

摘　　要：描述了ＮＹＺ－１８医用电子直线加速器的零空间色激９０°磁偏转系统。该系统由三块二极磁铁构成：二块小的具有相反极性的予偏磁铁和一个９０°的主伯磁铁。用计算机方法确定了系统的参数。二块予们磁铁采用串联结构，用同一线包激励。主偏磁铁为Ｃ型结构，对于２０ＭｅＶ电子束和６ｃｍ轨道半径，工作磁场为１１４００高斯，其磁化曲线是令人满意的。用屏蔽盒修正磁铁边缘场，屏蔽盒位置用Ｐｏｉｓｓｏｎ程序确定。在该系统的靶点已获得一个直径约２ｍｍ的园形束斑。该系统良好的消色散和聚焦特性较好地满足了医用电了直线加速器的设计要求。A non-dispersion 90°magnetic deflection system for NYZ-18 medical linac is described.It consists of three dipoles:two small magnets M1 and M2 with opposite polarity and one approximately 90°magnet M3. The parameters of the system are determined by a computer method.A small circular beam spot with 1.2 mm diameter and zero space dispersion property will be obtained at target point.M1 and M2 are in series,and excited with the same coils.Thus they are opposite in polarity and vary synchronously.Gaps of M1 and M2 are the same.M3 is a c-type magnet.For 20Mev electron ham and 6cm bending radius, operating fields of M3 the M1 are 11400 and 5700 Gauss respectively.The magnetisation curve of M3 is satisfactory.Due to the strong fringing of M1,the actual effective boundaries are more than predeterminate boundaries.Two shielding ion boxes are placed before and after the pOle of M1 respectively to limit fringing field.The positions of the shielding boxes are calculated by Poisson program.For M2 and M3,the same corrections for fringing field are also done.The system is set.A small circular spot with less than 2mm diameter is formed at target point. The good focusing the zero-dispersion properties and the edvantnge in configuration mate the system especially suitable for medical linac.

关 键 词：电子直线加速器 磁偏转系统 零空间色散 

分 类 号：R454.9[医药卫生—治疗学] TL503.8[医药卫生—临床医学]