Design and beam dynamic analysis of 270° achromatic deflection magnet system
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摘要: 对三种常用结构的270°偏转磁铁进行系统的分析研究,采用数值计算和模拟方法对双磁铁不对称偏转结构、三块90°磁铁偏转结构和70°+130°+70°偏转结构这三种不同的270°偏转磁铁系统进行模拟,给出偏转系统的消色散传输条件,并且分析了束流包络在偏转系统和出口管道中的变化情况。经过分析对比,详细列出了三种结构的优势与劣势。双磁铁不对称结构适用于医用加速器,三块90°磁铁偏转结构适用于需要在出口长距离漂移的辐照加速器,而70°+130°+70°偏转结构可以满足出口一定距离的无损漂移,同时实现相对较低的成本,是工业辐照加速器较为经济适宜的选择。
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关键词:
- 工业辐照电子加速器 /
- 270°磁铁偏转系统 /
- 束流动力学优化 /
- 消色散传输 /
- 射束偏转
Abstract: The 270° beam deflection system with magnets is widely used in medical electron linear accelerators and high-energy electron industrial irradiation accelerators. In this paper, three common structures of 270° deflection magnet are systematically analyzed and discussed. Numerical calculation and simulation methods are used for the two-magnet asymmetric deflection structure, the three 90° magnets deflection structure and the 70°+130°+70° deflection structure. The achromatic transmission conditions of the deflection systems are given, and the changes of beam envelope in the deflection and exit beam line are analyzed. After analysis and comparison, the advantages and disadvantages of the three structures are listed in detail, which has certain guiding significance for the selection of structures in specific application fields. The two-magnet asymmetric deflection structure is suitable for medical accelerators. The three 90° magnets deflection structure is suitable for irradiation accelerators that require long-distance drift at the exit. The 70°+130°+70° deflection structure can satisfy the non-destructive drift of a certain distance from the exit, and it achieves relatively low cost, therefore, it which is a more economical and suitable choice for industrial irradiation accelerators. -
表 1 两种270°偏转系统的结构参数
Table 1. Structural parameters of two 270° deflection systems
description magnet angle/(°) radius/m injection angle/(°) exit angle/(°) gap/m drift/m focus distance/m two magnets 165.4,104.6 0.1−1 5.73,−59.6 59.6,−14.3 0.03 0.023−0.23 0.1−1 three magnets 90,90,90 S2/1.4 10.2,10.2,10.2 10.2,10.2,10.2 0.07 0.2−1(S2) >2 表 2 两种270°偏转系统在不同弯转半径下出口1.5 m处发射度和束斑的变化
Table 2. Changes of emittance and beam spot size at 1.5 m exit point of two 270° deflection systems under different turning radius
R/m two magnets three magnets drift/m σx,σy/(mm, mm) drift/m σx,σy/(mm, mm) 0.2 0.046 33.8,32.5 0.28 8.72,8.07 0.3 0.069 23.3,21.7 0.42 8.53,8.05 0.4 0.092 18.1,16.3 0.56 8.41,8.04 0.5 0.115 14.3,12.4 0.7 8.31,8.03 表 3 70°+130°+70°磁铁组成的270°偏转系统结构参数
Table 3. Structural parameters of 270° deflection system composed of 70°+130°+70° magnets
magnet angle/(°) radius/m injection angle/(°) exit angle/(°) gap/m drift /m focus distance/m 70,130,70 0.2 0,8,−4.3 −4.3,8,0 0.04 0.1924 2 表 4 三种270°偏转系统结构参数及出口1.5 m处束流参数
Table 4. Structural parameters of three 270° deflection systems and beam parameters at 1.5 m
type magnet
angle/(°)radius/
minjection
angle/(°)exit angle/
(°)gap/
mdrift /
mfocus
length/mσx,σy/
(mm, mm)vertical
height/cmtwo magnets 165.4,104.6 0.5 5.73,−59.6 59.6,−14.3 0.03 0.115 short 14.3,12.4 98.4 three magnets 90,90,90 0.2 10.2,10.2,10.2 10.2,10.2,10.2 0.07 0.28 long 8.72,8.07 68 70°+130°+70° magnets 70,130,70 0.2 0,8,−4.3 −4.3,8,0 0.04 0.1924 medium 3.6,4.75 58 -
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