交变极性聚焦磁场抑制Corkscrew运动的机理

Confining corkscrew oscillations by usingan alternate solenoid field

分析了对强流相对论电子束采用交变极性聚焦磁场聚焦存在稳定解的条件 ,提出了采用交变极性聚焦磁场抑制 Corkscrew运动的机理。数值计算结果表明 ,在采用交变周期为 1 m、峰值磁场设为 0 .2 T的情况下 ,对于能量为 1 2 Me V的电子束 ,当聚焦布局长度为 2 .8m时 ,束质心位移可从 5mm(始端 )被抑制至近似 0 (终端 ) ;对于能量为 2 0 Me V的电子束 ,当聚焦布局长度为 4 .5m时 ,束质心位移可从 5mm(始端 )被抑制至近似 0 (终端 )。

High-resolution X-ray photographing needs to focus intense relativistic electronic beams of several thousand amperes on the bremsstrahlung converter target, thereon forming small and stable spots. In the ideal focusing case, electron beams can be focused to a point. However, due to the influence of such factors as the space charge effect, the beam emittance, the spherical aberration of a lens, and the chromatic aberration, the minimal spot size of electronic beams will be limited. Furthermore, the Corkscrew oscillation of the beam centroid will not only increase the spot size but also lead to the distortion of the spot shape. This paper analyzes the precondition transporting stably intense beams in an alternating solenoid field and presents the method confining Corkscrew oscillations by using the field. The results of numerical calculation show that the centroid transverse displacement is decreased from 5 mm (at the outset) to approximate 0 (at the terminal) when the 1 m alternating period and the 0.2 T peak magnetic field are used, and the 12 MeV beams are transported 2.8 m and the 20 MeV beams are transported 4.5 m.