交变极性聚焦磁场抑制Corkscrew运动的机理

 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1m、峰值磁场设为0.2T的情况下，对于能量为12MeV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20MeV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)。

Confining corkscrew oscillations by usingan alternate solenoid field

High resolution X ray photographing needs to focus intense relativist ic electronic beams of several thousand amperes on the bremsstrahlung converter target, thereo n forming small and stable spots. In the ideal focusing case, electron beams can be focuse d to a point. However, due to the influence of such factors as the space charge effect, the be am emittance, the spherical aberration of a lens, and the chromatic aberration, the minimal spot s ize of electronic beams will be limited. Furthermore, the corkscrew oscillation of the beam centro id 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 a lternating solenoid field and presents the method confining corkscrew oscillatio ns by using the field. The results of numerical calculation show that the centro id transverse displacement is decreased from 5mm (at the outset) to approximate 0 (at the terminal) when the 1m alternating period and the 0.2T peak magnetic field are used, and the 12MeV beams are transported 2.8m and the 20 Me V beams are transported 4.5m.