推导了柱对称相对论电子束在漂移管内的空间电荷势及相互作用势能,分析了势能在束流传输过程中的变化规律,并与束流均方根发射度的变化方程比较。指出一部分势能随束流传输过程中包络振荡而呈现出可逆的变化;而另一部分势能则在束流传输系统及束流本身非线性力的作用下,随着电荷密度分布变化而转为电荷横向热运动能量,从而导致束流归一化发射度的增长,这种转化是一个不可逆的过程。

The potential energy expression of cylindrically symmetric intense electron beams is derived and the differential equation of RMS emittance is presented in this paper. The decrease of beam potential energy which is leaded by change of charged particle density distribution during the transportation brings the growth of RMS emittance. The change of the charged particle density distribution is always toward to decreasing the potential energy,such as the growth of the emittance. Furthermore,based on the basic definition of emttance,different model transverse motions including beam envelope oscillation with no influence on emittance and ruleless thermal motion with influence on emittance are expatiated. Several factors of influencing beam emittance are discussed respectively and some methods to restrain the growth of emittance are presented.