Modeling of intense electron beam propagation with finite emittance in a technological vacuum chamber

A study is performed on the parameter evolution of a nonlaminar electron beam with finite emittance in case of space charge compensation. An approximate method based on hydrodynamic consideration of a zero beam emittance with axial symmetry has been developed. Beam evolition in phase space has been studied at increasing the longitudinal coordinate. The numerical calculations carried out describe the phase characteristics evolution as well as beam particles distribution. In case of ionic processes in the beam leading to space charge compensation and overcompensation the compensation degree distribution has been taken into account. Electron beam envelopes have been obtained for different values of the compensation degree. The approach described is implemented in a computer program for IBM PC/XT existing also as a module which is part of a program complex for calculation technological electron beam transport and transformation systems. Numerical modeling and results are presented. At significant space charge overcompensation degrees broadening along the beam axis has been observed. On the contrary, a beam carrying uncompensated negative charge along its axe propagates without broadening or without decrease in the value of its cross section. 10 figs., 23 refs