A study of the electron beam scattering under various gaseous environment

by 1974- He, Jing

There are three objectives in this work: to experimentally measure the profiles of electron beams scattered by interaction with a gas, to measure total scattering crosssections for gases and to apply the cross-section data in a suitable Monte Carlo simulation to predict beam scattering profiles for comparison with experiment. The experimentally measured profiles cover a wide range of intensity variation. There are two evidenced regions: an inner region and an outer skirt corresponding to inelastic (small angle) and elastic scattering respectively are appeared. These profiles use the planar p-n junction gives us an overall look at the electron beam spreading, including the oversize and shape of the profile. The experimental total scattering cross-section data obtained is of great interest. It shows the excellent agreement between experimental values and theoretical estimates of the total gas scattering cross-section and also confirms the predicted linear relationship between log (Ip/I0) and gas pressure. On the basis of the available evidence, gases tend to be molecular rather than atomic in nature in the pressure range used. The experimentally collected gas scattering cross-section data eventually was inserted into Monte Carlo simulation program. The established Monte Carlo simulation predicts the spatial distribution of the electron beam scattering under given beam energy and various other experimental conditions. The resulted beam profiles from the simulation are well agreed with the experimental measured profiles, with much higher accuracy and more variety of experimental conditions choices. iv