TOMOGRAPHIC IMAGING OF NONCIRCULAR AND IRREGULAR ELECTRON-BEAM CURRENT-DENSITY DISTRIBUTIONS

A computer tomography (CT) diagnostic method is presented for high res olution imaging of the current density distribution in electron beams. This technique measures the electron beam (EB) profile by integrating the current density of the beam a long a thin slit, and CT reconstruc ts the current density distribution from multiple profiles taken at eq ually spaced angles around the beam. Computer tomography imaging allow s the current density distribution of noncircular and irregular electr on beams to be accurately measured in order to characterize the qualit y of the electron optical system and the quality of the electron beam. In this investigation, sharp focused and defocused multi-kilowatt ele ctron beams, produced by hairpin and ribbon filaments, were examined u sing CT imaging to illustrate the differences that exist between the c urrent density distributions produced by these different filament shap es. The results of this investigation further showed the influence tha t beam current and beam focus have on the peak power density and the p ower density distribution of both hairpin and ribbon filaments. When u sed for process control and beam diagnostics, CT imaging will assist w ith the accurate transfer of welding parameters to different machines, improve the understanding of electron-beam/material interactions, and help to generate tailored power density distributions for improved el ectron beam welding and surface treating of materials.