Algebraic Reconstruction of Beam’s Spatial Characteristics in Electron Beam Welding

Abstract

In electron-beam welding, stability of the beam’s spatial characteristics is essential in order to ensure weld quality. For diagnostics and determination of the beam’s spatial and energy characteristics, a Faraday cup is employed, in combination with computer tomography. In determining the current density distribution of the electron beam from the set of projections recorded, Fourier methods are generally adopted. Deficiencies of such methods include poor numerical stability and applicability to a very limited class of objects. To accelerate data analysis, increase the accuracy, and decrease the noise of the measurements, an algebraic approach is proposed, in conjunction with synchronous data accumulation. An algorithm is developed for algebraic derivation and reconstruction of the energy density distribution and monitoring of beam focusing. The two-dimensional current density distribution obtained by analysis is used to obtain the parameters of beam focusing, such as the diameter calculated from the width of the energy density distribution at characteristic levels; the area of the distribution curve or the null central moment of the distributed normalized by the maximum distribution density; and the effective diameter, indicating the interval in which 68% of the beam energy is incident.