Visible cameras as a tool to study electron-beam shape

The characterization of the space distribution of particle trajectories, or the respective current distribution, in powerful electron beams is an important scientific and practical task, necessary to improve the quality of the electron beam technologies, which are employed in several scientific and technological environments. For various applications, a small divergence is required, in order to transport the electron beam over long distances and to focus it onto a small spot. To characterize an electron-beam, the simultaneous knowledge of accelerating voltage, beam current, focus coil current and vacuum level provides little insight into the properties of the beam itself. Visible cameras are used to study the shape of the electron beam when these parameters are varied. Series of pictures of the emission of the electrons composing the beam interacting with Ar background gas at different orientations are collected and use to reconstruct the 2-dimensional shape of the beam by means of tomographic inversion.