The electron-beam (e-beam) source’s high deposition rates and large evaporant
capacity make it convenient for production-scale coating machines. Solid
evaporant such as powder, granules, lumps, or shaped starter sources, is placed
in the source’s copper hearth or in a crucible liner. A high electron flux generated
by a hot filament placed below the source is electrostatically and magnetically
focused on the top of the evaporant. The electron beam’s energy raises the
evaporant’s surface temperature. Often the beam is rastered to increase the
evaporation area. Since the evaporation area is surrounded by cooler (often solid)
evaporant, unlike other thermal sources, the e-beam source’s vapor plume is largely
uncontaminated by crucible liner material.