foil window 632 on one side the foil window 632 is mounted on the underside of a center portion 642 of a conduit 640 the center portion 642 extends at an angle to an entrance portion 644 and an exit portion 645 at each end of the center portion the entrance and exit portions extending generally parallel to one another rollers 646 and 647 respectively positioned within the entrance portion 644 and exit portion 645 serve to guide the movement of the sheet metal 10 through the conduit 640 the electron gun assembly 620 includes tungsten filaments not shown and when high voltage is applied to the filaments a cloud of electrons is generated electrons are drawn from the cloud to areas of lesser voltage of the gun assembly and the electrons accelerate to extremely high speeds the electrons exit the vacuum chamber through and generally perpendicular to the foil window 632 and penetrate the coating of the underside of the sheet metal 10 moving through the conduit 640 as a result the coating is transformed into a solid through the process of polymerization and crosslinking electron beam polymerization is the process in which several individual groups of molecules combine together to form one large group called a polymer electron beam crosslinking is the process by which an interconnected network of chemical bonds or links develop between polymer chains to form a stronger molecular structure many coatings require a low oxygen environment during electron beam processing to be able to convert from.