Electron Beam

This article presents the construction of a fast, intense electron beam generator, several of its opera-tional properties and its preliminary applications. A fast filamentary discharge produced in a tube filled with Argon gas at pressure of about 0.1 torr. An electron beam is obtained ...

The effect of temperature in the 293-473 K range, on the secondary electron emission (SEE) yield of single crystal and polycrystalline diamond film surfaces is reported. For the polycrystalline films the SEE yield was found to decay as function of electron irradiation dose while for the single crystal an increase occurs first, followed by a decrease. For both surfaces, the

The spallation failure of a commercial thermal barrier coating (TBC), consisting of a single-crystal RENE N5 superalloy, a platinum aluminide (Pt-Al) bond coat, and an electron beam-deposited 7 wt pct yttria-stabilized zirconia ceramic layer (7YSZ), was studied following cyclic furnace testing. In the uncycled state and prior to deposition of the ceramic, the Pt-Al bond-coat surface contains a cellular network of ridges corresponding to the underlying bond-coat grain-boundary structure. With thermal cycling, the ridges and associated grain boundaries are the sites of preferential oxidation and cracking, which results in the formation of cavities that are partially filled with oxide. Using a fluorescent penetrant dye in conjunction with a direct-pull test, it is shown that, when specimens are cycled to about 80 pct of life, these grain-boundary regions show extensive debonding. The roles of oxidation and cyclic stress in localized grain boundary region spallation are discussed. The additional factors leading to large-scale TBC spallation are described.

The use of semiempirical multilayer depth-dose code EDMULT for evaluating the absorbed- dose coefficient K was studied with a personal computer. When multiplied by the charge per unit area, the coefficient gives the absorbed​ dose in the sample irradiated by electrons. This relation presupposes the model configuration of the plane-parallel beam normally incident on the four-layer slab absorber. The absorber consists of the accelerator window, the air layer, the sample and the substratum. The initial energies of electrons above 100 keV were considered. The values of K obtained agreed reasonably well with the values in the literature. The absorbed doses estimated from K were compared with the values measured by the radiochromic dosimeter for various sets of irradiation conditions. The r.m.s. deviation of the former from the latter was 6.7%. A calculated example of the effects of different substratum materials is given.