Study and Development of Active Sintered Controlled Porosity Dispenser Cathode

The sintered wire cathode offers a significant improvement in density and uniformity of emission. In the present technique of active sintering, an activator is introduced, which relaxes the sintering temperature of tungsten (W)-wire bunch significantly. The technique also offers well-opened columnar pores with a uniform distribution all across the cross section. The pellets are made out of the sintered bunch of W-wires, each of diameter 50 μm. The pellets are impregnated using triple carbonates and are integrated with potted heaters. The cathode assemblies are tested in an analytical system containing an anode and an Auger electron spectroscopy facility. The pulse emission measurements revealed that the emission density of these cathodes is higher than twice that of a conventional B-type cathode. This high emission is attributed to a relatively high Ba/W and O/W ratios on the surface as compared with those of a B-type cathode. The Miram curves, generated out of pulse emission data, exhibit sharp temperature-limited fully space charge-limited transition, indicating lower patchiness of emission as compared with that of a B-type. The theoretical studies are carried out to estimate the optimum wire gauge that can produce good coverage and recovery to the ion bombardment.