Control over the emission properties of impregnated dispenser cathodes via surface pore density

Metal injection molding (MIM) was used to fabricate impregnated dispenser cathodes. The emission properties of tungsten cathodes were adjusted by controlling the number of exposed surface pores via mechanical polishing after completion of the impregnation process with 4BaO:CaO:Al2O3 (4:1:1) at 1600 similar to 1900 degrees C. The average distance between neighboring pores decreased as the number of pores increased. Three cathode samples having various surface pore densities were compared. Emission improved as the surface pore density increased. An average distance between exposed pores of 3.32 mu m resulted in an emission current of 2.14 A (7.57 A/cm(2)) at 1030 degrees C-br, corresponding to a work function of 1.92 eV, which is comparable to that of an M-type cathode. Thus, control of the surface pore density of impregnated cathodes provides a simple, cost-effective means to produce high current density thermionic electron guns. (C) 2016 Elsevier B.V. All rights reserved.