High current density Sc2O3-W matrix dispenser cathode
ABSTRACT Sc2O3-W matrix dispenser cathodes have been prepared by powder metallurgy method and tested in Pierce electron guns. The emission current density can reach 72 A/cm2 at 900°C and over 100 A/cm2 can be achieved at a temperature higher than 950°C. The emission improves and then keeps stable with time throughout the life testing period of 330 h at a continuous loading of 88 A/cm2 pulsed current density with a pulse width of 10 μs and duty cycle of 0.2%. The cathode surface is covered by a semiconductor multilayer composed of Ba, Sc and O. The emission behavior of the cathode can be explained by a semiconductor model.
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ABSTRACT: The microstructure of a fully activated scandia doped dispenser (SDD) cathode has been studied by scanning electron microscope (SEM). The observation results display that nanoparticles appear at the growth steps and the surface of tungsten grains of the fully activated SDD cathode. To study the influence of the nanoparticles on the emission, the local electric field strengths around the nanoparticles have been calculated by Maxwell 2D code and Comsol. The calculation results show that the local electric field strengths are enhanced by 1.1 to 3.8 times to average value based on different model conditions. The highest field strength is about 1.54 × 105 V/cm at an average field strength of 40 KV/cm, which is related to a space-charge limited (SCL) current density of 100 A/cm2 in the experimental configuration. This implies the field strength is not high enough to cause field emission.Functional Materials Letters 08/2013; 6(4):50040-. DOI:10.1142/S1793604713500409 · 1.61 Impact Factor