Experimental investigation of electron guns for THz microwave vacuum amplifiers

Single-sheet and multiple beam electron emitters based on thermionic minicathodes for terahertz traveling-wave tubes have been studied. Data are presented for impregnated blade thermionic cathode with dimensions 0.1 $\times$ 0.7 mm and a maximum current density of 114 A/cm$^2$ in a pulsed mode. A variant of the five-beam electron gun with 0.25-mm-diameter cylindrical minicathodes in cells of a control grid is proposed that provides a current density of 85.5 A/cm$^2$ at a grid potential of 900–1000 V.