A New Impregnated Dispenser Cathode

To meet the demand of terahertz devices, we develop a new type impregnated dispenser cathode. This cathode is impregnated with an active substance with molar ratio of $26{\rm BaO}{\cdot}29{\rm SrO}{\cdot}8{\rm Sc}_{2}{\rm O}_{3}{\cdot}7{\rm CaO}{\cdot}{\rm Al}_{2}{\rm O}_{3}$. We test its emission performance, practical work function distribution, and surface composition, and analyze the mechanism of the high emission performance. At 1100 $^{\circ}{\rm C}_{\rm B}$, the pulse current density is $171.6\pm 2.8~{\rm A}/{\rm cm}^{2}$, 5.4 times of that of an M-type cathode. The peak work function of Miram curve is ${\sim}{\rm 1.570}~{\rm eV}$ . Ba, Sc, Ca, Al, and O atoms are detected on most surfaces of tungsten grains. It is proposed that the Ba–Sc–Al–Ca–O layer on the surface of the cathode is responsible for the excellent emission performance.