| 摘要 |
PURPOSE:To set the operating temperature low and enable sufficient emission to be taken out, by causing the cathode to comprise an oxide containing barium and an electron emission material consisting of silicon or magnesium impregnated in a hole of a base member and further to contain an oxide of rare earth element. CONSTITUTION:A cathode comprises a cathode cylinder 10 consisting of nickel, etc., a cup 20 consisting of nickel, etc., for closing an open end of this cathode cylinder 10, a heater 3, and impregnated cathode pellets 40. These pellets 40 include a heat resisting porous base member 50 obtained by baking tungsten powder containing the powder of an oxide of rare earth element 80 consisting of scandium oxide Sc2O3. The cathode is constituted by oxides containing barium oxide, alumina, and calcium oxide, and an electron emission material 70 consisting of silicon or magnesium. Therefore, the formation of barium is activated so that the amount of barium supplied to the surface of the base member 50 is increased. Thus, operating temperature can be lowered, and stable emission can be obtained in a short time at the startup. |
