| 摘要 |
PURPOSE:To obtain an electron gun which satisfies specific beam diameter and the brightness simultaneously, by constructing a chip with specific material while employing specific angle for the half top angle of cone at the tip of said chip. CONSTITUTION:A chip is formed with such material as LaB6, ZrC, HfC, TiC or TaC where the work function W of chip material and the temperature Te at which the vapor pressure of the chip is 1X10<-5> Torr have following relation W/Te<=1.5X 10<-3>ev/degree or such material as the impurities are mixed in said basic material, and the half top angle theta at the tip of said chip is made to be in the following range 50 deg.<theta<65 deg.. Consequently, a cathode having long life and high brightness can be obtained. |
