| 摘要 |
PURPOSE:To improve a withstand voltage property between a Wehnelt electrode and an anode while reducing an inner volume and shortening a manufacturing time by providing a heater electrode inside an insulated cylinder serving as well as a vacuum envelope between a heater cathode electrode and an anode. CONSTITUTION:A heater electrode 7 is provided in the position entering from the end part to the inside of an insulated cylinder 4 by using a metal cylindrical member 12 and a metal ring member 13 while shortening a Wehnelt electrode 2. And the electrode 2 is heated by heat of emission from the heater 8 while said heat is transferred quickly to the cathode electrode 3 for being radiated efficiently therefrom. Accordingly, the temperature of the part near the anode 1 of the electrode 2 is also lowered so as to be able to suppress generation of vacuum discharge. Further an inner volume of an electron gun can be also reduced while shortening time required for evacuation. |
