| 摘要 |
PURPOSE:To set the trimming plate to a lower voltage for tight grid electrode and prevent floating of secondary electrons at the outside of electron gun by connecting the grid electrode having the trimming plate and the trimming plate through a resistance body having a high resistance value. CONSTITUTION:A disk type trimming plate 13' made of a metal such as stainless is concentrically loaded to the inside of a high quality electrode of electron gun C, for example, the third grid electrode 3 through an annular insulation material 14, and the third grid electrode 3 and the trimming plate 13' are electrically connected through a resistance body 15 of high resistance value. At the time of trimming, a current path is formed by the electron beam to the cathode from the third grid electrode 3-resistance body 15-trimming plate 13' and thereby a current flows through the cathode. With voltage drop by resistance body 15, trimming plate 13' is set to a lower voltage for the third grid and the secondary electrons are attracted, absorbed and diminished in the high voltage third grid electrode 3. |
