| 摘要 |
PURPOSE:To prevent the occurrence of a false signal due to a reflected beam without requiring to decrease the diameter of an electron gun electrode or the strict trimming by adding to an electron gun a cylindrical shield electrode held at a lower potential than that of an acceleration electrode, encircling the cylindrical portion of the acceleration electrode, and facing part of a deflection electrode. CONSTITUTION:An electron gun enclosed in a glass bulb 11 has a cylindrical shield electrode 12 in addition to a conventional electrode configuration consisting of a cathode 1, a control electrode 2, and an acceleration electrode 3. A film-like deflectron-type deflection electrode 5 is arranged on the inner periphery of the glass bubl 11. The cylindrical shield electrode 12 is made of non-magnetic stainless steel or an alloy of nickel and copper, etc. like the acceleration electrode 3, it has a flange portion 12a, it is insulated and supported by an electrode supporting body structure 9, it coaxially encircles most of the cylindrical portion 3a of the acceleration electrode and it faces part of the deflection electrode 5. During the operation, a potential of about 200V is applied to the acceleration electrode 3, about 150V (average value) to the deflection electrode, and about 10V to the shield electrode 12, for instance. |
