ELECTROSTATIC FOCUSING TYPE IMAGE RECEIVING TUBE AND ITS MANUFACTURING METHOD

摘要

PURPOSE:To reduce the influence of the leakage field of a magnet by providing a magnetic shielding board around a magnet for in-tube ion trap located at the bent of focusing electrode of a bent gun. CONSTITUTION:An electron gun 3 comprising a cathode 4, a control grid electrode 5, an acceleration electrode 6, a bent focusing electrode 7 and an anode is inserted into a neck 2 of a glass bulb 1. On the other hand the bent 7' of the focusing electrode 7 is flexed to locate a ring-shaped ion trap magent 21. Moreover magnetic shielding boards 22, 23 composed of pure ion are provided while facing against both faces of said magnet 21, to prevent the leakage flux of said magnet 21 from entering into the side of main lens or prefocus lens. Consequently the electron beam can be prevented from being subjected to unnecessary deflection.