| 摘要 |
PURPOSE:To obtain an electron gun able to stabilize a beam current quantity while using the impregnation type cathode by constituting a control electrode of two thin plates, which are fixed to both faces of a mother plate while having minute openings respectively. CONSTITUTION:A control grid 2 consists of the basic material 20 and two thin plates 21 and 22 provided on its both faces, while the first thin plate 21 has a thickness of (t) and a minute opening having d1 in diameter and the second thin plate 22 has about the same thickness with that of the thin plate 21 and a minute opening of d2 in diameter. The diameter of the first minute opening facing the cathode 1 is set up to be not less than two times as in the former electron gun so that the diversity in the quantity of a beam current due to uneven emission in the cathode face can be avoided while balancing the electrons radiating from a broad region of the cathode 1 and being able to take them into the second minute opening. The first minute opening is set up to have about the same thickness with that of an electrode plate so that the weakening of the electric field for taking out electrons due to the opening may be reduced thus being able to electrofix a beam current quantity passing through the second minute opening. |
