| 摘要 |
<p>PURPOSE:To decrease the average intensity of electron emission on an electron emission cathode in the operation of a diode and reduce the deterioration of life span, by arranging the electron emission area of the cathode having convex shape opposing to the first grid. CONSTITUTION:A thermoelectron emission cathode is formed by providing a spherical cathode cap 12 on a cathode sleeve 6 in which a heater 5 is arranged whereby the convex side surface of said cap is facing the first grid 3, and coating the convex side of sphere surface with an electron emission material 11 and diode operation is performed by setting the first grid 3 at a positive potential against the cathode cap 12. As a result, a constant electric field can always be formed in the vicinity of a beam restricting aperture 4 independently of the inclination of the cathode cap 6 and the deterioration of the life span as an electron emission characteristic can be reduced while the average intensity of electron emission on the cathode and Joule heat are reduced.</p> |
