| 摘要 |
PURPOSE:To increase a collimation lens diameter to the maximum and reduce the image distortion at the periphery of an image by inserting and fixing an annular insulator, i.e., a mesh support base, between the large/small bore step section of a cylindrical electrode and a fixed ring coupled and fixed outside the small bore section of the cylindrical electrode next to a cathode in contact with the annular insulator. CONSTITUTION:An annular insulator 16a of a mesh support 15a base is coupled outside the small bore section of the fifth grid 7a in contact with a large/small bore step section, thereby no fixing ring is required. According to such constitution, the annular insulator 16a is not required to reduce its thickness (in the radial direction) unreasonably, thus the diameter of the fifth grid 7a and a mesh electrode 6 can be increased to the maximum while retaining the insulation effectively. |
