| 摘要 |
PURPOSE:To make both merits of an Nier type ion source and a BA gauge type ion source turn into a combined construction as well as to reduce the diameter of an ion beam as aiming at the promotion of high sensitivity, by setting up an electron beam focusing electrode in position between a cylindrical cage anode and an annular holt electrode. CONSTITUTION:An anode 1 is made up of a molybdenum metal plate which is formed into grid form (about 3mm. in width and 1mm. in grid pitch) of reticular form in part and then made round into cylindrical form of about 6.5mm. in diameter and about 15mm. in height by means of photoetching, while a hot cathode 2 is made up of a rhenium metal of 8mm. in width, 0.025mm. in thickness, which is coated with sodium oxide by means of an electro-deposition process and then rounded into a ring of about 12mm. in diameter. A shield electrode 3 is one that prevents an electron out of the hot cathode 2 from going directly to a doughnut plate of the anode 1 but it is constituted of a solid construction in a way of supporting two upper and lower ring electrodes 3' and 3' with two stays 3'a and welded to a doughnut plate 3a, and simultaneously doubles as a focusing electrode being situated in a little lower potential position than that of the hot electrode 2 and sandwiching a group of electron beams heading toward the anode 1 from the hot electrode 2 in between top and bottom, thus it serves as checking the diffusion of beams in addition to its regular function. |
