| 摘要 |
PURPOSE:To reduce the emission area of ion source substance thus to improve ion emission per unit area by covering the surface of ion generating section composed of porous W except the central portion with an ion inpermeable film having high melting point such as W. CONSTITUTION:A porous W5 cut into a conical shape is electron beam welded onto the tubular member 6 of Ta to form a conical ion generating section the surface of which is spattered with W7. Thereafter the leading edge is cut to have the diameter of 0.3-0.5mm. phi to remove collapsed portion from the cutting face through electrolytic grinding. Since the evaporated ion source substance will emit only through said cutting face 8 having small diameter, ion beam of high brightness can be produced. |
