| 摘要 |
<p>PURPOSE:To obtain ample electron emission at the same cathode temperature as that of an impregnation type cathode by impregnating an electron emissive material in a porous body with regard to a dot-type cathode that requires a high brightness electron beam and arranging a heater around it and heating it. CONSTITUTION:The one end of a tungusten rod is narrowed by machining. To make its tip still narrower, the tip is formed into a sharp end of 0.05 to 10mu by chemical abrasion such as electrolytic or alkaline melting. Then the pre-burnt mixtures of barium carbonate, calcium carbonate, and aluminum oxide and the like that are the raw materials of the electron emissive material is applied to the surface of the porous body and melted and impregnated at approximately 1,800 deg.C in a reduction atmosphere or vacuum in the same method of manufacturing a normal impregnation type cathode. This cathode can be manufactured by connecting the sharp end of such manufactured negative electrode portion and its reverse side to the cathode side electrode and arranging a heater apart from the external surface of the porous body.</p> |
