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Publication of BE404932ApublicationCriticalpatent/BE404932A/xx
H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
H01J1/02—Main electrodes
H01J1/13—Solid thermionic cathodes
H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment