PURPOSE: To realize the long service life.
CONSTITUTION: A pair of electrode devices 4A arranged opposite on both end sides of a glass tube 1 are composed of a column shape electrode 41 arranged in the tip part of an inner lead 3 and a cup shape electrode 42 to surround this column shape electrode 41. This column shape electrode 41 is formed by impregnating an emitter material as an electron emitting body or by applying it to a surface, and a groove 4a having a recessed shape cross section in the circumferential direction is formed almost in a central part of a main body of this column shape electrode 41, and thereby, an electric current flowing to this column shape electrode 41 is decreased and a calorific value is increased, and thermoelectron emitting efficiency is improved, and a scattering and vaporizing quantity of an electron emitting substance is reduced, and the service life is lenghtened.
OKUBO YOSHIYUKI
SATOU FUYUTOSHI
MAESO TAKESHI
SHIMOJO TOKUHIDE
UCHIYAMA MASAO
ISE ELECTRONICS CORP