PURPOSE: To prevent a rear electrode and a linear hot cathode from approaching to each other and effectively modulate an electron beam using low modulation voltage by arranging the linear hot cathode at the off-axis position in relation to the permeation hole of the electron beam extraction electrode, and applying modulation voltage to the rear electrode or the electron beam extraction electrode.
CONSTITUTION: A linear hot cathode 10 is arranged at the off-axis position in relation to the permeation hole 18 of an electron beam extraction electrode 12. That is to say, when the linear hot cathode 10 is projected on the electron beam extraction electrode 12, a part of the projection point PO is made to slightly cover the permeation hole 18, but not fully. An electron radiated from the linear hot cathode 10 passes through the permeation hole 18 of the electron beam extraction electrode 12 while its amount is being controlled depending on the negative potential applied to a rear electrode 11. An electron beam can fully be modulated by applying low modulation voltage to the rear electrode 11 using the double peak characteristics of the electron density distribution on the surface of the electron beam extraction electrode 12, when the potential of the rear electrode 11 is varied.
MIYAMA HIROSHI
TOMII KAORU
NISHIDA JIYUN
