The transmission secondary
electron emitter according to the present invention comprises a secondary
electron emitting layer 1 made of
diamond or a material containing
diamond as a main component, a supporting frame 21 reinforcing the
mechanical strength of the secondary
electron emitting layer 1, a first
electrode 31 formed on the surface of incidence of the secondary electron emitting layer 1, and a second
electrode 32 formed on the surface of emission of the secondary electron emitting layer 1. A
voltage is applied between the surfaces of the incidence and the emission of the secondary electron emitting layer 1 to form an
electric field in the secondary electron emitting layer 1. When the incidence of primary electrons into the secondary electron emitting layer 1 generates
secondary electrons in the secondary electron emitting layer 1, the
secondary electrons are accelerated in the direction to the surface of the emission by the
electric field formed in the secondary electron emitting layer 1, and emitted out of the transmission secondary electron emitter. Therefore, a transmission secondary electron emitter capable of efficiently emitting the
secondary electrons by the incidence of the primary electrons, and an electron tube using the same can be achieved.