Neutron accelerator tube having improved ionization section

A neutron accelerator tube having a target, a replenisher section for supplying accelerator gas and an ionization section located between the target and the replenisher section is claimed. The ionization section comprises: (a) an ionization chamber adapted to receive accelerator gas from the replenisher section, (b) first and second cathodes spaced from one another and having opposed active surfaces exposed to the interior of the chamber, the active surface of at least one of the cathodes being formulated of a beta ray emitting material, and (c) an anode located at a position intermediate the cathodes whereby, in reponse to an applied positive voltage, electrons are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons upon impacting an active cathode surface