[en] A gas-filled tube used to produce a pulsed neutron flux with the D(T,He⁴)n reaction is described. Deuterium and tritium ions generated in a reflex discharge are extracted and accelerated to 100 keV by means of an accelerator electrode onto a deutero--tritide target electrode. The electrodes are designed to focus the ion beam onto the target. Total tube currents consisting of extracted ions, unsuppressed secondary electrons, and ions generated by interactions with the background gas are typically 100 mA. Characteristics of the extracted ion beam are discussed. Accelerating voltages greater than 50 keV are required to focus the beam through the accelerator aperture for configurations that give beams with the proper energy density at the target. The perveance of the beam is defined. Maximum perveance values are 2--10 nanopervs. Tube focussing and neutron production characteristics are described