Abstract: This gun comprises a cathode K, a grid G, and an anode A between which the applied voltages are radio-frequency voltages. The cathode is disposed on the central conductor of a coaxial cavity, facing said grid terminating said cavity. Said cavity is terminated at the other end by a short-circuit and includes a coaxial branch line so as to resonate at two frequencies F.sub.1 and F.sub.2 multiple of f.sub.0, whose beating induces a radio-frequency grid-cathode voltage. Said grid terminates another coaxial cavity whose central conductor is hollow and whose end facing said grid forms the anode. said other coaxial cavity resonator is excited and resonates at a frequency F.sub.0 multiple of f.sub.0, which induces a radio-frequency anode-grid voltage.A proper selection of the frequencies F.sub.0, F.sub.1, F.sub.2 allows to obtain electrons bunches of very short duration.

Abstract: The invention concerns a power modulator provided with a transformer. This transformer having a high transformation ratio receives a low voltage impulse and transforms it into a high voltage impulse directly applicable on a high frequency or hyperfrequency tube in order to create a powerful impulse magnetic field. The transformer is particularized by the realization of its primary composed of a plurality of primary windings, all of which are connected in parallel and which, put end to end, extend along the entire lengths of the secondary. They are wound furthermore around the secondary and not inside it.

Abstract: The invention provides a self-focusing cavity for accelerating charged particles, intended to form the first or only cavity of a linear accelerating structure; this structure accelerating a charged particle beam along an axis merging with a longitudinal axis of this structure. The cavity of the invention comprises an input wall sloping with respect to said longitudinal axis so as to form a surface of revolution providing a charged particle focusing effect.