Abstract: An extractive electrode allowing to reduce the vertical focusing and defocusing effect of the hyperfrequency electrical field used for accelerating the particles of a beam within an accelerator of cyclotron type. The extractive electrode comprises a metallic block having a substantially prismatic shape and provided in its entry face facing the particle source with at least a window which opens onto a deep notch delimited by two curved lateral walls forming a channel C for the passage of the beam. A median element located within this channel C allows to obtain two separated channels for the passage of the two beams corresponding to two harmonic operating frequencies.

Abstract: A magnetic correcting device for locally modifying the strength of the magnetic field of a cylcotron in the zone of extraction of the accelerated particles to promote the extraction function and to ensure a suitable focusing of the emergent beam. In one embodiment, the device comprises a block of prismatic shape made of a composite laminated material formed by a stack of plates P.sub.1 and P.sub.2 of different permeabilities. The plates P.sub.1 are for example made of cobalt steel and those P.sub.2 of an non-magnetic material (copper for example).

Abstract: A high-frequency focusing device making it possible to achieve suitable horizontal and vertical focusing of a beam of charged particles issued from a particle source located substantially at the center of a cyclotron, this device comprising pairs of focusing electrodes fixed to the edges of parallel plates forming each sector-shaped Dees of the cyclotron, each pair of electrodes being arranged in such a manner that the particle beam passes between them, these electrodes which project into the acceleration space e of the cyclotron, making it possible to compensate for lack or excessive vertical focusing brought about by the magnetic field developed in the acceleration space e.

Abstract: The present invention relates to an hyperfrequency resonant system designed to accelerate a beam of charged particles, and comprising at least a first resonant cavity (or a group of resonant cavities similar to this first cavity) tuned at a fundamental frequency F and excited by means of an external electro-magnetic energy source and a resonant element which is, for example, a second resonant cavity tuned at harmonic frequency 2F and excited by means of the bunched particle beams. The invention is applicable, for example, to particle accelerators of the "microtron" kind.

Abstract: A particle accelerator for obtaining high energy particle beams, comprises an accelerating structure S.sub.A, one mirror or two mirrors constituted with magnetic achromatic and stigmatic deviators and a source K of particles located at the entry of the accelerating structure S.sub.A and having an annular shape allowing the accelerated particles having passed twice through the accelerating structure S.sub.A to cross the source K, the axis of the source K being coincidental with the axis of the accelerating stucture S.sub.A. Magnetic fields are determined in such a manner that the mirrors totally reflect the particles having a predetermined energy level and totally transmit the particles having an energy level higher than this predetermined energy level.