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 beam of charged particles is guided along a path including a looped section between two rectilinear stretches, each of these stretches being provided with focusing and centering means. A holder insertable into the outgoing stretch, ahead of a collimator, carries a target designed to emit photons upon being struck by incident particles. The target holder is linked with a retracting mechanism which also controls a diaphragm in the looped path section to narrow its aperture when the target is in place. A dose-equalizing filter utilized in the latter instance is movable jointly with the target holder out of the path of the exiting beam.

Abstract: A device for detecting the absence or improper positioning of detachable elements in their supports comprises a system for monitoring the fitting in position of selected elements on a mounting plate provided at its periphery with slots, these slots being associated with obturating-studs. These studs are retractable from the corresponding slots when a corresponding detachable element is appropriately positioned in the mounting plate which is immobilized by means of a safety locking system comprising an index which can be introduced into this corresponding slot after the retraction of the obturating-stud from it, this index enabling to actuate a safety electrical switch.

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: Device making it possible to check, prior to or after each irradiation treatment session, the proper operation of the dose-measuring systems associated with a radiotherapy apparatus and comprising at least one dose-measuring circuit equipped with a counter system of preselect design. This device comprises a pulse generator G, means for applying said pulses to the counter system of at least one of the measuring circuits and means making it possible to halt the generator G and reset the counter system to zero when coincidence occurs between the preselected number of pulses corresponding to a preselected dose level D and the displayed number of pulses corresponding to the dose level effectively delivered by an irradiation source S.

Abstract: Selective transmission systems for transmitting from an H.F. generator to a load device whose electrical characteristics may vary rapidly, a pulsed main H.F. signal of given frequency, and for eliminating the spurious signal or signals accommpanying the main H.F. signal at the beginning of the pulse, when the load impedance presented to the H.F. generator is not suitable. Several embodiments are described which take account of the frequency of the spurious signals in relation to the frequency of the main signal.

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: This device makes it possible to achieve upon a target of predetermined position, the simultaneous focusing of a beam of accelerated particles, in two mutually perpendicular planes, this, whatever the energies of said particles. The device comprises two electromagnets E.sub.1 and E.sub.2 whose entry and exit faces are parallel with one another, and a third electromagnet E.sub.3 whose entry and exit faces are at an angle .gamma.. Relationships are given to determine the different parameters defining the dimensions and positions of the electromagnets in relation to one another being linked by determinate relationships. The device can be utilized in physical and biological researches, as well as in medical irradiation units.

Abstract: A collimator arrangement, which, in association with a charged particle accelerator, makes it possible to produce a uniform irradiation beam throughout a predetermined zone, comprises: a first collimator system, provided with movable elements M.sub.1, M.sub.2, M.sub.3, M.sub.4 and m.sub.1, m.sub.2, m.sub.3, m.sub.4, and a second collimator system associated to the first collimator system and comprising sets of metal strips L.sub.1, L.sub.2, L.sub.3, L.sub.4 and l.sub.1, l.sub.2, l.sub.3, l.sub.4 fixed at four supporting-rods integral with the first collimator system.

Abstract: A system for measuring radiation doses in radiotherapy comprises two identical metering networks energized in parallel from a common radiation source, each network including an integrating amplifier whose time constant is variable by the short-circuiting of an input resistor. A manually or automatically reversible switch selectively foreshortens the time constant of one or the other amplifier whereby the corresponding metering network controls the cutoff of the radiation source whenever the emitted radiant energy reaches a predetermined value. The other network, acting as a backup, takes over the radiation cutoff upon failure of the controlling network; this takeover may be indicated by a set of signal lamps jointly controlled by the reversing switch and by a counting unit of the standby network.

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: An ionization chamber is peripherally bounded by a stack of four coaxial annular frames with rabbeted confronting faces forming three annular recesses on the peripheral chamber wall, the middle recess receiving a transverse partition whereas the other two recesses form seats for peripheral zones of two dielectric disks with discontinuous metallic coatings constituting mutually insulated segmental electrode elements. The segmental elements terminate short of the peripheral chamber wall, except for a tab extending from each element onto the peripheral disk zone received in the corresponding recess within which that tab is connected to an external lead. The tabs of the two disks are angularly offset from one another, as are the segmental boundaries of their conductive elements.

Abstract: An axial ion source comprising a tubular anode having an axis XX, at the two ends of which there are placed a cathode located along said axis XX and anticathode which comprises a circular plate having an axis YY parallel to the axis XX, this plate being able to revolve about this axis YY. A device controls the sequential rotation of the anticathode about the axis YY, the rotation of the anticathode enabling a new intact surface to be presented, when necessary, at the end of the anode. A cooling fluid can circulate in the grooves equipping the plate.

Abstract: A centering process for detecting the centering errors of a sweep beam impinging on a target and correcting them, this process comprising comparing a signal V.sub.E, corresponding to the difference between electric signals received on the two halves of an electrode, with threshold voltages .+-.v.sub.e and comparing a signal V.sub.B, corresponding to the voltage controlling the sweep of the beam, with threshold voltages .+-.v.sub.b, the transmission of a signal V.sub.p corresponding to V.sub.E < + v.sub.e and V.sub.B < - v.sub.b (or of a signal v.sub.n corresponding to V.sub.E < - v.sub.e and V.sub.B > + v.sub.b) indicating the direction of the centering error and its amplitude. The process permits controlling the centering of a sweep beam on secant axes making an angle .theta. therebetween.

Abstract: A shutter designed for temporarily closing off an opening O.sub.A formed in the wall P of an irradiation room, for the passage of a particle beam, comprises a cylindrical metal block K which can rotate about its axis XX and occupy two stable position which are 180.degree. from one another. The block K a cylindrical cage closed at its two ends by two circular plates equipped respectively with eccentric holes for the passage of the particle beam, the eccentric holes having axes YY parallel to the axis XX and located at an interval L therefrom -The block K is provided with a longitudinal passage through which there can pass the particle beam and a blind hole or "pit" disposed symmetrically to the longitudinal passage and which can black the particle beam according as the positioning of the block K by respect with the eccentric holes.

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.

Abstract: Multiperiodic linear accelerating structures comprising a succession of cylindrical accelerating cavities C.sub.a having a revolution axis X.sub.1 X.sub.2, and being coupled to each other by cylindrical coupling cavities C.sub.c having the axis X.sub.1 X.sub.2 as revolution axis, which coincides with the mean path of the beam of the particles to be accelerated, the radius R.sub.c of the coupling cavities C.sub.c being substantially equal to the radius R.sub.a of the accelerating cavities C.sub.a. Accelerating and coupling cavities are constituted by a stack of elements easy to machine and braze together.

Abstract: A microwave reflector device of small size, making it possible to deliver a predetermined quantity of the power generated by a high-power microwave generator, comprises a unidirectional element which imposes an appropriate constant load on the generator, and a reflector system constituted by a waveguide D tapped into the output waveguide T of the unidirectional element, said waveguide D being terminated at its free end by a metal plate carrying three quartz rods 10, 11, 12 designed to slide, parallel to the axis of the waveguide D, respectively in three metallic sleeves 13, 14, 15 having a circular shape and dimensioins such that they form cut-off waveguides at the operating frequency of the generator. The free end of each of the sleeves 13, 14, 15 provided with three respective rings 16, 17, 18 of absorber material.

Abstract: An auxiliary collimator is added to the main collimator of a radiotherapy apparatus and comprises a master-container filled with mercury and a localising container containing a block of non absorbent material having a predetermined shape; means being provided for automatically positioning these containers with respect to the main collimator and for allowing the mercury to enter the localising container when once it has taken its working position.

Abstract: A monitoring device transparent to ionizing radiation, designed to measure the orientation, intensity and uniformity of an incident beam, comprises a cylindrical housing forming at least one ionization chamber with one or more ion-collecting electrodes transverse to the housing axis, each electrode being subdivided into a plurality of mutually insulated conductive elements connected to respective amplifiers. The elements of at least one electrode include one or more outer elements surrounding or bracketing one or more inner elements to measure the radiation in a central zone and a peripheral zone. The outputs of the respective amplifiers are additively and subtractively combined in an evaluation circuit.