Irradiating system including a target-holder mounting in a radiation-protection enclosure and a device for deflecting an irradiation beam

Abstract

The present application relates to a system for irradiating a target (1), including a particle accelerator (10) configured to at least emit an irradiation beam (11) according to an axis, a target-holder mounting (20) outside the accelerator, including at least one port (21) configured to receive a target holder (22) for a target to be irradiated, and a radiation-protection enclosure (30) surrounding the target-holder mounting (20). The particle accelerator (10) is positioned outside the enclosure (30). The target-holder mounting (20) is stationary relative to the particle accelerator (10). The port (21) is offset relative to the axis of the irradiation beam (11) and the system (1) includes a deflection device (40), positioned in the radiation-protection enclosure (30) and configured to divert the irradiation beam (11) towards the port (21) of the target holder (22) in which the target to be irradiated is inserted.

Description

[0001] This application relates to a target irradiation system, and in particular an irradiation system comprising a particle accelerator.

[0002] Particle accelerators are devices designed to produce beams characterized primarily by the nature of the particles (protons, electrons, etc.), their energy, and the beam current. Depending on the application for which the accelerator is used (radioisotope production, X-ray or gamma ray radiotherapy, neutron production, etc.), the beam can interact with different types of targets, for example, mainly: Targets in which nuclear reactions take place, such as targets used with cyclotrons for the production of radioisotopes for imaging by Positron Emission Tomography (PET); Stop-stop targets which aim to stop and characterize the beam during accelerator tuning phases.

[0003] However, the interaction between the beam and the target can give rise to different types of reactions and consequently to different types of radiation from the target.

[0004] Indeed, an irradiated target typically emits radiation in turn, including high-energy neutrons and photons, in the form of X-rays or gamma rays. These neutrons and photons are called "primary" when they are produced directly by the nuclear reaction occurring in the target, and "secondary" when they result from reactions between the primary neutrons and photons and the surrounding matter.

[0005] A cyclotron is a particle accelerator often used in medical imaging for the production of radioactive isotopes with very short half-lives, even half-lives of two hours or less, such as the following elements: 18F (fluorine-18): 109.7 minutes, 68Ga (gallium-68): 67.7 minutes, 11C (carbon-11): 20.4 minutes. Other types of particle accelerators are of course possible, such as a linear accelerator (LINAC) or a synchrocyclotron.

[0006] For example, a cyclotron producing a proton beam (p) at 12 MeV and 20 µA (microamperes) interacting with a target containing water enriched to 95% in ¹⁸O (oxygen-18) produces ¹⁸F (fluorine-18) accompanied by a flux of neutrons (n) and photons in a certain proportion, typically 6 × 10¹¹ G / s (gamma rays per second) and 4 × 10¹¹ n / s (neutrons per second). This reaction is, for example, denoted -¹⁸O + p → ¹⁸F + n.

[0007] According to another example, the interaction between the same proton beam (p) but this time with a target containing 14< N (nitrogen 14) will produce 11< C (carbon 11) and high-energy photons and neutrons, but in different proportions than in the previous reaction, for example typically 1*10 12< G / s and 2*10 9< n / s at 20 µA.

[0008] The cumulative dose rate near the targets is therefore considerable (several Sv (Sieverts, with 1 Sv = 1 m².s⁻² = 1 J.kg⁻¹) per second in contact with a target producing 18°F and a 20 µA proton beam at 12 MeV (megaelectronvolts)). This intense radiation is ionizing and therefore dangerous for humans and the environment. The intensity of this radiation is approximately one million times greater than that emitted by an external ion-source cyclotron producing the beam described above, i.e., 20 µA of protons at 12 MeV. In the case of an internal ion source cyclotron, the radiation emitted by the acceleration of ions in the cyclotron is greater, which reduces this ratio of the order of a million between the radiation intensities of a cyclotron and a target, but the target remains the main radiation source.

[0009] In the example cited above, the energy spectrum of the particles emitted by the accelerator has a maximum averaging around 2 MeV; therefore, particles can be emitted at higher energies. The radiation from the targets is likely to interact with elements of the surrounding environment (air, equipment, walls, etc.) and activate them. Depending on the materials used for the targets, radioactive isotopes with short or even long half-lives (i.e., half-lives of at least 100 days, or even several years) can be created, which is a drawback for this type of technology.

[0010] It is therefore important to protect people and the environment from ionizing radiation to limit the risks of irradiation and activation of environmental elements during accelerator operation. In particular, it is necessary to protect people and the environment from radiation emitted by the target.

[0011] To protect people and the environment from this ionizing radiation, such systems are often installed in heavy, bulky, and expensive bunkers. Indeed, the walls of a bunker are generally very thick: on the order of 2 meters of concrete.

[0012] However, it is not always possible to build a casemate in existing facilities, such as in a hospital ward for example.

[0013] The development of certain applications is therefore hampered by constraints associated with the installation possibilities of these irradiation systems.

[0014] To reduce this bulk, particle accelerators are sometimes equipped with a so-called "local" radiation protection enclosure. This reduces radiation fluxes in the shielding unit but does not eliminate the need for a shielding unit altogether.

[0015] As an example of such radiation protection, in order to attenuate at least the high-energy photons, primary and / or secondary, emanating from the target, it is advantageous to use so-called "dense" materials. Concrete and lead are often used as "dense" materials, particularly for reasons of cost and ease of implementation. However, for the sake of compactness and weight reduction, it may be beneficial to use even denser materials, such as tungsten.

[0016] Neutron attenuation can occur in two stages: first, slowing down the neutrons, and then trapping them. Neutrons can be slowed down, for example, by elastic collisions with matter. Hydrogen-containing compounds (water, certain polymers, etc.) are well-suited for slowing neutrons. Once slowed, the neutrons can be trapped by a neutron trap or neutron poison. Boron, for example, can be used to capture neutrons. One solution involves loading a hydrogen-rich material, such as polyethylene, with boron at a concentration of a few percent, typically 1% to 8% (atomic). For the purposes of this application, "rich" means that the hydrogen content is equal to or greater than approximately 30% or even 40% atomic concentration in the loaded material.

[0017] However, the capture of neutrons in turn generates high-energy photons called "secondary" photons which must in turn be attenuated.

[0018] Thus, to mitigate these different radiations, a radiation protection enclosure for a target such as a production target of 18< F includes, for example, a succession of layers of hydrogen-rich material containing a neutron poison and layers of dense material.

[0019] In order to attenuate both neutrons and high-energy photons, primary and secondary, these functions can possibly be combined, for example by charging a resin with boron and a dense material such as lead or tungsten.

[0020] Furthermore, because the targets are generally positioned in the immediate vicinity of the acceleration region, or even mounted directly at the output of the particle accelerator used, the radiation protection enclosure therefore encompasses both the target and the particle accelerator.

[0021] The result is that such a radiation protection enclosure does not prevent radiation from the target from significantly activating the particle accelerator and that the mass of the radiation protection remains significant (typically 40 to 80 tonnes for cyclotrons producing protons of 10 to 18 MeV, to which must be added 10 to 20 tonnes for the particle accelerator itself).

[0022] These solutions therefore reduce the risks associated with non-residual radiation but do not protect the accelerator from activation by radiation from the target and, due to their mass, do not facilitate the installation of accelerators, or are sometimes even a barrier to installation in pre-existing buildings.

[0023] To avoid the activation of the particle accelerator by the target, one possibility is to move the target away from the accelerator, which makes it unnecessary to include the particle accelerator in the radiation protection enclosure and thus limit the radiation as close as possible to the target.

[0024] The activation of the accelerator is then much weaker when the target is remote and radio-protected than when the target is mounted directly on the accelerator and the whole assembly is radio-protected.

[0025] This also makes it possible to considerably reduce the size, and therefore the mass, of the radiation protection enclosure since it may then no longer contain the particle accelerator.

[0026] However, it is still possible for radiation to travel back along the irradiation beam emitted by the particle accelerator and activate the accelerator's interior. This is particularly problematic for neutrons, which bounce off the accelerator's metallic surfaces through elastic collisions. If installation constraints necessitate avoiding the construction of thick walls, this neutron rebound is even more problematic because it generates a significant dose rate on its own.

[0027] The use of a remote target therefore makes it possible to greatly reduce the mass of the radiation protection, but there remain risks of environmental irradiation linked to such neutron leakage.

[0028] Furthermore, for certain applications, it may be advantageous to be able to use different targets with the same accelerator.

[0029] One possible solution is to move the selected target in front of the radiation beam.

[0030] However, such a solution generally requires breaking a pre-existing void in the system, changing the target, then re-creating the void before the system can be reused.

[0031] Furthermore, to optimize target irradiation, the target must be positioned as directly in front of the beam as possible. This creates a direct path for ionizing radiation (high-energy neutrons and photons) from the target back to the cyclotron. This has two consequences. First, a portion of the cyclotron remains capable of being activated. Second, neutrons traveling back along the beam path bounce off the cyclotron's metal components, creating a secondary radiation source that must be shielded.

[0032] For example, document US5608224 describes a device with a rotating drum that allows the use of different targets. While this solution allows for target changes without breaking the vacuum, it also aims to ensure that the target to be irradiated is positioned as optimally as possible within the collimator of the irradiation beam. Such a solution, however, does not resolve the problem of neutron return to the particle accelerator.

[0033] Les documents CONARD et al.: "Operational experience and recent developments at the National Medical Cyclotron, Sydney", NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A: ACCELERATORS, SPECTROMETERS, DETECTORS, AND ASSOCIATED EQUIPMENT, ELSEVIER BV * NORTH-HOLLAND, NL, vol. A370, no. 2, 21 février 1996 (1996-02-21), pages 630-633, XP004006792, ISSN: 0168-9002; US 2012 / 313003A1 (TRBOJEVIC DEJAN [US]) 13 décembre 2012 (2012-12-13) et MALAY KANTI DEY et al.: "Setting up a 30 MeV high current cyclotron facility in Kolkata", PHYSICA STATUS SOUDI. C:CURRENT TOPICS IN SOLID STATE PHYSICS, vol. 6, no. 11, 1 novembre 2009 (2009-11-01), pages 2376-2379, XP055247018, DE ISSN: 1862-6351, DOI: 10.1002 / pssc.200982067 divulguent par exemple un ensemble de ciblerie.

[0034] Le document US 2013 / 020512 A1 (ROY MICHAEL P [US]) 24 janvier 2013 (2013-01-24) divulgue un assemblage de protection en couches modifiable.

[0035] The purpose of this request is to resolve, at least in part, the aforementioned drawbacks.

[0036] To this end, a target irradiation system is proposed, according to a first aspect, comprising at least: a particle accelerator configured to emit at least one irradiation beam along one axis, a target holder, positioned outside the accelerator opposite the irradiation beam, comprising at least one port configured to receive a target configured to receive a target to be irradiated, and a radiation protection enclosure surrounding the target holder, the particle accelerator being positioned outside the enclosure, the target support being fixed relative to the particle accelerator, the port being offset relative to the axis of the irradiation beam, and the system comprising a deflection device, positioned in the radiation protection enclosure and configured to deflect the irradiation beam towards the port of the target into which the target to be irradiated is introduced, and the system being characterized in that the radiation protection enclosure comprises an alternation of at least one layer comprising a dense material and at least one layer comprising a hydrogen-rich material comprising a neutron poison.

[0037] The solution proposed here involves using a beam deflection device that directs the beam towards a target inserted into a target array mounted on a fixed port and positioned outside the solid angle of departure of the irradiation beam, or allows targeting one of multiple pre-positioned targets on different ports. The deflection device thus acts as a target selector, or by analogy, a target changer.

[0038] Preferably, the target support has at least two ports, for example five ports.

[0039] For example, at least one of the ports, or even all of the ports, are misaligned with respect to the axis of the irradiation beam emitted by the particle accelerator.

[0040] According to one example of implementation, the ports are arranged in the same plane.

[0041] And for example, the plane in which the ports are arranged is a horizontal plane.

[0042] According to another example of implementation, the ports are arranged in a volume.

[0043] It then becomes possible to reach different targets surrounded by radiation shielding while minimizing leakage paths. Thus, the dose rate in the vicinity of the corresponding target and the particle accelerator, and the activation of surrounding equipment—that is, elements of the environment—are low, while the mass of radiation shielding is reduced.

[0044] The radiation protection enclosure helps to attenuate the residual and non-residual radiation generated by the interaction between the target and the beam, and the combination of the use of a beam deflection device and a radiation protection enclosure close around the targets makes it possible to reduce, or even eliminate, the direct leakage lines of radiation from the targets to the particle accelerator while making it possible to reduce the mass of the radiation protection, possibly by a factor of 5 to 15, while maintaining effective radiation protection.

[0045] For example, the hydrogen-rich material is polyethylene (PE) loaded with boron as a neutron poison at a level of about 5% to 7% (atomic).

[0046] For example, the dense material is tungsten (W) and / or lead (Pb).

[0047] Optionally, the radiation protection enclosure also includes an additional radiation protection component that surrounds the targets mounted on the target support. This additional component is, for example, positioned within a wall of the radiation protection enclosure. Such a component is, for example, attached to the target support.

[0048] Preferably, the radiation protection layer positioned closest to the targets, and the additional piece if necessary, is made of dense material.

[0049] In other words, a radiation shielding layer of the radiation shielding enclosure near an internal surface of the enclosure is a layer of dense material.

[0050] In one embodiment, the radiation protection enclosure includes a wall which has an additional thickness of hydrogen-rich material positioned between the additional radiation protection piece of the targets and the innermost layer of dense material.

[0051] In an example embodiment given for illustrative purposes, the additional radiation protection piece is made of tungsten (W) and has a thickness of between approximately 5 cm and approximately 15 cm, for example approximately 6 cm or 11 cm.

[0052] The wall of the radiation protection enclosure then includes, for example: The additional layer of hydrogen-rich material, with a thickness between approximately 5 cm and approximately 15 cm, is made of PE loaded with 5% boron; the innermost layer of dense material, with a thickness between approximately 3 cm and approximately 8 cm, is made of tungsten (W); a subsequent layer of hydrogen-rich material, with a thickness between approximately 25 cm and approximately 40 cm, is made of PE loaded with 5% boron; a subsequent layer of dense material, with a thickness between approximately 2 cm and approximately 8 cm, is made of lead (Pb); and the outermost layer of hydrogen-rich material, with a thickness between approximately 15 cm and approximately 30 cm, is made of PE loaded with 5% boron.

[0053] Such an enclosure then comprises four layers and an optional additional thickness, in addition to a possible extra room.

[0054] The thickness values ​​are of course given as an indication, to suggest an order of magnitude, and may vary by a few centimeters, for example by + / - 5 cm.

[0055] Such a speaker is particularly compact.

[0056] An order of magnitude for the wall thickness is then between approximately 50 cm and approximately 100 cm, in particular between approximately 60 cm and approximately 75 cm.

[0057] In a particularly interesting example, the radiation protection enclosure includes at least one spherical wall.

[0058] Such a wall, for example, has a maximum outside diameter of approximately 3 m (meters), or even 2 m.

[0059] In another example, the radiation protection enclosure includes at least one wall with a parallelepiped geometry, which helps reduce production costs. At least one of its dimensions—width, length, or height—is then possibly at most approximately 3 m (meters), or even 2 m.

[0060] Such a system therefore reduces the risks of exposure to radiation and minimizes the mass and volume constraints for the installation of such a system, for example in a hospital setting.

[0061] It should be noted, however, that there was a strong prejudice among those skilled in the art against the idea of ​​being able to use such a device.

[0062] Indeed, given the usual energy ranges of the irradiation beam, the deflection device must also implement significant energies.

[0063] This is all the more significant because, in order to achieve a deflection that best avoids neutron return to the particle accelerator and limits the overall mass, it is preferable for the deflection angle to be as large as possible relative to the initial beam axis, for example, at least 5°, or even 10°, for example, between 5° and 175° or between 5° and 40°, and in particular, for example, between approximately 19° and approximately 38°. Therefore, it is preferable for the deflection device to be positioned as close as possible to the target platform, or even at the entrance to the target platform.

[0064] Thus, in other words, the deflection device is then advantageously configured to deflect the beam, relative to the axis along which it is emitted by the particle accelerator, by an angle of at least 5°, or even 10°, for example between 5° and 175°, for example between 5° and 40°, and preferably between 19° and 38°.

[0065] For this purpose, it is configured, for example, to emit a magnetic field. For example, the magnetic field strength is between 1 and 2 Tesla (T). In one particular example, the magnetic field strength is around 1.4 Tesla.

[0066] In one interesting example, the deflection device includes at least one electromagnetic quadrupole positioned along the path of the irradiation beam, typically on the beam's emission axis from the particle accelerator. The electromagnetic quadrupole may, for example, contain one or even four electromagnets.

[0067] According to preferred examples, the deflection device comprises a single electromagnetic quadrupole, or two electromagnetic quadrupoles.

[0068] A dipole is preferable instead of a four-terminal network.

[0069] Other deflection devices can also be used depending on the type and energy of the accelerated particles, such as an electrostatic deflector for lighter particles (electron type) and / or lower energies.

[0070] The deflection device is also positioned within the radiation protection enclosure. It should be noted that the deflection device itself contributes to radiation protection. For this purpose, it is composed, for example, of a dense material, such as copper and / or iron, which makes it effective at attenuating photons. In the case of a quadrupole, this might consist of an iron frame surrounded by copper wire, for example, an iron yoke and a copper winding.

[0071] This raised a further prejudice against exploring such a solution since such a deflection device would then preferably be positioned inside the protective enclosure, another difficulty could lie in choosing the configuration of the passage of the power supplies necessary for the operation of the deflection device through the protective enclosure.

[0072] According to an interesting example of implementation, the passages for supplies, for example cables or pipes, are baffled.

[0073] Once these prejudices are overcome, thanks to such positioning, the deflection device itself contributes to radiation protection by attenuating high-energy photons.

[0074] Furthermore, if the target holder does have a port positioned along the beam axis, the target mounted on this port should preferably have a low neutron source term, meaning its neutron flux is at least 100 times lower than the primary photon flux (for example, here approximately 1 x 10⁻¹⁰ n / s). This could be, for example, a charge target (i.e., a target that allows the cyclotron to be tuned to be irradiated but does not produce radioactive products), for example, made of graphite for tuning, or possibly a carbon-11 production target, as this emits relatively few neutrons for a beam such as the one described above, i.e., 20 µA of protons at 12 MeV. Therefore, it is preferable to mount the target containing the least used target and / or the one with the weakest source term (a charge target for example) on the port in line with the beam axis.

[0075] Such a system also has the advantage of being more responsive than a mechanical target changer system. In other words, it is possible to switch the beam from one target to another positioned in two target arrays mounted on two different ports more quickly than with a conventional mechanical system and without breaking the vacuum, typically in one second.

[0076] According to an interesting embodiment, the system includes a device for adjusting the position of the irradiation beam and a device for adjusting the focusing of the irradiation beam, and the position adjustment device and the focusing adjustment device are positioned upstream of the deflection device.

[0077] In one embodiment, the deflection device differs from the position adjustment device.

[0078] In one embodiment, the position adjustment device and the focusing adjustment device are positioned outside the radiation protection enclosure.

[0079] In another embodiment, the position adjustment device and the focusing adjustment device are positioned at least partly inside the radiation protection enclosure, or even at least partly within the wall of the radiation protection enclosure.

[0080] In one example embodiment, the position adjustment device and the focusing adjustment device are jointly implemented by a pair of electromagnetic quadrupoles.

[0081] According to yet another interesting embodiment, the system includes a servo module comprising a control module and a command unit, the control unit being configured to integrate information and measurements concerning the position and focus of the irradiation beam and to send instructions to the command unit, and the command unit being configured to actuate the position adjustment device and / or the focus adjustment device and / or the deflection device in order to optimize an interaction between the irradiation beam and the target to be irradiated.

[0082] Another object covered by the invention is a targeting system, taken together with its radiation protection enclosure, but without the accelerator. More precisely, this other object is a targeting system having a reference direction along which it is intended to be subjected to an irradiation beam, comprising: a target support, intended to be positioned opposite said direction, comprising at least one port configured to receive a target configured to receive a target to be irradiated, and a radiation protection enclosure surrounding the target support and through which said direction passes. the target support being fixed with respect to said direction and the port being offset with respect to said direction, and the assembly comprising a deflection device, positioned in the radiation protection enclosure and configured to deflect a received radiation beam along said direction towards the port of the target into which the target to be irradiated is inserted, the assembly being characterized in that the radiation protection enclosure comprises an alternation of at least one layer comprising a dense material and at least one layer comprising a hydrogen-rich material containing a neutron poison.

[0083] Such a set is specifically configured for a system as defined above, comprising all or part of the characteristics described above.

[0084] The direction can be materialized in the radiation protection enclosure by a channel along which radiation protection is reduced, or even insignificant, for example a hollow channel.

[0085] Such a system is therefore particularly compact.

[0086] Thanks to such a system, it is therefore possible to avoid installing a complete wall between the particle accelerator and the targets.

[0087] Such a system can therefore be installed in a room of a building, for example a room in a hospital or research complex, and making it possible to avoid requiring a significant architectural transformation or adaptation, i.e. in a room with walls made of common building materials (such as concrete and / or metal reinforcements etc.).

[0088] For example, 40 cm concrete walls are sufficient, whereas 2 m walls were required for earlier devices.

[0089] Such a system, and in particular the radiation protection enclosure, is therefore independent of the room in which it is subsequently installed.

[0090] In other words, such a system is configured to be installed in a room of a building.

[0091] Another way to define the system is that, since it is housed in a room, or even an enclosure, that surrounds the entire system, the targets are then placed in an additional enclosure, the aforementioned radiation protection enclosure, so that the system is isolated from the external environment and the targets are isolated not only from the external environment but also from the particle accelerator, which, in such a system, is less active compared to prior art devices. The system thus exhibits autonomy.

[0092] Since the system can be installed in a single room, access to the system is facilitated. Furthermore, the system is easier to install.

[0093] The invention, according to an exemplary embodiment, will be better understood and its advantages will become clearer upon reading the following detailed description, given by way of example and in no way limiting, with reference to the attached drawings in which: There figure 1 schematically illustrates a target irradiation system according to an embodiment of the present invention, The figure 2 composed of figures 2a et 2b This schematically illustrates examples of geometric arrangements of port positions. figure 3 presents, for illustrative purposes, an evolution of the mass M (in tonnes, T) of a radiation protection enclosure as a function of its internal radius Ri (in millimeters, mm), and La figure 4 represents a schematic diagram of a control system for a position adjustment device and a focus adjustment device by a control module.

[0094] Identical elements represented in the aforementioned figures are identified by identical numerical references.

[0095] There figure 1 presents an irradiation system 1 comprising a particle accelerator 10, a target support 20 and a radiation protection enclosure 30.

[0096] The particle accelerator 10 is, for example, a cyclotron. It is configured, for example, to emit an irradiation beam 11 comprising a proton beam of several megaelectronvolts (MeV).

[0097] The radiation protection enclosure 30 surrounds the target support 20. The particle accelerator 10 is positioned outside the enclosure 30.

[0098] The radiation protection enclosure 30, for example, takes the form of a hollow sphere with a wall formed from a stack of successive layers.

[0099] The wall of the radiation protection enclosure 30 comprises an alternation of a layer of a so-called "dense" material 31 and a layer of a hydrogen-rich material 32.

[0100] The radiation protection enclosure comprises at least two layers, for example between two and ten layers, forming alternately a layer of dense material and a layer of hydrogen-rich material.

[0101] In order to limit the mass and bulk of the radiation protection, it is also advantageous to position a layer of dense material 31 as close as possible to targets 22 mounted on the target support 20, as described later, to attenuate the primary rays in the first place.

[0102] Next, layers of hydrogen-rich material 32, containing neutron poison, are alternated with layers of dense material 31 which attenuate the last primary rays as well as the secondary rays from neutron capture.

[0103] For illustrative purposes, in this example of implementation of the figure 1 , starting from the outermost layer, the wall comprises four layers alternating hydrogen-rich material 32 and dense material 31 so that the innermost layer, i.e. located closest to the targets 22, is a layer of dense material 31.

[0104] Furthermore, to enhance radiation protection, the targets 22 mounted on the ports 21 of the target support 20 are surrounded by an additional radiation shielding element 33, preferably made of a dense material. The wall of the radiation shielding enclosure thus includes an additional layer 34 of hydrogen-rich material positioned between the additional radiation shielding element 33 of the targets and the innermost layer of dense material 31.

[0105] The hydrogen-rich material 32 is, for example, polyethylene (PE), loaded with boron as a neutron poison at a concentration of approximately 5% to 7% (atomic). In the case of a cyclotron bombarding a production target of 18< F at 20 µA, numerical simulations have shown an attenuation optimum when the PE is loaded with boron at a concentration of approximately 7% (atomic).

[0106] The dense material 31, which primarily attenuates high-energy primary and secondary photons, is advantageously tungsten, for example. Because tungsten is very dense, it allows for a more compact and lightweight radiation shielding enclosure. However, since tungsten is difficult to machine, it can be replaced by other materials, such as lead. Lead being less dense than tungsten, replacing tungsten with lead slightly increases the diameter of the radiation shielding enclosure and consequently its mass.

[0107] In a preferred embodiment, the additional radiation shielding component 33 is made of tungsten (W) and is approximately 6 cm thick. The wall of the radiation shielding enclosure 30 then comprises: The additional layer 34 of hydrogen-rich material has an inner radius (Ri) of approximately 24 cm and an outer radius (Re) of approximately 30 cm, i.e., a thickness of approximately 6 cm, and is made of PE loaded with 5% boron; The innermost layer of dense material 31 has an inner radius (Ri) of approximately 30 cm and an outer radius (Re) of approximately 35.5 cm, i.e., a thickness of approximately 5.5 cm, and is made of tungsten (W); The next layer of hydrogen-rich material 32 has an inner radius (Ri) of approximately 35.5 cm and an outer radius (Re) of approximately 64.5 cm, i.e., a thickness of approximately 29 cm, and is made of PE loaded with 5% boron; The next layer of dense material 31 has an internal radius (Ri) of about 64.5 cm and an external radius (Re) of about 68.5 cm, i.e. a thickness of about 4 cm, and is made of lead (Pb);and The outermost layer of hydrogen-rich material 32 has an inner radius (Ri) of about 68.5 cm and an outer radius (Re) of about 88.5 cm, i.e. a thickness of about 20 cm, and is made of PE loaded with 5% boron. ;

[0108] For example, if the cyclotron and target support described here are used for up to 160 minutes per day and 23 days per month, it is possible to construct a radiation protection enclosure weighing approximately 6.6 tonnes with an internal radius of 240 mm. Such a radiation protection enclosure would then reduce the dose rate outside 30 cm thick ordinary concrete walls to less than 80 µSv / month, which is the limit set by the EURATOM directives for public areas.

[0109] The target support 20 is positioned opposite the irradiation beam 11, in the radiation protection enclosure 30.

[0110] It has several ports 21 configured to each receive a target 22, containing at the time a target to be irradiated, which are offset from the irradiation beam 11.

[0111] Here, in order to simplify the representation, the target support 20 has two ports 21 with a target 22 each, which are offset from the irradiation beam 11; as well as an additional port 21' positioned in the axis of the beam.

[0112] As illustrated by the figure 1 This allows, depending on the position of the port 21 considered, to more or less reduce direct lines of flight 12 produced when a target, inserted in the target mounted on the port 21 considered, is irradiated by the irradiation beam 11.

[0113] When targets of different types are inserted into ports 21 or 21', it is preferable to position the targets generating the most intense neutron flux in the ports 21 forming the highest angle with the irradiation beam 11. A target generating the least radiation and / or used less, such as a charge target, can be inserted into the port 21' which is in the axis of the beam when such a port exists.

[0114] For example, starting from the beam axis and moving away from it, one possible configuration would be to position a charge target in port 21' located in the beam axis 11, then a production target of 11< C, then a production target of 18< F. These targets are then ranked in ascending order of constant current neutron flux generation.

[0115] Note that if a port 21 or 21' is left vacant, i.e. no target is inserted into it, it is preferable to put a tape in it, forming a watertight plug, in order to better guarantee the watertightness of the system.

[0116] The number of ports 21, or even the existence of a port 21', depends on the needs related to the application in question.

[0117] In PET-type applications, it is advantageous to have at least two targets available, allowing the use of at least two different targets. For example, between two and ten targets can be used to accommodate up to ten different targets. Therefore, it is useful to have as many ports as there are targets required.

[0118] Depending on the existing space constraints within the application under consideration, the ports are arranged according to a plan as illustrated in the figures 1 et 2a , or in three dimensions, that is to say in volume, as illustrated on the figure 2b .

[0119] To address a target positioned in any of the target slots of the ports 21 from the same irradiation beam 11, the system 1 further includes an irradiation beam deflection device 40, configured to direct the irradiation beam 11 towards each of the ports 21, so that, for example, in operation, protons bombard a target positioned in one of the target slots mounted on one of the ports 21 of the target slot support 20.

[0120] The deflection device 40 is also positioned within the radiation protection enclosure 30. It should be noted that the deflection device 40 also contributes to radiation protection. For this purpose, it is composed, for example, of a dense material, such as copper and / or iron, which makes it effective at attenuating photons. In the context of a quadrupole, this might consist of an iron frame surrounded by a copper wire.

[0121] The deflection device 40 includes, for example, a deflector comprising, for example, a quadrupole made up of electromagnets, or preferably a dipole. Such a deflector is then positioned on a path of the irradiation beam 11 and is traversed by it, as schematically illustrated in the diagram. figure 1 Other deflection devices 40 can also be used depending on the type and energy of the accelerated particles, such as an electrostatic deflector for lighter particles (electron type) and / or lower energies.

[0122] In the case of a three-dimensional arrangement such as on the figure 2b , beam 11 must then be deflected in two dimensions (whereas a deflection in only one dimension is necessary within the framework of the arrangement of the figure 2a ), which may imply that the deflection device 40 will be larger, inducing an increase in the internal volume of the radiation protection enclosure 30, and consequently a larger internal radius Ri of the radiation protection enclosure 30, which then increases the mass M of the radiation protection enclosure 30, as illustrated by the figure 3 which could create additional complexity.

[0123] The distance between a target of a port 21 and the ground of the place where the system 1 is installed limits the maximum possible dimension of the radiation protection enclosure 30. Therefore, it is advantageous to arrange the ports 21 on a horizontal plane rather than a vertical one.

[0124] This also makes it possible to limit the dose rate at floor level and thus to more easily install system 1 on the upper floor of a building for example.

[0125] In the present embodiment, for the sake of compactness, the distance separating the particle accelerator 10 from the target support 20 is, for example, very slightly greater than the distance established between a port 21 and the ground.

[0126] In order to ensure the correct focusing and positioning of the irradiation beam 11 at the deflection device 40 and an input window of each port 21, the system 1 here includes a beam position adjustment device 51 and a beam focus adjustment device 52.

[0127] The deflection device 40 differs from the position adjustment device, notably in that the deflection device 40 allows the radiation beam to be deflected at angles of at least 5°, whereas a position adjustment device only allows adjustment of the position of the point of impact or focal point of the beam, i.e. over just a few tenths of a degree, typically less than 0.5°.

[0128] In this embodiment, the positioning and focusing devices are mounted upstream of the deflection device 40, it being understood that "upstream" here refers to the direction of emission of the radiation beam, from the accelerator towards the target support. Furthermore, they are both positioned outside the radiation shielding enclosure 30; however, they could also be positioned at least partially inside the radiation shielding enclosure, or even at least partially within the wall.

[0129] The position adjustment device 51 and the focusing adjustment device 52 are, for example, jointly implemented by a pair of electromagnetic quadrupoles. However, if the beam diverges sufficiently little, typically on the order of -0.5°, it is not necessary to use a focusing and / or position adjustment device.

[0130] To facilitate and improve the reliability of the use of such a device, the deflection device 40 is, for example, modifiable and remotely controllable in order to address a target selected from among the multiple targets that can be introduced into each of the target stores 22. In parallel, the position adjustment device 51 and the focusing adjustment device 52 of the irradiation beam can also be servo-controlled to optimize the irradiation of the target in question.

[0131] For this purpose, system 1 includes, for example, as is the case here, a servo module 60 comprising, for example, a control module 61 and a control unit 62.

[0132] It is then possible to control the position adjustment device 51 and the focusing adjustment device 52 in order to achieve the three-dimensional positioning of the focal point of the irradiation beam 11 relative to an input window of the port 21 considered, or even of the port 21'.

[0133] A geometric measurement module 63, for example of the Beam Position Indicator (BPI) type, is possibly used here to send information to the control module 61 concerning the position and dimensions of the beam 11 at the level of the input window of port 21, or even 21', containing the target to be irradiated.

[0134] A current measurement module 64 is also used, for example, to measure the current generated by the beam 11 on the target and to communicate the current measurements to the control module 61.

[0135] This information and these measurements allow the parameters of the adjustment devices in position 51 and in focus 52 as well as the deflection device 40 to be adjusted so that the interaction between the beam 11 and the target is optimal.

[0136] For this purpose, the control module 61 integrates the information and measurements provided by the module 63 and the measurement module 64 and sends instructions to the control unit 62 which actuates the position adjustment device 51 and / or the focusing adjustment device 52 and / or the deflection device 40.

Claims

1. A targetry assembly having a reference direction along an axis and according to which it is to be subjected to an irradiation beam (11), comprising: - a targetry support (20), to be positioned opposite said direction, comprising at least one port (21) configured to receive a targetry (22) configured to receive a target to be irradiated, and - a radiation protection enclosure (30) surrounding the targetry support (20) and having said direction passing therethrough, the targetry support (20) being fixed with respect to said direction and the port (21) being offset with respect to said direction, and the assembly comprising a deflection device (40), positioned in the radiation protection enclosure (30) and configured to deflect an irradiation beam (11) received along said direction towards the port (21) of the targetry (22) into which the target to be irradiated is introduced, the assembly being characterised in that the radiation protection enclosure (30) comprises an alternation of at least one layer comprising a dense material (31) - making it effective to attenuate photons in the form of X-rays or Gamma rays - and of at least one layer comprising a hydrogen-rich material (32) comprising a neutron poison.

2. A target irradiation system (1), comprising at least: - a particle accelerator (10) configured to at least emit an irradiation beam (11) along an axis, and - a targetry assembly according to claim 1, the targetry support (20) being positioned outside the accelerator opposite the irradiation beam (11), and the particle accelerator (10) being positioned outside the enclosure (30), the targetry support (20) being fixed with respect to the particle accelerator (10) and the port (21) being offset with respect to the axis of the irradiation beam (11).

3. The system according to claim 2, characterised in that a radiation protection layer of the radiation protection enclosure in proximity to an inner surface of the enclosure is a layer of dense material (31).

4. The system according to any one of claims 2 or 3, characterised in that the hydrogen-rich material (32) is polyethylene (PE) loaded with boron as a neutron poison at an amount of about 5% to 7% (atomic).

5. The system according to any one of claims 2 to 4, characterised in that the dense material is tungsten and / or lead.

6. The system according to any one of claims 2 to 5, characterised in that the radiation protection enclosure (30) further comprises an additional radiation protection part (33) that surrounds the targetries mounted to the targetry support, within a wall of the radiation protection enclosure.

7. The system according to claim 6, characterised in that the additional radiation protection part (33) is made of a dense material.

8. The system according to claim 3 and one of claims 6 or 7, characterised in that the radiation protection enclosure comprises a wall which comprises an additional thickness (34) of hydrogen-rich material positioned between the additional radiation protection part (33) of the targetries and the innermost layer of dense material (31).

9. The system according to claim 8, characterised in that the additional radiation protection part (33) is made of tungsten (W) and has a thickness between about 5 cm and about 15 cm and in that the wall of the radiation protection enclosure (30) then comprises: - The additional thickness (34) of hydrogen-rich material with a thickness between about 5 cm and about 15 cm, and is made of PE loaded with 5% boron; - The innermost layer of dense material (31) with a thickness of between about 3 cm and about 8 cm, and is made of tungsten (W); - A next layer of hydrogen-rich material (32) with a thickness of between about 25 cm and about 40 cm, and is made of PE loaded with 5% boron; - A next layer of dense material (31) with a thickness of between about 2 cm and about 8 cm, and is made of lead (Pb); and - An outermost layer of hydrogen-rich material (32) with a thickness of between about 15 cm and about 30 cm, and is made of PE loaded with 5% boron.

10. The system according to any one of claims 2 to 9, characterised in that the deflection device (40) is configured to emit a magnetic field between about 1 and 2 Tesla (T), for example the magnetic field is in the order of 1.4 Tesla.

11. The system according to any one of claims 2 to 10, characterised in that the deflection device (40) comprises at least one electromagnetic quadrupole positioned on a path of the irradiation beam.

12. The system according to any one of claims 2 to 11, characterised in that it comprises a position adjusting device (51) for the irradiation beam and a focus adjusting device (52) for the irradiation beam, and in that the position adjusting device (51) and the focus adjusting device (52) are positioned upstream of the deflection device (40).

13. The system according to claim 12, characterised in that the position adjusting device (51) and the focus adjusting device (52) are positioned outside the radiation protection enclosure (30).

14. The system according to any one of claims 12 or 13, characterised in that the position adjusting device (51) and the focus adjusting device (52) are jointly embodied by a pair of electromagnetic quadrupoles.

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