WO2025202800A1 - Fusion generated particle radiating device and radiating method thereof - Google Patents

Abstract

A radiation device comprises at least a vacuum chamber (1), an electromagnetic accelerator (8) for generating a primary energy beam of ions inside the vacuum chamber (1), and a layer of material (S) carried by a support (4) rotating in the vacuum chamber (1) to generate a flow of particles when a series of nuclear fusion reactions are triggered on the material (S) thanks to the energy of said beam, and wherein the support (4) is hollow and sealed defining a rotating three-dimensional surface that surrounds a containment volume for a cooling liquid in heat exchange with the layer of material (S), such rotating three-dimensional surface defining a heat exchange surface wetted by the liquid, and wherein a level of the free surface of the liquid on the heat exchange surface moves upwards in use due to the action of the centrifugal acceleration generated by the rotation of the support (4).

Description

Fusion generated particle radiating device and radiating method thereof

DESCRIPTION

FIELD OF INVENTION

The present invention relates to a particle flow irradiation device , preferably fast neutrons , for producing radioactive isotopes by volumetric irradiation, for example but not limited to Actinium-225 or Phosphorus- 32 from a target material based on Radium-226 or Sul fur- 32 respectively, for nuclear medicine applications such as radiotherapy . In general , the invention applies to neutron generation processes from locali zed nuclear fusion used to irradiate a precursor material .

BACKGROUND OF INVENTION

The radiotherapy use of Actinium-225 is of particular interest because it emits alpha particles characteri zed by a short path in human tissue , about 100 micrometers . In the therapy called Targeted Alpha Therapy ( TAT ) , this allows high doses of cytotoxic radiation to be directed to relatively targeted areas , thus limiting damage to surrounding healthy tissue .

In turn, Actinium-225 also decays to become Bismuth- 213 , which in turn is suitable for TAT . With reference to Phosphorus-32 , it is normally used as a beta particle emitter for targeted radiotherapy with a hal f-li fe suitable for the treatment of certain tumors and is currently produced in fission reactors . The invention therefore allows not to resort to fission reactors , simpli fying the production process .

For example , there is a need to increase the productivity of Actinium-225 and other radioisotopes which, at present , have a very low yield under normal conditions of surface irradiation by protons and require complex procedures of thin strati fication of the precursor materials , signi ficantly limiting the quantities exposed per unit of time . For such materials , it is more ef ficient to use volumetric irradiation by neutrons with an energy of 14 . 1 MeV generated by the deuterium-tritium fusion reaction, but in general , the invention applies , thanks to the notable penetration capacity of the generated neutrons , to all nuclear transmutation processes , activated by highly energetic particles . It is also possible to apply the invention to other fusion reactions that generate neutrons , such as the deuterium-deuterium reaction, the tritium-tritium reaction and the deuteriumhelium reaction .

SCOPES AND SUMMARY OF THE INVENTION

The scope of the present invention is to provide an improved irradiation device capable of satis fying the above-speci fied need .

The scope of the present invention is achieved by a device according to claim 1 .

The peripheral arrangement of the layer that can be activated by ions e . g . of Hydrogen allows for ef fective and easily controllable cooling, e . g . by regulating the number of revolutions of the support , following the nuclear fusion reaction triggered by the primary beam : thanks to the shape of the hollow support with bottom walls ascending towards the active layer, depending on the number of revolutions of the latter, the quantity of cooling liquid contained in the support e . g . water changes and thus the corresponding cooling capacity of the layer during the nuclear fusion reaction . When the particles participating in the nuclear reaction triggered by the bombing of the primary beam are also implanted in the lattice of the layer, the temperature control positively influences this process . In fact , the yield of the implantation process of the particles that , bombed, trigger the nuclear fusion reaction depends on the temperature .

Furthermore , according to this configuration, in the hal f-space of origin of the beam with respect to the nuclear reaction surface , the propagation is mostly spherical , except for slight asymmetries , which are not very relevant for the production of neutrons and are due to reasons of reaction physics , the neutron flux hits the target directly and this makes the nuclear reaction of production of the radioactive isotope in the target particularly ef fective . Being in the immediate vicinity of a vacuum chamber, the target can be placed at a variable distance from the layer of active material but, to collect the greatest number of neutrons emitted in the hal f-space of origin of the primary beam, it is necessary, in the hypothesis of a hemispherical geometry of the target , that the center of the hemisphere , of radius R, is as close as possible to the reaction plane tangent to the active layer at the point of incidence with the primary particle beam, compatibly with the si ze of the materials that constitute it , and the useful surface of this hemisphere is equal to 2nR2 minus the surface of the hole necessary for the passage of the primary beam . The choice of the dimension of R must be such as to maximi ze the activity produced in the target . Therefore , for the same target dimensions , the yield is maximum when the distance of the target from the reaction surface is minimum .

According to an embodiment of the present invention, the electromagnetic accelerator is configured to generate beams of Deuterium and/or Tritium ions so as to allow, with a single accelerator, both to trigger nuclear fusion on the active layer and to implant on the latter the ions subsequently used to trigger nuclear fusion . For the sole triggering of the reactions , it is also possible to use a Laser beam with suitable characteristics .

Other advantages of the present invention are discussed in the description and cited in the dependent claims .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below on the basis of nonlimiting examples illustrated by way of example in the following figures , which refer respectively to :

- - Fig . 1 a schematic section performed with a vertical plane of an irradiation device according to the present invention;

- - Fig . 2 an enlarged view of a detail of figure 1 ;

- - Fig . 3 a view of figure 2 ; and

- - Fig . 4 an interaction curve of fast neutrons with a target material precursor of a medical radioisotope .

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an irradiation device preferably for the production of a radioisotope for both medical and scienti fic uses in general with improved ef ficiency, comprising : a vacuum chamber 1 to reduce obstacles to the movement of generated neutrons ; a recovery window 2 to regenerate an adsorbing layer S for hydrogen isotopes , via an appropriate application of eroded material , for example through continuous vapor deposition ( CVD) , preferably continuous physical vapor deposition, via laser or other physical or chemical-physical process ; a flux of neutrons following the triggering of a nuclear fusion reaction by particles e . g . implanted ions and a primary flux of charged particles . In particular, such window 2 allows the passage of a laser beam suitable for regenerating, through sublimation and redeposition via laser sputtering, a quantity of a metallic material e . g . titanium eroded by nuclear fusion . The vacuum is generated by a special pump or other device that maintains a pressure of at least 1 . 5 10-5 Pa in the vacuum chamber 1 and reduces and/or eliminates obstacles to the motion of the ions accelerated by generator 8 towards layer S , which holds them in position . For example , the ions to be bombed by the primary beam of charged particles to trigger a nuclear fusion reaction are held in position because they are implanted in the crystal lattice of the ions themselves or in the form of metal hydrides composed of the metal of layer S and the hydrogen isotopes , which make the tritium and deuterium available .

Vacuum chamber 1 partially houses a hollow support 4 acting as a container for a liquid to cool layer S during the bombing of the primary energy beam of charged particles e . g . ions . In particular, hollow support 4 is a container having a lower portion Pl housed in vacuum chamber 1 and carrying layer S and an upper portion P2 preferably arranged outside vacuum chamber 1 . The liquid in hollow support 4 evaporates to cool active layer S and the vapors rise towards upper portion P2 , where the temperature is lower than that of lower portion Pl until they condense and then fall back by gravity into lower portion Pl . Hollow support 4 is rotatable so that the energetic beam of ions intercepts layer S , arranged peripherally on support 4 , along its entire length and, for this purpose , a rolling bearing B is arranged between vacuum chamber 1 and hollow support 4 . Furthermore , in order to maintain the low pressure or vacuum inside vacuum chamber 1 , a rotating seal 3 , preferably a ring of sealing gel with ferromagnetic properties , is arranged between hollow body 4 and vacuum chamber 1 . This ring is maintained in the desired sealing position by a plurality of permanent magnets (not visible in the figure ) and, during use , the centri fugal force due to the rotation of hollow support 4 pushes the seal radially against the wall of chamber 1 , further promoting the maintenance of the ring in the sealing position . Advantageously, this solution presents a locali zed erosion of the rotating seal reduced compared to other solutions , e . g . sliding seals , thus benefiting a greater longevity and reduced maintenance for the replacement of the seal when necessary .

According to a preferred embodiment , upper portion P2 is arranged in heat exchange with a heat exchanger 5 to accelerate the cooling and condensation of the steam in upper portion P2 . Exchanger 5 is external to vacuum chamber 1 and preferably comprises a plurality of noz zles (not illustrated) arranged at increasing heights along a direction parallel to an axis of rotation A of hollow support 4 . Preferably, the noz zles surround upper portion P2 , advantageously of a shape converging upwards , and the coolant is sprayed inside a chamber C so as to both ensure contact with the upper portion P2 and to maximi ze convection inside chamber C . Preferably but not limited to , the flow rate of water delivered into the exchanger is 160 m3/hour at a temperature of 18 ° C . Preferably, the coolant is water .

Hollow support 4 is driven into rotation by a preferably electric motor 6 so that layer S is exposed to the energy beam of ions in a homogeneous manner, i . e . the rotation speed is constant , and condensation is promoted in upper portion P2 . Furthermore , the rotation provides for centri fugal acceleration to increase the wetted surface in heat exchange with layer S because support 4 has a rotating three-dimensional surface that surrounds a containment volume for a cooling fluid that is used to cool the layer of active material . In particular, this surface defines a heat exchange surface wetted in use by the liquid and, during the rotation of support 4 , a level of the free surface of the liquid on this surface moves , i . e . it curves , upwards i . e . towards layer S due to the action of its own viscosity and the centri fugal acceleration generated by the rotation of the support . This surface wetted by the cool ing liquid is a bottom surface with walls diverging towards the layer S or even vertical . Other surface shapes are also possible that provide , during the rotation of support 4 , the free surface of the coolant to curve so that the periphery of the liquid approaches and/or is surrounded in use by layer S . Based on the variation in the level of the free surface of the coolant due to the variation in angular velocity of support 4 , the heat exchange with layer S also changes , in particular as the level of liquid increases towards layer

5 , the cooling ef fect on layer S increases . As illustrated in figure 1 , a bottom of support 4 is lower than layer S . In order to promote the heat exchange with the coolant , layer S comprises a metallic material , preferably comprising exclusively one or more metallic materials . Even more preferably, layer S is made of a metallic material that can be deposited by laser sputtering and CVD . Preferably, blades can extend radially from the rotating three-dimensional surface that are used to promote the raising of the level of the free surface of the liquid . In particular, through the presence of the blades it is pos sible to create a barrier that contrasts the relative rotation between the coolant and the support so that the component of the force resulting from acting on the quantity of liquid is such as to move the free surface of liquid upwards . Preferably but not limited to , the tangential speed can be 18 m/ s .

Preferably, hollow support 4 is carried by a portal structure 7 so that lower portion Pl is suspended inside vacuum chamber 1 , in turn suspended and fixed to portal structure 7 so as to be fixed to rotation . Heat exchanger 5 is preferably suspended and extends vertically between a head T of portal structure 7 and seal 3 , arranged externally to the exchanger itsel f . The cooling fluid inlet I is preferably arranged above e . g . on head T and outlet U of the exchanger is arranged between chamber C and vacuum chamber 1 .

Preferably portal structure 7 carries external and head walls so as to define a box-like casing (not illustrated) of a radiation-shielding material such as high-density polyethylene (HDPE) , while the portal structure is made of aluminum or low-activation steel to minimize the radioactive emission of the structural material .

Furthermore, a mechanical adjustment device is present to calibrate the verticality of axis A.

The irradiation device also preferably comprises a source and an accelerator of charged particles e.g. an ion beam which, reacting with ions previously implanted on layer S, produce neutrons through nuclear fusion reactions. This device can be of various embodiments as long as it comprises an ion source (deuterium, tritium and/or helium 3) and an ion accelerator; or a power generator of an electromagnetic beam e.g. laser capable of bombarding ions to trigger nuclear fusion.

Preferably, layer S is activated by implanting ions into the crystal lattice of the layer itself e.g. a metallic crystal lattice. Such implantation is preferably performed by the same primary beam with modalities e.g. energy and temperatures known empirically and in literature. In general, the invention covers any technique capable of retaining the ions on the substrate e.g. or inside or on the surface [so that the latter can be bombed by the primary beam to trigger the nuclear fusion reaction or by an energetic beam e.g. a power Laser having predefined features such to trigger fusion processes on ion couples e.g. Deuterium-Tritium already implanted.

Preferably, Deuterium and Tritium ions are implanted on active support S and the ion beam carries Deuterium and Tritium ions in order to trigger Deuterium-Tritium as well as Deuterium - Deuterium and Tritium - Tritium nuclear fusion reactions . The operating parameters of the invention can be adj usted in order to make one reaction more likely than the others . Preferably, the ion beam can accelerate a current of at least 800 mA of Tritium ions and Deuterium ions with a potential di f ference of 300 KeV . Preferably, the ion beam has a mark of 14- 15 cm in diameter . The Tritium and/or Deuterium ions that do not react with an ion previously implanted on layer S , bound to the metallic material of which the layer is made , preferably Titanium, and form stable hydrides that ensure that they remain in the crystal lattice of layer S waiting to be impacted by an incoming ion and react with it . However, when the temperature of layer is higher than a threshold, e . g . 200 ° C, the hydrides dissociate and the implanted ions are released and cannot participate in the fusion, so that a temperature preferably lower than this threshold is maintained by the cooling liquid .

According to a preferred embodiment , the beam emitted by generator 8 i s a combination of Deuterium and Tritium ions mixed together, according to the fusion reaction to be favored and accelerated towards layer S . In this way, the same generator 8 can implant both ions on layer S and subsequently bomb them with other ions to trigger the nuclear fusion reaction . Preferably, embodiments can be provided in which di fferent reactions between the ions are possible , such as Deuterium-Deuterium by introducing only Deuterium into the plasma . In general , it is also possible to implant other ions, such as Helium! and Deuterium and even only Tritium. In general, each ion species requires its own generator or accelerator 8 but Deuterium and Tritium ions have such affinities that a single generator or accelerator 8 can be used for both.

In addition, due to the fusion reactions triggered on layer S, the crystal lattice is damaged. The restoration of layer S is carried out at regular intervals by a known technique, for example continuous vapor deposition (CVD) . The vapors of the restoration metal are produced by a dedicated laser device e.g. by sputtering a sample so that they deposit on layer S after the erosion caused by the nuclear fusion reactions. The restoration process is very fast and can also be performed during the working phase as it is located in a different angular position e.g. opposite to that of the primary ion beam. The material of layer S is preferably Titanium but all metals that have affinity with hydrogen to form stable metal hydrides can be used.

As shown in figure 1, an average incidence direction of the ion beam i.e. an average axis of such a beam during bombing is between 30° and 60°, preferably 45°, so as to involve a greater surface of active layer 4. This is achieved by means of a special inclined junction P made on vacuum chamber 1. Furthermore, such inclination locates the generator at a higher vertical height than that of layer S and outside vacuum chamber 1, so that manual maintenance by the personnel is easier because the generator is less exposed to radiation. Qualitatively, the average direction of the ion beam is identified by a tunnel D of generator 8, e.g. from an axis of tunnel D. During the ion implantation operation on the active layer S , the angle of incidence changes and is between 80 ° and 100 ° , preferably 90 ° as illustrated in figure 1 : in this way the ions are deposited on a suf ficiently large surface of layer S , such as to limit the intense local heating that would otherwise prevent their permanence in active layer S .

Figure 2 shows an enlarged vacuum chamber 1 with a track of the sphere that exempli fies the motion of neutrons generated during the nuclear fusion reaction . The neutrons intercept a target F comprising a target material based on an isotope that , in the presence of fast (high energy) neutrons , is activated producing a radioisotope that can be used for example for medical applications such as internal radiotherapy . In the case of Actinium-225 , the target F is based on Radium-226 , preferably Radium-226 chloride . I f instead it is necessary to produce Phosphorus- 32 , the target F is based on Sul fur-32 .

According to a preferred embodiment , target F is contained in a casing external to vacuum chamber 1 so that it can be more easily removed and manipulated by a robot or other automated mechanical device . Therefore , the materials of the walls of vacuum chamber 1 are suitably made to oppose a predetermined obstacle to the movement of the neutrons so as to provide particles with the energy that maximi zes the probability of interaction with target material F . For example , i f this probability is maximum with particles having an energy in the vicinity of the statistical maximum of the energy of the particles generated by nuclear fusion triggered on layer S , as is the case of Radium-226 and Sulphur-32 , then the mediator material must be as transparent as possible to neutrons , such as Aluminium and its alloys , such as 6082 T2 Anticorodal . In other cases , the mediator material allows to slow down or de-energi ze the neutrons generated by the nuclear fusion of layer S in order to bring the neutron energy to the ideal conditions of maximum interaction with target F . An example of a useful curve for the selection of the mediator material is shown in figure 4 . The D-D and D-He3 fusion reactions can generate alpha particles and/or monochromatic protons . I f it is preferred to use the particles that are generated by the D-D and D-He3 reactions , the wall that separates the vacuum chamber from target F must be completely removed since the protons and alpha particles are slowed down very ef fectively by the interaction with the matter . The highly energetic protons generated in this way also have many scienti fic and nuclear medicine applications . For example , target F is housed inside the vacuum chamber in a position suitable for maximi zing the ef fect of the particle flux generated by the nuclear fusion . Even more preferably, target F is a container for the isotope or its compound, made precisely from a non-neutron-shielding material such as that used in the walls of the vacuum chamber 1 .

Advantageously, since the neutron irradiation traj ectories follow a spherical shape G, in order to increase the probability that the neutrons generated during nuclear fusion intercept target F, the latter has a toroidal or semi-toroidal shape and is positioned around the j unction of tunnel D to the vacuum chamber 1 so as to reduce the distance from the active layer S as much as possible .

According to a variant embodiment , the fusion reaction is activated by a circular accelerator instead of a linear one to direct the ions towards the S layer and remain trapped either in the ionic state in the crystal lattice or by forming a chemical bond with the material of the S layer forming hydrides .

Claims

1. Irradiation device comprising at least one vacuum chamber (1) , an electromagnetic power device (8) for generating a primary energy beam, and a layer (S) capable of receiving ions and carried by a rotatable support (4) in the vacuum chamber (1) to generate a flow of particles when a plurality of nuclear fusion reactions is initiated on the layer (S) by the energy of said beam applied to the ions carried by the layer (S) , and wherein the support (4) is hollow defining a rotating three-dimensional surface surrounding a containment volume for a cooling liquid in heat exchange with the layer (S) ; said rotating three- dimensional surface defining a heat exchange surface wetted by the liquid, and wherein a free surface level of the liquid on the heat exchange surface curves towards the layer (S) as the speed varies due to the action of its viscosity and the centrifugal acceleration generated by the rotation of the support

(4) , the layer (S) being arranged superiorly to a bottom of the support (4) .

2. Irradiation device according to claim 1, wherein a lower portion (Pl) of the support (4) is housed in the vacuum chamber (1) and an upper portion (P2) of the support (4) is external to the vacuum chamber (1) and in cooling heat exchange with a heat exchanger

(5) to promote condensation of the liquid evaporated during the nuclear fusion reaction.

3. Irradiation device according to claim 2, wherein the heat exchanger (5) defines a cooling chamber (C) housing the upper portion (P2) .

4. Device according to any one of the preceding claims, comprising a target (7) made of a precursor material, preferably radioactive, arranged externally or internally to the vacuum chamber (1) and preferably carried by it to be intercepted by the flow of particles and thus transformed into a radioisotope.

5. Device according to claim 4, wherein walls of the vacuum chamber (1) comprise a mediator material to pre-def initively decrease the energy of the particles reaching the target (7) and achieve the desired transformation .

6. Device according to any one of the preceding claims, wherein the electromagnetic power device (8) is configured so that a central axis of the energy beam intersects at an inclination angle with respect to the radial direction of the layer (S) , preferably such that the electromagnetic power device (8) is located on the same side as the upper portion (Pl) relative to the lower portion (P2) .

7. Device according to any one of the preceding claims, wherein the electromagnetic power device (8) is configured to generate a beam of charged particles.

8. Device according to claim 7, wherein the electromagnetic power device (8) is configured to simultaneously generate Tritium ions and Deuterium ions .

9. Device according to any one of the preceding claims, comprising a first connection (2) for the electromagnetic power device (8) defining a first angle of incidence and a second connection (P) for an additional electromagnetic power device having a second angle of incidence to activate a physical or physico-chemical process with a feed material and allow restoration of the layer (S) .

10. Device according to any one of the preceding claims, comprising a rotating seal (3) , preferably f errof luidic .

11. Irradiation method in a vacuum chamber inside of which a hollow rotating support (4) and a layer (S) are arranged, comprising the steps of:

- A) Bringing a target (7) close to the layer (S) , the target comprising a precursor element, for example, an isotope or its chemical compound such as a salt, said isotope or its compound being a precursor of a radioisotope preferably for a nuclear medicine machine .

B) Emitting, through an electromagnetic power device (8) , a primary energy beam to initiate a nuclear fusion reaction through ions carried by the rotating layer (S) , whose particles intercept the target (7) to transform the precursor and generate the desired radioisotope;

- C) Cooling the support (4) by means of a liquid arranged inside the support (4) and in heat exchange with the layer (S) so that a heat exchange surface of the liquid with the layer (S) increases as the number

17 of rotations of the support (4) increases due to the action of centrifugal acceleration and the viscosity of the liquid due to the fact that a bottom of the support (4) is arranged below the layer (S) .

12. Method according to claim 11, wherein a target containing Radium-226 is bombarded by neutrons generated on the layer (S) to obtain Actinium-225.

13. Method according to claim 11, wherein a target containing Sulfur-32 is bombarded by neutrons generated on the layer (S) to obtain Phosphorus-32.

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