Patent Application
20230125432
The subject matter described herein relates generally to systems, devices, and methods for converting neutron beams from a raw form to a deliverable form.
Boron neutron capture therapy (BNCT) is a modality of treatment of a variety of types of cancer, including some of the most difficult types. BNCT is a technique that selectively aims to treat tumor cells while sparing the normal cells using a boron compound. The boron compound allows for efficient uptake by a variety of cell types and selective drug accumulation at target sites, such as tumor cells. Boron loaded cells can be irradiated with neutrons (e.g., in the form of a neutron beam). The neutrons react with the boron to eradicate the tumor cells.
Neutron beams for BNCT can be generated through various techniques. One such technique involves irradiation of a suitable neutron generating target with a charged particle beam, such as a proton beam or deuteron beam. The charged particles react with nuclei in the target to emit a beam of raw neutrons that can be used for BNCT. The neutrons are raw in the sense that, immediately after generation in the target, a significant fraction of the neutrons may be propagating in various directions not directly towards the patient and may have energy levels too high or too low for administration to the patient. The raw neutrons may also be accompanied by undesired gamma radiation. Existing techniques for modifying the raw neutrons suffer from drawbacks, such as an insufficient ability to redirect neutrons in the desired direction, an insufficient ability to scatter neutrons to the desired energy range, and an insufficient ability to remove undesired photon and low energy neutron radiation. Accordingly, a need exists for improved systems, devices, and methods for neutron beam modification or conversion.
The subject matter described herein relates generally to systems, devices, and methods for converting a raw neutron beam to a specified deliverable format having a targeted energy range, size, and direction, as well as for removing undesirable non-neutronic radiation. Embodiments of a neutron beam converter (NBC) are described in an example context of a BNCT system configured to output a neutron beam in an epithermal energy range. The NBC can include numerous regions based on location, function, dimension, and/or constituent material. The regions can include a central region oriented along a beam axis between a beam input and a beam output of the NBC. The central region can be configured to primarily perform the function of scattering high energy neutrons down to the epithermal range, and achieving and/or maintaining a forward-facing beam (e.g., a beam propagating primarily in the direction of the patient). The central region can perform other functions such as redirection and neutron absorption. An intermediate region can be located laterally outside of the central region, and can function to redirect neutrons back into the central region while scattering towards or into the epithermal range, for output to the patient. The intermediate region can also absorb photons in the form of gamma radiation and can scatter neutrons propagating away from the beam axis down to epithermal and lower energy levels for more ready absorption. A peripheral region can be located laterally outside of the intermediate region and can function to scatter neutrons down to and into the epithermal and thermal energy ranges to absorb neutrons and to absorb photons in the form of gamma radiation. A frontal region can be located on the side of the NBC facing the patient and can also function to scatter neutrons down to and into the epithermal and thermal energy ranges, absorb neutrons, and absorb photons in the form of gamma radiation. Numerous example embodiments of NBC arrangements are disclosed that perform some or all of these functions in the central, intermediate, peripheral, and frontal regions. Numerous exemplary materials are disclosed with capabilities to perform one or more of these functions.
Other systems, devices, methods, features and advantages of the subject matter described herein will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the subject matter described herein and be protected by the accompanying claims. In no way should the features of the example embodiments be construed as limiting the appended claims, absent express recitation of those features in the claims.
The details of the subject matter set forth herein, both as to its structure and operation, may be apparent by study of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the subject matter. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.
This disclosure is not limited to the particular embodiments described as such may, of course, vary. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present disclosure will be limited only by the appended claims.
The term “particle” is used broadly herein and, unless otherwise limited, can be used to describe an electron, a proton (or H+ ion), or a neutron, as well as a species having more than one electron, proton, and/or neutron (e.g., other ions, atoms, and molecules).
Example embodiments of systems, devices, and methods are described herein for neutron beam conversion, which can be used in combination with a neutron beam system (e.g., including a reactor or a particle accelerator). The embodiments described herein can be used with any type of neutron beam system in which neutron beam conversion or modification is desired. Embodiments herein can be used in numerous applications, an example of which is a neutron beam system for generation of a neutron beam for use in boron neutron capture therapy (BNCT). BNCT uses a beam of epithermal neutrons (e.g., with an energy spectrum between one electronvolt (eV) and thirty kiloelectronvolts (keV)) for cancer treatment. In BNCT, the neutrons can be generated from nuclear reactions of charged particles (e.g., a proton beam) colliding with either a beryllium or a lithium target device. The generated neutron beam has a broad range of energies and is emitted in a variety of directions. Thus the target can be contained within a larger neutron beam converter (NBC) that functions to convert the generated neutron beam into a primarily forward directed beam within the desired epithermal energy range, which is then output to the patient.
The example embodiments of neutron beam converters described herein are not intended to be viewed in isolation from each other. All features, elements, components, and functions described with respect to any converter embodiment provided herein are intended to be freely combinable and substitutable with those from any other converter embodiment. If a certain feature, element, component, and function is described with respect to only one converter embodiment, then that that feature, element, component, and function can be used with every other converter embodiment described herein unless explicitly stated otherwise. This paragraph therefore serves as antecedent basis and written support for the introduction of claims, at any time, that combine features, elements, components, and functions from different converter embodiments, or that substitute features, elements, components, and functions from one converter embodiment with those of another, even if the following description does not explicitly state, in a particular instance, that such combinations or substitutions are possible. It is explicitly acknowledged that express recitation of every possible combination and substitution is overly burdensome, especially given that the permissibility of each and every such combination and substitution will be readily recognized by those of ordinary skill in the art.
For ease of description, the embodiments described herein will be done so in the context of generating a neutron beam for use in BNCT, although the embodiments are not limited to such. The embodiments can be applied to other applications that generate significant neutron radiation, even those outside of BNCT applications utilizing different energy ranges.
Neutron beam converter (NBC) 200 is positioned close to and around target 60 to perform various functions on the neutrons of beam 70 emanating from target 60. These functions include reducing the energy of generated neutrons from energies above the desired range to within the desired range, focusing the generated neutrons in a forward-facing direction towards the patient, removing generated neutrons that are outside the desired range, and removing other radiation byproducts (e.g., such as photons) at energy levels that are undesirable. The desired neutron energy range can vary based on the application. For the BNCT applications described herein, the desired energy range can be, for example, one eV to ten keV, or one eV to thirty keV, with the neutron distribution peaking near the upper end of the desired range. For example, a one eV to 30 keV beam can be configured to output at least 90% of the neutrons in that energy range with a peak neutron distribution and an average energy between 10 keV and 30 keV. By way of another example, a one eV to ten keV beam can be configured to output at least 90% of the neutrons in that energy range with a peak neutron distribution and an average energy between three keV and 10 keV. For convenience these ranges will be described as epithermal energy ranges. Neutrons at energies beneath these ranges will be referred to as thermal neutrons (e.g., beneath one eV), and those above these ranges will be referred to as fast neutrons (e.g., above 30 keV).
LEBL 30 transfers a negative ion beam (e.g., H− ions) from ion source 20, through pre-accelerator 26 which boosts the energy level of the ion beam and converges the ion beam, to an input (e.g., an input aperture) of accelerator 40. Accelerator 40 is powered by a high voltage power supply 42 coupled thereto. Accelerator 40 includes a vacuum tank, a charge-exchange tube, accelerating electrodes, and a high voltage feedthrough. Accelerator 40 can, in some implementations, accelerate a hydrogen ion beam to produce a proton beam with an energy generally equal to twice the voltage applied to the accelerating electrodes positioned within accelerator 40. The energy level of the proton beam can be achieved by accelerating the beam of negative hydrogen ions from the input of accelerator 40 to the innermost high-potential electrode, stripping two electrons from each ion, and then accelerating the resulting protons downstream by the same voltages encountered in reverse order.
HEBL 50 can transfer the proton beam from the output of accelerator 40 to the neutron-generating target 60 positioned at the end of a branch 71 of the beamline extending into a patient treatment room. Beam system 100 can be configured to direct the proton beam to one or more targets 60 and associated target areas. In some implementations, HEBL 50 includes multiple (e.g., three) branches 71, 81, and 91 configured to extend to multiple different patient treatment rooms, with each branch terminating in a target 60 and NBC 200. HEBL 50 includes a pumping chamber 51, quadrupole magnets 52 and 72 to prevent de-focusing of the beam, dipole or bending magnets 56 and 58 to steer the beam towards one or more targets, beam correctors 53, diagnostics such as current monitors 54 and 76, a fast beam position monitor 55 section, and a scanning magnet 74 for branch 71. Branches 81 and 91 can contain components similar to branch 71.
The design of HEBL 50 depends on the configuration of the treatment facility (e.g., a single-story treatment facility, a two-story treatment facility, and the like). The beam can be delivered to target 60 (e.g., positioned near a treatment room having a patient 80) with the use of the bending magnet 56. Quadrupole magnets 72 can be included to then focus the beam to a certain size at target 60. The beam can pass one or more scanning magnets 74, which provide lateral movement of the beam onto the target surface in a desired pattern (e.g., spiral, curved, stepped in rows and columns, combinations thereof, and others). The beam lateral movement can enable generation of smooth and even time-averaged distribution of the proton beam on the target 60, preventing overheating of the target and making the particle (e.g., neutron) generation as uniform as possible within the target (e.g., neutron generating layer 121 of
Scanning magnets 74 can be configured to direct the beam to a current monitor 76, which measures beam current. The beam current value can be used to operate a safety interlock. The target assembly 65 containing target 60 can be physically separated from the high-energy beamline volume with a valve 77. A function of valve 77 is to separate the vacuum volume of the beamline from the target 60 during removal of a used target and loading of a new target. In some implementations, instead of being bent by 90 degrees by a bending magnet 56, the beam can be directed straight to one or more quadrupole magnets 52 located in the horizontal beamline. The beam could be bent by another bending magnet 58 to a preset angle, depending on a setting requirement (e.g., location of a patient or a room configuration). In some implementations, bending magnet 58 can be arranged at a split in the beamline and can be configured to direct the beam in one of two directions for two different treatment rooms located on the same floor of a medical facility.
System 100 as described with respect to
NBC 200 is configured to have a beam input 201 adjacent to, or in close proximity with, target installation location 69. In some embodiments, the distance between input 201 and location 69 is 10 to 60 centimeters (cm), more preferably 25 to 40 cm. NBC 200 has a beam output 202 downstream of the generated neutron flow, which is located in proximity with recess 206. An axis 203 extends from input 201 to output 202 and, in this embodiment, is located generally centrally within NBC 200. For convenience, the position of elements within NBC 200 will be referred to with respect to axis 203 and lateral directions 204, which are perpendicular to axis 203. The terms upstream and downstream are referenced with respect to charged particle beam flow into the target and subsequent neutron flow, both of which proceed in the general direction from left to right on
NBC 200 has a rear (upstream-most) face or side 301, a front (downstream-most) face or side 302, and a lateral face or side 303. NBC 200 includes four general regions: central region 210 which is traversed by axis 203; intermediate region 230; peripheral region 250; and frontal region 270. In this embodiment, central region 210 has a generally cylindrical shape. Intermediate region 230 also has a generally cylindrical shape and surrounds the lateral sides and the upstream side of central region 210. Peripheral region 250 has a generally cylindrical shape as well and surrounds the lateral sides and the upstream side of intermediate region 230. Regions 210, 230, and 250 can be configured to form generally concentric housings about axis 203, with the housings being in concentric cylindrical or pseudo-cylindrical multi-sided shapes.
The various cylindrical shapes enable conditioning of neutrons emanating from target 60 on all lateral sides of the beam axis. The shape can be symmetrical in both the axial and lateral profiles, or asymmetric in either or both profiles. An asymmetric axial profile can have a variable diameter that increases or decreases progressing in an upstream-to-downstream direction (see section 251 of
Frontal region 270 is present across the downstream sides of regions 210, 230, and 250, although not necessarily in contact with each region. Recess 206 can be filled with a vacuum or ambient gas to aid in forming neutron beam 70 in the forward direction. NBC 200 can be mounted within a structural support 95 that maintains NBC 200 in position with respect to the upstream neutron beam system 100 and the downstream patient treatment room.
Each of regions 210, 230, 250, and 270 are configured to perform a different array of functions on the neutrons and other particles generated by system 100. Central region 210 has the primary function of scattering fast neutrons emitted by target 60 in the forward direction without significant directional change, and without absorbing a substantial amount of neutrons. The fast neutrons are preferably scattered such that their energies descend into and remain within the target range (e.g., epithermal energies) until output from NBC 200. This preferably occurs without simultaneously scattering a significant number of neutrons down out of the target range.
The amount and type of material within central region 210, in any given direction, is proportional to the change in energy required to scatter and reduce the most probable neutron energy emitted in that direction. For example, more material is required in the forward direction since the neutrons emitted from target 60 in that direction are more energetic than those traveling in the backward direction.
Intermediate region 230 functions to redirect neutrons back towards central region 210 to conserve those neutrons and allow them to be utilized in beam 70, but in such a way that minimal energy loss and absorption occurs. Region 230 also scatters fast neutrons emitted at large forward angles from target 60 that laterally traversed central region 210, and provides photon shielding for prompt gamma rays produced by neutron captures in both central region 210 and peripheral region 250.
Peripheral region 250 functions to remove neutrons of all energies as it is unlikely those neutrons can be redirected back into central region 210. This is accomplished by further scattering the neutrons to thermal or near thermal energy levels for easier absorption by region 250. Region 250 also provides photon shielding to reduce the number of photons produced in the inner area of NBC 200 from entering the facility.
The effectiveness of a material to scatter and reduce the energy of a neutron is inversely proportional to its atomic mass number A, governed by the number of protons and neutrons in the nucleus. The maximum and average fractional energy loss for a material is approximated by the following equation:
As an example, a neutron interacting with a hydrogen nucleus (A≈1) will lose on average half of the initial energy per collision, and can lose up to all its energy in that single collision. For comparison, a neutron interacting with a nucleus of lead-208 (Pb-208, A≈208) or beryllium-9 (Be-9, A≈9) will result in ≈1% and 18% average energy losses, respectively, with maximum energy losses of ≈2% and 36%. This makes hydrogen 50 times more effective than lead and 2.5 times better than beryllium as a scattering material. For BNCT, however, a more effective scattering material is not necessarily more useful since a small value of a means a few collisions is sufficient to push the neutron below the epithermal energy range. The α value must be balanced with the other functions of NBC 200.
The number of collisions, on average, a neutron must undergo to down scatter from some incident neutron energy to a specific energy is based on another parameter ζ, which is given by the relationship:
The number of collisions, N, can be approximated using the following relationship:
From this equation it can be shown that on average 24 times more collisions are needed in lead than in beryllium to reduce the incident neutron energy by half.
Each material, in addition to mass, has an energy dependent probability that a neutron will interact within the material, called the total macroscopic cross-section (Σtot), or probability of collision per unit distance (e.g., 1/unit distance). At energies above thermal and below the first nuclear state the cross section is generally constant, and is referred to herein as the non-resonant region. Higher energies are referred to as the resonant region (defined by the discrete nuclear states) where peaks and valleys for the cross section are present, with the peaks corresponding to the energy of each discrete nuclear state and the valleys corresponding to the energy regions between resonances. If a neutron encounters a material with a large cross section resonance at the energy of the neutron, the probability of scattering to a lower energy is high. Conversely, relatively few scattering events will occur for neutron energies in a cross-section valley.
The type and amount of material present within each region can be selected to perform these various functions. Materials adept at scattering neutrons, classified generally herein as “S” materials, can be further classified as having substantial cross-sections for scattering from fast to epithermal energies (“Fast-S”), from fast and epithermal energies to lower energies (“Epi-S”), and as having substantial cross-sections in non-resonant regions (“NR-S”) for scattering fast and/or epithermal neutrons. Different scattering materials, regardless of class, can be indicated by a numeric suffix (e.g., S1, S2, and S3). Materials adept at absorbing thermal neutrons are generally referred to herein as “Ab” materials. Materials adept at redirecting neutrons are generally referred to herein as “R” materials.
Particularly useful Fast-S elements can have an atomic number (Z) of nine or greater, examples of which are magnesium, fluorine, and aluminum.
Aluminum is a highly versatile material with structural strength, relative ease of manufacture, and the ability to be combined with other elements in a wide variety of compounds. Aluminum alloy blends are divided into three different categories based on the alloying material, which can be other elements such as magnesium and silicon with desirable scattering properties. Aluminum 6000 series alloys include greater than 97% aluminum (by weight percent) and the remaining elements can be either silicon or magnesium. Aluminum 5000 series alloys include greater than 90% aluminum with the dominant alloying element being up to 10% magnesium. Some 5000 series cast metals can have as little as 32% aluminum with the remainder being magnesium. Aluminum 4000 series alloys include greater than 85% aluminum and up to 12.5% silicon, with the remaining balance being magnesium, manganese, or copper. Some 4000 series cast metals can have up to 22% silicon.
The scattering properties of fluorine can be utilized effectively within NBC 200 with one or more other materials in the form of a compound. For example, fluorine can be combined as an alloy with aluminum (e.g., AlF3), titanium (e.g., TiF3), barium (e.g., BaF2), bismuth (e.g., BiF3), lead (e.g., PbF2), tungsten (e.g., WF6), vanadium (e.g., VF3), magnesium (e.g., MgF2), calcium (e.g., CaF2), or with carbon and hydrogen (e.g., ethylene tetrafluoroethylene (ETFE, C4H4F4)). By mass the fluorine content can generally range from approximately 15% (as with lead fluoride (PbF2)) to 54% (as with TiF3) or 68% (as with AlF3).
The materials within NBC 200 that undergo relatively high radiation exposure, such as within central region 210, preferably exhibit sufficient radiation resistance to prevent degradation within NBC 200. In various embodiments the materials of NBC 200 are radiation tolerant up to a minimum of 10,000 Gray (Gy). Some fluorine bearing polymers, like polytetrafluoroethylene (PTFE, C2F4), have poor radiation resistance, where physical changes (e.g., degradation, crumbling) can occur as low as 100 Gy, and are not suited for NBC 200.
The fast-scattering effect of aluminum and fluorine can be enhanced by combination of those elements with magnesium into compounds of two or more elements, such as magnesium fluoride (see
Epi-S elements for NBC 200 can have an atomic number (Z) of 12 or greater. Particularly useful examples of these Epi-S elements are titanium and vanadium, and to a lesser extent magnesium.
Certain elements exhibit a broad non-resonant region for cross-sections at lower energies after termination of the 1/V region and extending to higher energies where resonance cross-sections commence. The non-resonance region of the cross-section can have a constant slope, e.g., flat, and can be decreasing (to a substantially lesser extent than in the 1/V region) or constant. These elements are referred to herein as non-resonant scattering materials (“NR-S”), examples of which include hydrogen, lithium, boron, beryllium, carbon, nitrogen, and oxygen. In many embodiments, the NR-S material exhibits deviation of 20% or less over the target energy range (e.g., epithermal), more preferably 10% or less (e.g., like carbon's cross-section up to ˜120 keV).
Certain elements exhibit a broad 1/V region with significant cross-sections that can extend across the thermal energy region and at least a substantial portion of the epithermal energy region. The 1/V region of the cross-sections can have a constant slope, e.g., flat, and can be decreasing with a substantial slope. These elements are particularly useful at absorbing neutrons and are referred to herein as absorption materials (“Ab”), examples of which include hydrogen, lithium, boron, and carbon. These materials can be referred to either as Ab materials or as NR-S materials given the context.
Ab materials can be used in regions of NBC 200 where elimination of the neutrons is desirable, such as near the rear and lateral extremes of NBC 200, and near the front on surfaces surrounding output 202. All Ab elements can be used in the embodiments of NBC 200 alone, in combination with each other, or in combination with other materials (e.g., Fast-S, Epi-S, NR-S, R) to achieve the desired structural characteristics and absorptive capability. Additional examples of combinations include hydrogenous materials such as polymers like polyethylene (PE) and boronated polyethylene (B-PE). Additional examples of Ab materials include cadmium (Cd), gadolinium (Gd), indium (In), and hafnium (Hf)
Certain elements tend to redirect neutrons through elastic scattering within minimal neutron energy loss. This process is proportional to the Z value of the element in contrast to the structure of the cross-section. Each element with a Z value of from and including 74 (tungsten) up to and including 92 (uranium) are elements that are particularly adept at redirecting neutrons, and are referred to generally herein as redirection (“R”) materials. These materials are also adept at absorbing gamma radiation.
Carbon, nitrogen and oxygen are NR-S materials that can be combined with other scattering elements to add or enhance non-resonant scattering capabilities of the overall material. For example, aluminum is a Fast-S element that can be formed as an oxide (e.g., Al2O3), carbide (e.g., Al4C3), and nitride (e.g., AlN). Examples of each are depicted in the cross-section versus energy graph of
Selection of materials and material dimensions is dependent on the energy profile of neutrons generated by a particular target 60. Because the neutron energy profiles are dependent on the design, material, and construction of target 60 as well as the characteristics (e.g., energy and current) of the incident charged particle beam, or other mechanism utilized for generating the neutrons, numerous examples of embodiments of NBC 200 are disclosed herein.
Some of these embodiments utilize stacked or layered arrangements where sections with different materials are placed adjacent to each other to form a sequence that acts upon neutrons passing therethrough. Such stacked arrangements permit more complex functions to be performed on the neutrons in terms of the scattering of different energies, redirection, and absorption. Stacked layers permit a relatively high degree of tunability of effects for a particular raw neutron profile. These effects can be tuned axially and laterally along all directions of neutron propagation from target 60 by stacking layers along axis 203 (see
In these embodiments, shell 208 can extend upstream past the installed position of target 60. Shell 208 can terminate upstream within NBC 200 or can extend all the way to the upstream terminus of NBS 200 (e.g., the rear-most face). The upstream terminus of shell 208 can be offset apart from assembly 65 as shown in
In the embodiments of
In the embodiment of
Each section 211, 212, and 213 preferably includes or is formed of a different scattering (S) material, such that the S material of section 211 (indicated by S1) is different from the S material of section 212 (indicated by S2), which in turn is different from the S material of section 213 (indicated by S3 for embodiments having section 213). Shell 208, if present, can also include an S material that is the same (S1, S2, or S3) or different (S4) than the S materials of sections 211, 212, and 213. The S material for sections 211, 212, 213 and shell 208 can be Fast-S, Epi-S, or NR-S types, or a combination of any two or three types. In embodiments where the desired energy output is in the epithermal range, the S materials are preferably either Fast-S or NR-S materials.
The following tables set forth example embodiments of the material combinations that can be used within central region 210. Each of sections 211, 212, and 213 can be combined with a redirection (R) material as desired. Combination with an R material intensifies the amount of local scattering, as neutrons passing through can be redirected numerous times by the R material without significant loss of energy, and thus increase the likelihood of encountering the S material and scattering in the preferential manner according to that S materials resonance or non-resonance cross-section.
Table 1 sets forth four examples for embodiments having two sections 211 and 212 and no shell 208. Tables 2A and 2B set forth sixteen examples for embodiments having two sections 211 and 212 and a shell 208, which can be of the same material (S1 or S2) as sections 211 and 212 or a different material (S3), with or without an R material. To illustrate by reference to Table 1, example 1 (“Ex. 1”) sets forth a configuration where section 211 includes a combination of an R material and an S1 material and section 212 includes an S2 material with no R material (as indicated by the absence of “R”). Example 2 (“Ex. 2”) sets forth a configuration where section 211 includes an S1 material with no R material and section 212 includes a combination of an R material and an S2 material. Example 3 (“Ex. 3”) sets forth a configuration where section 211 includes an S1 material and section 212 includes an S2 material neither having an R material. Example 4 (“Ex. 4”) sets forth a configuration where section 211 includes a combination of an R material and an S1 material and section 212 includes a combination of an R material and an S2 material, where the R materials of example 4 can be the same or different. The same convention is used for Tables 2A and 2B.
The examples set forth in the remaining Tables 3, 4A, 4B, 4C, and 4D follow the same convention as Tables 1, 2A, and 2B. Table 3 sets forth eight examples for embodiments of central region 210 having three sections 211, 212 and 213 and no shell 208, whereas Tables 4A, 4B, 4C, and 4D set forth 32 examples for embodiments having three sections 211, 212, and 213 and a shell 208. In these embodiments shell 208 can be of the same material as one of sections 211, 212, and 213 (S1, S2, or S3) or a different material (S4), with or without an R material. If the same material is used, then shell 208 can be contiguous (e.g., seamless) with and unified with the section (211, 212, or 213) having the same material. If shell 208 is unified with section 212 for example, then shell 208 can enclose or encapsulate all or substantially all of section 211 (or any combination of sections contained within shell structure 208), with beam axis 203 extending parallel to the walls of section 208 and then traversing section 208/212. Similarly, if shell 208 is unified with section 213, then it can enclose or encapsulate sections 211 and 212.
The S materials (e.g., S1 through S4) can include one or more that exhibit resonances within the energy range of neutrons produced by the target 60 and above the desired output energy range, for example, a Fast-S material when the desired energy range is epithermal. The S materials can also include one or more NR-S materials that exhibit non-resonance characteristics within the energy range of neutrons produced by the target 60 and at least above the desired output energy range, for example, to fill gaps between Fast-S material resonances. In some example embodiments, central region 210 includes a combination of at least one S material exhibiting resonance characteristics, with at least one S material exhibiting non-resonance characteristics. These materials can be separated in different sections or combined in a single section (e.g., aluminum oxide). Table 5 sets forth eight examples of configurations of the S materials for embodiments having two sections 211 (S1) and 212 (S2). Tables 6A and 6B sets forth fourteen example configurations of the S materials for embodiments having three sections 211 (S1), 212 (S2) and 213 (S3). For example, referring to Ex. 1 of Table 5, the S1 material includes both a Fast-S material (indicated by the X in the F column) and an NR-S material (indicated by the X in the NR column), while the S2 material includes only a Fast-S material (indicated by the X in the F column and the absence of an X in the NR column). The remaining examples use the same convention in Tables 5, 6A, and 6B. The example configurations of Table 5 can be used with all two section examples of Tables 1, 2A, and 2B, while the example configurations of Tables 6A and 6B can be used with all three section examples of Tables 3, 4A, 4B, 4C, and 4D.
In some embodiments upstream section 211 can include an S1 material with scattering resonance cross-sections at relatively high energies (e.g., fast) within the range of neutron energies produced by target 60, with the immediately downstream section 212 being an S2 material with one or more resonance cross-sections at relatively lower energies, and the most downstream section 213 being an S3 material with one or more resonance cross-sections at still lower energies at or just above the desired energy range (e.g., epithermal) of the converted beam 70. Additionally, or alternatively, the sections 211, 212, and 213 can have resonance cross sections at the same or similar energies, but with upstream section 211 having the relatively largest cross-section at relatively high energies (e.g., fast) within the range of neutron energies produced by target 60 as compared to the cross-sections of sections 212 and 213 at the same or similarly high energies, immediately downstream section 212 having the relatively largest cross-section at a relatively lower energies as compared to the cross-sections of sections 211 and 213 at the same or similar energies, and the most downstream section 213 having the relatively largest resonance cross-section at still lower energies at or just above the desired energy range (e.g., epithermal) of the converted beam 70.
The energies of these neutrons can be progressively lowered by each section such that the neutrons exiting output 202 have been down-scattered into the desired range. Similarly, in some embodiments the materials used in the various sections are selected to have resonance energies that do not fully overlap and at least partially complement each other to provides more uniform scattering. For example magnesium fluoride and aluminum have resonances that only partially overlap from approximately 20 keV to 70 keV as shown in
The R material can also provide benefits such as gamma radiation absorption. Placement of the R material in the relatively more upstream section (e.g., 211) allows more time and volume for other parts of NBC 200 to redirect neutrons that are inadvertently redirected out of section 211, as these neutrons can be redirected back into central region 210 by intermediate region 230. The downstream section(s) (e.g., 212, 213) can perform scattering without substantial redirection to maintain the forward-directed beam shape.
As a combination of an R and S material, lead fluoride has diverse functions due to the nuclear properties of lead and fluorine, as well as several material properties. The fluorine atoms have a series of large resonant scattering peaks, amplified due to the high mass density of the compound, that preferentially scatter neutrons above the epithermal range without excessive energy loss (9.5% on average). The lead can serve two roles: as a reflector, only making small changes in the neutron energy spectrum until another fluorine atom is encountered, and a photon shield to attenuate prompt gamma rays generated within the NBC 200. This material will lead to low neutron flux levels at fluorine peak energies and higher fluxes at valley energies. Energy reduction of the valley fluxes can be accomplished by alternating sections of lead fluoride with a non-resonance material like beryllium or beryllium oxide. Thicknesses of sections of beryllium can be set corresponding to the amount of material that on average will provide the appropriate number of collisions to advance neutrons from one fluorine resonance to the next. As shown in the equations above beryllium is much more efficient at this process than lead or fluorine, thus, the use of beryllium or beryllium oxide can reduce the overall size of central region 210.
The stacked sections within central region 210 can be configured in numerous ways, with different shapes, thicknesses, and combinations as shown in the example embodiments depicted in the cross-sectional views of
In the embodiment of
These embodiments are illustrative of the many different configurations that can be implemented, and features of each embodiment can be combined with features of any and all of the other embodiments.
When used in combination with central region 210 having shell 208 as described with respect to
In
In
In some embodiments, placement of a titanium-boron alloy or boron carbide in frontal region 270, or in or near beam output 202 or recess 206), substantially eliminates the low energy tail in the emitted neutron spectrum of converted beam 70, which consequently increases the average cosine theta of beam 70 upon exit (e.g., makes the neutrons more forward-directed out of NBC 200), as scattering laws dictate that the most probable scattering angle goes from isotropic to more forward directed as neutron energy increases. Placement within peripheral region for Epi-S and Ab functions is also advantageous, Ti—B alloys such as titanium diboride and B—C alloys like boron carbide are very hard ceramics that are highly shapeable, and thus can be made into specialized shapes for NBC 200, such as the transition section described with respect to the embodiment of
In the embodiment of
In the embodiment of
Table 7 sets forth ten examples of material combinations that can be used for the embodiments of
In the embodiment of
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In the embodiment of
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Table 8 sets forth ten examples of material combinations that can be used for the embodiments of
Certain materials exhibit excellent properties for use in neutron beam conditioning and shielding, while at the same time being shapeable to facilitate construction of NBC 200 and the surrounding support structure. For example, the aforementioned embodiments of NBC 200 having various regions and sections that are cylindrical, or substantially cylindrical (e.g., being cylinder-like around a beam), having a curved outer surface that might be prone to roll, shift, or is otherwise not as convenient to work with and install as a flat surface.
Any of the sections of peripheral region 250 can be used to perform this transition, including the innermost section (e.g., section 251), the outermost section (e.g., section 253), and sections located therebetween (e.g., sections 252 and 254). The transition is facilitated if the transition section is composed of a material that can be easily shaped, molded, machined, and/or 3D printed. Examples of such materials are ceramic titanium diboride, ceramic boron carbide, polymers like polyethylene (PE) (e.g., boron-doped polyethylene of section 254) and ETFE. The materials of sections placed outside of the transition section can then be configured as blocks or plates without significant curved surfaces that are relatively easy to manufacture and assemble into NBC 200's complete structure.
The cylindrical and polygonal lateral sides or shapes need not be perfect geometrical cylinders or polygons. Those of ordinary skill in the art, upon reading this description, will recognize that such sides or shapes can be substantially cylindrical or polygonal, and those of ordinary skill in the art will readily recognize sides or shapes that are substantially cylindrical or polygonal. For example, some flatness can be present on the lateral cylinder sides or shapes, where that flatness has a negligible effect on the overall neutron beam profile output from the beam output. Similarly, some roundness or curvature can be present on the lateral polygonal sides or shapes, where that roundness or curvature also has a negligible effect on the overall neutron beam profile output from the beam output. In some embodiments, a substantially cylindrical shape varies by no more than 5% of the overall lateral dimension from a geometric cylinder. In some embodiments, a substantially polygonal shape varies by no more than 5% of the overall lateral dimension from the corresponding geometric polygon.
NBC 200, including each section of regions 210, 230, 250, and 270 can be fabricated according to the process that provides the desired balance between manufacturability, performance, and cost. Portions of NBC 200 making up a section one of regions 210, 230, 250, and 270 can be fabricated separately and then assembled to form the larger section, or even larger region. The materials for NBC 200 can be in contiguous solid form (e.g., a sheet of lead). The combination of first and second materials, such as R and S materials or different types of S materials (e.g., Fast-S and NR-S materials), can be in the form of a bonded chemical compound. Elementary materials and combined materials can be in a raw granular or powdered form and then set into the desired shape through casting, molding, sintering, or mixing with additives (e.g., adhesives like epoxy or enamel blends, etc.). The materials can also be in granular or powdered form and maintained or held in the desired shape using a metallic housing or casement.
Various aspects of the present subject matter are set forth below, in review of, and/or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments and the aspects thereof. In other words, an emphasis is on the fact that each aspect of the embodiments can be combined with each and every other aspect unless explicitly stated or taught otherwise.
In a first group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons from a neutron generation target; a beam output configured to output neutrons; a central region traversed by an axis between the beam input and the beam output, where the central region is configured to scatter neutrons to a treatment energy range; an intermediate region located laterally around the central region and configured to redirect and scatter neutrons, where the intermediate region includes a first intermediate section and a second intermediate section each including a different material; and a peripheral region located laterally around the intermediate region and configured to absorb neutrons and gamma radiation, where the peripheral region includes a first peripheral section and a second peripheral section each including a different material.
In some embodiments of the first group, the central region can include a first section, a second section, and a third section, where each of the first, second, and third sections include a different material, and where each of the first, second, and third sections are traversed by the axis. The first section can include fluorine, the second section can include magnesium, and the third section can include aluminum.
In some embodiments of the first group, the central region can include a first material and a second material. The first material can include aluminum and the second material can include magnesium. The first material can be configured to scatter generated neutrons towards or into a treatment energy range and configured to redirect generated neutrons, and the second material can be configured to non-resonantly scatter generated neutrons. The first material can include lead and fluorine. The second material can include beryllium. The second material can include at least one of an oxide, a carbide, or a nitride. The second material can be configured as a layer between a first central section including the first material and a second central section including the first material. The first central section, the layer, and the second central section can be traversed by the axis. The central region can include a third material that includes at least one of: aluminum, fluorine, and magnesium.
In some embodiments of the first group, the central region can include a cylindrical portion that extends from the beam input to the beam output. The cylindrical portion can have a first terminus upstream of an installed location of the neutron generation target. The cylindrical portion can have a first terminus along an upstream-most face of the neutron beam converter. The cylindrical portion can have a second terminus in proximity with the beam output. The cylindrical portion can be configured to act as a low resistance pathway for neutrons relative to the intermediate region. The cylindrical portion can include a tubular portion. The cylindrical portion can be configured to act as a low resistance pathway for neutrons relative to the intermediate region and a material within the tubular portion. The tubular portion can include at least one of: aluminum, fluorine, and magnesium, and laterally surrounds a first central section including a first material and a second material. The cylindrical portion can include at least one of: aluminum, fluorine, and magnesium. The cylindrical portion can traverse the axis.
In some embodiments of the first group, the converter can have a downstream-most surface and a recess from the downstream-most surface at the beam output. The recess can have a sidewall portion including a neutron redirector. The neutron redirector can include at least one of lead, nickel, bismuth, and tungsten. The recess can be cylindrical and the converter can include a tubular liner including beryllium, the tubular liner located in proximity with a sidewall of the recess.
In some embodiments of the first group, the central region can include: a first central section traversed by the axis and configured to scatter neutrons to the treatment energy range; a second central section traversed by the axis, located downstream of the first central section, and configured to scatter neutrons in an epithermal energy range to lower energies; and a third central section traversed by the axis, located downstream of the second central section, and configured to absorb neutrons scattered to the lower energies.
In some embodiments of the first group, the central region can include a solid section spaced apart from an installation location of the neutron generation target, where the solid section can be traversed by the access and located downstream of the installation location of the target. The solid section can be spaced apart from the installation location of the target by at least 10 centimeters.
In some embodiments of the first group, the first intermediate section can be relatively closer to the central region than the second intermediate section, and the first intermediate section can be configured to scatter generated neutrons and the second intermediate section is configured to redirect generated neutrons. The second intermediate section can be configured to redirect generated neutrons and absorb photons. The first intermediate section can be further configured to redirect neutrons. The first intermediate section can include at least one of fluorine, aluminum, and magnesium, and the second intermediate section can include at least one of lead, nickel, bismuth, and tungsten. The first intermediate section can include lead and the second intermediate section can include lead.
In some embodiments of the first group, the first intermediate section can be located laterally around the central region and the second intermediate section can be located laterally around the first intermediate section. The first intermediate section can be in contact with the central region, and the second intermediate section can be in contact with the first intermediate section.
In some embodiments of the first group, the intermediate region can extend laterally across a rear face of the central region.
In some embodiments of the first group, the second intermediate section can be located laterally around the first intermediate section, and the first intermediate section can be configured to scatter neutrons and the second intermediate section can be configured to redirect neutrons and absorb gamma radiation. The intermediate region can include a third intermediate section located laterally around the second intermediate section, where the third intermediate section can be configured to scatter neutrons from a first energy in an epithermal energy range to a second energy lower than the first energy. The intermediate region can include a fourth intermediate section located laterally around the third intermediate section, where the fourth intermediate section can be configured to absorb neutrons. The intermediate region can include a fifth intermediate section located laterally around the fourth intermediate section, where the fifth intermediate section can be configured to absorb gamma radiation.
In some embodiments of the first group, the first peripheral section can be relatively closer to the intermediate region than the second peripheral section, and the first peripheral section can be configured to absorb neutrons and the second peripheral section can be configured to absorb photons. The peripheral region can include a third peripheral section located relatively closer to the intermediate section than the first peripheral section, where the third peripheral section can be configured to scatter epithermal neutrons. The peripheral region can include a third peripheral section located relatively closer to the intermediate section than the first peripheral section, where the third peripheral section can be configured to absorb photons. The first and second peripheral sections can include titanium. The first peripheral section can include titanium and vanadium. The second peripheral section can include boron. The first peripheral section can be located laterally around the intermediate and central regions and the second peripheral section can be located laterally around the first peripheral section. The first peripheral section can be in contact with the intermediate region, and the second peripheral section can be in contact with the first peripheral section. The peripheral region can extend laterally across a portion of the rear of the central region and a portion of the rear of the intermediate region.
In some embodiments of the first group, the converter includes a frontal region extending laterally across the converter. The frontal region can be configured to absorb neutrons and photons. The frontal region can include a first frontal section configured to absorb photons and a second frontal section configured to absorb neutrons. The first frontal section can be located downstream of the second frontal section. The first frontal section can include an aperture for a recess at the beam output. The first frontal section can include at least one of lead, nickel, bismuth, and tungsten. The second frontal section can include at least one of lithium, cadmium, boron, titanium, gadolinium, indium, hafnium, and a hydrogenous polymer. The converter can include a third frontal section configured to scatter epithermal neutrons. The third frontal section can be located upstream of the second frontal section. The frontal region can form a continuation of the peripheral region.
In a second group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; a first region traversed by an axis between the beam input and the beam output; and a second region located laterally around the first region, where the second region includes an alloy including titanium and vanadium.
In some embodiments of the second group, the second region can include: a first section including the alloy; and a second section including boron. The first section can be located laterally around the first region and the second section can be located laterally around the first section. The converter can include a third region interposed between the first region and the second region, where the first region is a central region, the third region is an intermediate region, and the second region is a peripheral region. The second region can include lead. The second region can include a hydrogenous polymer.
In a third group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; a first region traversed by an axis between the beam input and the beam output; and a second region located either laterally around the first region or along a frontal region proximate to a treatment room, where the second region includes boron.
In some embodiments of the third group, the second region can include: a first section including an alloy of titanium and vanadium; and a second section including boron. The first section can be located laterally around the first region and the second section can be located laterally around the first section. The converter can include a third region interposed between the first region and the second region, where the first region is a central region, the third region is an intermediate region, and the second region is a peripheral region. The boron can be in ceramic titanium diboride or ceramic boron carbide.
In some embodiments of the third group, the second region includes a hydrogenous polymer.
In some embodiments of the third group, the converter includes the frontal region having boron, where the frontal region is located across a downstream front side of the converter.
In some embodiments of the third group, the second region exhibits an inverse velocity cross-section over a thermal and at least part of an epithermal neutron energy range.
In some embodiments of the third group, the second region exhibits a resonance peak cross-section in an epithermal neutron energy range.
In some embodiments of the third group, the second region is located laterally around the first region.
In some embodiments of the third group, the second region is located along the frontal region.
In a fourth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; and a central region traversed by an axis between the beam input and the beam output, where the central region includes a plurality of first sections and a plurality of second sections, where the plurality of first sections is traversed by the axis and configured to resonantly down scatter neutrons, and where the plurality of second sections is traversed by the axis and configured to non-resonantly down scatter neutrons.
In some embodiments of the fourth group, the plurality of first sections and the plurality of second sections are in a stacked alternating arrangement.
In some embodiments of the fourth group, the plurality of second sections can include beryllium.
In some embodiments of the fourth group, the plurality of first sections can include at least one of magnesium, aluminum, and fluorine.
In some embodiments of the fourth group, the plurality of first sections can include lead and fluorine.
In some embodiments of the fourth group, the converter can include a plurality of third sections traversed by the axis and configured to resonantly down scatter neutrons, where the plurality of first sections includes a different material than the plurality of third sections. At least a portion of the plurality of second sections and the plurality of third sections can be in a stacked alternating arrangement.
In some embodiments of the fourth group, the converter includes a plurality of third sections traversed by the axis and configured to resonantly down scatter neutrons, where the plurality of first sections is interleaved with the plurality of second sections and the plurality of third sections, where the plurality of first sections includes at least one of magnesium, aluminum, or fluorine, where the plurality of second sections includes beryllium, and where the plurality of third sections includes a material including lead and fluorine.
In some embodiments of the fourth group, the plurality of first sections can be continuous.
In a fifth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; a central region between the beam input and the beam output; an intermediate region located laterally around the central region; and a peripheral region located laterally around the intermediate and central regions, where the central region includes a first material including lead and fluorine, where the first material is traversed by an axis between the beam input and beam output, where the intermediate region includes a second material including lead and fluorine, and where a third material is located between the first material of the central region and the second material of the intermediate region.
In some embodiments of the fifth group, the first and second materials are the same.
In some embodiments of the fifth group, the first and second materials can be lead fluoride.
In some embodiments of the fifth group, the third material can include at least one of magnesium and aluminum.
In some embodiments of the fifth group, the third material can be a magnesium-aluminum alloy.
In some embodiments of the fifth group, the intermediate region includes: a first section having the second material; and a second section having a fourth material that includes at least one of lead, nickel, bismuth, and tungsten. The second section can be located laterally around the first section.
In some embodiments of the fifth group, the peripheral region can include at least one of lead, nickel, bismuth, and tungsten.
In a sixth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons from a neutron generation target; a beam output configured to output neutrons; and a central region between the beam input and the beam output, where the central region includes at least one section including beryllium.
In some embodiments of the sixth group, the section including beryllium is separated from the beam input by another material.
In some embodiments of the sixth group, the at least one section is configured as a plate, where a central axis of the converter extending from the beam input to the beam output is normal to the plate.
In some embodiments of the sixth group, the at least one section is one of a plurality of first sections located at intervals between the beam input and the beam output, where each of the plurality of first sections includes beryllium.
In some embodiments of the sixth group, each adjacent pair of first sections in the plurality of first sections is separated by one of a plurality of second sections. Each of the plurality of second sections can be configured to resonantly scatter neutrons to a lower energy.
In some embodiments of the sixth group, the plurality of first sections can be configured as plates, where a central axis of the converter extending from the beam input to the beam output is normal to each first section of the plurality of first sections.
In some embodiments of the sixth group, the at least one section can include beryllium oxide.
In some embodiments of the sixth group, the at least one section can be configured to non-resonantly down scatter neutrons to a lower energy.
In a seventh group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons from a neutron generation target; a beam output configured to output neutrons; a first region between the beam input and the beam output; and a second region located laterally around the first region, where the second region includes a first section having an outer diameter that varies along a length of the first section.
In some embodiments of the seventh group, the first section has a maximum diameter at a first location aligned with a neutron generation target installation location. The diameter of the first section can decrease from the first location to a second location at a downstream terminus of the first section. The diameter of the first section can decrease from the first location to a second location at an upstream terminus of the first section.
In some embodiments of the seventh group, the first region is a central region, the second region is a peripheral region, and the converter includes an intermediate region between the central and the peripheral regions.
In some embodiments of the seventh group, an inner surface of the first section has a cylindrical shape with uniform diameter.
In some embodiments of the seventh group, the first section can be configured to down scatter epithermal neutrons.
In some embodiments of the seventh group, the first section can include titanium.
In some embodiments of the seventh group, the second region can have a cylindrical outer surface of uniform diameter.
In some embodiments of the seventh group, the second region includes a second section located laterally around the first section, where the second section has an inner diameter that varies corresponding to the outer diameter of the first section. The second section can have an outer diameter that is uniform along a length of the second section.
In an eighth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; and a central region between the beam input and the beam output, where the central region includes a plurality of first sections in a stacked alternating arrangement with a plurality of second sections, where a first one of the plurality of first sections has a thickness relatively less than a thickness of a second one of the plurality of first sections.
In some embodiments of the eighth group, each of the plurality of first sections can have a different thickness.
In some embodiments of the eighth group, the thickness of the first one of the plurality of first sections is at least 10% less than the thickness of the second one of the plurality of first sections.
In some embodiments of the eighth group, the first one of the plurality of first sections can be located relatively closer to the beam output than the second one of the plurality of first sections.
In some embodiments of the eighth group, the first one of the plurality of first sections can be located relatively farther from the beam output than the second one of the plurality of first sections.
In some embodiments of the eighth group, thicknesses of the plurality of first sections can incrementally decrease in an upstream to downstream direction.
In some embodiments of the eighth group, thicknesses of the plurality of first sections can incrementally increase in an upstream to downstream direction.
In some embodiments of the eighth group, the plurality of first sections can have a different composition than the plurality of second sections.
In some embodiments of the eighth group, each of the plurality of first sections can be configured as plates.
In some embodiments of the eighth group, each of the plurality of first sections can be configured to non-resonantly scatter neutrons and each of the plurality of second sections can be configured to resonantly scatter neutrons.
In some embodiments of the eighth group, each of the plurality of first sections can be configured to resonantly scatter neutrons and each of the plurality of second sections can be configured to non-resonantly scatter neutrons.
In some embodiments of the eighth group, every one of the plurality of second sections can have the same thickness.
In some embodiments of the eighth group, each of the plurality of second sections can be thicker than each of the plurality of first sections.
In a ninth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons; a beam output configured to output neutrons; and a central region between the beam input and the beam output, where the central region includes a plurality of first sections interleaved with a plurality of second sections, where the plurality of first sections includes a non-planar first section.
In some embodiments of the ninth group, the non-planar first section can have a cross-sectional profile that is chevron-shaped. The chevron-shaped cross-sectional profile can have an open side and a relatively more pointed side, where the relatively more pointed side faces the beam input. The chevron-shaped cross-sectional profile can have an open side and a relatively more pointed side, where the relatively more pointed side faces the beam output.
In some embodiments of the ninth group, each of the plurality of first sections can have a cross-sectional profile that is chevron-shaped.
In some embodiments of the ninth group, the non-planar first section can have a cross-sectional profile that is curved. The curved cross-sectional profile can have a concave side and a convex side, where the convex side faces the beam input. The curved cross-sectional profile can have a concave side and a convex side, where the concave side faces the beam input.
In some embodiments of the ninth group, each of the plurality of first sections can have a cross-sectional profile that is curved.
In some embodiments of the ninth group, the non-planar first section can be bowl-shaped.
In some embodiments of the ninth group, the non-planar first section can have a cross-sectional profile with a non-uniform thickness.
In some embodiments of the ninth group, the non-planar first section can have a cross-sectional profile that is curved, and the plurality of first sections can include a chevron-shaped first section.
In a tenth group of embodiments, a neutron beam converter is provided, the converter including: a beam input configured to receive neutrons from a neutron generation target; a beam output configured to output neutrons; a first region or section between the beam input and the beam output, where the first region or section has a first lateral outer surface that is curved around an axis between the beam input and beam output; and a second region or section located laterally around the first region or section, where the second region or section has a second lateral outer surface that is substantially multi-sided.
In some embodiments of the tenth group, the first lateral outer surface can be substantially cylindrical or cylindrical.
In some embodiments of the tenth group, the first region or section can be a first section of a central region of the converter. The second region or section can be a second section of the central region of the converter.
In some embodiments of the tenth group, the first region or section can be a central region of the converter. The second region or section is a section of an intermediate region of the converter. The second region or section is an intermediate region of the converter. The intermediate region can be configured to redirect and scatter generated neutrons.
In some embodiments of the tenth group, the second region or section can be a section of a peripheral region of the converter, and where the converter includes an intermediate region located between the central region and the peripheral region.
In some embodiments of the tenth group, the second region or section can be a peripheral region of the converter, and where the converter includes an intermediate region located between the central region and the peripheral region.
In some embodiments of the tenth group, the central region can be configured to scatter generated neutrons towards or into a treatment energy range.
In some embodiments of the tenth group, the second lateral outer surface can have four or more lateral sides and at least two end sides.
In some embodiments of the tenth group, the second lateral outer surface can have six or more lateral sides and at least two end sides.
In some embodiments of the tenth group, the second region or section can include a lateral inner side that corresponds in curvature to the first lateral outer side.
In some embodiments of the tenth group, the converter includes: two or more first sections of a central region, the two or more first sections of the central region each having a lateral outer side that is curved around the axis between the beam input and beam output; and two or more second sections of an intermediate region and/or a peripheral region of the converter, the two or more second sections each having a lateral outer side that is substantially multi-sided around the axis.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can be configured to output a neutron beam in an epithermal energy range from the beam output.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can be configured to output a neutron beam in an energy range from one electron volt to thirty kiloelectron volts. The converter can be configured to output the neutron beam with a peak neutron distribution and an average energy between 10 kiloelectron volts and 30 kiloelectron volts. The converter can be configured to output the neutron beam with at least 90% of the neutrons in the energy range from one electron volt to thirty kiloelectron volts.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can be configured to output a neutron beam in an energy range from one electron volt to ten kiloelectron volts. The converter can be configured to output the neutron beam with a peak neutron distribution and an average energy between three kiloelectron volts and ten kiloelectron volts. The converter can be configured to output the neutron beam with at least 90% of the neutrons in the energy range from one electron volt to ten kiloelectron volts.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can be configured for use in a boron neutron capture therapy system.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can include a neutron generation target. The neutron generation target can include lithium and can be configured to generate neutrons according to the reaction p+7Li→n+7Be. The neutron generation target can be configured to generate neutrons from a proton beam having an energy in the range of 1.9 to 3.0 megaelectron volts.
In the embodiments of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups, the converter can be configured to receive a raw neutron beam from the neutron generation target and output a converted neutron beam, where the converted neutron beam has a relatively more focused forward direction than the raw neutron beam, a variation in intensity that is relatively less than the raw neutron beam, and a variation in energy that is relatively less than the raw neutron beam.
In an eleventh group of embodiments, a method of converting a neutron beam is provided, the method including: propagating a charged particle beam at a neutron generation target located within a neutron beam converter such that a neutron beam is emitted from a neutron beam output of the neutron beam converter, where the neutron beam converter is configured in accordance with any embodiment of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups of embodiments.
In a twelfth group of embodiments, a method of treating a patient with boron neutron capture therapy (BNCT) is provided, the method including: propagating a neutron beam at the patient, where the neutron beam is emitted from a neutron beam output of a neutron beam converter, where the neutron beam converter is configured in accordance with any embodiment of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth groups of embodiments.
To the extent the embodiments disclosed herein include or operate in association with memory, storage, and/or computer readable media, then that memory, storage, and/or computer readable media are non-transitory. Accordingly, to the extent that memory, storage, and/or computer readable media are covered by one or more claims, then that memory, storage, and/or computer readable media is only non-transitory.
As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that these embodiments are not to be limited to the particular form disclosed, but to the contrary, these embodiments are to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any features, functions, steps, or elements of the embodiments may be recited in or added to the claims, as well as negative limitations that define the inventive scope of the claims by features, functions, steps, or elements that are not within that scope.
This application claims priority under 35 U.S.C. 119 to Provisional Application Nos. 63/272,670, filed Oct. 27, 2021, and 63/331,290, filed Apr. 15, 2022, both which are incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63272670 | Oct 2021 | US | |
| 63331290 | Apr 2022 | US |
