Materials and construction for the protection of the intended material

Abstract

Passivation regions and device configurations are described herein. The passivation region can be configured to seal against diffusion of a target material from an underlying region into the passivation region and / or through the passivation region. The passivation region can also be configured to seal against diffusion of an external supply or ambient substance into the passivation region towards the underlying region and / or through the passivation region.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 170,108, entitled "MATERIALS AND CONFIGURATIONS FOR PROTECTION OF OBJECTIVE MATERIALS," filed April 2, 2021, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0002] (Technical field) The subject matter described herein relates generally to the protection or passivation of target materials, for example, the passivation of lithium layers in neutron generating devices. [Background technology]

[0003] There are numerous applications in which it is desirable to protect or passivate materials in devices. One such application is boron neutron capture therapy (BNCT), which represents a relatively new modality for the treatment of various types of cancer, including the most difficult types. BNCT is a technique that aims to selectively treat tumor cells while sparing normal cells using boron compounds. A substance containing boron is injected into the blood vessels, and the boron collects in the tumor cells. The patient then receives radiation in the form of a neutron beam. The neutrons are generated by the interaction of the proton beam with a neutron-generating material, such as lithium or beryllium, positioned on the target substrate. The resulting neutron beam is slowed down and focused on the patient, where the neutrons react with the boron, selectively killing the tumor cells.

[0004] Neutron generating materials can be positioned as layers, coverings, or coatings that can interact with certain types of particles or plasmas. Lithium is a classic example, but it is a highly reactive and corrosive metal that is difficult to handle in normal ambient conditions (e.g., air at room temperature, such as those found in a typical laboratory space). Lithium reacts violently with moisture, nitrogen, and / or oxygen in atmospheric air, quickly discoloring and / or oxidizing. Lithium turns into nitrides and hydroxides (e.g., lithium hydroxide (LiOH and LiOH-H2O), lithium nitride (Li3N), and lithium carbonate (Li2CO3, which is the result of a secondary reaction between LiOH and CO2)), which can flake off from the substrate in the form of dust. Air and moisture act as catalysts for such reactions.

[0005] For safe handling, in one example, lithium may be mounted on a substrate inside a glove box and filled with an inert pure gas (e.g., argon). Transfer of lithium from the glove box to the work area requires the use of a "dry room" where the amount of moisture in the air is low enough to prevent the lithium from oxidizing or tarnishing too significantly. However, humans working in the dry room naturally introduce moisture, eliminating the benefits provided by the dry room. Furthermore, construction of dry rooms is complex and expensive.

[0006] Attempts to address the above drawbacks have met with limited or no success, depending on the particular application in which lithium is used. Synthesis of Li3N on the surface of a lithium target has been proposed. Disadvantages of such an approach include the inability to control the thickness of the Li3N layer and the high diffusion coefficient of lithium in Li3N. Furthermore, such an approach does not eliminate the risk of contamination or oxidation, even under ultra-high vacuum (UHV) conditions.

[0007] A thick layer of lithium, covered or protected by a thin layer of stainless steel (SS), has also been proposed as a solution. Such an approach suffers from a limited time interval (e.g., only 10 minutes) during which the lithium is protected and viable. Furthermore, approaches associated with thick coatings applied over the accelerator target material result in a slowdown of the accelerator particles and therefore a lower yield or a complete blockage of the desired reaction.

[0008] Oxidation-resistant layers of beryllium (Be) and / or aluminum (Al) have also been proposed. Drawbacks associated with such approaches include the high reactivity between lithium and aluminum when they come into contact, and the rapid diffusion of aluminum through lithium. Furthermore, beryllium is hazardous and difficult to handle.

[0009] For these and other reasons, a need exists for improved systems, devices, and methods that promote the passivation of materials. Summary of the Invention [Means for solving the problem]

[0010] Exemplary embodiments of systems, devices, and methods for protection or passivation of a target material are described herein. The passivation region can be configured to seal against diffusion of the target material from an underlying region into (and / or through) the passivation region. The passivation region can also be configured to seal against diffusion of external supplies or ambient materials into (and / or through) the passivation region toward the underlying region. Passivation regions having single and multi-layer configurations are described. Exemplary embodiments are described in the context of a neutron generation application in which the target material is lithium.

[0011] Other systems, devices, methods, features, and advantages of the subject matter described herein will be, or become, apparent to one with skill in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, be within the scope of the subject matter described herein, and be protected by the accompanying claims. No features of the example embodiments should be construed as limiting the appended claims in any way unless there is an express recitation of those features in the claims. [Brief description of the drawings]

[0012] Details of the subject matter described herein, both as to its structure and operation, may be apparent from examination of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, with emphasis instead being placed on illustrating the principles of the subject matter. Also, all illustrations are intended to convey concepts, and relative sizes, shapes, and other detailed attributes may be illustrated diagrammatically, rather than literally or precisely.

[0013] [Figure 1A] FIG. 1A is a schematic diagram of an exemplary embodiment of a neutron beam system.

[0014] [Figure 1B] FIG. 1B is a schematic diagram of another exemplary embodiment of a neutron beam system.

[0015] [Diagram 2] FIG. 2 is a cross-sectional view depicting an exemplary embodiment of a target assembly subsystem.

[0016] [Figure 3-1] 3A, 3B, and 3C are cross-sectional, front perspective, and rear perspective views depicting an exemplary embodiment of a neutron generating target. [Figure 3-2] 3A, 3B, and 3C are cross-sectional, front perspective, and rear perspective views depicting an exemplary embodiment of a neutron generating target.

[0017] [Figure 4] 4A-4B are cross-sectional views depicting an exemplary embodiment of a neutron generating target.

[0018] [Diagram 5] FIG. 5 is a cross-sectional view depicting an exemplary embodiment of a neutron generating target.

[0019] [Figure 6] 6A-6C are cross-sectional views depicting exemplary embodiments of neutron generating targets.

[0020] [Figure 7] 7A-7B are cross-sectional views depicting an exemplary embodiment of a neutron generating target.

[0021] [Figure 8] FIG. 8 is a graph depicting X-ray photoelectron spectroscopy (XPS) data experimentally collected from a sample coupon.

[0022] [Figure 9] FIG. 9 includes a time series of top-down photographs depicting an exemplary embodiment of a target with a passivation region comprising lithium fluoride.

[0023] [Figure 10] 10A-10C include a time series of top-down photographs depicting a bare lithium substrate (left) adjacent to an exemplary embodiment of a target (right).

[0024] [Figure 11] FIG. 11 is a graph depicting the XPS data experimentally collected from a sample coupon. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Before the present subject matter is described in detail, it is to be understood that this disclosure is not limited to particular embodiments described, which may, of course, vary. It is also to be understood that 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.

[0026] Neutron generating targets and other high energy devices or structures often have corrosive and / or mobile chemical components, such as lithium. Exemplary embodiments of systems, devices, and methods for passivation or protection of these corrosive and / or mobile materials are described herein. For ease of discussion, the material that is intended to be passivated or protected may be referred to herein as the target material. The passivation region can be configured to hold or maintain the target material in place by inhibiting diffusion of the target material into (and through) the passivation region. The passivation region can also be configured to isolate the target material from chemicals in the surrounding environment, thereby protecting the target material from contaminants (e.g., air components such as nitrogen and oxygen or water components such as hydrogen and oxygen) and other undesired corrosive reactions.

[0027] The applications in which the target material is used may vary widely. Exemplary embodiments of passivation for target materials in this wide variety of applications are described herein. A non-exhaustive list of applications includes: nuclear reactors for research or energy generation and commercialization, such as nuclear fusion and fission reactors; particle accelerators used for medical applications (such as medical diagnostic systems, medical imaging systems, or radiotherapy systems), scientific tools, industrial or manufacturing processes (such as semiconductor chip manufacturing), material property modification (such as surface treatment), food irradiation, or pathogen destruction in medical sterilization; and imaging applications such as cargo or container inspection.

[0028] For ease of explanation, many of the embodiments described herein will be so conducted in the context of a radiation therapy system that uses a lithium target material as a neutron generating material in a neutron generating target configured for use in BNCT. The embodiments can be used with other neutron generating materials, such as beryllium (Be). The embodiments are not limited to neutron production or BNCT applications. (Example BNCT Applications)

[0029] Turning in detail to the figures, FIG. 1A is a schematic diagram of an exemplary embodiment of a beam system 10 for use with embodiments of the present disclosure. In FIG. 1A, the beam system 10 includes a source 12, a low energy beam line (LEBL) 14, an accelerator 16 coupled to the low energy beam line (LEBL) 14, and a high energy beam line (HEBL) 16 extending from the accelerator 16 to a target 100. The LEBL 14 is configured to transport a beam from the source 12 to an input of the accelerator 16, which is then configured to generate a beam by accelerating the beam transported by the LEBL 14. The HEBL 18 transfers the beam from an output of the accelerator 16 to the target 100. The target 100 may be a structure configured to generate a desired result or modify a property of the beam in response to a stimulus applied by the incident beam. The target 100 may be a component of the system 10 or may be a workpiece that is prepared or manufactured, at least in part, by the system 10.

[0030] FIG. 1B is a schematic diagram illustrating another exemplary embodiment of a neutron beam system 10 for use in boron neutron capture therapy (BNCT). Here, the source 12 is an ion source and the accelerator 16 is a tandem accelerator. The neutron beam system 10 includes a preaccelerator system 20 that serves as a charged particle beam injector, a high voltage (HV) tandem accelerator 16 coupled to the preaccelerator system 20, and a HEBL 18 that extends from the tandem accelerator 16 to a neutron target assembly 200 that houses a target 100 (not shown). In this embodiment, the target 100 is configured to generate neutrons in response to being struck by protons of sufficient energy and may be referred to as a neutron generating target. The neutron beam system 10 and the preaccelerator system 20 may also be used for other applications, such as those other examples described herein, and are not limited to BNCT.

[0031] The preaccelerator system 20 is configured to transport the ion beam from the ion source 12 to the input (e.g., input aperture) of the tandem accelerator 16, and thus also serves as the LEBL 14. The tandem accelerator 16, powered by a coupled high-voltage power supply 42, is capable of generating a proton beam with an energy generally equal to twice the voltage applied to acceleration electrodes located within the accelerator 16. The energy level of the proton beam can be achieved by accelerating a beam of negative hydrogen ions from the input of the accelerator 16 to the innermost high potential electrode, stripping two electrons from each ion, and then accelerating the resulting protons downstream with the same applied voltage.

[0032] The HEBL 18 can transport the proton beam from the output of the accelerator 16 to a target in a neutron target assembly 200, which is positioned at the end of a beamline branch 70 that extends into a patient treatment room. The system 10 can be configured to direct the proton beam to any number of one or more targets and associated treatment areas. In this embodiment, the HEBL 18 includes three branches 70, 80, and 90 that can extend into three different patient treatment rooms, where each branch can terminate in a target assembly 200 and downstream beam shaping devices (not shown). The HEBL 18 can include a pump chamber 51, quadrupole magnets 52 and 72 to prevent beam defocusing, dipole or bending magnets 56 and 58 to steer the beam into the treatment room, a beam corrector 53, diagnostic devices such as current monitors 54 and 76, a fast beam position monitor 55 section, and a scanning magnet 74.

[0033] The design of the HEBL 18 depends on the configuration of the treatment facility (e.g., one-story configuration of the treatment facility, two-story configuration of the treatment facility, etc.). The beam can be delivered to a target assembly (e.g., located near the treatment room) 200 by use of bending magnets 56. Quadrupole magnets 72 can then be included to focus the beam to a size at the target. The beam then passes through one or more scanning magnets 74, which provide lateral movement of the beam onto the target surface in a desired pattern (e.g., spiral, curvilinear, stepped in rows and columns, combinations thereof, and others). The lateral movement of the beam can help achieve a smooth and uniform time-averaged distribution of the proton beam on the lithium target, prevent overheating, and make neutron generation within the lithium layer as uniform as possible.

[0034] After entering the scanning magnet 74, the beam can be delivered into a current monitor 76 that measures the beam current. The target assembly 200 can be physically separated from the HEBL volume using a gate valve 77. The main function of the gate valve is to separate the vacuum volume of the beamline from the target during target loading and / or replacement of a used target with a new one. In an embodiment, the beam may not be bent 90 degrees by the bending magnet 56, but rather it travels straight to the right in FIG. 1B and then enters the quadrupole magnet 52 located in the horizontal beamline. The beam may subsequently be bent to the required angle by another bending magnet 58, depending on the building and room configuration. Otherwise, the bending magnet 58 may be replaced with a Y-shaped magnet to split the beamline into two directions for two different treatment rooms located on the same floor.

[0035] FIG. 2B is a cross-sectional drawing depicting an exemplary embodiment of the target assembly subsystem 200 of the neutron beam system 10 shown in FIG. 1B. In this embodiment, the neutron generating target 100 is enclosed between the cap 202 and the vacuum or near-vacuum interior region 210 of the HEBL 18. Arrow B indicates the direction of the charged particle (e.g., proton) beam that first impinges on the upstream face 112. Cooling of the target 100 can be accomplished on the opposite downstream side 114 (from which the neutron beam exits the target 100). The cap 202 is bolted to the HEBL 18 and can thus provide both a vacuum-tight seal 206 between the target 100 and the vacuum region 210 of the HEBL 18 and a water-tight seal 205 between the target 100 and the coolant inlets 204 and outlets 208. Exemplary Embodiments of Passivation Regions

[0036] FIG. 3A is a cross-sectional view depicting an exemplary embodiment of a passivated neutron generating target 100 for BNCT. FIGS. 3B and 3C are perspective views of the upstream side 112 and downstream side 114 of the target 100, respectively. The target 100 includes a target material in a region 110. Some examples of target materials are lithium (e.g., naturally abundant lithium or lithium-7) and beryllium. At a location upstream (e.g., above) the region 110, the target 100 includes a passivation region 302 configured to protect the region 110, such as by inhibiting diffusion as described herein. The passivation region 302 and the region 110 can be configured in a variety of different shapes, including, for example, being planar, concave, convex, round, spherical or hemispherical, conical, irregular, and / or any combination thereof.

[0037] In this embodiment, region 110 is configured as a planar neutron generating layer that is bonded to a substrate structure 120 on a first (or upstream) surface 121 of substrate 120. A proton beam propagating in direction B (e.g., from tandem accelerator 16 along HEBL 18 (not shown)) passes through passivation region 302 and then interacts with layer 110, generating neutrons that then pass through substrate 120 and exit downstream side 114 of target 100. The neutron generation process converts the target material (e.g., lithium) into a radioactive isotope (e.g., beryllium, 7Be).

[0038] The substrate 120 can be configured for heat removal to dissipate the high energy level of the incident proton beam. The passivation region 302 and the neutron generating layer 110 preferably have a total thickness that allows the protons to exit the layer 110 relatively soon after the proton energy falls below the nuclear reaction threshold for neutron formation (e.g., 1.88 MeV for lithium-7). This avoids further energy dissipation in the layer 110, which would be inefficient and lead to heating of the layer 110 without neutron production. The protons can penetrate the neutron generating material layer 110 to the substrate 120 and dissipate their remaining energy in the substrate 120, or partially in the substrate 120 and partially in another component located downstream of the target 100. The substrate 120 can be made of a material with high thermal conductivity, such as, for example, copper (Cu), copper-diamond powder composite, CVD diamond, etc. The target 100 can include one or more materials to inhibit blistering, such as a tantalum layer between the layer 100 and the substrate 120. The downstream side 114 of the substrate 120 can be actively cooled by coolant flow through channels 122 designed to remove heat (e.g., about 25 kilowatts (kW) of heat output). The channels 122 can have a spiral configuration as depicted in FIG. 3C or another configuration as desired.

[0039] The target material of layer 110 may be a highly mobile or diffusive material, such as lithium. Passivation region 302 may be configured to inhibit (e.g., seal against, substantially inhibit, or completely prevent) diffusion of the target material within layer 110 in a downstream-to-upstream direction into (or through) region 302, where the target material may come into contact with another substance or the surrounding environment. Inhibition of diffusion of the target material may be accomplished by one or more different materials in one or more layers of region 302. In some exemplary embodiments, passivation region 302 is configured to inhibit diffusion of at least 1×10 -13 Square centimeters per second (cm 2On the other hand, having a diffusion coefficient for the target material of less than (units per second), in another embodiment, region 302 can have a diffusion coefficient for the target material of 1×10 -14 cm 2 / second or less, and still in another embodiment, region 302 can have a diffusion coefficient for the target material of 1×10 -15 cm 2 / second or less. An exemplary embodiment of the passivation region 302 where the target material is lithium has a diffusion coefficient for lithium of 5×10 -14 cm 2 / second or less, and in some embodiments can have a diffusion coefficient for lithium of 5×10 -15 cm 2 / second or less. All of the foregoing coefficients are measured at 25 degrees Celsius and can be a property of any one or more of the materials or layers of region 302 (e.g., layer 310 and / or layer 410), or of region 302 as a whole. For ease of explanation, this property of suppressing the diffusion of the target material may be referred to herein as the target barrier property. In the embodiments of FIGS. 3A - 3C, layer 310 is configured to exhibit this target barrier property.

[0040] In embodiments where lithium is employed as the target material, this property may also be referred to as the lithium barrier property. The lithium barrier property can be exhibited in the passivation region 302 by a variety of different materials. Examples of such materials that can be used with all of the embodiments described herein are one or more of lithium fluoride (LiF), lithium sulfide (Li2S), or any other compound that is thermodynamically stable with Li, magnesium fluoride (MgF2), carbon (C), diamond - like carbon, (ultra)nanocrystalline diamond, or a polymer such as parylene (or can include them). Other materials known to suppress the diffusion of lithium can also be used without departing from the scope of the present disclosure. Similarly, without departing from the scope of the present disclosure, these or other materials, such as beryllium, for example, can be used for embodiments where the target material is different from lithium.

[0041] In neutron generation applications, materials exhibiting reactant barrier properties that also include a neutron generating material (e.g., lithium or beryllium) can provide additional benefits of neutron generation during use (e.g., in addition to the neutron generating layer). In embodiments in which the neutron generating material is lithium, the material exhibiting lithium barrier properties can therefore be, by way of example, lithium fluoride and / or lithium sulfide. Lithium-containing materials such as lithium nitride (Li3N), lithium oxide (Li2O), and lithium hydroxide (LiOH) do not exhibit substantially low lithium diffusion coefficients and, in certain embodiments, are not used to exhibit lithium barrier properties (e.g., as layer 310). Preferably, the lithium barrier material does not directly contaminate or corrode lithium and is not (or does not include) a material such as aluminum or an alloy of aluminum. In some embodiments, the lithium barrier material is not beryllium or a combination of metals such as beryllium and aluminum.

[0042] In some embodiments, the target barrier material does not form a eutectic combination with the target material (a combination that has a melting point less than the melting points of the constituent materials taken individually. When the target material is lithium, some embodiments can omit materials that form a eutectic combination with lithium, such as aluminum, silver, gold, bismuth, palladium, or zinc, or alloys of aluminum, silver, gold, bismuth, palladium, or zinc.

[0043] Region 302 can also be configured to seal against ingress and diffusion of externally supplied substances (e.g., substances from the ambient environment such as any one or combination of air, moisture, oxygen, nitrogen, carbon dioxide, hydrogen, or other gases) in an upstream-to-downstream direction into (or through) region 302. If such substances get into target 100, they can potentially contaminate or react with (e.g., oxidize) the target material in layer 110. For ease of explanation, this property may be referred to herein as ambient barrier property. Ambient barrier property may be exhibited in environments with normal atmospheric pressure (e.g., 1 atmosphere (atm)), higher pressure environments, or lower pressure environments (e.g., vacuum or near vacuum). Ambient barrier property may be exhibited in passivation region 302 by a variety of different materials. Examples of such materials are (or may include) one or more of aluminum, silver, gold, titanium, stainless steel, aluminum silicon (AlSi), molybdenum, tungsten, tungsten carbide, tantalum, platinum, or other contamination barrier materials. Other materials known to inhibit or prevent the diffusion of contaminants in the target material may also be used without departing from the scope of the present disclosure.

[0044] In some exemplary embodiments, the ambient barrier properties are gas permeabilities ((cubic centimeters (cc) x millimeters (mm)) / (square meters (m) at 25 degrees Celsius) for oxygen, nitrogen, and carbon dioxide of 100 or less, preferably 3.1 or less. 2 In some exemplary embodiments, in addition to any of these gas permeabilities, the ambient barrier properties can have a water vapor transmission rate (WTVR) (measured in (grams (g)×mm) / (m at 100° F. and 90% relative humidity) of 0.6 or less, more preferably 0.09 or less. 2 The patient may have a mean age of 18 years or more (measured in 100 × days).

[0045] The target and ambient barrier properties need not be permanent, but rather may be robust to inhibit diffusion for a length of time that is practically useful for a particular application, which may vary as described herein (e.g., one or more hours, one or more days, one or more weeks, one or more months).Embodiments of the passivation region 302 disclosed herein can be used to protect neutron generating materials for periods of time as long as one month or more.

[0046] Passivation region 302 may be immediately adjacent and in contact with layer 110, or may be separated by one or more other layers or regions. In the embodiment of Figures 3A-3C, passivation region 302 is comprised of only one layer 310 that exhibits reactant barrier properties (e.g., lithium fluoride). Layer 310 may be further configured to exhibit ambient barrier properties (e.g., lithium fluoride for short duration applications).

[0047] 4A is a cross-sectional view depicting another exemplary embodiment of a neutron generating target 100 with a passivation region 302. In this embodiment, region 302 includes a passivation layer 310 (positioned upstream of layer 110 as in the previous embodiment) and an additional passivation layer 410 positioned upstream and adjacent to layer 310. Layer 410 may be referred to as the upstream layer 410, and layer 310 may be referred to as the downstream layer 310. The upstream layer 410 may be placed on a first upstream surface of the downstream layer 310, which in turn may be placed on a first upstream surface of layer 110. One or more additional layers or films may be present in region 302, such as the intervening layers described with respect to FIG. 4B.

[0048] In the embodiment of FIG. 4A, downstream layer 310 exhibits lithium barrier properties and inhibits the lithium of layer 110 from diffusing upward to layer 410. Layer 310 can be, for example, lithium fluoride or any of the other lithium barrier materials disclosed herein. Upstream passivation layer 410 exhibits ambient barrier properties and inhibits the ingress and diffusion of externally sourced substances that may contaminate or corrode the lithium of layer 110. Layer 410 can be, for example, aluminum or any of the other ambient barrier materials described herein. Thus, the bilayer configuration of region 302 allows layer 410 to be composed of a material with excellent sealing or barrier properties that would otherwise corrode the lithium of layer 110 and reduce the effectiveness of the lithium's neutron generating capabilities. Layer 310 serves as a non-reactive barrier that inhibits the migration of lithium in contact with layer 410, thus minimizing any damaging or otherwise undesirable reactions. Such a configuration is particularly desirable when the target material is highly mobile, as is the case with lithium.

[0049] In some exemplary embodiments, the thickness of passivation region 302 (e.g., the thickness of layer 310 when present alone, or the combined thickness of layers 310 and 410) does not exceed 3 microns in BNCT applications to minimize energy reduction of incoming protons, although region 302 is not so limited. In other embodiments, region 302 does not exceed 10 microns in thickness, and in still other embodiments, region 302 does not exceed 50 microns in thickness. The particular thickness selected depends on the application, e.g., accelerating voltage or other potential difference, etc. For region 302 with multiple layers (e.g., 310 and 410), the thickness of each layer depends on the specific application and the desired degree of diffusion inhibition. Thus, a wide range of thicknesses is within the scope of the present disclosure.

[0050] 4B is a drawing of a cross-section depicting another exemplary embodiment of a neutron generating target 100 with multi-layer passivation. Here, region 302 includes three passivation layers: downstream layer 310, upstream layer 410, and intermediate layer 450 located between layers 310 and 410. Intermediate layer 450 can promote adhesion between layers 310 and 410, assist in stress relief (e.g., as a polymer, shape memory alloy, etc.), or perform other functions. Intermediate layer 830 can also prevent diffusion of materials between layers 310 and 410. In some embodiments, the layers can be deposited sequentially such that downstream layer 310 is deposited on the upstream surface of neutron generating material 110, intermediate layer 450 is deposited on the upstream surface of layer 310, and upstream layer 410 is deposited on the upstream surface of intermediate layer 450. Layers 310, 410, and / or 450 can be positioned (e.g., on layer 110) through any applicable manufacturing technique, such as deposition (e.g., chemical vapor deposition), sputtering, or by use of adhesives, mechanical forces, or other mechanisms for attachment. The desired thickness of intermediate layer 450 depends on the specific application and environment for the neutron generating target. Thus, a variety of thicknesses are within the scope of this disclosure.

[0051] Figures 5-7B will be used to illustrate additional exemplary embodiments with passivation. These embodiments have either a single passivation layer in region 302 (Figure 7A) or two passivation layers in region 302. However, the embodiments of Figures 5-7B can be configured with one, two, three or more passivation layers in region 302, respectively.

[0052] 5 is a cross-sectional view depicting an additional exemplary embodiment of a neutron-generating target 100 in which passivation covers both the top and sides of the neutron-generating layer 110. Here, the passivation region 302 includes layers 310 and 410 that are deposited (or otherwise positioned) over the top upstream face 111A of the neutron-generating layer 110 and over the lateral sides 111B and 111C (which may be the same sides, e.g., as in the case of a round target 100). Both layers 310 and 410 terminate at a location downstream of (e.g., below) the downstream face 121. In this embodiment, the lateral sides 111B and 111C of layer 110 are flush with the sides of the substrate 120, although that may vary. Additionally, although passivation layers 310 and 410 are depicted as thinning as they extend from upstream face 111A to side faces 111B and 111C, their thickness can be maintained across all surfaces (e.g., an even or uniform coverage).

[0053] 6A-6C are cross-sectional views depicting additional exemplary embodiments of the target 100 with passivation. In these embodiments, the substrate 120 includes sidewalls 602B and 602C that partially enclose an interior volume, such as a recess or cavity, in which the neutron generating material 110 is deposited (or otherwise located). The downstream surface of the material 110 is bonded to the upstream surface 121 of the recess of the substrate 120, such as through adhesion, interference fit, or other manner of attachment. The recess in the substrate 120 can be machined or etched into the substrate 120. The substrate 120 can also (or alternatively) be of multi-piece construction, with relatively tall sidewall portions 602B (adjacent to 111B) and 602C (adjacent to 111C) attached to a central portion 602D to form the recess. In these embodiments, side protection is provided primarily by the substrate 120 to the layer 110.

[0054] In the embodiment of Figure 6A, passivation region 302 includes two passivation layers 310 and 410, both of which are also located within a recess in substrate 120. In some embodiments, the furthest upstream surface 411 of region 302 (e.g., of layer 402) may be flush with the furthest upstream surface 611 of substrate 120, as shown in Figure 6A. In the embodiment of Figure 6B, layer 110 is again located within a recess, and passivation region 302 again includes two passivation layers 310 and 410. However, in this example, both passivation layers 310 and 410 are located above a recess in layer 110 and substrate 120. Here, the furthest upstream surface 111A of layer 110 is flush with the furthest upstream surface 611 of substrate 120, although embodiments may vary. In the embodiment of Figure 6C, layer 110 and downstream passivation layer 310 are positioned within a recess, while upstream passivation layer 410 is positioned above a recess in layer 310 and substrate 120. Here, the furthest upstream surface 311 of layer 310 is flush with the furthest upstream surface 611 of substrate 120, but again, embodiments may vary. In embodiments with intermediate layer 450, that layer 450 can be positioned within a recess with layers 310 and 410 (Figure 6A), above a recess with layers 310 and 410 (Figure 6B), or either within or above the recess (as is permitted in the embodiment of Figure 6C).

[0055] 7A and 7B are cross-sectional views depicting additional exemplary embodiments of a neutron generating target 100. In the embodiment of FIG. 7A, layer 110 is located on the upstream surface 611 of substrate 120. Passivation region 302 includes layer 310 positioned over layer 110 such that all surfaces 111A, 111B, and 111C are covered. In the embodiment of FIG. 7B, region 302 includes layer 310 positioned over layer 110 such that all surfaces 111A, 111B, and 111C are covered, and layer 410 positioned over layer 310 such that all surfaces of layer 310 are covered. In other words, layer 310 encapsulates layer 110, and layer 410 encapsulates both layers 310 and 110. These embodiments can be relatively easy to manufacture, for example, using sequential deposition steps for each of the layers (eg, 110, 310, and 410) without the formation of recesses.

[0056] In the embodiments of Figures 3A and 4A-7B, the various layers (e.g., layers 110, 310, 410, and / or 450) are shown with thicknesses not to scale relative to one another and relative to the thickness of substrate 120, with emphasis instead being placed on the relative positions of the layers with respect to one another. Additionally, to the extent that the layers (e.g., layers 110, 310, 410, and / or 450) are shown as having various cross-sectional profiles, such as rectangular side profiles with sharp edges (e.g., Figures 3A, 4A, 4B, and 6A-6C), or spherically shaped profiles with rounded edges (e.g., Figures 5 and 7A-7B), or definite linear boundaries between layers, those representations are merely examples and may vary according to the needs of a particular application. Each embodiment described herein can be comprised of layers having any cross-sectional profile, blended boundaries or definite linear or nonlinear boundaries, and / or any combination thereof.

[0057] Among other benefits, the exemplary embodiments described herein can dramatically simplify the transport of target materials (e.g., lithium) from a production location (e.g., laboratory space, dry room, glove box, or other) to a working environment (e.g., for producing neutrons for BNCT applications). In applications where the target material is the plasma-facing component, the upstream (e.g., most upstream) passivation layer of the passivation region can be configured so that it interacts with the plasma without contaminating the plasma. Alternatively, the upper passivation layer can be configured to burn off during initial plasma interaction or chamber wall conditioning. In such an embodiment, the target material would remain exposed to the plasma for interaction purposes, and one or more passivation layers would have succeeded in providing a protective coating for the transport of the target material from the production location to the working environment. (Experimental Results)

[0058] FIG. 8 is a graph depicting experimentally collected data from a sample piece in which high purity aluminum was deposited on clean lithium metal, which was then exposed to air. X-ray photoelectron spectroscopy (XPS) was used to collect the spectral data depicted here, which shows the composition of species on the surface of the deposited aluminum (within a few nanometers) two weeks after the original aluminum deposition. These results show that no aluminum remained on the surface at this point. For this sample, it was concluded that the lithium diffused easily through the surface layer of aluminum and then reacted with components in the air. The aluminum may have diffused into the underlying lithium layer. In embodiments in which the target material is lithium or another highly mobile species, the passivation region 302 preferably has the ability to substantially inhibit or even prevent lithium from diffusing through the passivation region to locations where it could react without other components (e.g., oxygen, water, and carbon dioxide).

[0059] FIG. 9 includes a series of top-down photographs (upstream to downstream) depicting an exemplary embodiment of a target 100 configured as depicted in the cross-sectional view of FIG. 7A, in which a neutron-generating layer 110, consisting primarily of naturally abundant lithium, is covered by a passivation region 302 having only one passivation layer 310, consisting of lithium fluoride. In this example, layer 310 has a thickness of 500 nm. The target 100 was removed from the inert gas atmosphere in a glove box and placed in an ambient laboratory setting with a normal atmosphere having a humidity level of 50%. Each photograph was taken at a specific time measured from approximately the first moment (time zero) that the target 100 was first exposed to the atmosphere in the laboratory setting. Time zero is the photograph at zero minutes (0 min) labeled at the top left, the second photograph from the left on the top row was taken 30 seconds (0.5 min) after time zero, the middle photograph on the top row was taken 1 minute (1 min) after time zero, and so on until the final photograph is taken 170 minutes after time zero (bottom row, far right).

[0060] Naturally abundant lithium typically reacts almost immediately with the surrounding atmosphere (e.g., 20-60% relative humidity) and can form a dark lithium nitride (Li3N) topcoat within seconds (e.g., 10-30 seconds) of air exposure. Here, at time zero, the lithium visible through the LiF topcoat appears shiny (the same appearance as it would have in a glove box), indicating little or no reaction of the lithium with its surroundings. After a few minutes, the color of the target 100 turns yellow (e.g., 2 minutes), then brown (e.g., 4 minutes), and then finally turns dark purple or black after 1 or 2 hours, indicating Li3N formation on the lithium-LiF interface 311. Thus, the LiF passivation layer 310 substantially retards lithium contamination, thereby providing a substantial improvement over targets without passivation and those with only an aluminum passivation layer as described with respect to FIG. 8.

[0061] 10A-10C include a series of top-down photographs (upstream to downstream) depicting a bare lithium substrate 900 (left) adjacent to an exemplary embodiment of a target 100 (right). Substrate 900 comprises a copper substrate with a bare coating of naturally abundant lithium and has no passivation regions. The lithium is available to react freely with the surrounding atmosphere. The target 100 is configured as depicted in the cross-sectional view of FIG. 7B, in which the neutron generating layer 110 is made of naturally abundant lithium, which is covered by a passivation region 302 having two passivation layers 310 and 410. The cooling channels have been omitted. Layer 310 is made of LiF with a thickness of 900 nm, and layer 410 is made of aluminum with a thickness of 400 nm.

[0062] Both samples were removed from the inert gas atmosphere in a glove box and placed in an ambient laboratory setting with a normal atmosphere having 50% humidity. The photograph in FIG. 10A was taken 1 minute after the approximate moment that the target 100 and substrate 900 were first exposed to the air in the laboratory setting. The photograph in FIG. 10B was taken 3 minutes after the first exposure, and the photograph in FIG. 10C was taken 125 minutes after the first exposure. The bare lithium substrate 900 reacted almost immediately with the ambient atmosphere, already discoloring at 1 minute, turning a darker shade of purple at 3 minutes, and finally turning black at 125 minutes. Conversely, the target 100 shows little or no discoloration even at 125 minutes. The absence of lithium discoloration was subsequently confirmed by inspection upon removal of the aluminum layer 410. These results, when considered in combination with those in FIGS. 8 and 9, show that the bilayer passivation region 302 adequately protects the lithium layer 110 from contamination such as nitride formation, even after 2 hours of exposure. In other words, LiF layer 310 substantially inhibited lithium from diffusing upstream through layer 310, and aluminum layer 410 substantially inhibited atmospheric reactants from diffusing downstream through layer 410.

[0063] FIG. 11 is a graph depicting experimentally collected data from an exemplary target 100 constructed similarly to that described with respect to FIGS. 10A-10C, where a layer of naturally abundant lithium was coated with a LiF layer 310 (900 nm thick), which was then coated with an aluminum layer 410 (400 nm thick). The target was then exposed to air for several days. X-ray photoelectron spectroscopy (XPS) was used to collect the spectral data depicted in FIG. 11. Unlike the results of FIG. 8, where no aluminum remained on the surface of the aluminum coating, the results here show that the surface composition of the aluminum layer 410 still includes aluminum. This indicates that although some lithium is present on the surface, the LiF layer 310 has substantially prevented the migration of lithium to the aluminum surface where it would otherwise have reacted and hidden the aluminum, as occurred in the example of FIG. 8. Exemplary Embodiments of Passivation Region Thickness

[0064] Tables 1-4 provide modeled values ​​to facilitate describing thickness characteristics of several embodiments of passivation regions 302 used with an exemplary BNCT application in which a proton beam collides with a target lithium layer on a substrate to generate neutrons. Neutron generating targets typically do not lend themselves to the use of a thick passivation region over the neutron generating material because the thick passivation region reduces the energy of the incident protons, decreasing the effectiveness of neutron generation.

[0065] Table 1 illustrates the range (sometimes referred to as the stopping range) of incident proton particles in naturally abundant lithium (about 92% lithium-7) for several proton energies. In the right column, the variable "depth to threshold" is listed and represents the distance an average proton travels inside the material before it slows down to the threshold energy for the 7Li(p,n)7Be reaction (about 1.88 MeV). After a proton is slowed down beyond this threshold energy, it can no longer produce neutrons. For example, for a proton energy of 2.50 megaelectron volts (MeV), a high-energy proton enters the lithium material and then travels about 90 microns in the lithium until it slows down to the threshold energy. In this example, if the lithium thickness is less than 90 microns (μm), the neutron yield is reduced and the lithium material is not utilized most efficiently. It is practically desirable to have a lithium layer that is thick enough for a neutron production target, but not so thick (eg, 200 μm) that the drop in proton energy below the threshold dissipates excess heat in the lithium. [Table 1]

[0066] In embodiments with a protective coating over the lithium, the protective coating will further slow down the protons. Table 2 shows the proton ranges for the same incident protons as in Table 1, but for the data in Table 2, a protective coating consisting of a 1 micron thick layer of lithium fluoride (LiF) has been added on top of the naturally abundant lithium. [Table 2]

[0067] For a proton incident energy of 2.5 MeV, a 1 micron thick LiF layer will slow down the protons by 0.03 MeV (2.5 MeV - 2.47 MeV), which slightly reduces the depth to threshold by about 4.5 microns.

[0068] Table 3 illustrates the proton ranges associated with an embodiment having a 1 micron thick downstream passivation layer 310 (LiF) and a 0.5 micron thick upstream passivation layer 410 made of aluminum over an underlying lithium layer. This configuration is similar to that described with respect to Figures 7 and 10. [Table 3]

[0069] Table 3 illustrates that a 1.5 micron thick two-layer passivation region does not slow down the protons significantly. Because the passivation region having multiple passivation layers is thin, no significant incident particle energy loss is experienced within the region.

[0070] In contrast, if the passivation region is relatively thick, the proton energy is significantly reduced, which is not necessarily desirable for a practical neutron generating device since it may be difficult to accelerate the particles to higher energies. Table 4 illustrates how a relatively thick (10 micron) protective layer of Parylene C performs when placed over naturally abundant lithium. Parylene C is a widely used polymer composed mostly of low-Z elements and is used to passivate electronic devices because Parylene C protects against moisture.

[0071] In Table 4, for the same energy of 2.50 MeV, a 10 micron layer of Parylene C slows down protons by about 0.20 MeV, thus reducing the depth to threshold by nearly 30% compared to bare lithium (Table 1), further illustrating the dependence of the depth to threshold on the thickness of the passivation region. Most metal passivations of comparable thickness will slow down protons better than polymeric Parylene C. [Table 4]

[0072] The passivation region of the embodiments described herein can form a relatively thin passivation coating. The ideal thickness of the passivation region 302 depends on the particular application, which can vary as described herein. For example, in some embodiments, the overall thickness of the passivation region 302 (measured from upstream to downstream along the beam axis (see, for example, item 303 in FIGS. 3A, 4A, and 4B)) is 100 microns or less. In some embodiments, the thickness of the passivation region 302 is 50 microns or less. In some applications, such as BNCT, an even thinner passivation region 302 is desirable but not required. For example, in these and other embodiments, the thickness of the passivation region 302 is 10 microns or less, or in some embodiments, the thickness of the passivation region 302 is 5 microns or less, or in some other embodiments, the thickness of the passivation region 302 is 3 microns or less, and in some other embodiments, the thickness of the passivation region 302 is 1 micron or less.

[0073] The thickness of the target material may be as desired to meet the needs of the application. For BNCT applications, the desired thickness may depend on the incident proton energy and may range, for example, from 10 microns to 300 microns. In an exemplary embodiment where the energy of the incident proton beam is 1.88 MeV to 3 MeV, the thickness of the lithium layer may be 10 to 200 microns, and in an exemplary embodiment where the energy of the incident proton beam is 2.25 MeV to 2.75 MeV, the thickness of the lithium layer may be 40 to 150 microns. In one exemplary embodiment, the lithium layer has a thickness of 40 to 150 microns, over which is located the bilayer passivation region 302. The downstream layer 310 may be lithium fluoride, and the upstream layer 410 may be a metal such as aluminum, titanium, stainless steel, alloys thereof, etc. The thickness of the region 302 may be according to any of the embodiments described herein. In one exemplary embodiment, layer 310 has a thickness in the range of 200-400 nm and layer 410 has a thickness in the range of 500-800 nm.

[0074] In some exemplary embodiments, the passivation region 302 (e.g., all or a portion thereof, such as layers 310, 410, 450, etc.) can be removed during operation of the system in which it is installed. For example, in BNCT applications, the incidence of a particle beam on the passivation region 302 can remove (e.g., ablate or burn) the region 302 from the target 100 during operation. The removal can be the result of an increase in temperature within the region 302 as a result of the high energy particle beam. The resulting neutron generating reaction can also facilitate this decomposition of the region 302. The removal of the region 302 can increase the efficiency of neutron generation by the neutron generating layer 110 by reducing the energy loss experienced by incoming particles slowing down through the passivation region 302. The particle beam can be moved (e.g., rastered) across the target surface, and all or a portion of the region 302 can be removed over a small area of ​​the target's surface where the incidence of the particle beam on the target is at a relatively highest level (e.g., duration) compared to surrounding areas of the target.

[0075] The embodiments described herein may also find applicability in battery design and manufacturing. The rapidly developing lithium battery industry suffers from the limited sensitivity of lithium to humid atmospheres. The embodiments described herein may be applied when the device to be protected or passivated is a metallic lithium anode of a battery. The embodiments may simplify and reduce the cost of fabricating metallic lithium anodes that are stable and dendrite-free in ambient atmosphere (e.g., air).

[0076] Various aspects of the present subject matter are described below with a review of and / or in supplement to the previously described embodiments, with emphasis placed on the interrelationships and compatibility of the following embodiments, in other words, the fact that each feature of the embodiments can be combined with any and all other features, unless expressly stated otherwise or logically impossible.

[0077] In various embodiments, the neutron generating target includes a substrate, a neutron generating region positioned over the substrate, and a passivation region positioned over the neutron generating region, In some of these embodiments, the neutron generating region includes a target material configured to generate neutrons, and the passivation region is configured to seal against diffusion of the target material into the passivation region.

[0078] In some of these embodiments, the passivation region is 1×10 -13 Square centimeters per second (cm 2 / sec) or less for the target material. In some of these embodiments, the passivation region has a diffusion coefficient of 1×10 -14 cm 2 In some of these embodiments, the passivation region has a diffusion coefficient for the target material of less than 1×10 -15 cm 2 1 / sec or less for the target material.

[0079] In some of these embodiments, the target material is lithium. In some of these embodiments, the passivation area is 5×10 -14 cm 2 1 / sec or less.

[0080] In some of these embodiments, the target material is lithium. In some of these embodiments, the passivation area is 5×10 -15 cm 2 1 / sec or less.

[0081] In some of these embodiments, the passivation region comprises lithium fluoride.

[0082] In some of these embodiments, the passivation region comprises lithium fluoride, lithium sulfide, magnesium fluoride, carbon (C), diamond-like carbon, (ultra)nanocrystalline diamond, or a polymer.

[0083] In some of these embodiments, the passivation region includes lithium. In some of these embodiments, the passivation region does not include lithium nitride, lithium oxide, or lithium hydroxide.

[0084] In some of these embodiments, the passivation region comprises a layer in contact with the target material, hi some of these embodiments, the layer does not comprise aluminum or beryllium.

[0085] In some of these embodiments, the passivation region has a thickness of 10 microns or less.

[0086] In some of these embodiments, the passivation region has a thickness of 3 microns or less.

[0087] In some of these embodiments, the target is configured for use in a boron neutron capture therapy (BNCT) procedure.

[0088] In some of these embodiments, the target is configured to generate neutrons when exposed to a proton beam having an energy between 1.88 and 3.0 megaelectron volts (MeV).

[0089] In some of these embodiments, the passivation regions are configured to be removed during operation.

[0090] In some of these embodiments, the target material comprises lithium.

[0091] In some of these embodiments, the passivation region does not include a eutectic combination of the target material with another material.

[0092] In various embodiments, the neutron generating target includes a substrate, a neutron generating region positioned over the substrate and including a target material configured to generate neutrons, and a passivation region positioned over the neutron generating region and including a downstream layer and an upstream layer, In some of these embodiments, the downstream layer is configured to seal against diffusion of the target material into the passivation region.

[0093] In some of these embodiments, the downstream layer is 1×10 -13 Square centimeters per second (cm 2 / sec) or less for the target material. In some of these embodiments, the downstream layer has a diffusion coefficient of 1×10 -14 cm 2 In some of these embodiments, the downstream layer has a diffusion coefficient for the target material of less than 1×10 -15 cm 2 1 / sec or less for the target material.

[0094] In some of these embodiments, the target material is lithium. In some of these embodiments, the downstream layer is 5×10 -14 cm 2 1 / sec or less.

[0095] In some of these embodiments, the target material is lithium. In some of these embodiments, the downstream layer is 5×10 -15 cm 2 1 / sec or less.

[0096] In some of these embodiments, the downstream layer comprises lithium fluoride.

[0097] In some of these embodiments, the downstream layer comprises lithium fluoride, lithium sulfide, magnesium fluoride, carbon (C), diamond-like carbon, (ultra)nanocrystalline diamond, or a polymer.

[0098] In some of these embodiments, the downstream layer comprises lithium. In some of these embodiments, the downstream layer does not comprise lithium nitride, lithium oxide, or lithium hydroxide.

[0099] In some of these embodiments, the downstream layer contains neither aluminum nor beryllium.

[0100] In some of these embodiments, the upstream layer is configured to seal against diffusion of ambient materials into the passivation region.

[0101] In some of these embodiments, the upstream layer is configured to seal against diffusion of materials from the atmosphere into the passivation region.

[0102] In some of these embodiments, the upstream layer is configured to seal against the diffusion of oxygen, nitrogen, and water into the passivation region.

[0103] In some of these embodiments, the upstream layer is configured to seal against diffusion of ambient materials that contact the downstream layer through the upstream layer of the passivation region.

[0104] In some of these embodiments, the upstream layer comprises aluminum, titanium, platinum, nickel, steel, silver, gold, stainless steel, aluminum silicon, molybdenum, tungsten, tungsten carbide, and / or tantalum.

[0105] In some of these embodiments, the upstream layer has a gas permeability for oxygen, nitrogen, and carbon dioxide of 100 or less, measured in (cubic centimeters x millimeters) / (square meters x day x atmosphere).

[0106] In some of these embodiments, the upstream layer has a gas permeability for oxygen, nitrogen, and carbon dioxide of 3.1 or less, measured in (cubic centimeters x millimeters) / (square meters x day x atmosphere).

[0107] In some of these embodiments, the upstream layer has a water vapor transmission rate (WTVR) of 0.6 or less, measured in (grams x millimeters) / (square meter x day).

[0108] In some of these embodiments, the upstream layer has a water vapor transmission rate (WTVR) of 0.09 or less, measured in (grams x millimeters) / (square meter x day).

[0109] In some of these embodiments, the upstream layer is in contact with the downstream layer.

[0110] In some of these embodiments, the passivation region includes an intermediate layer between the upstream and downstream layers.

[0111] In some of these embodiments, the passivation region has a thickness of 10 microns or less.

[0112] In some of these embodiments, the passivation region has a thickness of 3 microns or less.

[0113] In some of these embodiments, the target is configured for use in a boron neutron capture therapy (BNCT) procedure.

[0114] In some of these embodiments, the target is configured to generate neutrons when exposed to a proton beam having an energy between 1.88 and 3.0 megaelectron volts (MeV).

[0115] In some of these embodiments, at least a portion of the passivation region is configured to be removed during operation.

[0116] In some of these embodiments, the target material comprises lithium.

[0117] In various embodiments, a method of manufacturing a target for boron neutron capture therapy includes applying a neutron-generating region to a substrate and applying a passivation region over the neutron-generating region. In some of these embodiments, the neutron-generating region includes a target material configured to generate neutrons, and the passivation region is configured to seal against diffusion of the target material into the passivation region.

[0118] In some of these embodiments, the layer downstream of the passivation region is configured to seal against diffusion of the target material into the passivation region.

[0119] In some of these embodiments, the method further includes applying an upstream layer of the passivation region over the downstream layer, hi some of these embodiments, the upstream layer contacts the downstream layer and / or the downstream layer contacts the neutron-generating region.

[0120] In some of these embodiments, the neutron generating region and the passivation region are configured according to any of the previously described embodiments.

[0121] In some of these embodiments, the neutron generating region and the passivation region are configured according to any of the previously described embodiments.

[0122] In various embodiments, a method of generating neutrons includes applying a particle beam to a target such that particles from the particle beam generate neutrons when they traverse a passivation region and impact a neutron-generating region of the target. In some of these embodiments, the passivation region is configured to seal against diffusion of material of the neutron-generating region into the passivation region. In some of these embodiments, the method further includes continuing to apply the particle beam to the target such that at least a portion of the passivation region is removed.

[0123] In some of these embodiments, the target is configured according to any of the previous embodiments.

[0124] In some of these embodiments, the passivation region includes an upstream layer and a downstream layer, in some of these embodiments, both the upstream layer and the downstream layer are removed by continued application of the particle beam within the region of the target.

[0125] In some of these embodiments, the method is performed as part of a boron neutron capture therapy (BNCT) procedure.

[0126] In various embodiments, the target device includes a substrate including a recess, a neutron-generating region within the recess of the substrate, and a passivation region positioned over the neutron-generating region. In some of these embodiments, the passivation region includes an upstream layer and a downstream layer. In some of these embodiments, the downstream layer is located within the recess.

[0127] In some of these embodiments, the upstream layer is located within the recess. In some of these embodiments, the substrate includes a sidewall adjacent to the recess. In some of these embodiments, the downstream layer does not extend over an upstream surface of the sidewall.

[0128] In some of these embodiments, the upstream layer does not extend over the upstream face of the sidewall.

[0129] In some of these embodiments, the upstream layer extends over the upstream surface of the sidewall.

[0130] In some of these embodiments, the target is configured according to any of the previous embodiments.

[0131] In various embodiments, the target device includes a substrate and a neutron-generating region positioned over the substrate. In some of these embodiments, the neutron-generating region includes an upstream face and a sidewall face. In some of these embodiments, the target device further includes a passivation region positioned over the upstream face and the sidewall face of the neutron-generating region.

[0132] In some of these embodiments, the passivation region and the substrate enclose the neutron generating region.

[0133] In some of these embodiments, the target is configured according to any of the previous embodiments.

[0134] In various embodiments, the device includes a substrate, a first region positioned over the substrate and including lithium, and a passivation region positioned over the first region, In some of these embodiments, the passivation region is configured to seal against diffusion of lithium into the passivation region.

[0135] In some of these embodiments, the first material is lithium. In some of these embodiments, the passivation region is 5×10 -14 cm 2 1 / sec or less.

[0136] In some of these embodiments, the first material is lithium. In some of these embodiments, the passivation region is 5×10-15 cm 2 1 / sec or less.

[0137] In some of these embodiments, the passivation region comprises lithium fluoride.

[0138] In some of these embodiments, the passivation region comprises lithium fluoride, lithium sulfide, magnesium fluoride, carbon (C), diamond-like carbon, (ultra)nanocrystalline diamond, or a polymer.

[0139] In some of these embodiments, the passivation region includes lithium. In some of these embodiments, the passivation region does not include lithium nitride, lithium oxide, or lithium hydroxide.

[0140] In some of these embodiments, the passivation region has a thickness of 100 microns or less.

[0141] In some of these embodiments, the passivation region has a thickness of 50 microns or less.

[0142] In various embodiments, the device includes a substrate, a first region overlying the substrate and including lithium, and a passivation region overlying the first region and including a downstream layer and an upstream layer, In some of these embodiments, the downstream layer is configured to seal against diffusion of lithium into the passivation region.

[0143] In some of these embodiments, the downstream layer is 5×10 -14 cm 2 1 / sec or less.

[0144] In some of these embodiments, the downstream layer is 5×10 -15 cm 2 1 / sec or less.

[0145] In some of these embodiments, the downstream layer comprises lithium fluoride.

[0146] In some of these embodiments, the downstream layer comprises lithium fluoride, lithium sulfide, magnesium fluoride, carbon (C), diamond-like carbon, (ultra)nanocrystalline diamond, or a polymer.

[0147] In some of these embodiments, the downstream layer comprises lithium. In some of these embodiments, the downstream layer does not comprise lithium nitride, lithium oxide, or lithium hydroxide.

[0148] In some of these embodiments, the downstream layer contains neither aluminum nor beryllium.

[0149] In some of these embodiments, the upstream layer is configured to seal against diffusion of ambient materials into the passivation region.

[0150] In some of these embodiments, the upstream layer is configured to seal against diffusion of materials from the atmosphere into the passivation region.

[0151] In some of these embodiments, the upstream layer is configured to seal against the diffusion of oxygen, nitrogen, and water into the passivation region.

[0152] In some of these embodiments, the upstream layer is configured to seal against diffusion of ambient materials that contact the downstream layer through the upstream layer of the passivation region.

[0153] In some of these embodiments, the upstream layer has a gas permeability for oxygen, nitrogen, and carbon dioxide of 100 or less, measured in (cubic centimeters x millimeters) / (square meters x day x atmosphere).

[0154] In some of these embodiments, the upstream layer has a gas permeability for oxygen, nitrogen, and carbon dioxide of 3.1 or less, measured in (cubic centimeters x millimeters) / (square meters x day x atmosphere).

[0155] In some of these embodiments, the upstream layer has a water vapor transmission rate (WTVR) of 0.6 or less, measured in (grams x millimeters) / (square meter x day).

[0156] In some of these embodiments, the upstream layer has a water vapor transmission rate (WTVR) of 0.09 or less, measured in (grams x millimeters) / (square meter x day).

[0157] In some of these embodiments, the upstream layer comprises aluminum, titanium, platinum, nickel, steel, silver, gold, stainless steel, aluminum silicon, molybdenum, tungsten, tungsten carbide, and / or tantalum.

[0158] In some of these embodiments, the upstream layer is in contact with the downstream layer.

[0159] In some of these embodiments, the passivation region includes an intermediate layer between the upstream and downstream layers.

[0160] In some of these embodiments, the passivation region has a thickness of 100 microns or less.

[0161] In some of these embodiments, the passivation region has a thickness of 50 microns or less.

[0162] In various embodiments, a neutron beam system includes an accelerator and a beamline extending from the accelerator to a neutron generating target configured according to any of the previously described embodiments.

[0163] It should be noted that all features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combinable and substitutable with those from any other embodiment. When a feature, element, component, function, or step is described with respect to only one embodiment, it should be understood that the feature, element, component, function, or step may be used with all other features described herein, unless expressly stated otherwise. This paragraph therefore serves as a predicate and descriptive aid for the introduction of claims that combine features, elements, components, functions, and steps from different embodiments or substitute features, elements, components, functions, and steps from one embodiment with those of another embodiment at any time, even if the following description does not expressly state that such combinations or substitutions are possible in a particular case. In particular, it is expressly acknowledged that an explicit enumeration of all possible combinations and substitutions would be unduly burdensome, given that the permissibility of any and all such combinations and substitutions would be readily recognized by those skilled in the art.

[0164] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0165] While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof are shown in the drawings and described in detail herein. It is to be understood, however, that these embodiments are not limited to the particular forms disclosed, but on the contrary, these embodiments are intended to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, negative limitations that define the scope of the invention of the claims by any feature, function, step, or element of the embodiments and features, functions, steps, or elements not within its scope may be recited in or added to the claims.

Claims

1. A neutron generating target, the neutron generating target comprising: A substrate; a neutron generating region positioned over the substrate; a passivation region positioned over the neutron generating region, the passivation region comprising a first layer and a second layer; Equipped with A neutron generating target, wherein the neutron generating region comprises a target material configured to generate neutrons, the first layer of the passivation region is configured to seal against diffusion of the target material into the passivation region, the first layer being between the second layer and the target material.

2. The passivation area is 1×10 －１３ Square centimeters per second (cm ２ 13. The target of claim 1, having a diffusion coefficient for the target material of less than or equal to 1 / sec.

3. The passivation area is 1×10 －１４ cm ２ 13. The target of claim 1, having a diffusion coefficient for the target material of less than or equal to 1 / sec.

4. The passivation area is 1×10 －１５ cm ２ 13. The target of claim 1, having a diffusion coefficient for the target material of less than or equal to 1 / sec.

5. The target of claim 1 , wherein the target material is lithium.

6. The passivation region is 5 × 10 －１５ cm ２ 6. The target of claim 5, having a diffusion coefficient for lithium of 1000 .mu.m / sec or less, or 5.times.10.sup.-14 cm.sup.2 / sec or less.

7. The target of claim 1 , wherein the first layer of the passivation region comprises lithium fluoride.

8. 10. The target of claim 1, wherein the passivation region comprises lithium fluoride, lithium sulfide, magnesium fluoride, carbon (C), diamond-like carbon, (ultra)nanocrystalline diamond, or a polymer.

9. 10. The target of claim 1, wherein the passivation region comprises lithium and does not comprise lithium nitride, lithium oxide, or lithium hydroxide.

10. 10. The target of claim 1, wherein the passivation region comprises a layer in contact with the target material, the layer comprising no aluminum or no beryllium.

11. The target of claim 1 , wherein the passivation region has a thickness of 10 microns or less.

12. The target of claim 1 , wherein the passivation region has a thickness of 3 microns or less.

13. 10. The target of claim 1, configured for use in a boron neutron capture therapy (BNCT) procedure.

14. The target of claim 13 , configured to generate neutrons when exposed to a proton beam having an energy between 1.88 and 3.0 megaelectron volts (MeV).

15. The target of claim 1 , wherein the passivation region is configured to be removed during operation.

Images