Multi-beam spallation source for intense neutron generation

Abstract

A neutron generation system that includes an irradiation test cavity, a first target region housing a first solid beam target comprising an impingement surface, a second target region housing a second solid beam target comprising an impingement surface, a first beam accelerator system comprising a first beamline having a first beam pathway that impinges the impingement surface of the first solid beam target at a non-orthogonal angle, and a second beam accelerator system comprising a second beamline having a second beam pathway that impinges the impingement surface of the second solid beam target at a non-orthogonal angle.

Description

Attorney Docket No. SHINE-44080.601MULTI-BEAM SPALLATION SOURCE FOR INTENSE NEUTRON GENERATION CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 606,225, filed December 5, 2023, which is incorporated herein by reference in its entirety. TECHNOLOGY

[0002] The present disclosure is generally related to neutron generation systems. More particularly, the present disclosure is directed to accelerator-based neutron generation systems, which may be used for radiation effects testing. SUMMARY

[0003] According to one embodiment of the present disclosure, a neutron generation system includes an irradiation test cavity, a first target region housing a first solid beam target comprising an impingement surface, a second target region housing a second solid beam target comprising an impingement surface, a first beam accelerator system comprising a first beamline having a first beam pathway that impinges the impingement surface of the first solid beam target at a non-orthogonal angle, and a second beam accelerator system comprising a second beamline having a second beam pathway that impinges the impingement surface of the second solid beam target at a non-orthogonal angle.

[0004] According to another embodiment of the present disclosure, a method of generating neutrons includes directing a first ion beam generated by a first beam accelerator system of a neutron generation system into an impingement surface of a first solid beam target, thereby generating first neutrons via a spallation reaction between the first ion beam and the first solid beam target, wherein the first ion beam reaches the impingement surface traveling in a first beam direction and impinges the impingement surface of the first solid beam target at a non- orthogonal angle, and directing a second ion beam generated by a second beam accelerator system into an impingement surface of a second solid beam target, thereby generating second neutrons via a spallation reaction between the second ion beam and the second solid beam target, wherein the second ion beam reaches the impingement surface traveling in a secondAttorney Docket No. SHINE-44080.601beam direction and impinges the impingement surface of the second solid beam target at a non- orthogonal angle.

[0005] According to yet another embodiment of the present disclosure, a method of generating neutrons includes directing a first ion beam generated by a first beam accelerator system of a neutron generation system into an impingement surface of a first solid beam target, thereby generating first neutrons via a spallation reaction between the first ion beam and the first solid beam target and directing a second ion beam generated by a second beam accelerator system into an impingement surface of a second solid beam target, thereby generating second neutrons via a spallation reaction between the second ion beam and the second solid beam target, wherein the first neutrons and the second neutrons irradiate an irradiation test cavity with a neutron flux that varies by 20% or less throughout the irradiation test cavity.

[0006] These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0008] FIG. 1 schematically depicts a neutron generation system, according to one or more embodiments shown and described herein;

[0009] FIG. 2A schematically depicts a transverse view of an example neutron generation system comprising multiple solid beam targets, an irradiation test cavity, and a neutron reflector, according to one or more embodiments shown and described herein;

[0010] FIG.2B schematically depicts an aerial view of the example neutron generation system of FIG.2A, according to one or more embodiments shown and described herein;

[0011] FIG. 3A schematically depicts a transverse view of an example neutron generation system comprising multiple solid beam targets, an irradiation test cavity, a lightAttorney Docket No. SHINE-44080.601water-moderated subcritical assembly, a neutron reflector, according to one or more embodiments shown and described herein;

[0012] FIG.3B schematically depicts an aerial view of the example neutron generation system of FIG.3A, according to one or more embodiments shown and described herein;

[0013] FIG. 4A schematically depicts a transverse view of an example neutron generation system comprising multiple solid beam targets, an irradiation test cavity, a heavy water-moderated subcritical assembly, a neutron reflector, according to one or more embodiments shown and described herein;

[0014] FIG.4B schematically depicts an aerial view of the example neutron generation system of FIG.4A, according to one or more embodiments shown and described herein;

[0015] FIG.5A graphically depicts a neutron energy spectrum generated by an 18 MeV proton beam striking beryllium (Be), tantalum (Ta), tungsten (W), and uranium (U) solid beam targets, according to one or more embodiments shown and described herein;

[0016] FIG.5B graphically depicts a neutron forward-peaking profile generated by an 18 MeV proton beam striking Be, Ta, W, and U solid beam targets, according to one or more embodiments shown and described herein;

[0017] FIG.6A graphically depicts a neutron energy spectrum generated by a 30 MeV proton beam striking Be, Ta, W, and U solid beam targets, according to one or more embodiments shown and described herein;

[0018] FIG. 6B graphically depicts a neutron forward-peaking profile generated by a 30 MeV proton beam striking Be, Ta, W, and U solid beam targets, according to one or more embodiments shown and described herein;

[0019] FIG.7A graphically depicts a neutron energy spectrum generated by a 70 MeV proton beam striking Be, Ta, W, and U solid beam targets, according to one or more embodiments shown and described herein;

[0020] FIG. 7B graphically depicts a neutron forward-peaking profile generated by a 70 MeV proton beam striking Be, Ta, W, and U solid beam targets, according to one or more embodiments shown and described herein;Attorney Docket No. SHINE-44080.601

[0021] FIG. 8A depicts a thermal flux map of an example operation of the neutron generator system of FIGS. 2A and 2B, according to one or more embodiments shown and described herein;

[0022] FIG. 8B depicts a total flux map of an example operation of the neutron generator system of FIGS. 2A and 2B, according to one or more embodiments shown and described herein;

[0023] FIG. 9A depicts a thermal flux map of an example operation of the neutron generator system of FIGS. 3A and 3B, according to one or more embodiments shown and described herein;

[0024] FIG. 9B depicts a total flux map of an example operation of the neutron generator system of FIGS. 3A and 3B, according to one or more embodiments shown and described herein;

[0025] FIG. 10A depicts a thermal flux map of an example operation of the neutron generator system of FIGS. 4A and 4B, according to one or more embodiments shown and described herein;

[0026] FIG. 10B depicts a total flux map of an example operation of the neutron generator system of FIGS. 4A and 4B, according to one or more embodiments shown and described herein;

[0027] FIG. 11 graphically depicts the neutron energy spectra for the neutron generation systems of FIGS.2A and 2B, FIGS.3A and 3B, and FIGS.4A and 4B, respectively, according to one or more embodiments shown and described herein;

[0028] FIG.12 graphically depicts a normalized version of the neutron energy spectra for the neutron generation systems of FIGS.2A and 2B, FIGS.3A and 3B, and FIGS.4A and 4B, respectively, according to one or more embodiments shown and described herein; and

[0029] FIG. 13 graphically depicts a neutron energy spectrum of a variety of neutron generation systems, according to one or more embodiments shown and described herein.Attorney Docket No. SHINE-44080.601DETAILED DESCRIPTION

[0030] Referring generally to the figures, embodiments of the present disclosure are directed to a neutron generation system comprising an irradiation test cavity, multiple beam accelerator systems and multiple solid beam targets for generating neutrons via spallation reactions and optimizing the generated neutron flux in the irradiation test cavity. Each solid beam target is positioned in a target region and the beamlines of each beam accelerator system terminate at the target region such that ion beams generated by the beam accelerator systems impinge the solid beam targets. In some embodiments, the neutron generation system includes an irradiation test cavity positioned near the target regions. For example, the solid beam targets and the irradiation test cavity are positioned relative to each other to generate a substantially uniform neutron flux throughout the irradiation test cavity. Indeed, the neutron generation system described herein generates an intense, uniform neutron flux that may be useful for material testing, for example, radiation effects testing. For example, a test sample may be located in the irradiation test cavity and the neutrons generated by the neutron generation system irradiate the test sample, causing neutron-induced damage to occur. Because the neutron generation systems described herein generate a uniform neutron flux throughout the irradiation test cavity, test samples undergo uniform irradiation, improving the accuracy of neutron-induced damage test as the whole test sample is subjected to unform irradiation conditions. Moreover, the material of the solid beam targets may be adjusted (e.g., interchanged), allowing the neutron spectrum to be tailored and tuned to a particular test sample.

[0031] In some embodiments, the neutron generator system described herein relies on higher-energy ions (such as protons) striking solid beam targets, resulting in (p,xn) reactions that can be characterized as a form of spallation reaction. Without intending to be limited by theory, spallation is a process in which a light projectile (proton, or other light ion) with sufficiently high kinetic energy interacts with a heavy nucleus and causes the emission of many hadrons (mostly neutrons) or fragments. Spallation has two stages: an initial impact that results in high-energy intra-nucleus cascades and associated emission of particles with energies up to the incident energy, and deexcitation (evaporation or fission), which results in the emission of particles of much lower energy. The deexcitation phase is often a multi-body process that results in a wide energy spectrum of the resulting neutrons. For example, the9Be (p,n) reaction leaves the daughter9B nuclei in an excited state. The neutrons are then produced in multipleAttorney Docket No. SHINE-44080.601discrete peaks based on the excited state of the resultant9B. In addition, other threshold reactions can occur such as (p,np) and (p,nα) that produce neutrons with a continuum of energies. The specific neutron energy spectrum is highly dependent on both the incoming beam energy and the material the protons strike.

[0032] Referring now to FIG. 1, a neutron generation system 100 is schematically depicted. The neutron generation system 100 is a multi-beam system that includes at least a first beam accelerator system 110A configured to generate a first ion beam 125A and a second beam accelerator system 110B configured to generate a second ion beam 125B, and an irradiation test cavity 105. It should be understood that additional beam accelerator systems for generating additional ions beams are contemplated. The first beam accelerator system 110A comprises a first beamline 120A, which provides a first beam pathway 122A for the first ion beam 125A. The first beamline 120A extends from a first beam source 112A to a first target region 130A, which houses a first solid beam target 140A (FIGS. 2A-4B). A first accelerator column 114A and a first magnet 116A are positioned along the first beamline 120A and operate to accelerate and focus the first ion beam 125A. In operation, the first accelerator column 114A and the first magnet 116A help direct the first ion beam 125A into the first target region 130A. Similarly, the second beam accelerator system 110B comprises a second beamline 120B, which provides a second beam pathway 122B for the second ion beam 125B. The second beamline 120B extends from a second beam source 112B to a second target region 130B, which houses a second solid beam target 140B (FIGS. 2A-4B). A second accelerator column 114B and a second magnet 116B are positioned along the second beamline 120B and operate to accelerate and focus the second ion beam 125B. Indeed, in operation, the second accelerator column 114B and the second magnet 116B help direct the second ion beam 125B into the second target region 130B. While not depicted, vacuum system may be fluidly coupled to the first and second beamlines 120A, 120B to provide a low pressure pathway for the first and second ion beams 125A, 125B, minimizing unwanted particle interactions along the beamlines 120A, 120B. In some embodiments, the first ion beam 125A and the second ion beam 125B are proton beams. However, it should be understood that any ion beams are contemplated.

[0033] Referring also to FIGS. 2A-4B, three embodiments of the neutron generation system 100 of FIG.1 are depicted. FIGS.2A and 2B depict a neutron generation system 200 that includes a neutron reflector 150 but does not include a subcritical assembly. FIGS. 3A-Attorney Docket No. SHINE-44080.6014B depict neutron generation systems 300 (FIGS. 3A, 3B) and 400 (FIGS. 4A and 4B) that include the neutron reflector 150 and a subcritical assembly 160. The subcritical assembly 160 of the neutron generation system 300 is moderated by light water (H2O) and the subcritical assembly 160 of the neutron generation system 400 is moderated by heavy water (D2O).

[0034] Referring now to FIGS. 1-4B, the neutron generation systems 100, 200, 300, 400 described herein each comprise a first target region 130A that houses a first solid beam target 140A comprising an impingement surface 142A and a second target region 130B that houses a second solid beam target 140B comprising an impingement surface 142B. The first and second target regions 130A, 130B may be an end region of respective first and second beamlines 120A, 120B, for example, the first and second target regions 130A, 130B may be contiguous with the remainder of the first and second beamlines 120A, 120B. The first solid beam target 140A and the second solid beam target 140B each comprise beryllium, tantalum, tungsten, uranium, lithium, or a combination thereof. Embodiments of the first and second solid beam targets 140A, 140B that comprise uranium may comprise natural uranium or depleted uranium. In some embodiments, the irradiation test cavity 105 is positioned between the first target region 130A and the second target region 130B. For example, in the depicted embodiments, the impingement surface 142A of the first solid beam target 140A and the impingement surface 142B of the second solid beam target 140B each face the irradiation test cavity 105. The neutron reflector 150 comprises beryllium (Be) or beryllium oxide (BeO) and is positioned around the irradiation test cavity 105, the first target region 130A, and the second target region 130B. In operation, the neutron reflector 150 increases thermal flux, for example, thermal flux in the irradiation test cavity 105.

[0035] As depicted in FIGS. 2A-4B, the impingement surface 142A of the first solid beam target 140A is non-orthogonal (e.g., slanted) with respect to the first beam pathway 122A such that, in operation, the first ion beam 125A impinges the impingement surface 142A at a non-orthogonal angle. Similarly, the impingement surface 142B of the second solid beam target 140B is non-orthogonal (e.g., slanted) with respect to the second beam pathway 122B such that, in operation, the second ion beam 125B impinges the impingement surface 142B at a non-orthogonal angle. This non-orthogonal orientation of the impingement surfaces 142A, 142B with respect to the corresponding ion beams 125A, 125B spreads out the beam power over a larger surface area of impingement surfaces 142A, 142B (and correspondingly over a larger volume of the respective solid beam targets 140A, 140B), facilitating the generation ofAttorney Docket No. SHINE-44080.601a more uniform flux, particularly within the irradiation test cavity 105. In addition, spreading the beam and beam power over a larger surface area of the impingement surfaces 142A, 142B reduces power density and extends the lifetime of the solid beam targets 140A, 140B due to reduced sputtering.

[0036] In some embodiments, the first beam pathway 122A (and thus, in operation, the first ion beam 120A) impinges the impingement surface 142A of the first solid beam target 140A at a non-orthogonal angle in a range of from greater than 0° to 80° (where 0° is orthogonal the first impingement surface 142A and 90° is parallel the first impingement surface 142A), such as a range of from 10° to 75°, from 15° to 70°, from 20° to 65°, from 25° to 60°, from 30° to 60°, and from 40° to 50°, for example, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. In some embodiments, the second beam pathway 122B (and thus, in operation, the second ion beam 120B) impinges the impingement surface 142B of the second solid beam target 140B at a non-orthogonal angle in a range of from greater than 0° to 80° (where 0° is orthogonal the second impingement surface 142B and 90° is parallel the second impingement surface 142B), such as a range of from 10° to 75°, from 15° to 70°, from 20° to 65°, from 25° to 60°, from 30° to 60°, and from 40° to 50°, for example, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints.

[0037] In operation, the angle that the first and second ion beams 120A, 120B strike the impingement surface 142A, 142B of the first and second solid beam targets 140A, 140B, respectively, effects the neutron production profile of the first neutrons and the second neutrons, respectively, as the oval shape that each ion beam 120A, 120B forms at each impingement surface 142A, 142B is dependent, in part, on the angle, effecting the intensity of the spallation reaction and the location from which neutrons are generated. Thus, by altering the angle, the ion density striking each impingement surface 142A, 142B is varied and both the power density of heat to be removed from each solid beam target 140A, 140B and the neutron production profile may be modified. Increasing the angle to further spread out the power density of heat may reduce the cooling requirements. Indeed, embodiments are completed in which the angle is adjustable, by adjusting the positioning of the solid beam target(s) 140A, 140B, the beamline(s) 120A, 120B, or both. This adjustability provides more power densityAttorney Docket No. SHINE-44080.601adjustability and neutron production profile adjustability, allowing the neutron production profile to be tuned for a particular test sample and / or particular measurement. However, it should be understood that embodiments of the neutron generations systems 100, 200, 300, 400 described herein are also contemplated in which the first and second beam pathway 122A, 122B (and thus, in operation, the first and second ion beams 120A, 120B) impinge the first and second impingement surfaces 142A, 142B of the first and second solid beam targets 140A, 140B, respectively, at an orthogonal angle (e.g., at 0°).

[0038] Referring now to FIGS.3A-4B, the neutron generation system 300, 400 further comprises a subcritical assembly 160. The subcritical assembly 160 is positioned around the irradiation test cavity 105, the first target region 130A (and thus the first solid beam target 140A), and the second target region 130B (and thus the second solid beam target 140B) and the neutron reflector 150 is positioned around the subcritical assembly 160. The subcritical assembly 160 comprises a fluid chamber 162. The fluid chamber 162 may house light water (e.g., H2O) or heavy water (e.g., D2O). In some embodiments, a plurality of fuel pins 165 is positioned in the fluid chamber 162, for example embodiments in which light water or heavy water is also housed in the fluid chamber 162. The plurality of fuel pins 165 may comprise uranium fuel pins. In other embodiments, the subcritical assembly 160 is a homogeneous subcritical assembly in which the fluid chamber 162 houses a uranium solution in light water or heavy water without the presence of fuel pins 165. For example, the volume fraction ("vf") of uranium in the homogenous subcritical assembly may be in a range of from 0.1% to 4%, for example, from 0.1% to 3 %, from 0.2% to 3 %, from 0.3 % to 3%, from 0.1% to 2%, from 0.1% to 1.5%, from 0.1% to 1%, from 0.1% to 0.9%, from 0.1% to 0.8%, from 0.1% to 0.7%, from 0.1% to 0.6%, from 0.1% to 0.5%, from 0.1% to 0.4%, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. In some embodiments, a portion of the fluid chamber 162 is positioned between the first target region 130A and the second target region 130B. Indeed, portions of the fluid chamber 162 may be positioned between the first target region 130A and the irradiation test cavity 105 and between the second target region 130B and the irradiation test cavity 105. The neutron generation systems 300, 400 with the subcritical assembly 160 operate with a Keffin a range of from 0.80 to 0.999, for example, from 0.85 to 0.999, from 0.90 to 0.999, from 0.95 to 0.999, from 0.90 to 0.995, from 0.95 to 0.995, from 0.90 to 0.99, from 0.95 to 0.99, from 0.90 to 0.985, from 0.95 to 0.985, from 0.90 to 0.98, from 0.95 to 0.98, any range having any two ofAttorney Docket No. SHINE-44080.601those values as endpoints, or any number in a range having any two of those values as endpoints.

[0039] Referring again to FIGS. 1-4B, the neutron generation systems 100, 200, 300, 400 are used to generate neutrons by directing the first ion beam 125A into the impingement surface 142A of the first solid beam target 140A directing the second ion beam 125B into the impingement surface 142B of the second solid beam target 140B. In operation, the first and second beam sources 112A, 112B ionize particles, such as hydrogen particles, which are then accelerated from the first and second beam sources 112A, 112B by the first and second accelerator columns 114A, 114B, respectfully, forming the first and second ion beams 125A, 125B that strike the first and second solid beam targets 140A, 140B. In some embodiments, the ionized hydrogen particles are H+ ions (i.e., H+ protons), such that the first and second ion beams comprise proton beams. The first ion beam reaches the impingement surface 142A of the first solid beam target 140A traveling in a first beam direction BD1 and the second ion beam 125B reaches the impingement surface 142B of the second solid beam target 140B traveling in a second beam direction BD2. The first beam direction BD1 is different than the second beam direction BD2. In some embodiments, the first beam direction BD1is opposite the second beam direction BD2. In some embodiments, the first ion beam 125A impinges the impingement surface 142A of the first solid beam target 140A at a non-orthogonal angle and the second ion beam 125B impinges the impingement surface 142B of the second solid beam target 140B at a non-orthogonal angle.

[0040] In some embodiments, the first and second ion beams 125A each comprise a beam power of at least 15 MeV, for example, at least 10 MeV, at least 15 MeV, at least 20 MeV, at least 25 MeV, at least 30 MeV, at least 35 MeV, at least 40 MeV, at least 45 MeV, at least 50 MeV, at least 55 MeV, at least 60 MeV, at least 65 MeV, at least 70 MeV at least 75 MeV, at least 80 MeV, at least 85 MeV, at least 90 MeV, at least 95 MeV any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the first and second ion beams 125A, 125B may each comprise a beam power in a range of from 10 MeV to 100 MeV, such as from 10 MeV to 90 MeV, from 10 MeV to 80 MeV, from 10 MeV to 75 MeV, from 15 MeV to 75 MeV, from 25 MeV to 75 MeV, from 15 MeV to 70 MeV, from 25 MeV to 70 MeV, from 35 MeV to 70 MeV, from 45 MeV to 90 MeV, from 50 MeV to 75 MeV, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints.Attorney Docket No. SHINE-44080.601

[0041] In some embodiments, the first and second ion beams 125A each comprise a beam current of at least 100 μA, for example, at least 150 μA, at least 200 μA, at least 250 μA, at least 300 μA, at least 350 μA, at least 400 μA, at least 450 μA, at least 500 μA, at least 550 μA, at least 600 μA, at least 650 μA, at least 700 μA, at least 750 μA, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the first and second ion beams 125A, 125B may each comprise a beam power in a range of from 100 μA to 800 μA, such as from 150 μA to 750 μA, from 150 μA to 700 μA, from 150 μA to 650 μA, from 200 μA to 600 μA, from 200 μA to 550 μA, from 200 μA to 500 μA, from 250 μA to 500 μA, from 250 μA to 750 μA, from 250 μA to 600 μA, from 200 μA to 700 μA, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints.

[0042] Upon impingement of the first and second ion beams 125A, 125B into the first and second solid beam targets 140A, 140B, first neutrons are generated via a spallation reaction between the first ion beam 125A and the first solid beam target 140A and second neutrons are generated via a spallation reaction between the second ion beam 125B and the second solid beam target 140B. The first neutrons and the second neutrons comprise fast neutrons. As used herein, "fast neutrons" refer to neutrons with energies of 1 MeV or greater. The first and second neutrons collectively comprise a source strength of at least 1x1013n / s, for example, at least 5x1013n / s, at least 1x1014n / s, at least 5x1014n / s, at least 1x1015n / s, at least 5x1015n / s, at least 1x1016n / s any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints.

[0043] Moreover, in embodiments comprises the neutron reflector 150 and embodiments comprising the neutron reflector 150 and the subcritical assembly 160, these first and second neutrons may be moderated (e.g., by undergoing scattering events at the neutron reflector 150 and / or the subcritical assembly 160) and may induce additional fission reactions to generate additional neutrons. The moderated neutrons and the additional neutrons may comprise thermal neutrons, epithermal neutrons, and combinations thereof. As used herein, "thermal neutrons" refer to neutrons with energies of 0.5 eV or less and "epithermal neutrons" refer to neutrons with energies of greater than 0.5 eV and less than 1 MeV.

[0044] As used herein, the first neutrons, second neutrons, and any moderated neutrons and additional neutrons may be collectively referred to as "total generated neutrons." It should be understood that in embodiments without the subcritical assembly 160, the total generatedAttorney Docket No. SHINE-44080.601neutrons may comprise the first neutrons and the second neutrons (some of which may be moderated into attenuated neutrons by scattering events at the neutron reflector 150), while in embodiments that include the subcritical assembly 160, the total generated neutrons may comprise the first neutrons and the second neutrons, (some of which may be moderated into attenuated neutrons by scattering events at the neutron reflector 150 and the subcritical assembly 160), as well as additional neutrons generated by fission reactions in the subcritical assembly 160.

[0045] The thermal flux in the irradiation test cavity 105 formed by the total generated neutrons may comprise at least 1x1011n / cm2-s, for example, at least 5x1011n / cm2-s, at least 1x1012n / cm2-s, at least 5x1012n / cm2-s, at least 1x1013n / cm2-s, at least 5x1013n / cm2-s, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the thermal flux in the irradiation test cavity 105 formed by the total generated neutrons may be in a range from 1x1011n / cm2-s to 5x1013n / cm2- s, such as from 7.1x1011n / cm2-s to 3.7x1013n / cm2-s. The epithermal flux in the irradiation test cavity 105 formed by the total generated neutrons may comprise at least 5x1011n / cm2-s, for example, at least 1x1012n / cm2-s, at least 5x1012n / cm2-s, at least 1x1013n / cm2-s, at least 5x1013n / cm2-s, at least 1x1014n / cm2-s, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the epithermal flux in the irradiation test cavity 105 formed by the total generated neutrons may be in a range from 5x1011n / cm2-s to 1x1014n / cm2-s, such as from 9.6x1011n / cm2-s to 9.3x1013n / cm2-s. The fast flux in the irradiation test cavity 105 formed by the total generated neutrons may comprise at least 1x1011n / cm2-s, for example, at least 5x1011n / cm2-s, at least 1x1012n / cm2-s, at least 5x1012n / cm2-s, at least 1x1013n / cm2-s, at least 5x1013n / cm2-s, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the fast flux in the irradiation test cavity 105 formed by the total generated neutrons may be in a range from 1x1011n / cm2-s to 5x1013n / cm2-s, such as from 3.5x1011n / cm2-s to 3.1x1013n / cm2-s. The total neutron flux is the sum of the thermal flux, epidermal flux, and the fast flux. The total neutron flux in the irradiation test cavity 105 formed by the total generated neutrons may comprise at least 1x1012n / cm2-s, for example, at least 5x1012n / cm2-s, at least 1x1013n / cm2-s, at least 5x1013n / cm2-s, at least 1x1014n / cm2-s, at least 5x1014n / cm2-s, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. For example, the total neutron flux in theAttorney Docket No. SHINE-44080.601irradiation test cavity 105 formed by the total generated neutrons may be in a range from 1x1012n / cm2-s to 5x1014n / cm2-s, such as from 2.0x1012n / cm2-s to 1.4x1014n / cm2-s.

[0046] Referring still to FIGS.1-4B, a test sample may be housed within the irradiation test cavity 105 and at least some of the first neutrons and at least some of the second neutrons irradiate the test sample. That is, the first neutrons and the second neutrons may be used in radiation effects testing of the test sample. In embodiments comprising the subcritical assembly 160, additional neutrons generated by the subcritical assembly 160 may also irradiate the test sample. Subsequent to irradiating the test sample, the test sample may be removed from the irradiation test cavity 105 and the neutron induced damage to the test sample is analyzed to determine one or more material properties of the test sample, for example, the radiation hardiness of the test sample. For example, the neutron induced damage may be determined by measuring the displacements per atom (DPA) of the irradiated test sample. In some embodiments, an example irradiated test sample that comprises natural iron may have a DPA of at least 0.01, for example, at least 0.02, at least 0.05, at least 0.75, at least 0.1, at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1.0, at least 1.2, at least 1.3, at least 1.4, at least 1.5, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. It should be understood that the DPA of any particular test sample is dependent on the material(s) of the test sample and that the natural iron DPA values are listed to provide additional performance parameters of the neutron generation systems 100, 200, 300, 400.

[0047] In operation, the total generated neutrons irradiate the irradiation test cavity 105 with a thermal flux that varies by 50% or less throughout the irradiation test cavity 105, such as 40% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less, 5% or less, 2.5% or less, 2% or less, 1% or less 0.5% or less, 0.1% or less, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. The total generated neutrons also irradiate the irradiation test cavity 105 with a epithermal flux that varies by 50% or less throughout the irradiation test cavity 105, such as 40% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less, 5% or less, 2.5% or less, 2% or less, 1% or less 0.5% or less, 0.1% or less, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. The total generated neutrons also irradiate the irradiation test cavity 105 with a fast flux that varies by 50% or less throughout the irradiation test cavity 105, such as 40% or less,Attorney Docket No. SHINE-44080.60130% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less, 5% or less, 2.5% or less, 2% or less, 1% or less 0.5% or less, 0.1% or less, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. Moreover, the total generated neutrons also irradiate the irradiation test cavity 105 with a total neutron flux that varies by 50% or less throughout the irradiation test cavity 105, such as 40% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less, 5% or less, 2.5% or less, 2% or less, 1% or less 0.5% or less, 0.1% or less, any range having any two of those values as endpoints, or any number in a range having any two of those values as endpoints. Thus, test samples positioned in the irradiation test cavity 105 undergo substantially uniform irradiation, improving the accuracy of neutron-induced damage test as the whole test sample is subjected to substantially unform irradiation conditions. EXAMPLES

[0048] Embodiments will be further clarified by the following examples.

[0049] The Examples provided below were modeled using the Monte Carlo N-Particle (MCNP) code. MCNP, which is developed and maintained by Los Alamos National Laboratory, is an internationally recognized Monte Carlo radiation transport code. MCNP allows for precise tracking of different types of radiation, including neutrons and photons, and their interactions within the system. The modeling results presented in these examples used MCNP version 6.2. The ENDF / B-VIII.0 nuclear data library was used for all particle transport, which can be found at D. A. Brown, et al., "ENDF / B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards, and Thermal Scattering Data," Nuclear Data Sheets, vol. 148, no. Special Issue on Nuclear Reaction Data, pp. 1-142, 2018. DPA production values were calculated assuming the test sample was natural iron, and the FENDL-3.1 nuclear data library was used for these quantities, which can be found at R. A. Forrest, R. Capote, N. Otsuka, T. Kawano, A. J. Koning, S. Kunieda, J.-C. Sublet and Y. Watanbe, "FENDL-3 Library – Summary documentation," IAEA Nuclear Data Section, Vienna, 2012. Example 1

[0050] Example 1 provides a characterization of the neutron yield, energy spectrum, and angular distribution of neutrons created by proton bombardment onto two solid beam targets of various materials, that is, simultaneous proton bombardment of a first proton beamAttorney Docket No. SHINE-44080.601onto a first solid beam target of various materials and a second proton beam onto a second solid beam target of various materials. Example 1 considers two cylindrical solid beam targets, surrounded by void, where the solid beam targets are a minimal thickness that still stops the entire proton beam in the material. In other words, the solid beam targets are just thick enough that the entire proton beam is be stopped in the material of the solid beam target, but not any thicker than that to minimize neutron attenuation inside the solid beam target. The total neutron yield and the energy spectrum was calculated by determining the number of neutrons leaving the target per source proton.

[0051] Tables 1-3, below, show the calculated results of bombarding pairs of beryllium, tantalum, tungsten, and uranium solid beam targets with pairs of 18 MeV proton beams with a combined beam current of 300 μA (Table 1), 30 MeV proton beams with a combined beam current of 1200 μA (Table 2), and 70 MeV proton beams with a combined beam current of 700 μA (Table 3). FIGS.5A-7B show the energy spectrum and forward-peaking profile of neutrons produced in the various reactions. FIG. 5A and 5B graphically depict a neutron energy spectrum (FIG.5A) and a neutron forward peaking profile (FIG.5B) generated by an 18 MeV proton beam striking a beryllium (Be), tantalum (Ta), tungsten (W), and uranium (U) solid beam targets. FIG. 6A and 6B graphically depict a neutron energy spectrum (FIG. 6A) and a neutron forward peaking profile (FIG. 6B) generated by a 30 MeV proton beam striking Be, Ta, W, and U solid beam targets. FIG.7A and 7B graphically depict a neutron energy spectrum (FIG. 7A) and a neutron forward peaking profile (FIG. 7B) generated by a 70 MeV proton beams striking Be, Ta, W, and U solid beam targets. Target Neutrons Total Neutron Avg Neutron % Neutrons % Neutrons VNeutrons Total Neutron Avg Neutron % Neutrons % NeutronsAttorney Docket No. SHINE-44080.601W 0.016 1.2×10142.09 91.9 99.7 U 0.028 2.1×10141.83 94.8 99.8Target Neutrons Total Neutron Avg Neutron % Neutrons % Neutrons per Proton Yield [n / s] Energy [MeV] < 5 MeV < 20 MeV

[0052] As shown by Tables 1-3, at a proton beam energy of 18 MeV, beryllium produces the most neutrons among the target materials tested. At 30 MeV, the differences between materials are not as pronounced. At 70 MeV, uranium produces the most neutrons, and it has the added benefit of producing neutrons with the lowest average energy, which makes them easier to thermalize. Example 2

[0053] Example 2 provides details of an example operation of the neutron generation system 200 of FIGS.2A and 2B, which includes the neutron reflector 150 but does not include a subcritical assembly. In Example 2, the first and second beamlines 120A, 120B are each 70 MeV proton beamlines and the first and second solid beam targets 140A, 140B are each depleted uranium targets. The first and second beamlines 120A, 120B each comprise a 350 μA proton current. The spallation reaction between the proton beams and the depleted uranium targets in Example 2 results in two mostly isotropic planar sources of neutrons with a combined source strength of 1.2×1015n / s. In Example 2, the irradiation test cavity 105 comprises a length of 30 cm and a diameter of 10 cm and is located between the two neutron sources (i.e., between the first and second solid beam targets 140A). FIGS. 8A and 8B depict a thermal flux map (FIG. 8A) and a total flux map (FIG.8B) of an operation the neutron generator system 200 of FIGS.2A and 2B according to the parameters of Example 2. Example 3Attorney Docket No. SHINE-44080.601

[0054] Example 3 provides details of an example operation of the neutron generation system 300 of FIGS. 3A and 3B, which includes the neutron reflector 150 and a subcritical assembly 160, which, in the neutron generation system 300, comprises uranium fuel pins 165 dispersed in light water that is housed in the fluid chamber 162. The parameters of the system of Example 3 are in Table 4, below. Parameter Driver 70 MeV, 700 μA HEP

[0055] In Example 3, the first and second beamlines 120A, 120B are each 70 MeV proton beamlines and the first and second solid beam targets 140A, 140B are each depleted uranium targets. The first and second beamlines 120A, 120B each comprise a 350 μA proton current. The spallation reaction between the proton beams and the depleted uranium targets in Example 2 results in two mostly isotropic planar sources of neutrons with a combined source strength of 1.2×1015n / s. In Example 3, the irradiation test cavity 105 comprises a length of 30 cm and a diameter of 10 cm and is located between the two neutron sources (i.e., between the first and second solid beam targets 140A). FIGS. 9A and 9B depict a thermal flux map (FIG. 9A) and a total flux map (FIG.9B) of an operation the neutron generator system 300 of FIGS. 3A and 3B according to the parameters of Example 3. Example 4

[0056] Example 4 provides details of an example operation of the neutron generation system 400 of FIGS. 3A and 3B, which includes the neutron reflector 150 and a subcriticalAttorney Docket No. SHINE-44080.601assembly 160, which, in the neutron generation system 300, comprises comprising uranium fuel pins 165 dispersed in heavy water that is housed in the fluid chamber 162. The parameters of the system of Example 4 are in Table 5, below. Parameter Driver 70 MeV, 700 μA HEP

[0057] In Example 4, the first and second beamlines 120A, 120B are each 70 MeV proton beamlines and the first and second solid beam targets 140A, 140B are each depleted uranium targets. The first and second beamlines 120A, 120B each comprise a 350 μA proton current. The spallation reaction between the proton beams and the depleted uranium targets in Example 2 results in two mostly isotropic planar sources of neutrons with a combined source strength of 1.2×1015n / s. In Example 4, the irradiation test cavity 105 comprises a length of 30 cm and a diameter of 10 cm and is located between the two neutron sources (i.e., between the first and second solid beam targets 140A). FIGS.10A and 10B depict a thermal flux map (FIG. 10A) and a total flux map (FIG. 10B) of an operation the neutron generator system 400 of FIGS.4A and 4B according to the parameters of Example 4.

[0058] Table 6, below, lists the performance results of each of Examples 2-4. 235U Thermal Epithermal Fast DPA Helium Helium / Thermal Helium / DPA a]Attorney Docket No. SHINE-44080.6014 1.83 3.2×10131.5×10131.7×10120.091 0.041 80 0.91 Table 6ron generation systems 200, 300, and 400 of FIGS. 2A and 2B, FIGS. 3A and 3B, and FIGS. 4A and 4B, respectively. FIG. 12 graphically depicts a normalized version of the neutron energy spectra for the neutron generation systems 200, 300, and 400 of FIGS. 2A and 2B, FIGS. 3A and 3B, and FIGS.4A and 4B, respectively. Example 5

[0060] Example 5 provides details of an example operation of a variety of neutron generation systems, including high energy proton (HEP) systems and low energy deuteron systems (LED). The neutron generation systems 100, 200, 300, 400, described herein, are HEP systems. In contrast, LED systems are ion accelerator systems operating at nominally 300-400 keV with deuterium ions (deuterons) being accelerated into a gas target comprising tritium. Operational results of a variety of HEP and LED systems are shown in Table 7, below. FIG. 13 graphically depicts the neutron energy spectrum of HEP and LED systems of Table 7. As shown in Table 7, thermal flux levels for the higher energy HEP systems with subcritical assemblies can achieve 10-20% of the thermal neutron flux levels in typical fission reactors. Lower-energy HEP systems result in correspondingly lower thermal flux levels due to their lower neutron production rates. Driver Sub-Critical FIG.13235U Mass N. Source Th. Flux (Avg) DPA He / DPA Assembly Reflector Ref. [kg] [n / s] [n / cm2-s] [dpa / fpy] [appm / dpa]Attorney Docket No. SHINE-44080.601HEP, 70 MeV, U target None BeO 9 0 1.2×10152.4×10120.032 0.70similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical values or idealized geometric forms provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0062] The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, optical, or fluidic.

[0063] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0064] Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partialAttorney Docket No. SHINE-44080.601concurrence, unless specified differently above. Such variation may depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations of the described methods could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.

[0065] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims

Attorney Docket No. SHINE-44080.601CLAIMS What is claimed is:

1. A neutron generation system comprising: an irradiation test cavity; a first target region housing a first solid beam target comprising an impingement surface; a second target region housing a second solid beam target comprising an impingement surface; a first beam accelerator system comprising a first beamline having a first beam pathway that impinges the impingement surface of the first solid beam target at a non-orthogonal angle; and a second beam accelerator system comprising a second beamline having a second beam pathway that impinges the impingement surface of the second solid beam target at a non- orthogonal angle.

2. The neutron generation system of claim 1, wherein the irradiation test cavity is positioned between the first target region and the second target region.

3. The neutron generation system of claim 2, wherein the impingement surface of the first solid beam target and the impingement surface of the second solid beam target each face the irradiation test cavity.

4. The neutron generation system of claim 1, further comprising a neutron reflector positioned around the irradiation test cavity, the first target region, and the second target region.

5. The neutron generation system of claim 4, wherein the neutron reflector is a Be or BeO reflector.

6. The neutron generation system of claim 1, further comprising a subcritical assembly positioned around the irradiation test cavity, the first target region, and the second target region.Attorney Docket No. SHINE-44080.6017. The neutron generation system of claim 6, wherein the subcritical assembly comprises a fluid chamber and a plurality of fuel pins positioned in the fluid chamber.

8. The neutron generation system of claim 7, wherein the fluid chamber houses light water.

9. The neutron generation system of claim 7, wherein the fluid chamber houses heavy water.

10. The neutron generation system of claim 7, wherein a portion of the fluid chamber is positioned between the first target region and the second target region.

11. The neutron generation system of claim 6, wherein the subcritical assembly is a homogeneous subcritical assembly comprising a fluid chamber housing a uranium solution in light water.

12. The neutron generation system of claim 6, further comprising a neutron reflector positioned around the subcritical assembly.

13. The neutron generation system of claim 1, wherein: the first beam accelerator system is configured to accelerate a first proton beam along the first beam pathway such that the first proton beam impinges the impingement surface of the first solid beam target at a non-orthogonal angle, thereby generating neutrons in the first target region via a spallation reaction; and the second beam accelerator system is configured to accelerate a second proton beam along the second beam pathway such that the second proton beam impinges the impingement surface of the second solid beam target at a non-orthogonal angle, thereby generating neutrons in the second target region via a spallation reaction.

14. The neutron generation system of claim 1, wherein the first solid beam target comprises beryllium, tantalum, tungsten, uranium, or lithium.

15. The neutron generation system of claim 1, wherein the second solid beam target comprises beryllium, tantalum, tungsten, uranium, or lithium.

16. The neutron generation system of claim 1, wherein:Attorney Docket No. SHINE-44080.601the first beam pathway impinges the impingement surface of the first solid beam target at an angle in a range of from 10° to 75°, and the second beam pathway impinges the impingement surface of the second solid beam target at an angle in a range of from 10° to 75°.

17. The neutron generation system of claim 1, wherein: the first beam pathway impinges the impingement surface of the first solid beam target at an angle in a range of from 30° to 60°; and the second beam pathway impinges the impingement surface of the second solid beam target at an angle in a range of from 30° to 60°.

18. A method of generating neutrons, the method comprising: directing a first ion beam generated by a first beam accelerator system of a neutron generation system into an impingement surface of a first solid beam target, thereby generating first neutrons via a spallation reaction between the first ion beam and the first solid beam target, wherein the first ion beam reaches the impingement surface traveling in a first beam direction and impinges the impingement surface of the first solid beam target at a non-orthogonal angle; and directing a second ion beam generated by a second beam accelerator system into an impingement surface of a second solid beam target, thereby generating second neutrons via a spallation reaction between the second ion beam and the second solid beam target, wherein the second ion beam reaches the impingement surface traveling in a second beam direction and impinges the impingement surface of the second solid beam target at a non-orthogonal angle.

19. The method of claim 18, wherein: the first ion beam comprises a beam power in a range of from 15 MeV to 75 MeV and a beam current in a range of from 200 μA to 500 μA; and the second ion beam comprises a beam power in a range of from 15 MeV to 75 MeV and a beam current in a range of from 200 μA to 500 μA.

20. The method of claim 18, wherein: the first ion beam comprises a beam power of at least 15 MeV and a beam current of at least 200 μA; andAttorney Docket No. SHINE-44080.601the second ion beam comprises a beam power of at least 15 MeV and a beam current of at least 200 μA.

21. The method of claim 18, wherein the first neutrons and the second neutrons collectively comprise a source strength of at least 1x1014n / s.

22. The method of claim 18, wherein the first neutrons and the second neutrons collectively comprise a source strength of at least 1x1015n / s.

23. The method of claim 18, wherein the first beam direction is different than the second beam direction.

24. The method of claim 18, wherein the second beam direction is opposite the second beam direction.

25. The method of claim 18, wherein the first neutrons and the second neutrons comprise fast neutrons.

26. The method of claim 18, wherein the neutron generation system further comprises an irradiation test cavity.

27. The method of claim 26, further comprising irradiating a test sample housed within an irradiation test cavity with at least some of the first neutrons and at least some of the second neutrons.

28. The method of claim 27, further comprising, subsequent to irradiating the test sample, determining one or more material properties of the test sample.

29. The method of claim 26, wherein the neutron generation system further comprises a neutron reflector and a subcritical assembly, each positioned around the irradiation test cavity, the first solid beam target, and the second solid beam target, wherein interaction between the first and second neutrons and the neutron reflector and the subcritical assembly attenuates at least a portion of the first and second neutrons into attenuated neutrons thermal or epithermalAttorney Docket No. SHINE-44080.601neutrons and generates additional neutrons via a fission reaction, wherein the attenuated neutrons comprise thermal neutrons, epithermal neutrons, or a combination thereof.

30. The method of claim 29, wherein the first neutrons, the second neutrons, the attenuated neutrons, and the additional neutrons collectively comprise total generated neutrons, wherein the total generated neutrons irradiate the irradiation test cavity with a thermal flux in a range of from 1x1011n / cm2-s to 5x1013n / cm2-s.

31. The method of claim 29, wherein the first neutrons, the second neutrons, the attenuated neutrons, and the additional neutrons collectively comprise total generated neutrons, wherein the total generated neutrons irradiate the irradiation test cavity with an epithermal flux in a range from 5x1011n / cm2-s to 1x1014n / cm2-s.

32. The method of claim 29, wherein the first neutrons, the second neutrons, the attenuated neutrons, and the additional neutrons collectively comprise total generated neutrons, wherein the total generated neutrons irradiate the irradiation test cavity with a fast flux in a range of from 1x1011n / cm2-s to 5x1013n / cm2-s.

33. The method of claim 29, wherein the first neutrons, the second neutrons, the attenuated neutrons, and the additional neutrons collectively comprise total generated neutrons, wherein the total generated neutrons irradiate the irradiation test cavity with a total neutron flux in a range of from 1x1012n / cm2-s to 5x1014n / cm2-s.

34. A method of generating neutrons, the method comprising: directing a first ion beam generated by a first beam accelerator system of a neutron generation system into an impingement surface of a first solid beam target, thereby generating first neutrons via a spallation reaction between the first ion beam and the first solid beam target; and directing a second ion beam generated by a second beam accelerator system into an impingement surface of a second solid beam target, thereby generating second neutrons via a spallation reaction between the second ion beam and the second solid beam target, wherein the first neutrons and the second neutrons irradiate an irradiation test cavity with a total neutron flux that varies by 20% or less throughout the irradiation test cavity.Attorney Docket No. SHINE-44080.60135. The method of claim 34, wherein: the first ion beam reaches the impingement surface traveling in a first beam direction and impinges the impingement surface of the first solid beam target at a non-orthogonal angle; and the second ion beam reaches the impingement surface traveling in a second beam direction and impinges the impingement surface of the second solid beam target at a non- orthogonal angle.

36. The method of claim 34, wherein the first neutrons and the second neutrons irradiate the irradiation test cavity with a total neutron flux that varies by 10% or less throughout the irradiation test cavity.

37. The method of claim 36, wherein the first neutrons and the second neutrons irradiate the irradiation test cavity with a total neutron flux that varies by 5% or less throughout the irradiation test cavity.

38. The method of claim 36, wherein the neutron generation system further comprises an irradiation test cavity.

39. The method of claim 38, further comprising irradiating a test sample housed within an irradiation test cavity with at least some of the first neutrons and at least some of the second neutrons.

40. The method of claim 39, further comprising, subsequent to irradiating the test sample, determining one or more material properties of the test sample.

41. The method of claim 38, wherein the neutron generation system further comprises a neutron reflector and a subcritical assembly, each positioned around the irradiation test cavity, the first solid beam target, and the second solid beam target, wherein interaction between the first and second neutrons and the neutron reflector and the subcritical assembly attenuates at least a portion of the first and second neutrons into thermal or epithermal neutrons and generates additional neutrons via a fission reaction, wherein the first neutrons, second neutrons, attenuated neutrons, and additional neutrons collectively comprise total generated neutrons.Attorney Docket No. SHINE-44080.60142. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with a thermal flux in a range of from 1x1011n / cm2-s to 5x1013n / cm2-s.

43. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with an epithermal flux in a range from 5x1011n / cm2-s to 1x1014n / cm2-s.

44. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with a fast flux in a range of from 1x1011n / cm2-s to 5x1013n / cm2-s.

45. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with a total neutron flux in a range of from 1x1012n / cm2-s to 5x1014n / cm2-s.

46. The method of claim 41, wherein the total generated neutrons irradiate an irradiation test cavity with a total neutron flux that varies by 20% or less throughout the irradiation test cavity.

47. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with a total neutron flux that varies by 10% or less throughout the irradiation test cavity.

48. The method of claim 41, wherein the total generated neutrons irradiate the irradiation test cavity with a total neutron flux that varies by 5% or less throughout the irradiation test cavity.

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