Pebble-bed beam converter

Abstract

A converter is provided for converting the electron beam into photons. The converter preferably comprises a plurality of spherical beads made of a high atomic number material (high-Z material) disposed within a cooling fluid. The converter preferably has an inlet and an outlet for the cooling fluid. The cooling fluid preferably flows in a direction opposite to the direction of the electron beam.

Description

[Technical Field]

[0001] The present disclosure relates generally to converters, and in particular to devices and apparatus adapted to produce high-energy x-rays of characteristic wavelength, intensity, and duration from an energetic electron beam, and more particularly to converters that generate a flux of high-energy photons from a high-energy electron beam.

[0002] [Citation of Related Applications] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 398,107 (titled "Pebble Bed Beam Converter"), filed on August 15, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] The generation of radioisotopes (in the medical and life science fields, "radioisotopes" and "isotopes" are often referred to as "radioisotopes" and "isotopes," respectively; therefore, the latter terms will be used herein) requires equipment for generating high-energy x-rays from electron beams. For example, technological pursuits to bridge the gap between the severely constrained availability of 225Ac and the high global demand are key drivers in nuclear medicine. Demand for 225Ac stems from its use in targeted alpha therapy (TAT). The radioisotope 225Ac and its daughter, 213Bi, are used medically to treat prostate, brain, and neuroendocrine cancers. The half-life of 213Bi is approximately 45.61 months. However, 225Ac exhibits a relatively short half-life (T1 / 2) of approximately 9.92 days. Thus, maintaining the 225Ac supply can be difficult, as it quickly decays.

[0004] The usual production method is to produce 225Ac by beta decay of 225Ra, which itself is produced by the (γ,n) reaction on a high-purity 226Ra (T1 / 2 = 1600 years) target. High-energy photons are produced by converter action in a high atomic number (high-Z) material, such as tantalum, by the bremsstrahlung mechanism, which can result from the deceleration of highly energetic accelerated electrons striking the converter material. Summary of the Invention [Problem to be solved by the invention]

[0005] However, most existing converters are limited in beam power because they must extract the thermal power stored within the converter at a temperature low enough to maintain the mechanical strength of the converter material. For example, typical existing converters are often limited to accepting beam powers of less than 50 kilowatts (kW), limiting their photon generation potential to only a small fraction of the beam power that can be generated by high-power converters. As accelerators become capable of producing relatively high powers, converters suitable for accepting relatively high beam powers are desired.

[0006] Conventionally, converters suitable for high power applications (e.g., greater than 100 kW, up to 500 kW or more) are extremely rare and mechanically complex. For example, existing high-power converters utilize a large rotational surface to reduce the time-averaged thermal output at certain locations on the disk surface, heating some areas on the disk for a small fraction of the rotation while allowing the remainder to cool. However, these types of converters are subject to catastrophic or runaway failure due to their mechanical complexity. Therefore, there is a need for a thermally and mechanically reliable converter suitable for high beam power applications that has less dependency on auxiliary machinery, such as motors. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a converter capable of generating a high flux of high-energy photons (e.g., greater than 5 MeV) from an electron beam. In some embodiments, the electron beam can be 40 MeV or greater, and the effective beam power can be 125 kW or greater. In some embodiments, the converter can be used for applications up to about 500 kW.

[0008] Another aspect of the present disclosure relates to a transducer including a structured or unstructured grating of a high-Z material in the form of a geometric shape of globules, random particles, mesh, or other porous array. The transducer is configured to receive an electron beam from a first side and generate and emit photons from a second side opposite the first side, while also allowing for simultaneous coolant flow through the transducer in a direction parallel or perpendicular to the electron beam. Various coolants can be used. The coolant can be a fluid, such as a liquid, e.g., water, or a gas, e.g., helium, or other suitable substance.

[0009] Yet another aspect of the present disclosure relates to a method for converting an electron beam into photons, the method comprising the steps of providing a converter comprising a plurality of spherical beads disposed in a fluid coolant; directing one or more electron beams at the converter from a first side of the converter; and generating and emitting photons from a second side of the converter opposite the first side.

[0010] Another aspect of the present disclosure relates to providing a fluid coolant to the transducer parallel to the direction of impingement of the electron beam.

[0011] In one embodiment, an electron beam converter is provided having a plurality of spherical beads disposed within a fluid coolant within the converter, the converter configured to receive an electron beam from a first side and generate and emit photons from a second side opposite the first side.

[0012] In one embodiment, the plurality of spherical beads are made of a high atomic number (high Z) material.

[0013] In one embodiment, a plurality of spherical beads are packed and distributed approximately randomly within the transducer.

[0014] In one embodiment, the fluid coolant enters the converter through an inlet located on the second side and exits the converter through an outlet located on the first side.

[0015] In one embodiment, a first screen is disposed over the inlet and a second screen is disposed over the outlet, and the plurality of spherical beads are adapted to pass through the first and second screens and into the transducer.

[0016] In one embodiment, a system for producing radioisotopes is provided that includes an accelerator, a beamline, and a target system, the target system having a porous media converter with a plurality of spherical beads, a target, an inlet designed to allow a flow of a cooling fluid to enter the porous media converter and surround the plurality of spherical beads, and an outlet designed to allow the cooling fluid to exit the porous media converter.

[0017] In one embodiment, the accelerator is mounted on a common axis with the target system.

[0018] In one embodiment, the accelerator is located on a first axis and the target system is located on a second axis different from the first axis.

[0019] In one embodiment, the system includes a target cooling system in fluid communication with the target system.

[0020] In one embodiment, the system includes a hot cell in fluid communication with the target system.

[0021] In one embodiment, the system includes an accelerator vault designed to house an accelerator, beamline, and target system.

[0022] In one embodiment, the system includes a first radiation zone disposed within an accelerator vault, the first radiation zone designed to house an accelerator and a beamline.

[0023] In one embodiment, the system includes a second radiation zone located within the accelerator vault, the second radiation zone designed to house a target system.

[0024] In one embodiment, the system includes a beamline window positioned in front of the porous media converter.

[0025] In one embodiment, the system includes a passageway designed to form a fluid passageway located between an inlet and an outlet to form a flow loop.

[0026] In one embodiment, a method for converting an electron beam into photons is provided, the method including the steps of providing a converter comprising a plurality of spherical beads disposed in a fluid coolant, directing one or more electron beams at the converter from a first side of the converter, and generating and emitting photons from a second side of the converter opposite the first side.

[0027] In one embodiment, the method includes providing a plurality of spherical beads made from a high atomic number (high Z) material.

[0028] In one embodiment, the method includes providing a plurality of spherical beads in a transducer that are closely packed and generally randomly distributed.

[0029] In one embodiment, the method includes providing a fluid coolant into the converter from an inlet on the second side and allowing the fluid coolant to exit the converter from an outlet on the first side.

[0030] In one embodiment, the method includes providing a first screen disposed over the inlet and a second screen disposed over the outlet, wherein a plurality of spherical beads pass through the first screen and the second screen and are disposed within the transducer. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a schematic diagram of an example system 100 for producing an isotope, such as 225Ac, according to an example embodiment. [Figure 2] FIG. 1 is a block diagram of a beamline in accordance with an example embodiment. [Figure 3] FIG. 1 illustrates a perspective view of a pebble bed transducer in accordance with an example embodiment. [Figure 4] FIG. 1 illustrates a cross-sectional view of a pebble bed transducer in accordance with an example embodiment. [Figure 5] A diagram of the average energy loss through a material. [Figure 6] 1 is a cross-sectional view of a target area according to an exemplary embodiment. [Figure 7] FIG. 7 is another view of the target area of ​​FIG. 6. [Figure 8] FIG. 7 is a heat map view of the target area of ​​FIG. 6 when the target area is bombarded with an electron beam. DETAILED DESCRIPTION OF THE INVENTION

[0032] Before describing the embodiments of the disclosed subject matter of the present invention in detail, it should be understood that the application of the present invention is not limited to the details of the specific arrangements shown, as the present invention may be practiced in other embodiments. Illustrative embodiments are described in the referenced figures of the drawings. The embodiments and figures disclosed herein should be considered as illustrative rather than limiting of the present invention. Furthermore, the terminology used herein is for the purpose of description and not limitation.

[0033] While the present invention may be embodied in a wide variety of forms, specific embodiments have been shown and described in detail with the understanding that this disclosure is an example of the principles of the invention. It is not intended that the invention be limited to the specific illustrated embodiments. The features of the invention disclosed in the text, drawings, and claims herein may be meaningful to the operation of the invention both individually and in any combination required with respect to its various embodiments. Features of one embodiment may be used in other embodiments of the invention.

[0034] Referring to Figure 1, an exemplary system 100 for producing an isotope, particularly 225Ac, is shown. In particular, the system 100 may include an accelerator 110 coupled to a beamline 120. The beamline 120 may impact a target system 130. The target system 130 may be a device in which a target isotope, such as 226Ra, is held for irradiation. The target system 130 may include a converter 132 and a target 134. The target system 130 may be further coupled to a target cooling system 140 (also referred to as a process cooling system) and a hot cell 150.

[0035] The accelerator 110, the beamline 120, and the target system 130 may be shielded and housed within an accelerator vault 160. In an exemplary embodiment, the accelerator vault 160 may be further separated into a first radiation zone 162 that houses the accelerator 110 and the beamline 120 and a second radiation zone 164 that houses the target system 130.

[0036] In an exemplary embodiment, accelerator vault 160 can have interior walls that are used to form first radiation zone 162 and / or second radiation zone 164. Accelerator vault 160, the interior walls, zones within accelerator vault 160, and other building rooms can be constructed of high-density (HD) concrete blocks, such as those provided by Veritas Medical Solutions of Harleysville, PA, USA. HD concrete performs better per unit volume than medium-density concrete at shielding gamma rays, the primary source of radiation generated during the process.

[0037] While other materials, such as steel or lead, can be used for the accelerator vault, these materials are relatively expensive and are not as efficient as boron-loaded HD concrete at stopping prompt neutrons that are also generated during the process. In particular, prompt radiation refers to radiation that is emitted instantaneously during operation of the accelerator 110, which is distinct from residual or induced radiation caused by active components within the accelerator vault 116 and beamlines 120.

[0038] The accelerator 110 can generate accelerated electrons for irradiating Ra held within the target system 130. In an exemplary embodiment, the electron accelerator 110 can provide an average power of about 20 to about 250 kW with electrons at about 25 to about 100 MeV. Preferably, the average power value is about 60 to about 200 kW, and more preferably about 80 to about 125 kW. Preferably, the electrons are at about 25 to about 55 MeV.

[0039] To illuminate the target system 130, a dedicated beamline may be used to bend each electron beam at an angle toward the target system 130. In an exemplary embodiment, the beamline 120 bends the electron beam by 90° toward the target system 130. The present invention is not limited to 90° and can include other angles, such that the beamline illuminates the target 134 from various directions or angles. As a result, the target system 130 can be positioned on a different axis than the accelerator 110. Alternatively, in an exemplary embodiment, the accelerator 110 is offset from the target system 130 as shown in FIG. 1 . The accelerator 130 can also be positioned on a common axis with the target system 130.

[0040] Additionally, a control system may be provided that integrates the individual control systems of the accelerator 110, the beamline 120, the target cooling system 140, the hot cell 170, and other components of the system for producing radioisotopes, such as 225Ac. For example, a combined control system may be used to time the generation of beam pulses by the accelerator 110 so that they reach the target 134.

[0041] In operation, beamline 120 may receive an electron beam from accelerator 110. Beamline 120 may then bend the corresponding beam to strike target system 130, thereby avoiding backflow radiation. After bending, beamline 120 may aim the beam at a desired spot at target system 130 and analyze the beam's energy, or pass the beam straight to an awaiting beam analyzer and dump.

[0042] According to a first embodiment, a Rhodotron® electron beam (E-beam) accelerator 110 manufactured by IBA Industrial, Louvain-La-Neuve, Belgium, is used. Unlike conventional linear accelerators (linacs), Rhodotron® E-beam accelerators are continuous-wave electron beam accelerators that combine high power and high energy. The high energy characteristics of Rhodotron® E-beam accelerators help improve the production efficiency of 225Ac, which cannot be achieved using conventional linacs. Furthermore, Rhodotron® E-beam accelerators are compact in size, thereby allowing the accelerator setup to occupy a small area (in square feet) within an isotope production facility.

[0043] A preferred Rhodotron® type E-beam accelerator can produce electron beams with diameters of approximately 7 mm (FWHM), approximately 12 mm FWHM, or approximately 25 mm FWHM. Gaussian beams with a standard deviation of 3 sigma correspond to diameters of 8.9 mm and 15 mm. The accelerator's ability to operate at a large FWHM reduces the maximum volumetric heat power deposition in the converter 132 by distributing the beam's energy over a large volume of converter material. The target 134 may be approximately 25 mm in diameter and approximately 0.060198 mm thick (RaBr2).

[0044] FIG. 2 illustrates an example beamline 200. The beamline 200 may be the beamline 120 of FIG. 1. As shown, the beamline 200 may include first beam optics 210 that receive the electron beam from the accelerator 110. The beam optics 210 may be used to correct and steer the electron beam received from the accelerator. The beam optics 210 may be coupled to a diagnostic component 220 that may be used to analyze the current or position of the electron beam. The diagnostic component 220 may further be coupled to second beam optics 230 that are used to focus the electron beam. The second beam optics 230 may be coupled to third beam optics 240 to further correct and steer the electron beam. The third beam optics 240 may then be coupled to fourth beam optics 250, which may include an achromatic bending system. In an exemplary embodiment, to facilitate bending of the electron beam, a pair of 270° magnet achromatic bending systems may be used to bend the electron beam.

[0045] From the fourth beam optics 250, the electron beam can travel down one of three paths. If the electron beam meets predetermined criteria for manufacturing, the electron beam can be bent by the fourth beam optics 250 toward the second diagnostic component 260 for further analysis of the electron beam current or position. The second diagnostic component 260 can be coupled to the fifth beam optics 270 for correction and steering, which can be further coupled to the sixth beam optics 280 for focusing. The sixth beam optics 280 can be coupled to the third diagnostic component 290 for further analysis of the electron beam current and position, before transmitting the electron beam to a target (e.g., 226Ra housed within the targeting system 130 described above with reference to FIG. 1).

[0046] Alternatively, if the electron beam does not meet predetermined criteria for manufacturing, the fourth beam optics 250 can send the electron beam to a fourth diagnostic component 292 and a beam dump or beam stop. Finally, if the electron beam is not to be used for manufacturing, the fourth beam optics 250 can send the electron beam to a fifth diagnostic component 294, such as a spectrometer, for further analysis.

[0047] In the illustrated embodiment, the electron beam may enter and exit the fourth beam optics 250 in substantially the same plane. That is, the achromatic bending system of the fourth beam optics 250 does not affect the vertical height position of the electron beam. However, in other embodiments, the electron beam may exit the fourth beam optics 250 in a plane different from the plane at which the electron beam enters the fourth beam optics 250.

[0048] As can be appreciated, other variations can be made to beamline 200, such as the addition or omission of certain components, and such variations are within the spirit of the present disclosure.

[0049] 3 shows a beam converter system 300 suitable for high-power use according to an example embodiment. The beam converter system 300 may include a converter 332, which may be converter 132 of FIG. 1. The converter 332 may be positioned in front of a target 334 in a target system 330, after which the beamline 320 approaches the target 334. The beamline 320, the target system 330, and the target 334 may be beamline 120, the target system 130, and the target 134, respectively, of FIG. 1.

[0050] As shown in FIG. 3, the beam converter 332 may be configured as a volume of porous medium 340 containing a matrix of solid "high-Z" beam converter material and flowing fluid coolant 350. Alternatively or additionally, the converter 332 may further include a matrix of solid "medium-Z" material, such as silver or copper. Many geometries for such a matrix are possible, such as packed irregular particles, a structured woven mesh of wires, or unstructured "wool"-like fibers. In an exemplary embodiment, randomly packed spherical beads may be used, as shown in FIGS. 3 and 4.

[0051] In exemplary embodiments, the beads may be made of a high-Z material, such as tantalum, tungsten, gold, platinum, thorium, or other suitable material. Other materials or compositions may also be utilized depending on the specific system requirements regarding hydraulic properties, thermal power dissipation, mechanical strength, and photon yield of the coolant in the implemented system. For example, gold-coated tungsten beads may be used to improve chemical compatibility with water coolants, or low-Z silver may be used to reduce localized thermal power buildup. In some embodiments, the beads may be less than about 2 millimeters (mm) in diameter. In other embodiments, the beads may be between about 0.1 mm and about 1 mm in diameter.

[0052] In some embodiments, the beads may be densely packed and arranged in a generally random distribution. The beads may be contained in "packs" with a diameter bounded by the FWHM (full width at half maximum) of the incident electron beam and a depth correlated to the porosity and composition of the porous high-Z material. The containment volume for the beads may be approximately 15 mm in diameter and approximately 9 mm deep. The beads may be packed in place and secured at the flow inlet and flow outlet by a fine-woven stainless steel mesh with an opening size smaller than the sphere of the transducer.

[0053] Highly porous converter configurations can provide large convective heat transfer coefficients (at the interface to water-based liquid or chemically inert gas coolants) and a significantly larger heat transfer surface area per unit volume of converter material. This allows for significantly higher volumetric heat power storage than nonporous converters constrained by equivalent material or thermohydraulic properties, such as the converter melting point material, coolant boiling temperature, or critical boiling heat flux. Thus, compared to nonporous converters, porous converters can dissipate greater heat power and more efficiently generate photons. In some embodiments, photon generation efficiencies can be greater than 50% radiant power. More specifically, in some embodiments, photon generation efficiencies can be approximately 60% radiant power.

[0054] The coolant flow direction may be perpendicular to or parallel to the electron beam. In some embodiments, porous media geometry, such as a structured mesh, allows the porosity of the media to be controlled independently of the solid feature size using wire diameter and spacing. Such a configuration can increase heat transfer while minimizing coolant pressure drop.

[0055] Due to their high heat transfer coefficient and large heat transfer surface area per unit volume, porous transducers can operate at lower temperatures than conventional non-porous transducer geometries, thereby avoiding or minimizing thermal distortion of the transducer material. Thermal distortion that occurs in porous transducers is less likely to result in a thermal performance penalty than thermal distortion that occurs in non-porous transducer geometries. For example, in a packed bed of spherical particles, the individual spheres and the overall volume of the packed bed expand with increasing temperature, but the pores may remain open, allowing coolant to flow through the matrix of spheres in the expanded state.

[0056] In an exemplary conventional converter configured with a set of solid parallel plates separated by cooling channels and with the electron beam traveling perpendicular to the plate surfaces and coolant flow, buckling can occur because the electron beam causes a non-uniform temperature distribution in the plates, changing the geometry of the coolant channels and potentially degrading the thermal performance of the overall converter structure.

[0057] Still referring to FIG. 3 , converter 332 may have an inlet 360 and an outlet 370. Inlet 360 and outlet 370 allow coolant 350 to form a flow loop. As shown in FIG. 3 , in one embodiment, beamline 320 may be directed toward converter 332 from a first direction, and coolant 350 may flow through converter 332 from a second direction opposite the first direction. Additionally, target system 334 may be aligned with beamline 320 and converter 332 such that beam 320 may be converted into bremsstrahlung through converter 332 as beam 320 approaches target 334.

[0058] As mentioned above, in some embodiments, the porous media 340 is allowed to expand and / or contract due to thermal expansion. In the case of porous media beads, the expansion and / or contraction of the beads may result in slow movement of individual damaged beads as a result of the phenomenon of random spherical packing or packing auto-arrangement. In some embodiments, the beads may be held in place via fine metal (e.g., stainless steel) screens placed over the inlet 360 and outlet 370. In some embodiments, the porous material may be sintered together.

[0059] Referring now to Figure 4, a pebble bed beam converter 400 is shown. The pebble bed beam converter 400 is similar to the beam converter system 300 of Figure 3. However, in this case, the pebble bed beam converter 400 may have a beam line window 410 that can direct the beam line 320 toward the converter 332. Additionally, the target system 420 may include a target capture 430 and a target cavity 440.

[0060] Referring now to FIG. 5, a graphical representation of average electron energy versus distance is shown as the electron beam travels through a series of coolants (eg, water) and high-Z materials (eg, tantalum).

[0061] 6 and 7 show a target area 600. The target area 600 may include a target system 630, which houses a transducer 632 and a target 634. In some embodiments, the target system 630, the transducer 632, and the target 634 may be the target system 130, the transducer 132, and the target 134, respectively, of FIG. 1. In some embodiments, the target system 630, the transducer 632, and the target 634 may be the target system 330, the transducer 332, and the target 334, respectively, of FIG. 3.

[0062] The target area 600 may further include a cooling system 630. The cooling system 610 may include an inlet coolant pipe 612 and an outlet coolant pipe 614. The inlet coolant pipe 612 and the outlet coolant pipe 614 may be connected to each other via a passage 616 to form a flow loop.

[0063] In embodiments utilizing parallel coolant flow, a flow loop can be provided that includes an inlet flow and an outlet flow, such that the inlet flow and outlet flow are perpendicular to the beam, with a through flow directed into the converter 632. In some embodiments, a second through flow between the inlet coolant tube 612 and the outlet coolant tube 614 can be provided ahead of or beyond the converter 632 to continue to force the coolant forward and through the converter 632.

[0064] For example, the second throughflow can be throttled by reducing the cross-sectional area of ​​the channel by adding an in-line adjustable valve. Such a configuration can prevent recirculation zones in the coolant near the inlet and outlet regions of converter 632 (e.g., inlet 360 and outlet 370 in FIG. 3) by allowing consistent coolant flow rates at the surfaces of the containment structure (which experience thermal power buildup from the electron beam and therefore must be cooled by the fluid coolant).

[0065] With particular reference to FIG. 6 , converter 632 minimizes the coolant flow length by aligning the coolant flow direction parallel to the beamline, thereby reducing pressure drop. In such a configuration, the width of converter 632 is not limited by thermal performance. For example, in one embodiment, only 9 mm of porous tantalum is required to stop 40 MeV electrons, which is shorter than the width of conventional converters that can be made to accommodate the FWHM from an accelerator. Furthermore, by reducing the flow length, the total temperature change of the coolant can also be reduced, thus increasing cooling efficiency. This concept can be understood in FIG. 8.

[0066] As shown in Figure 8, the photon flux produced by this model in MCNP (C.J. Werner, et al., "MCNP6.2 Release Notes," Los Alamos National Laboratory, Report LA-UR-18-20808 (2018)) showed only a 3.7% decrease in photon flux at energies between 10 and 30 MeV compared to results from a model consisting of two solid tantalum converter disks similar in design to another paper (Diamond, William & Ross, Carl.) (2021), Actinium-225 Production by Electron Accelerator, Journal of Applied Physics, 129, 104901, 10.1063 / 5.0043509).

[0067] Thus, the systems and methods disclosed herein absorb and dissipate a high fraction of the beam power from the beamline, effectively shielding the target from high-power storage loads. This relaxes thermal design constraints on the target and enhances passive safety by shifting most of the system burden to non-radioactive components. A further benefit of reducing the heat load on the target with a porous bed converter is that it allows the target to be cooled by contact conduction rather than by direct convection in a fluid. This simplifies target handling and reduces the risk of accelerator-based cooling systems becoming contaminated with target material by providing an additional safety barrier to prevent the system from contaminating groundwater.

[0068] Each of the patents, patent applications, and publications cited herein is hereby incorporated by reference. As used herein, the articles "a" or "an" include one or more.

[0069] The above description and examples are intended to be illustrative and should not be construed as limiting the invention. Further variations within the damping and scope of the invention are contemplated and will readily occur to those skilled in the art.

[0070] Specific examples of pebble bed converters according to the present invention have been described for purposes of illustrating how the invention can be constructed and used. It should be understood that other variations and modifications of the invention and its different aspects will be apparent to those skilled in the art, and the invention is not limited to the specific embodiments described. Features described in one embodiment may be embodied in other embodiments. The present disclosure should be understood to include the invention and any and all modifications, variations, or equivalents that fall within the spirit and scope of the underlying basic principles disclosed and claimed herein.

Claims

1. 1. A converter of electron beams, comprising: a plurality of spherical beads disposed in a fluid coolant within the transducer; The converter is configured to receive the electron beam from a first side and generate and emit photons from a second side opposite the first side.

2. The transducer of claim 1 , wherein the plurality of spherical beads are made of a high atomic number (high Z) material.

3. 2. The transducer of claim 1, wherein the plurality of spherical beads are packed and substantially randomly distributed within the transducer.

4. The converter of claim 1 , wherein the fluid coolant enters the converter through an inlet on the second side and exits the converter through an outlet on the first side.

5. 5. The converter of claim 4, wherein a first screen is disposed over the inlet and a second screen is disposed over the outlet, and wherein the plurality of spherical beads pass through the first and second screens and are contained within the converter.

6. 1. A system for producing radioisotopes, comprising: The accelerator and Beamlines and a targeting system, the targeting system comprising: a porous media converter comprising a plurality of spherical beads; The target, an inlet designed to allow a flow of a cooling fluid to enter the porous media converter and surround the plurality of spherical beads; an outlet configured to allow the cooling fluid to exit the porous media converter.

7. 7. The radioisotope production system of claim 6, wherein the accelerator is mounted on a common axis with the target system.

8. 7. The radioisotope production system of claim 6, wherein the accelerator is disposed on a first axis and the target system is disposed on a second axis different from the first axis.

9. The radioisotope production system of claim 6 , further comprising a target cooling system in fluid communication with the target system.

10. 7. The radioisotope production system of claim 6, including a hot cell in fluid communication with the target system.

11. The radioisotope production system of claim 6 , including an accelerator vault designed to house the accelerator, the beamline, and the target system.

12. 12. The radioisotope production system of claim 11, comprising a first radiation zone disposed within the accelerator vault, the first radiation zone designed to accommodate the accelerator and the beamline.

13. 12. The radioisotope production system of claim 11, further comprising a second radiation zone disposed within the accelerator vault, the second radiation zone being designed to accommodate the target system.

14. The radioisotope production system of claim 6 , wherein the target system includes a beamline window positioned in front of the porous media converter.

15. The radioisotope production system of claim 6 , wherein the target system includes a passageway configured to define a fluid passageway located between the inlet and the outlet to form a flow loop.

16. 1. A method for converting an electron beam into photons, the method comprising: providing a transducer comprising a plurality of spherical beads disposed in a fluid coolant; directing one or more electron beams at the transducer from a first side of the transducer; generating and emitting photons from a second side of the converter opposite the first side.

17. 17. The method of claim 16, wherein the plurality of spherical beads are made of a high atomic number (high Z) material.

18. 17. The method of claim 16, wherein the plurality of spherical beads are closely packed and substantially randomly distributed within the transducer.

19. providing the fluid coolant into the converter through the second side inlet; The method of claim 16 , further comprising: allowing the fluid coolant to exit the transducer through an outlet on the first side.

20. 20. The method of claim 19, wherein a first screen is disposed over the inlet and a second screen is disposed over the outlet, and the plurality of spherical beads are adapted to pass through the first screen and the second screen and into the transducer.

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