WO2024036411A1 - A target for subsequent exposure to an accelerated proton beam and method of making same - Google Patents

Abstract

Disclosed herein are methods for producing a radium or barium target. The methods include providing an organic-aqueous electrolyte bath solution comprising radium or barium ions, exposing a deposition surface of a target substrate to the electrolyte bath solution, wherein the target substrate comprises at least one of copper and aluminum, and wherein the deposition surface comprises at least one of copper, aluminum, gold, platinum, rhodium or silver, and applying an electric potential between an anode and the target substrate for a deposition cycle time, thereby electrodepositing a layer of radium or barium containing material out of the bath solution and onto the deposition surface. Also disclosed are targets for subsequent exposure to an accelerated proton beam.

Description

A TARGET FOR SUBSEQUENT EXPOSURE TO AN ACCELERATED PROTON BEAM AND METHOD OF MAKING SAME

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is related to and claims the benefit of co-pending U.S. provisional patent application no. 63/371,985 filed August 19, 2023 and entitled “Methods For Producing A Radium Target For The Production Of Actinium-225 Via An Accelerated Proton Beam”, the entirety of which is incorporated herein by reference.

FIELD

[0002] The present disclosure relates to targets and methods and processes for producing a target, such as by deposit the target material on a carrier substrate, that can be used in the subsequent production of a desired material, such as, for example, by subjecting the target to an accelerated proton beam. Some examples of the teachings herein can relate to the methods and processes for producing a radium target which may be used for the production of actinium-225, for example, via an accelerated proton beam; more specifically, radium targets of deposited radium on a metal plate. This disclosure can also relate to methods and processes for producing a barium target, which may be used for the production of lanthanum- 133 and lanthanum-135, for example, via an accelerated proton beam.

BACKGROUND

[0003] Canadian patent no. 2,542,178 (Bermudez et al.) discloses methods and processes relating to a radium target as well as to a method for producing it for the production of radionuclides by means of accelerated protons, wherein an electrodeposition of radium out of at least one organic-aqueous solution containing ²²⁶Ra ions is carried out on at least one aluminum surface, wherein the aluminum surface is connected as cathode. With the ²²⁶Ra target according to the disclosure, ²²⁵Ac/²¹³Bi, which can be used, for example, for radioimmunotherapy for cancer treatment, can be produced continuously and in sufficient quantities at a reasonable price. [0004] Canadian patent no. 2,564,895 (Harfensteller et al.) discloses a method for producing a radium target for the production of radionuclides by means of accelerated protons, whereby at least one radium containing material out of an aqueous-organic solution or suspension of such a material is applied by means of a dispersing device on a surface in such a way that the dispersing device and the surface are moving relatively towards each other and that the solvent is removed substantially spontaneously. Further, the publication refers to a radium target that is created in such a way that it may exhibit an activity of up to 1.5 curie. The radium targets serve to produce the radionuclide 225 Ac, which may be used in nuclear medicine in the treatment of cancer, particularly in form of its daughter nuclide 213Bi.

[0005] International patent publication no. WO 2005/039647 (PCT/EP/2004/011510) discloses a radium target as well as to a method for producing it for the production of radionuclides by means of accelerated protons, wherein an electrodeposition of radium out of at least one aqueous organic solution containing ²²⁶Ra ions is carried out on at least one aluminum surface, wherein the aluminum surface is connected as cathode. With the ²²⁶Ra target according to the present invention, ²²⁵Ac/²¹³Bi, which can be used, for example, for radioimmunotherapy for cancer treatment, can be produced continuously and in sufficient quantities at a reasonable price.

SUMMARY

[0006] Molecular plating is a technique used for electrodepositing compounds from an organic solvent. It may be performed in a cell containing two electrodes, where the cations are electrodeposited onto the working electrode, i.e. the cathode. The term “molecular plating” emerged in a publication from Parker & Falk in 1962 ⁽Parker, W. and Falk, R. (1962). Molecular plating: “A method for the electrolytic formation of thin inorganic films”. Nuclear Instruments and Methods, 16, 355-357) where numerous elements were claimed to be deposited onto aluminum substrates from solutions of isopropanol (2 -propanol, IP A), utilizing much higher voltages (ca. 600 Vdo) than conventional electroplating. The authors of this work made specific note that the molecular plating of barium compounds was challenging at least partially by the low solubility of barium salts in alcohol solutions. Initially the authors assumed that the compound deposited on the substrate was in the same salt form as that introduced to the alcohol solution originally. It was discovered in a later work that this assumption was incorrect, and that the deposited material may consist of a hydroxide or carbonate compound of the present metal.

[0007] Since these initial publications, there have been numerous publications utilizing the molecular plating technique for nuclear science applications, including accelerator target preparation. Therefore, there is a need for methods and processes of molecular plating barium/radium that addresses one or more of these drawbacks.

[0008] In accordance with one broad aspect of the teachings described herein the present disclosure relates to methods and processes for producing a radium target that can be suitable for subsequent use as part of the production of actinium 225, such as via an accelerated proton beam.

[0009] In accordance with one broad aspect of the teachings described herein the present disclosure relates to methods and processes for producing a barium target that can be suitable for subsequent use as part of the production of lanthanum- 133 and/or lanthanum-135, for example, via an accelerated proton beam.

[0010] In accordance with one broad aspect of the teachings described herein, which may be used alone or in combination with any other aspects described herein, there is provided a method for producing a radium target, the method comprising: a) providing an organic-aqueous electrolyte bath solution comprising radium ions; b) exposing a deposition surface of a target substrate to the electrolyte bath solution, wherein the target substrate comprises at least one of copper and aluminum, and wherein the deposition surface comprises at least one of copper, aluminum, gold, platinum, rhodium or silver; and c) applying an electric potential between an anode and the target substrate for a deposition cycle time, thereby electrodepositing a layer of radium containing material out of the bath solution and onto the deposition surface.

[0011] The method may have an organic-aqueous electrolyte bath solution comprising at least one mineral acid, at least one organic solvent and a radium salt. [0012] The method may have a radium salt comprising one or more of radium chloride, radium nitrate, radium bromide, radium oxide, or radium hydroxide.

[0013] The method may have an organic-aqueous electrolyte bath solution comprising about 1-18% water, about 82-99% organic solvent, about 0-0.01 mol/L mineral acid and about 0.001-3 mmol of the radium salt.

[0014] The method may have a mineral acid comprising one or more of hydrochloric acid, nitric acid, or hydrobromic acid.

[0015] The method may have a layer of radium containing material comprising substantially radium carbonate.

[0016] The method may have a layer of radium containing material having an effective thickness of 0.03 to 23 mg/cm² as the elemental form of the radium cation.

[0017] The method may have a layer of radium containing material having a melting temperature of at least 800°C, more preferably over 950°C, most preferably over 1000°C.

[0018] In accordance with another broad aspect of the teachings described herein, which may be used alone or in combination with any other aspects described herein, there is provided a method for producing a barium target, the method comprising: a) providing an organic-aqueous electrolyte bath solution comprising barium ions; b) exposing a deposition surface of a target substrate to the electrolyte bath solution, wherein the target substrate comprises at least one of copper and aluminum, and wherein the deposition surface comprises at least one of copper, aluminum, gold, platinum, rhodium or silver; and c) applying an electric potential between an anode and the target substrate for a deposition cycle time, thereby electrodepositing a layer of barium containing material out of the bath solution and onto the deposition surface.

[0019] The method may have an organic-aqueous electrolyte bath solution comprising at least one mineral acid, at least one organic solvent and a barium salt. [0020] The method may have a barium salt comprising one or more of barium chloride, barium nitrate, barium bromide, barium oxide, or barium hydroxide.

[0021] The method may have an organic-aqueous electrolyte bath solution comprising about 1-18% water, about 82-99% organic solvent, about 0-0.01 mol/L mineral acid and about 0.001-3 mmol of the barium salt.

[0022] The method may have a layer of barium containing material comprising substantially barium carbonate.

[0023] The method may have a mineral acid comprising one or more of hydrochloric acid, nitric acid, or hydrobromic acid.

[0024] The method may have a layer of barium containing material having an effective thickness of 0.03 to 23 mg/cm² as the elemental form of the barium cation.

[0025] The method may have a layer of barium containing material having a melting temperature of at least 800°C, more preferably over 950°C, most preferably over 1000°C.

[0026] The method may further include maintaining a pH of the organic-aqueous electrolyte bath solution at or above 4 during at least a majority of the deposition cycle time.

[0027] The method may include maintaining a pH of the organic-aqueous electrolyte bath solution at or above 4 for the entire deposition cycle time.

[0028] The method may include maintaining the pH within a range of about 4 to about 8, and preferably within a range of about 4 to about 6.

[0029] The method may include maintaining the pH comprising providing an alkaline additive to the organic-aqueous electrolyte bath solution.

[0030] The method may have the alkaline additive comprising an aqueous solution of ammonium hydroxide.

[0031] The method may have an aqueous solution having a concentration of about 2% to about 30% ammonium hydroxide. [0032] The method may have an alkaline additive further comprising isopropanol.

[0033] The method may have a deposition surface that has been roughened prior to the electrodeposition of the layer of radium containing material such that the deposition surface has a roughness between about 0.125 pm and about 2.5 pm.

[0034] The method may have a target substrate comprising a cover layer comprising gold, platinum or rhodium that covers at least a portion of the target substrate and provides the deposition surface, whereby the deposition occurs on an exposed portion of the cover layer.

[0035] The method may have a cover layer that is electroplated, electroless plated, application rolled, PVD, or foiled onto the target substrate.

[0036] The method may have a cover layer that has a thickness of between about 0.1 pm and about 2 pm.

[0037] The method may have a cover layer formed from gold.

[0038] The method may have a relative volume ratio of organic solvent to aqueous solvent in the organic-aqueous electrolyte bath solution greater than about 4.8, prior to contact with the target substrate.

[0039] The method may have an organic solvent comprising an alcohol.

[0040] The method may have an alcohol comprising one or more of ethanol or isopropanol.

[0041] The method may have a relative volume ratio that is maintained during the deposition cycle time by addition of organic.

[0042] The method may have an organic-aqueous electrolyte bath solution at a temperature of between about 10°C and about 50°C.

[0043] The method may further include an electric potential between the anode and the metal plate between about 20 and about 600 V, and preferably between about 100 V and about 200 V. [0044] The method may have electrodepositing carried out at a current of between about 0.01 and about 0.1 A.

[0045] The method may have electrodepositing carried out at a current density of between about 0.0005 and about 0.02 A/cm²

[0046] The method may have an anode comprising platinum.

[0047] The method may further include organic-aqueous electrolyte bath solution recirculated in the cell by means of an external pump.

[0048] The method may have a deposition cycle time between 0.1 and 24 hours.

[0049] The method may have a target substrate comprising at least one of a plate and a foil formed from at least one of copper and aluminum.

[0050] The method may have a target substrate comprising a copper plate.

[0051] The method may further include deaerating the aqueous bath solution with a carrier gas during the deposition cycle time.

[0052] The method may have a carrier gas comprising an inert gas that is non-reactive with the aqueous bath solution.

[0053] The method may have a carrier gas comprising argon.

[0054] In accordance with another broad aspect of the teachings described herein, which may be used alone or in combination with any other aspects described herein, there is provided a target for subsequent exposure to an accelerated proton beam, the target comprising: a target substrate formed from copper or aluminum; a cover layer being formed from gold, platinum, silver, or rhodium, the cover layer covering at least a portion of the target substrate and provides a deposition surface; and a layer of radium or barium containing material electrodeposited on the deposition surface. [0055] The target may have a deposition surface that is at least partially concave and the layer of radium or barium containing material has a non-uniform thickness whereby an exposed upper surface of the layer of radium or barium is relatively flatter than the deposition surface.

[0056] The target may have a deposition surface having a surface roughness of between about 0.125 pm and about 2.5 pm.

[0057] Other aspects and features of the disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Embodiments of the disclosure will now be described in greater detail with reference to the accompanying drawings, in which:

[0059] FIGURE 1 is a flow chart depicting steps of a method for producing a radium target.

[0060] FIGURE 2 is a schematic of an electrolytic cell.

[0061] FIGURE 3 is a schematic of the electrolytic cell of Fig. 2 with a layer of deposited material on a cathode.

[0062] FIGURE 4 is a schematic of the electrolytic cell of Fig. 2 with a cover layer/film on the cathode.

[0063] FIGURE 5 is a schematic of the electrolytic cell of Fig. 4 with a layer of deposited material on the cover layer/film.

[0064] FIGURE 6 is a digital rendering of a High Current Solid Target Station (HCSTS) target faceplate with material deposited in an elliptical shape.

[0065] FIGURE 7 is a photograph of a copper rod deposited with barium compound.

[0066] FIGURE 8 is a photograph of an experimental electrolytic cell for HCSTS faceplate deposition experiments. [0067] FIGURES 9A and 9B are photographs of barium deposits formed by molecular plating. Figure 9A shows a plate with a surface roughness as-milled and Figure 9B shows a plate with a surface roughed with 150 grit sandpaper.

[0068] FIGURE 10 is a photograph of a barium deposit formed from isopropanol based electrolyte, with lower current density and initial pH > 4.

[0069] FIGURE 11 is a photograph of a barium deposit formed at pH < 3.

[0070] FIGURE 12 is a graph depicting electrolyte barium concentration during electrodeposition in experiments with uncontrolled and controlled pH. Also depicted are polynomial (poly) fit lines.

[0071] FIGURES 13A and 13B are photographs of barium electrodeposits prepared on substrates plated in gold. Figure 13A depicts a substrate conventionally electroplated with gold. Figure 13B depicts a substrate with electroless plated gold.

[0072] FIGURE 14 is an FTIR spectrum of three analyzed Ba deposits prepared by molecular plating and the reference FTIR spectrum of witherite (BaCCh).

[0073] FIGURE 15 is a schematic showing embodiments of targets having a relatively flat deposition surface and a relatively concave deposition surface.

DETAILED DESCRIPTION

[0074] One or more illustrative embodiments have been described by way of example. Described herein are methods and processes relating producing a target, such as a radium target that can be used, for example, as a target in the production of actinium- 225, such as via an accelerated proton beam. It will be appreciated that embodiments and examples are provided for illustrative purposes intended for those skilled in the art and are not meant to be limiting in any way. All references to embodiments, examples, aspects, formulas, compounds, compositions, solutions, and the like is intended to be illustrative and non-limiting. Other targets, which may be used in the production of other materials, can also be created using the methods and processes described herein, such as a barium target. For example, the methods and processes described herein can be used to produce a target that includes barium, a barium target, which can be used for the production of materials other than actinium-225, such as the production of lanthanum-133 and lanthanum-135 via electrodeposition or other suitable plating/ deposit! on techniques.

[0075] Unless expressly stated to the contrary, all ranges cited herein are inclusive; i.e., the range includes the values for the upper and lower limits of the range as well as all values in between. As an example, temperature ranges, percentages, ranges of equivalents, and the like described herein include the upper and lower limits of the range and any value in the continuum there between. Numerical values provided herein, and the use of the term "about", may include variations of + 1%, 2%, 3%, 4%, 5%, 10%, + 15%, and 20% and their numerical equivalents.

[0076] Actinium-225 is a compound that is used in a variety of commercial and medical applications. Methods and processes for producing commercially useful quantities of actinium-225 can help meet the anticipated need/ demand for actinium-225. One method of producing actinium-225 includes bombarding a target object containing radium (herein referred to as a target) with an accelerated proton beam, thereby transforming the radium nuclei into the desired actinium-225 nuclei.

[0077] Lanthanum-133 and lanthanum-135 are isotopes that may be used in the imaging and therapy of cancer and could potentially be used as a theranostic pair for actinium-225. One method of producing lanthanum-133 and/or lanthanum-135 includes bombarding a target object containing barium (herein referred to as a target) with an accelerated proton beam, thereby transforming the radium nuclei into the desired lanthanum-133 or -135 nuclei.

[0078] The specific conditions, and apparatuses, used to achieve the proton bombardment can vary in different embodiments and for the different materials described herein, but having a suitable target object that includes a desired amount of the radium or barium material is a part of most such processes. The teachings herein are, in one broad aspect, directed to methods and processes for producing targets that can carry radium or barium material and that can be used as inputs in a desired actinium- 225 and/or lanthanum-133 and/or lanthanum-135 production processes. In some embodiments, methods and processes for producing a radium target that can be suitable for use for the production of actinium-225 via an accelerated proton beam are disclosed herein. In other embodiments, methods and processes for producing a barium target that can be suitable for use for the production of lanthanum-133 and/or lanthanum-135 via an accelerated proton beam (or analogous process) are disclosed herein.

[0079] Referring to Figure 1, in one embodiment, the method 100 can include, at step 102 providing an organic-aqueous plating bath solution that includes a suitable concentration of radium or barium ions (as required and/or appropriate for the given target that is being created). A target substrate, that in the examples described herein can include a metal plate, can be submerged in or wetted with the organic-aqueous plating bath solution. The target substrate includes a deposition surface that is configured to receive and be coated with the radium-containing or barium-containing deposition material, and preferably that has an exposed surface portion that includes copper, aluminum, gold or possibly other suitable metals. Optionally, in some embodiments the target substrate can be provided as a metal foil (such as a copper foil or aluminum foil) rather than the thicker, stiffer metal plate. In some conditions, the use of a foil as the target substrate may permit the proton beam (used in the later deposition processes) to pass through the foil substrate, whereas utilizing a thicker substrate plate may block at least some of the proton beam and may, depending on the plate thickness and attributes, arrest the proton beam completely.

[0080] In some examples the target substrate may be formed from copper, or aluminum, or combinations thereof. As between copper and aluminum, aluminum may have a relatively lower thermal conductivity than copper (where good thermal conductivity may help facilitate heat management during deposition processes, such as via cyclotron bombardment). However, in some cases aluminum may have a relatively better chemical resistance for the post-cyclotron recovery of desired radionuclides, as copper may tend to be less acid resistant (which may lead to contamination of the aqueous product solution with undesirable species under some operating conditions). Optionally, as described herein, the target substrate may be coated with one or more intervening layers, such as the gold cover fdm/layer (see cover fdm/layer 240) described in some of the examples herein, which may alter some of the properties of the target substrate. The presence or absence of a cover layer of this nature may be combined with any of the other designs described herein.

[0081] At step 104, the method 100 can include applying an electric potential between an anode and the target substrate (e.g., the metal plate) using any suitable controller, power source and other related equipment. Applying the electric potential can lead to the electrodepositing/molecular plating of a layer of radium-containing or barium- containing material out of the bath solution and onto the deposition surface of the target substate, at step 106. In the methods and processes described herein, the target substrate (for example, a metal plate) and organic-aqueous bath solution may be placed in or connected to an electrolytic cell prior to applying the electric potential.

[0082] During steps 104 and/or 106, one or more parameters of the cell 200 and the organic-aqueous bath solution may be monitored and/or maintained at substantially the same value during the plating process.

[0083] For example, the pH of the organic-aqueous bath solution may be maintained at or above a desirable operating value, such as greater than about 4, 4.5, 5, 5.5, 6, or 6.5 and preferably between about 4 to about 5, about 4 to about 6, about 4 to about 7, and about 4 to about 8 (step 108). The inventors have determined that conducting the processes at a pH that is at or above 4, and preferably maintaining the pH at or approximately at that level during at least the majority (and optionally at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% 90% and 95%) of the deposition period can improve the quality of the deposited barium or radium layer, as compared to an electroplating process conducted at a pH of less than 4. In some preferred examples, the pH may be maintained at or above 4 for the entire deposition period.

[0084] The pH at step 108 may be monitored via a suitable method/apparatus, such as a pH meter. Preferably, the pH of organic-aqueous bath solution may be monitored and maintained at the operating value for at least most or a majority of the deposition cycle time, at step 108, via a suitable method. The pH adjusting/maintaining can be achieved using a suitable process/technique, such as via the ongoing, or intermittent/ on-demand addition of a suitable alkaline additive, such as a solution of ammonium hydroxide to the organic-aqueous bath solution or into another portion of the process apparatus that can have an effect on the pH within the bath solution (such as in a bath solution reservoir or other upstream process location/vessel). In these examples, the alkaline additive reacts with hydrogen ions in the organic-aqueous bath solution thereby reducing the amount of free hydrogen ions in the organic-aqueous bath solution which helps counteract decreases in the pH of the organic-aqueous bath solution during the deposition cycle time. In some embodiments, the alkaline solution is a relatively dilute aqueous solution that is added dropwise to the bath solution.

[0085] As described herein, in some examples the alkaline additive can include an aqueous solution of ammonium hydroxide having a concentration of between 2% to 30% or a mixture of said aqueous ammonium hydroxide solution and an alcohol, such as isopropanol.

[0086] Another parameter of the processes described herein that can be manipulated, in combination with or independently from other features described herein, is the temperature of the organic aqueous-bath solution during the deposition cycle time. Optionally, the temperature of the organic- aqueous bath solution may also be monitored (step 112) and maintained at a specific, process value or within a desired range during the deposition cycle time.

[0087] During steps 104 and/or 106, the organic-aqueous bath solution may optionally be sparged or deaerated (step 110). This may help control some of the parameters of the organic-aqueous bath solution. Deaerating may comprise removing gas from the aqueous bath solution. An inert carrier gas, such as argon, may be bubbled through the solution to displace and remove unwanted, relatively more reactive gases gas.

[0088] Optionally, prior to steps 102, 104 and/or 106, the target substrate, such as a metal plate, metal foil or the like, may be prepared (step 114). For example, the deposition surface of the target substrate may be roughened using a suitable roughening method. In some cases, a cover film/layer of a suitable material, such as gold, may be applied to the underlying plate or foil to cover at least a portion of its outer surface and to form the target deposition surface that will ultimately receive the barium or radium in the described examples.

[0089] Referring to Figures 2-5, one example of an electrolytic cell 200 that is suitable for preparing the targets described herein is schematically illustrated. In this example, the cell 200 includes a housing, with a base 204 and sidewalls 206, that is configured to hold a desired aqueous bath solution 206. The electrolytic cell 200 may have one or more sidewalls for mounting one or more metal plates. The sidewalls 206 can be formed from any suitable material, and preferably may be formed of an inert or chemically compatible material, such as polytetrafluoroethylene (PTFE) or poly ether ether ketone (PEEK). While shown as generally rectangular in the schematic, the housing may have any suitable shape.

[0090] A target substrate, in the form of a metal plate 208 in this example, is positioned so that its deposition surface 210 is in contact with the solution 206 within the housing 206. In the schematic illustration the plate 208 is submerged within the solution 206, but other arrangements are possible, including having the plate 208 form at least part of the base 204 or sidewalls 206 of the cell 200 so that only the desired target area is wetted with bath solution.

[0091] To help facilitate the deposition processes described herein, the cell 200 can include one or more suitable electrodes, and may be configured (as illustrated) so that the metal plate 208 is be connected such that it acts as a cathode and a suitable anode 212, such as platinum, is provided in communication with the solution 206. A power source 214, to provide the desired electric potential between the electrodes 208 and 212 can be provided, a suitable system controller 216 (such as a computer, PLC or the like) can be provided to control the operation of the cell 200.

[0092] Optionally, the cell 200 can be configured so that it holds a fixed volume of the solution 206 during the deposition process. Alternatively, as schematically illustrated in this example, the cell 200 may be configured as a flow-through cell in which the solution 206 flows through the interior of the cell while the system is in use. This may help facilitate keeping the parameters of the solution 206 relatively consistent/stable while the cell 200 is in use, and/or may allow significant portions of the solution 206 to be processed (such as heated or cooled, pH maintained and/or other processing) at a location that is outside the cell 200 which can then to flow into (and subsequently out of) the cell 200 when the system is in use. In this example, the cell 200 is illustrated as including at least one inlet port 218, through which solution 206 can enter the cell 200, and at least one outlet 220, through which solution 206 can be extracted from the cell 200.

[0093] Between the ports 218 and 220, a solution processing circuit 222 can be provided, which can allow the desired fluid flow and can include liquid circulation hardware 224, such as a reservoir or liquid source, a pump, valves and other such equipment that is not illustrated in detail in this schematic. In some examples, the ports 218 and 220 can be configured for recirculation of electrolyte solution 206 via a suitable method and the hardware 224 can include at least a peristaltic or syringe pump. The inlet/outlet ports 218 and 220 may also be used for filling and draining of the electrolyte fluid solution 206 prior to and following deposition. In some cases, a separate inlet/outlet port 218 and 220 are used as illustrated. In other examples, a single port may alternatively function as both the inlet port 218 and outlet port 220. The recirculated liquid solution 206 may be sampled or adjusted, such adjusting pH or aeration, prior to returning to the cell 200. Alternatively, or in addition to processing the solution 206 outside the cell 200, the cell 200 may also have a direct monitoring or measuring device, such as a thermocouple for temperature monitoring.

[0094] Referring also to Figure 3, When the methods and processes described herein are performed, which may include the use of a cell similar to cell 200, the material that is to be deposited onto the target 226 (e.g., containing radium in the commercial embodiments and barium in the experimental tests or in an alternative commercial embodiment) can be driven from the solution 206 in the presence of the electric potential, and can be deposited onto the deposition surface 210 to form the layer of deposited material 230 (e.g., a layer of radium-containing material, a layer of barium- containing material, etc.).

[0095] The layer of deposited material 230 can, in some examples, be formed to have relatively high porosity and a desired thickness 232 commensurate with a mass load per unit area in a desire range, which can be between about 0.03 to 43 mg/cm² expressed for the elemental form of the radium or barium cation.

[0096] The thickness 232 of the deposit material layer is, in most embodiments, substantially less than the thickness 234 of the plate 208 (measured in the same direction). In the examples described herein, the plate 208 can be a copper plate and the thickness 234 may be between about 1mm and 10mm, and preferably may be between equal to or greater than about 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm or more, and may be less than about 10mm, 9.5mm, 9mm, 8.5mm, 8mm, 7.5mm, 7mm, 6.5mm or 5mm, and in some preferred embodiments the thickness may be between about 4 mm and about 5 mm. In some embodiments of the methods and processes described herein, the electric potential is applied in the cell for a deposition cycle time that can be selected so that a desired amount of material is deposited in the deposited layer 230. The deposition time in a given embodiment may be affected by a variety of system parameters, including the concentration of the target material in the solution 206, the operating conditions of the cell 200, the electric potential applied between the electrodes 208 and 212 and the like. Appropriate cycle time may be chosen according to desired coating area and layer thickness. In some examples, the deposition cycle time can be between 0.1 and 24 hours, such as 14 hours. The deposition cycle time may be understood by a person of skill in the art as the time interval that an electric potential is applied between the anode and the metal plate.

[0097] In some embodiments, plural deposition cycles could be employed. In some other embodiments employing plural cycles, depleted electrolyte solution is drained after the first cycle and replenished with fresh electrolyte, where this could be repeated for up to 10 cycles. Plural cycle lengths may be shorter by the factor that is the number of plural cycles, for example a 24-hour single cycle may be approximately split into 4 x 6 hour cycles.

[0098] The metal plate provided in the methods described herein may be formed from pure, or at least substantially pure copper and can be referred to as a copper plate. This can also include metal with some alloying materials or impurities that do not have a material impact on the properties and performance of the copper plate as described herein. In other examples, the plate may be formed from another suitable metal, such as aluminum, gold, platinum or rhodium or an alloy thereof. The copper plate may have any suitable shape/configuration, such as a rectangle as illustrated in the present examples, but may be square, or have other shapes in other arrangements. In some cases, the metal plate may comprise a material with a suitable thermal conductivity, such as ~4 W cm’¹ K'¹ r. Optionally, instead of the relatively thick plate, the substrate may be a foil.

[0099] The deposition surface 210 of the substrate may, in this example, be understood as an exposed portion substrate that is in communication with the solution 206 during the electrodeposition process. In cases where a copper plate 208 is used, the deposition surface 210 may comprise an exposed portion of the copper plate. In examples where a cover layer of a different material is provided on the substrate then the cover layer may provide the deposition surface that will receive the radium or barium, as applicable. [00100] Optionally, the deposition surface may be treated to help facilitate the deposition of barium/radium during the processes described herein, for example using mechanical and/or chemical surface treating processes or techniques. For example, the deposition surface may be chemically treated to modify is surface properties and/or may be mechanically treated to modify its shape, texture, surface roughness or other such parameters. This may change the way that the deposited material interacts with the deposition surface and, in some configurations, may help promote deposition and/or may alter the features or configuration of the layer of deposited material.

[00101] For example, modifying the shape and/or flatness of the deposition surface may change the shape of the resulting layer of the layer of deposited material. Optionally, the deposition surface on the target substrate may be flat, or at least substantially flat or planar enough such that it can be considered flat on the relevant size scales described herein. Alternatively, the deposition surface on the target substrate need not be flat, but instead may be shaped to help accommodate expected differences in the thickness of the target material that will eventually be collected on the target. Counterintuitively, providing a shaped, or non-flat deposition surface, on the target substrate could therefore help provide a relatively flatter, final surface on the postdeposition layer of deposited material.

[00102] For example, as shown in Fig. 3, the layer of radium or barium material 230 that is deposited via the electrodeposition process may not have a uniform thickness across its lateral extent and may be relatively thicker toward its center than it is toward its periphery (or possibly vice versa), such as layer 231. In such circumstances, the deposition surface 210A of plate 208A could be intentionally formed to be at least partially concave with a central, recessed region that is lower than the surrounding peripheral regions (Fig. 15). When the layer of radium or barium material is deposited onto the deposition surface the relative thickness at the center of the deposited layer may be accommodated by the concavity of the depressed central region of the deposition surface 210A, resulting in an upper, exposed surface of the layer of radium or barium material 230A that is relatively flatter than would be achieved if the deposition surface was itself flat. For example, layer 230A may not extend past plane 260 defined by the periphery of plate 208A. Alternatively, if a given process tended to product a deposited material layer that is thicker at its periphery than its center then the deposition surface of the target substrate could be configured to be generally convex, with a relative high point toward its center and relatively lower portions around its periphery so that the resulting layer of material 230 would be relatively flatter than the initial deposition surface.

[00103] As another example of how changing the properties of the deposition surface may affect the processes describe herein, a relatively smooth deposition surface may result in one type of deposited material layer, while a relatively rougher deposition surface may result in a deposited material layer that has different characteristics. Preferably, the deposition surface is configured to have a desired, suitable roughness.

[00104] For example, the roughness of the deposition surface, such as surface 210, may be unaltered, or “as-milled” roughness of the metal plate that is used to form the substrate 208. In other cases, the deposition surface may be intentionally surface treated and roughened prior to electrodeposition, such as by using a roughening material, such as sandpaper. Such pre-roughening steps may be used in the processes described herein. Various roughening material may be used to achieve a desired roughness for the deposition surface 210, such as 150 grit sandpaper or other abrasive materials. In some cases, a suitable range to be achieved for surface roughness may be about 0.125pm to about 2.5pm. Modifying the roughness of the deposition surface by mechanically and/or chemically pre-roughening the surface prior to electrodeposition may be used in combination with either flat or concave-shaped (or optionally convexshaped) deposition surfaces as described herein, such that the smoothness/roughness of the deposition surface may be considered separately from its shape/flatness.

[00105] In some embodiments, after the deposition surface has been mechanically roughened, it may be further cleaned by one or more of: (1) treating the plate ultrasonically in a solution of Borax (sodium tetraborate) to remove fine particles on the surface of the roughened plate and to remove oils and greases on the surface; (2) “anodically” cleaning the plate by assembling it in another electrolytic cell, and connect it as the “anode” and driving current through it toward a stainless steel cathode. Voltage applied may be between 0-5 V and current may be less than 0.5 A. The electrolyte may be a 3% solution of each of: sodium hydroxide, EDTA (ethylene diaminetetraacetic acid), and citric acid; and (3) briefly exposing the plate to 10% sulfuric acid by “dipping” it into the sulfuric acid solution, or brushing the plate with a wetted lint free towel soaked in 10% sulfuric acid.

[00106] Referring also to Figures 4 and 5, optionally the target deposition substrate may include two or more layers, such as an underlying plate or foil or other suitable carrier structure that has a fdm or other layer of a different material on its outer surface. The outer layer of material may have different electrical, chemical and/or thermal properties than the underlying plate material, which may help provide different results during the deposition process. In some embodiments, the outer layer of material or cover layer/fdm comprises a metal known to have relatively lower reactivity with nitric, hydrochloric, and hydrobromic acid such as gold, platinum, silver, or rhodium. For example, a two-layer target may include a copper plate or a copper foil that is at least partially covered with a cover layer of gold, platinum, silver, or rhodium. Such cover layers may be advantageous when utilizing copper as the base target substrate material, because an exposed copper target substrate may not be sufficiently inert to withstand the expected post-bombardment chemical recovery of the product nuclide (i.e. it and its bombardment products were taken into solution too). It has been discovered that the presence of the non-copper cover layer of material may also have some other benefits in some operating conditions, as it may help stabilize/improve the radium/barium electrodeposition onto the deposition surface as compared to an exposed copper deposition surface. Blistering may be reduced, and overall smoothness may be improved when using a gold layer.

[00107] A similar cover layer may be used in combination with an aluminum target plate or foil, for example, and may have analogous effects. One example of a substrate having this arrangement is schematically illustrated in Figure 4, where the substrate includes a plate 208 and a cover layer/film 240 that covers at least a portion of the underlying plate 208. In this arrangement, the deposition surface 210 of the two- layer substrate is provided by the exposed surface of the layer 240 rather than a face of the underlying plate 208. The layer 240 is preferably formed from a different material than the underlying plate 208 and defines a film/layer thickness 242 that is preferably less than the thickness 234 of the plate 208. While the thickness 242 is shown somewhat exaggerated in Figure 4 for illustrative purposes, the thickness 242 may be on the order of microns or tens of microns. [00108] In one embodiment that is described herein, the metal plate 208 may include a copper body portion 244 and the cover layer 240 is applied such that it covers a portion of the copper body portion 244 and provides the deposition surface 210. In such embodiments, the cover layer 240 is exposed to electrodeposition solution 206 such that barium/radium is deposited onto the surface of the cover layer 240, thereby forming the deposited layer 230 (Figure 5). In other examples a copper foil may be used instead of the plate 208. In other examples that can be used in combination with the features and processes described herein the substrate may be an aluminum plate, an aluminum foil or other suitable material.

[00109] As noted above, the cover layer may preferably include one or more components/materials that are not present in the metal plate 208. For example, in the examples described herein the cover layer 240 is formed from gold rather than copper, but could be comprised of other metals such as platinum or rhodium. The cover layer may also comprise an alloy of such suitable metals.

[00110] The cover layer 240 may be deposited on to the surface of the metal plate 208 (or suitable foil, etc.) via a suitable method, such as electroplating, electroless plating, a Physical Vapor Deposition method or other methods that can be used to provide a relatively thin layer of the intermediary cover material (e.g., gold, platinum, rhodium, etc.) onto the underlying substrate plate or foil. Alternatively, instead of deposition of this nature the intervening cover layer may also be introduced in the form of a separate foil that can be laminated onto the underlying substrate plate or foil, or by other laminated means. The cover layer may have any suitable thickness that can help impart the desired properties for the resulting target. In some examples, the thickness 242 of the cover layer may be between about 0. 1 pm and about 2pm.

[00111] The aqueous bath solution 206 may be at atarget pH when the deposition cycle time starts, and the process is underway. Unlike some conventional processes in which the parameters of the solution 206 are set to their desired ranges only at the beginning of the deposition cycle, in some of the embodiments described herein, the parameters and characteristics of the solution 206 can be monitored, and can also be preferably actively adjusted/compensated during the deposition cycle so that the solution stays at, or at least acceptably close to its starting parameters during most, or preferably all of the anticipated deposition cycle. This may help maintain the relative level of performance of the cell 200 during a longer portion of the deposition cycle than could be achieved if the solution parameters are not monitored/adjusted while the system is in use.

[00112] Without specific intervention by the operators, it has been observed by the inventors that over the course of the electrodeposition processes described herein (for applying the barium and/or radium onto the target plate or foil), the pH of the electrolyte bath may tend to generally decrease with the generation of acid (H⁺) at the anode in the electrolysis of water molecules in the aqueous solution. As demonstrated by the examples described herein, the inventors have discovered that maintaining the pH within a specific range during the deposition cycle, or above a threshold value may require the appropriate stepwise addition of a suitable alkaline additive, which may have performance advantages over similar, but un-regulated, plating processes. Such an additive will react with the hydrogen ions in the organic-aqueous bath solution thereby reducing the amount of free hydrogen ions in the bath solution and hence counteracting decreases in pH during the deposition cycle time. One example of a suitable alkaline additive can include an aqueous solution of ammonium hydroxide having a concentration of 2% to 30%, or it may include a mixture of aqueous ammonium hydroxide solution and a suitable alcohol, such as isopropanol.

[00113] For example, in one test, performed without any ongoing pH adjustment, starting with an initial electrolyte pH of between 4 and 5, the organic-aqueous bath reached a pH in the range 2 - 3 by the end of the deposition cycle. Testing has been performed to show that the control of the pH via additions of ammonium hydroxide solution to the electrolytic cell resulted in an increased deposition yield.

[00114] For example, the target pH of the solution 206 may be maintained within a suitable range during at least part of the deposition cycle time. Such a suitable target may be a pH range of between 4 and 6 when the deposition cycle time starts; where a further requirement may be to maintain the pH of the organic-aqueous bath solution within that target pH range as much as possible during the entire deposition cycle time, and may further require ensuring that the pH does not decrease below 4 or increase above 8. In some cases, the target pH range is between 4-9, such as 4-8, 4-6, and others. [00115] Maintaining the target pH may be done using a variety of techniques, including providing the alkaline additive described herein, to the aqueous bath solution. In some cases, the additive is a weak base, such as ammonium hydroxide. Without being limited to theory, the buffer additive may react with hydrogen ions in the aqueous bath solution thereby reducing the amount of free hydrogen ions in the aqueous bath solution and preventing large decreases in the pH of the aqueous bath solution during the deposition cycle time.

[00116] In other embodiments, such as where the pH change during the deposition process is already sufficiently well-characterized, the pH may be maintained (without constant monitoring of the pH) within a suitable process pH range by the precalculated addition of an alkaline additive. The alkaline additive may be added continuously, or in one or more batches.

[00117] In some cases, the target pH of the aqueous bath solution is monitored before, during, and/or after the deposition cycle time via a suitable method, such as a pH meter. The target pH may be a suitable range, such as about 4 to about 6. In some cases, the target pH is about 4 to about 5.

[00118] Alternatively, or in addition to adding an alkaline additive, maintaining the target pH may include deaerating or sparging the aqueous bath solution with a carrier gas. A flow of carrier gas may be introduced to the aqueous bath solution to help urge hydrogen gas out of the solution. The carrier gas may comprise an inert gas that is non-reactive with the aqueous bath solution, such as argon. The organic-aqueous bath solution may have a suitable composition. For example, the organic-aqueous plating bath solution may comprise at least one aqueous component and at least one organic solvent and a radium (or barium) salt. The organic solvent may comprise at least one alcohol, such as isopropanol, ethanol and others.

[00119] In some specific embodiments, the preferred composition range of the solvent part of the plating bath solution is between 1 - 18 volume % water and 82 - 99% alcohol. The bath may additionally comprise a necessary amount of radium (or barium) salt. The necessary amount of radium (or barium salt) will depend on the size of the target and desired deposition thickness being plated. In some examples, a suitable amount of salt would be between 0.001-3 mmol, such as 0.004 - 3 mmol, expressed as Ba²⁺ or Ra²⁺ ions. The bath may additionally also include dilute mineral acid introduced during the bath preparation to dissolve the radium (or barium) salt. The bath may therefore comprise 0 - 0.1, such as 0-0.01 mol/L mineral acid.

[00120] The at least one alcohol that is used in the aqueous bath solution may include at least one of ethyl alcohol and isopropyl alcohol, a combination of these and/or other suitable alcohols.

[00121] The radium salt that is used in the aqueous bath solution 206 may include radium chloride, or other radium salts that are soluble in the bath solution 206, such as radium nitrate, radium bromide, radium oxide, and radium hydroxide. In embodiments for generating a barium-containing layer, the barium salt may include barium chloride, barium nitrate, barium bromide, barium oxide, or barium hydroxide

[00122] The mineral acid of the organic-aqueous bath solution may include hydrochloric acid, nitric acid or hydrobromic acid either alone or in combination with each other or other acids. Suitable acids may include acids that do not react or degrade one or more of the deposition substrate or cover layer.

[00123] A further possible requirement for the organic-aqueous bath solution is that the relative volume ratio of the organic solvent to water, where the organic solvent may be an alcohol and may preferably be isopropanol is greater than about 4.8 when the deposition cycle time starts, and is further maintained at or near that value during the deposition cycle. This may be necessitated by the ongoing evaporation of the organic solvent during the deposition process and can be addressed by the ongoing, stepwise addition of the neat organic solvent (e.g. isopropanol). In some embodiments this addition is determined by maintaining the bath volume at a constant volume (by assuming that any volume loss is due to evaporation of the alcohol.

[00124] The cell 200 may be operated, including applying the electric potential between the anode and the metal plate, under suitable conditions and with predetermined operating parameters, such as having process/target potential, current, current density, pH, temperature, voltage and pressure. For example, the current density used in the examples described herein may be between about 0.5 and about 20 mA/cm², and more preferably between about 4 and about 16 mA/cm². Further, the electric potential between an anode and the metal plate can be maintained between about 20 and about 600 V, and more preferably between about 100 V and about 200 V. During the deposition step, a current of between about 0.01 and about 0.1 A can be employed. Suitable current densities may include a range of about 0.0005 to about 0.02 A/cm²

[00125] Layers of radium or barium containing material may have a melting temperature of at least 800°C, more preferably over 950°C, most preferably over 1000°C.

[00126] The processes described herein may help facilitate the deposition of a layer of radium-containing (or barium-containing) material that has a concentration that is commercially useful and is suitable for use as a target as describe herein. For example, the processes can be conducted so that the resulting layer of deposited material contains at least about 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more of a desired, radium-containing material, such as radium carbonate or a desired barium- containing material, such as barium carbonate.

[00127] The electrolytic cell comprises a suitable anode. The anode may be made of a suitable material, such as platinum or graphite.

[00128] To demonstrate the viability of the processes and methods described herein, testing was conducted, and barium material was successfully deposited onto the copper and/or gold deposition surfaces of a target substrate. A summary of some these tests is included below. The chemistry of radium and barium are analogous. Due to the radioactive nature of radium, it is common practice to use barium as a surrogate or proxy for radium (as taught in "The Radiochemical and Radiopharmaceutical Applications of Radium" Open Chemistry, vol. 14, no. 1, 2016, pp. 118-129. It is therefore believed that the positive results obtained using barium as a proxy test material will be reproduceable in substantially the same way, and with substantially the same successful results when using a deposition solution substituting radium for barium.

[00129] Referring to Figure 8, one example of an experimental apparatus/ cell 200 that was used to test the processes described herein is shown. This experimental apparatus is configured as a cell 200 with two metal plates 208 secured to an outer surface of the side walls, with their respective deposition surfaces 210 being exposed to the interior of the cell and in liquid communication with a solution container therein. An anode 212 is provided and is connected to a suitable power source to apply the desired potential within the cell 200.

[00130] The anode 212 and the aqueous bath solution (not shown in this photo) may be placed within the electrolytic cell 200. In this example, the cell 200 also has inlet and outlet ports 218 and 220 for recirculation of electrolyte solution via a suitable method, such as a peristaltic external pump. The recirculated liquid may be sampled or adjusted, such adjusting pH or aeration, prior to returning to the cell. This recirculation of the electrolyte may further promote homogenization of the radium/barium ions in the bath solution and also ensure effective delivery of the radium/barium ions to the deposition surface.

[00131] In this experimental example, the deposition surface 210, which includes an exposed portion of the metal plate 208 may be framed by an aperture 250 in the otherwise non-reactive/ conductive of the sidewall 252 of the electrolytic cell, such as depicted in Figure 8. This may help control the shape of the exposed deposition surface 210, and resulting deposited layer 230, but may be different in other examples. In some cases, the sidewall 252 covers a portion of the plate 208 and the aperture 250 defines the shape of the deposition surface. For example, a perimeter of the aperture 250 may have a substantially elliptical shape, resulting in a substantially elliptical layer of deposited material 230 (Figure 10).

Examples

[00132] To help investigate the potential for the processes described herein to be used in the commercial production of radium-containing targets - and ultimately the production of commercially viable quantities of ²²⁵ Ac (such as from cyclotron bombardment of ²²⁶Ra), the preparation of surrogate cyclotron targets using barium compounds has been investigated and tested as described herein. The use of barium as a test material is common and was chosen because ²²⁶Ra is radioactive and is relatively difficult and dangerous to handle when conducting experiments. Accordingly, the testing described herein was conducted utilizing what the inventors consider to be a sufficiently close chemical analogue of ²²⁶Ra, barium (Ba). Barium may also be used in the production of quantities of lanthanum- 133 and lanthanum-135. [00133] The Examples herein have demonstrated the viability of the processes described herein and have used some examples of suitable technology and hardware that could be used for target preparation via electrodeposition of barium compounds onto copper-based target faceplates from mixed aqueous/organic electrolytes containing barium salts, commonly referred to as “molecular plating”. Other hardware and production apparatuses could be used to conduct the described processes/methods in other examples and/or in commercial applications. While the testing was conducting using barium as the plated material, barium is a relatively well-known substitute for radium for testing and analysis purposes, and the results obtained from the barium- based experiments described herein are expected to apply to radium-based processes that may be employed for commercial target production.

EXAMPLE 1 : Target Design for ²²⁵ Ac Production

[00134] The approach for a cyclotron target system for ²²⁵ Ac production has been focussed on the use of technology available from Advanced Cyclotron Systems Inc. (ACSI). The High Current Solid Target Station (HCSTS) available from ACSI has been chosen based on its suitability to produce quantities of ²²⁵ Ac up to or exceeding established business requirements. In the HCSTS, the material to be bombarded is typically deposited onto a metallic faceplate, illustrated as one example of the substrate/plate 208 presented in the rendering shown in Figure 6. Deposition of the material in an elliptical shape on the faceplate may allow for uniform bombardment when positioned in the beamline. Copper may be considered a desirable base metal for the faceplate due to its high thermal conductivity (~4 W cm'¹ K'¹) and cost efficiency.

EXAMPLE 2: Barium Molecular Plating

[00135] Referring to Figure 7, initial experiments of molecular plating of barium onto 3/16” diameter copper rods 270 (as a substitute for the plates 208 described herein) from solutions of 85% ethyl alcohol, 15% 0.05 M hydrochloric acid, and 0.1 M barium chloride with current densities of 16 mA/cm² yielded positive results. A representative image of these initially generated deposits (see layer 230 on rod 270) is shown in Fig. 7. To transfer this methodology and further develop toward the HCSTS target faceplate geometry, an electrolytic cell was designed and built to facilitate further experimentation (Figure 8). The electrolytic cell 200 of Fig. 8 has the following features: sealed elliptical cut-out sidewalls 252 for the deposition substrate and counter electrode 212 (e.g. platinum anode); Teflon®(PTFE) construction for chemical compatibility; inlet and outlet ports 218 and 220 for recirculation of electrolyte via peristaltic pump; a combined inlet/outlet port (not labelled) for filling and draining of the electrolyte prior to and following a deposition test; open access to the recirculating liquid to allow for sampling, pH adjustment, and gas bubbling of the electrolyte; and electrolyte temperature monitoring via submersed thermocouple.

[00136] Initial experiments were performed using replicate conditions of those performed with the small copper rods (ethanol/HCl electrolyte, 16 mA/cm²). The initial tests suggested that the barium deposits formed were very flaky, non-dense, and relatively poorly adhered to the copper substrate (Fig. 9A). While this may be useful in some applications, a deposition layer having different properties may be desired in some commercial applications. One observation from this experiment was the existence of blister-like imperfections in the deposited layer 230, that may be due to the generation of hydrogen bubbles at the copper cathode 208 from electrolysis of water in the solution 206. It was identified in these early tests that roughing the as-milled surface of the copper plates with 150 grit sandpaper appeared to generally increase the quality of the deposited layer 230 in terms of density and adhesion, as shown in the photo of the test results in Fig. 9B. This pre-roughing of the substrate was used in the additional tests described herein, but it is believed that the same general results could be obtained using a substrate that was not pre-roughened.

[00137] To help further improve the physical structure of the electrodeposited barium, the organic solvent in the cell 200 was changed from ethyl alcohol to isopropanol, and the current density in the cell 200 was reduced to about 4 mA cm'². As well, the initial and final pH of the electrolyte solution 206 was monitored and controlled during the duration of the test cycle time. The first tests in IPA based electrolyte with initial pH of 4-5 displayed what appears to be a marked improvement in the quality of the deposited material layer 230 (Fig. 10). The presence of blistering in the deposits was also observed, possibly stemming from cathodic hydrogen generation. [00138] Continued testing efforts to refine the quality of the barium deposits were initially focused on manipulation and adjustment of the electrolyte composition (e.g., organic: aqueous ratio, pH, deaerating).

[00139] The initially prepared electrolyte may have an IPA concentration of at least 78% by volume, however experimentation at lower concentrations has not been performed. The electrodeposition testing performed within this limit has not yet shown a definitive correlation to deposition yield or deposit quality. It may be advantageous to explore the deposition at lower IPA concentrations, as having an increased aqueous component may benefit the solubility of barium in the electrolyte and may reduce the overall required electrolyte volume. This volume may impact equipment footprint that would be required in a hot cell environment for the preparation of targets with ²²⁶Ra.

[00140] The organic: aqueous ratio of the electrolyte plating bath may affect the yield of the electrodeposition process. Experiments conducted in purely aqueous electrolyte solution 206 yielded relatively low barium deposition.

[00141] The testing established that the pH of the electrolyte solution 206 has an impact on the deposition yield and quality of the electrodeposition. An initial electrolyte pH below 3 was observed to cause the deposit to form in a relatively inconsistent geometry and may display a lack of deposition around the sealing edges of the electrolyte cell wall (Figure 11). Re-dissolution of the deposited barium compound may occur more rapidly under more acidic conditions.

[00142] It has also been observed that over the course of the electrodeposition process, the pH of the electrolyte may generally decrease. This behavior may be attributed to the generation of acid (H⁺) that occurs at the anode via electrolysis of water. In the case of tests performed with an initial electrolyte pH of 4-5, the final pH may result in the 2-3 range. Testing has been performed to show that the control of the pH via additions of ammonium hydroxide to the electrolytic cell may result in an increased deposition yield. In Figure 12, it can be seen that when pH is not adequately controlled (orange line), the electrodeposition process may effectively cease after a given time and may actually begin to leach deposited barium back from the substrate. In the case where pH is controlled (blue line), the deposition process may be much more effective. EXAMPLE 3: Advances in Substrate Preparation Effects

[00143] Exploratory work has been performed where the copper faceplate has a layer of gold (Au) applied to the pre-roughed and cleaned copper faceplate. Gold layers have been applied utilizing conventional electroplating (using a DC power supply to drive the coating process), and electroless plating (no external power supply). Electrodeposits of barium prepared on a gold layer may be uniform, have higher molecular plating efficiency (mg of Ba deposited/mAh), and may be free of major defects such a blistering. Figures 13A and 13B show examples of these experiments.

[00144] Without wishing to be bound by theory, one hypothesis of the increase of deposition later quality is from the relative chemical inertness of Au to the electrolyte solution (compared to that of a copper surface with no such cover layer). It may also be that the plated Au layer modifies or moderates high energy nucleation sites on the copper surface, resulting in more stable or controlled deposition of the radium- containing (or barium-containing) layer. It may also be that the increased exchange current density of Au over Cu has a positive effect on the kinetics of the desired radium- containing (or barium-containing) deposition.

[00145] Another potential benefit to the coating of the substrate in gold may be that the dissolution of the barium or radium material in acid solution would have a reduced impurity profile following bombardment, possibly due to the improved chemical inertness of the gold layer. This may benefit the product radioisotope quality and may reduce burden on the purification of the target material for subsequent recycled target preparation.

EXAMPLE 4: Developments in Deposit Chemical Characterization

[00146] To assess the chemical form of the barium deposit formed from molecular plating from aqueous/isopropanol solutions, solid samples of three deposits were analyzed by Fourier Transform Infrared Spectroscopy (FTIR). The spectrum for each of these samples is shown in Figure 14. Each of MP13, MP19 and MP21 was produced using slightly different deposition conditions, but all were produced within the preferred deposition process variable ranges disclosed herein. Comparison of the result with reference spectra strongly suggests that the chemical form of each deposit is relatively pure, crystalline, barium carbonate (BaCCL). As is therefore evident for each sample, even with some differences in process parameters (within the ranges disclosed), the resulting deposition product remains dominantly barium carbonate.

[00147] All citations are hereby incorporated by reference. In the event of conflicting information with statements between any reference to or incorporated herein, and the present disclosure, the present disclosure will act as the guiding authority.

[00148] What has been described is merely illustrative of the application of the principles of the disclosure. However, it will be apparent to a person skilled in the art that a number of variations and modifications can be made without departing from the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method for producing a radium target, the method comprising: a) providing an organic-aqueous electrolyte bath solution comprising radium ions; b) exposing a deposition surface of a target substrate to the electrolyte bath solution, wherein the target substrate comprises at least one of copper and aluminum, and wherein the deposition surface comprises at least one of copper, aluminum, gold, platinum, rhodium or silver; and c) applying an electric potential between an anode and the target substrate for a deposition cycle time, thereby electrodepositing a layer of radium containing material out of the bath solution and onto the deposition surface.

2. The method of claim 1, wherein the organic-aqueous electrolyte bath solution comprises at least one mineral acid, at least one organic solvent and a radium salt.

3. The method of claim 2, wherein the radium salt comprises one or more of radium chloride, radium nitrate, radium bromide, radium oxide, or radium hydroxide.

4. The method of any one of claims 2-3, wherein the organic-aqueous electrolyte bath solution comprises about 1-18% water, about 82-99% organic solvent, about 0- 0.01 mol/L mineral acid and about 0.001-3 mmol of the radium salt.

5. The method of any one of claims 2-4, wherein the mineral acid comprises one or more of hydrochloric acid, nitric acid, or hydrobromic acid.

6. The method of any one of claims 1-5, wherein the layer of radium containing material comprises substantially radium carbonate.

7. The method of any one of claims 1-6, wherein the layer of radium containing material has an effective thickness of 0.03 to 23 mg/cm² as the elemental form of the radium cation.

8. The method of any one of claims 1-7, wherein the layer of radium containing material has a melting temperature of at least 800°C, more preferably over 950°C, most preferably over 1000°C.

9. A method for producing a barium target, the method comprising: a) providing an organic-aqueous electrolyte bath solution comprising barium ions; b) exposing a deposition surface of a target substrate to the electrolyte bath solution, wherein the target substrate comprises at least one of copper and aluminum, and wherein the deposition surface comprises at least one of copper, aluminum, gold, platinum, rhodium or silver; and c) applying an electric potential between an anode and the target substrate for a deposition cycle time, thereby electrodepositing a layer of barium containing material out of the bath solution and onto the deposition surface.

10. The method of claim 9, wherein the organic-aqueous electrolyte bath solution comprises at least one mineral acid, at least one organic solvent and a barium salt.

11. The method of claim 10, wherein the barium salt comprises one or more of barium chloride, barium nitrate, barium bromide, barium oxide, or barium hydroxide.

12. The method of any one of claims 10-11, wherein the organic-aqueous electrolyte bath solution comprises about 1-18% water, about 82-99% organic solvent, about 0-0.01 mol/L mineral acid and about 0.001-3 mmol of the barium salt.

13. The method of any one of claims 9-12, wherein the layer of barium containing material comprises substantially barium carbonate.

14. The method of any one of claims 10-13, wherein the mineral acid comprises one or more of hydrochloric acid, nitric acid, or hydrobromic acid.

15. The method of any one of claims 9-14, wherein the layer of barium containing material has an effective thickness of 0.03 to 23 mg/cm² as the elemental form of the barium cation.

16. The method of any one of claims 9-15, wherein the layer of barium containing material has a melting temperature of at least 800°C, more preferably over 950°C, most preferably over 1000°C.

17. The method of any one of claims 1-16, further comprising maintaining a pH of the organic-aqueous electrolyte bath solution at or above 4 during at least a majority of the deposition cycle time.

18. The method of claim 17, wherein the pH of the organic-aqueous electrolyte bath solution is maintained at or above 4 for the entire deposition cycle time.

19. The method of claim 17 or 18, wherein the pH is maintained within a range of about 4 to about 8, and preferably within a range of about 4 to about 6.

20. The method of any one of claims 17-19, wherein maintaining the pH comprises providing an alkaline additive to the organic-aqueous electrolyte bath solution.

21. The method of claim 20, wherein the alkaline additive comprises an aqueous solution of ammonium hydroxide.

22. The method of claim 21, wherein the aqueous solution has a concentration of about 2% to about 30% ammonium hydroxide.

23. The method of any one of claims 21-22, wherein the alkaline additive further comprises isopropanol.

24. The method of any one of claims 1-23, wherein the deposition surface has been roughened prior to the electrodeposition of the layer of radium containing material such that the deposition surface has a roughness between about 0.125 pm and about 2.5 pm.

25. The method of any one of claims 1-24, wherein the target substrate comprises a cover layer comprising gold, platinum or rhodium that covers at least a portion of the target substrate and provides the deposition surface, whereby the deposition occurs on an exposed portion of the cover layer.

26. The method of claim 25, wherein the cover layer is electroplated, electroless plated, application rolled, PVD, or foiled onto the target substrate.

27. The method of any one of claims 25-26, wherein the cover layer has a thickness of between about 0.1 pm and about 2 pm.

28. The method of any one of claims 25-27, wherein the cover layer is formed from gold.

29. The method of any one of claims 1-28, wherein a relative volume ratio of organic solvent to aqueous solvent in the organic-aqueous electrolyte bath solution is greater than about 4.8, prior to contact with the target substrate.

30. The method of claim 29, wherein the organic solvent comprises an alcohol.

31. The method of claim 30, wherein the alcohol comprises one or more of ethanol or isopropanol.

32. The method of any one of claims 29-31, wherein the relative volume ratio is maintained during the deposition cycle time by addition of organic.

33. The method of any one of claims 1-32, wherein the organic-aqueous electrolyte bath solution is at a temperature of between about 10°C and about 50°C.

34. The method of any one of claims 1-33, wherein an electric potential between the anode and the metal plate is between about 20 and about 600 V, and preferably at between about 100 V and about 200 V.

35. The method of any one of claims 1-34, wherein the electrodepositing is carried out at a current of between about 0.01 and about 0.1 A.

36. The method of any one of claims 1-35, wherein the electrodepositing is carried out at a current density of between about 0.0005 and about 0.02 A/cm²

37. The method of any one of claims 1-36, wherein the anode comprises platinum.

38. The method of any one of claims 1-37, wherein the organic-aqueous electrolyte bath solution is recirculated in the cell by means of an external pump.

39. The method of any one of claims 1-18, wherein the deposition cycle time is between 0.1 and 24 hours.

40. The method of any one of claims 1-39, wherein the target substrate comprises at least one of a plate and a foil formed from at least one of copper and aluminum.

41. The method of claim 40, wherein the target substrate comprises a copper plate.

42. The method of any one of claims 1-41, further comprising deaerating the aqueous bath solution with a carrier gas during the deposition cycle time.

43. The method of claim 42, wherein the carrier gas comprises an inert gas that is non-reactive with the aqueous bath solution.

44. The method of claim 43, wherein the carrier gas comprises argon.

45. A target for subsequent exposure to an accelerated proton beam, the target comprising: a target substrate formed from copper or aluminum; a cover layer being formed from gold, platinum, silver, or rhodium, the cover layer covering at least a portion of the target substrate and provides a deposition surface; and a layer of radium or barium containing material electrodeposited on the deposition surface.

46. The target of claim 45, wherein the deposition surface is at least partially concave and the layer of radium or barium containing material has a non-uniform thickness whereby an exposed upper surface of the layer of radium or barium is relatively flatter than the deposition surface.

47. The target of any one of claims 45-46, wherein the deposition surface has a surface roughness of between about 0.125 pm and about 2.5 pm.