Introduction Solid targets for PET and SPECT radionuclides are getting popular. For radiohalogens the limiting factor, beside the high cost of enriched target material is beam current due to poor heat conductivity of the target material(s). We have designed a honeycomb solid target which has advantages over the traditional circular hole de-sign: 1) Even distribution of target material, 2) it takes higher beam current, 3) less target material loss during distillation (1) and 4) no “creeping” (surface tension phenomena) of the target material during distillation. Material and Methods The target (see FIG. 1.) consists of 19 hexagonal 0.3 mm deep openings (see FIG. 2.) thus having 84% transparency/transmission, in a 24×2 mm platinum disk. There is a 10mm circular cavity on the reverse side giving a 200µm thickness of the platinum. The irradiations were performed on an IBA twin 18/18 Cyclon equipped with a Costis sold target system. The target material thickness was ~300mg/cm2 124TeO2 (> 99.9% I.E., Isoflex) with 5% w/w Al2O3 (99.99%, Sigma-Aldrich). The target was irradiated with 14.8MeV protons (18 MeV degraded by 500µm aluminium). Results and Conclusion The target was able to take beam current up to ~35 µA (higher BCs have not yet been investigated); our “traditional” target (10mm circular hole) has a limit of ~ 20 µA. This means that the effective yield is ~ 50 % higher with the honeycomb as compared with the “traditional” target design.

Introduction A new high current (up to 50 kW) solid target irradiation system is being built. While retaining the same beam power capability of the previous target generation, the system is a totally new design with many improvements, simplified constriction, more reliable operation and a novel approach to target handling, beam collimation and beam diagnostic. Unlike the previous, three-part soldered target, the new target is fabricated from a single piece of metal. Material and Methods The target (or rather the target-material holder) is a single metal plate (usually copper or silver) incorporating the seals and the cooling channels (FIG. 1). The target is placed in the beam at 7°. Depending on target material and coolant flow the target can handle beam powers up to 50 kW (FIG. 2). Target transfer (utilizing a special shuttle) is pneumatic. Part of the transfer pipe is shown above the target station. Except the target o-rings (a part of each target) there are no elastomer seals in the system; all is of soldered/welded construction and metal seals. Sectional view (FIG. 3.) shows that target in place in the chamber. The target and the chamber are electrically insulated from the rest of the system, thus forming a Faraday cup for accurate current measurement. The collimator is formed of a two part silver casting. It is designed to handle up to 10 kW of beam power. Four-sector silver mask in front of the collimator allows precise beam cantering. The collimator parts were cast using 3D printed wax patterns. This allowed to create a complex pattern of cooling channels that are difficult to produce by machining (FIG. 4.) All the actions of target shuttle landing and the target placing are performed by three air cylinders. All three are fitted with Vespel SP22 (Du Pond) seals. Unlike previous systems that used mechanical grabbers to manipulate the target, low vacuum is employed to hold the target during removal from the shuttle and placing in the irradiation chamber. This greatly simplifies the operation and is more reliable. The pneumatic transfer system is using two vacuum producer to transfer the target shuttle between the target station and the hotcell. Both landing terminals in the target station and hotcell, as well as the transfer line itself, are under negative pressure preventing any spread of contamination. The hotcell landing terminal incorporates a fully automatic target-material dissolution system. After landing, the target is removed from the shuttle and the active face pressed against a reaction vessel where the dissolution takes place (FIG. 5.) All the functions of target transfer, placing and manipulations are controlled by a simple PLC (FMD88-10 PLC, Triangle Research) Results and Conclusion While intended mostly for cladding with metallic target materials, a special version of the target was designed to handle salts or oxides that can be fused and retained in grooves on the target face (FIG. 6.) Despite the poor thermal conduc-tivity of most of those materials, this target can handle high beam currents. FIGURE 7 shows a thermal modelling of the cen-tral 10×25 mm segment of the target (highest heat flux region under a Gaussian beam). Copper target with rubidium chloride fused in 0.8 mm wide and 1.7 mm deep grooves and spaced by 0.5 mm (60% coverage). Beam of 70 MeV energy and 400 μA intensity is collimated 20 % (320 μA on target). Cooling-water flow is set to 25 l/min. Cladding the target face with a thin metallic layer can help containing the target material. This process is currently under development. Most aspects of the system operation and con-striction were successfully used in the previous “generations” of targets in the last 30 years. The new system will provide improved performance with a simpler and more reliable design, lower maintenance and lower consumables cost. FIGURE 8 shows the “4th generation” system and target (2005). Dozens variants of this design are in use all over the world.

Introduction Temperature modeling using Finite Element Analysis (FEA) is widely used by particle beam-line designers as a useful tool to determine the thermal performance of an irradiated target system. A comparison study was performed between FEA calculated temperatures on platinum with experimental results using direct thermocouple measurements. The aims are to determine the best beam model for future solid target design, determine the maximum target current for different target materials and the temperature tolerance for any modification to our existing solid targetry system. Material and Methods The theoretical temperature of the target sys-tem was determined using SolidWorks 2013 with Flow Simulation Analysis (FSA) module. The FSA module determines the maximum temperature inside the target material given the global conditions (material specification, flow rates, boundary conditions, etc.) for a given target current. The proton beam was modeled as a volumetric heat source inside the target material based on the distribution of energy loss in the material along the beam axis. The method used by Comor, et al1 was used in this study. The method segmented the target material into five individual layers, each layer being 50 m thick. The energy lost per layer was calculated using SRIM3 and converted into the power lost per layer. A thickness of 250 μm of platinum completely stops the impinging proton beam at 11.5 MeV with the highest deposition of power per layer corresponding to the Bragg peak. The target material used in the simulation reflects the physical target disk used for temperature measurements (platinum, dia. 25.0 mm, thickness 2.0 mm) with two K-type thermocouples (dia. 0.5 mm, stainless steel sheath) embedded in the platinum disk. One thermocouple is located in the geometric center, while the other is located at a radial position 8 mm from center. The outer thermocouple is to determine the peripheral temperature near the o-ring seal. Temperature was maintained below the melting point for the material (Viton®, melting point 220 °C) during the irradiation to ensure the integrity of the water cooling system. The solid targetry system used in this study is an in-house built, significantly modified version2 of a published design1. The solid target system is mounted onto an 18/18MeV IBA Cyclotron with dual ion source, on a 300mm beam-line with no internal optics or steering magnets. A graphite collimator reduces the beam to 10mm in diameter and a degrader is used to reduce the proton beam energy to 11.5 MeV, considered suitable for production of radiometal PET isotopes 89Zr and 64Cu. Temperature was measured with and without the 300 mm beam-line to compare the effects of beam divergence on the solid target (FIGS. 1 and 2). The experiment was conducted using both H− ion sources with different ion-to-puller extraction gaps (ion source 1 is 1.55 mm with ion source 2 at 1.90 mm). The setting of the ion-to-puller gap changes the focusing of the accelerated beam inside the cavity. Results and Discussion The segmented beam model was used to calculate the temperature on and within the target, as well as the maximum temperature of the bulk material. The first segment is the leading segment of the material irradiated by the incident proton beam. Results are shown in TABLE 2. Target temperatures were measured experimentally under two different conditions; target attached at the end of a 300mm beam-line and target attached directly to the cyclotron. The temperature was measured experimentally using the platinum disk with 2 thermocouples inside the bulk target material irradiated on the end of a 300mm beam-line. The measured temperature is shown in TABLE 2. The variation between ion source 1 and 2 for the temperature measured in the center was 11–15 %, while the variation on the radial position was 2–6 %. A smaller ion-to-puller extraction distance (ion source 1) reduces the cross-sectional area of the accelerated beam; the consequent high proton current density (10mm diameter collimated beam) increases the temperature inside the bulk material for a fixed target current. The highest observed radial temperature was 93 °C, with target current of 50 μA using ion source 1. This is well below the melting point for the o-ring seal. The temperature measured experimentally using the same platinum disk with no beam-line is shown in TABLE 4. A temperature difference of up to 7 % was measured between ion source 1 and 2 at the exit port without the beam-line, while the maximum variation on the radial position was 3 %. A comparison between the calculated theoretical and measured temperatures is shown in FIGS. 3 to 6. The temperatures calculated by the FEA model underestimate the temperature regardless of target position (with or without the beam-line) and for both ion sources. The temperature difference between the FEA model and the experimental results increases with increasing target currents. As shown in Figure 3, at the target center the FEA model underestimated the temperature by 22–32 % for ion source 1 and 13–22 % for ion source 2. This is consistent with the difference between the two ion sources due to the difference in the ion-to-puller gap size. With the target mounted at the exit port the theoretical and measured temperature for the center of the platinum disk is shown in FIGURE 4. The FEA model underestimates the temperature at the center of the platinum disc by 2–10 % for both ion sources. As shown with the previous experiment, the margin of error increases with increasing target current. Comparison between FIGS. 3 and 4 shows the measured temperature at the center of the platinum disk is significantly lower when the target is attached to exit port of the cyclotron. Localised area of high current density (hot spots) is not registered as higher temperature in the bulk material. True temperature inside the bulk material is highly dependent on the thermal conductivity of the target material and the resolution of the thermocouple. The cross-sectional area of the beam ‘hot-spot’ will be greater due to beam divergence at the end of the beam line compared with the exit port. The ‘hot’ area of the expanded beam becomes a significant portion of the overall collimated beam (collimator dia. 10.0 mm). A more uniform beam profile (less heterogeneity) evenly distributed the area of high current density across the disk surface, effectively increasing the temperature of the bulk material while decreasing the sensitivity required to measure the true temperature. As observed from this comparative study it appears that a more homogeneous current density leads to a higher temperature measurement at the target center. With the solid target at the end of the beam-line, target current lost on the collimator and beam-line was >55%. The effect of beam divergence is clearly observed in TABLE 5. With the target mounted directly at the exit port the current lost was reduced to < 40 %. Although the average proton current density is the same for any set target current, irrespective of target position, the contribution of the peripheral beam to the total target current should not be underestimated. A loss of ~40 μA on the collimator and beam-line places greater reliance on the center of the ‘hot’ beam to maintain the same target current. The temperature at the radial position (FIG. 5) observes the same trend as for the temperature measured in the center. The error increases for higher target currents and the FEA model underestimated the temperature by 19–40 %. The error at this location is due partly to the model’s assumption of a uniform heat source, applied to the material on a single axis (perpendicular to the material surface) and does not account for any scattering or divergence of the incident proton beam. FIGURE 6 shows that the FEA model underestimated the radial temperature by 16–37 %, when the target is connected to the exit port, for reasons discussed previously. Comparison with FIG. 5 (target on the beam-line) shows the same margin of error between the FEA and the experimental results (19–40 %). The temperature difference between the FEA model and measured temperature at the radial position is independent of the beam profile and beam divergence. The FEA model underestimated the temperature at the radial location with or without the beam-line and for both ion sources. The significance difference in temperature between the FEA model and the experimental is due to our model assumption that the maximum radial temperature is on the irradiated surface and not inside the material corresponding to the layer with the maximum energy lost. In addition, the FEA model does not ac-count for the divergence of the proton beam as it travels through the material. Given the temperature at 50 μA target current is > 90 °C (TABLES 3 and 4) we have capped the experi-ment below this point to prevent any damage the o-ring seal. Conclusion The segmented FEA model was inadequate in determining the temperature for the target at the end of a 300mm beam-line (> 30 % difference). A combination of beam divergence and greater uniform coverage of high current density beam resulted in a higher than predicted temperature reading. However, the segmented FEA model provides a good estimation (< 10 % difference) for the observed temperature of the bulk material at the exit port. The simplistic FEA model was unable estimate the temperature at the radial position (~ 40 % difference) regardless of ion source or target position. A comparison between the two ion sources with different ion-to-puller extraction gap, leading to different focusing of the accelerated beam yield minimal temperature difference. Although a 15% difference was observed between the ion sources at the end of the beam-line, a major contributing factor is beam divergence beyond the magnetic field rather than the beam size of the accelerated beam. Further studies are underway to determine the beam profile (quantitatively using radiographic film), quantify the contribution of the peripheral beam to the total beam current by comparing different size collimators and to investigate other FEA models by applying different beam models (heterogeneous and homogeneous beam) and different heat sources (surface vs. volumetric). Currently the RAPID Lab solid targetry is placed at the end of the beam-line for easy loading and unloading, since multiple target irradiations are performed per month2. However, RAPID is presently developing a new solid targetry sys-tem which eliminates the need for a beam-line and will be able to manage a maximum extracted target current of 150 μA.

Introduction The expansion of our PET isotope production with a new TR-19 cyclotron necessitated a suitable solid target transport system. None of the known existing and proposed solid target transport systems (STTS) was able to meet the technical and budget requirements of the MIR cyclotron facility [5]. A unique carrier design allowed us to develop a fully automated 50.8 mm inner diameter pneumatic tube STTS with an in-hot-cell compact form factor receiving station. The cyclotron or vault side loading station is a mere vertically symmetric version of the in-hot-cell station. The carrier is able to accommodate any of our inhouse developed 86Y, 64Cu, 76Br, 89Zr and 99mTc target holders without further modifications. Material and Methods Technical constraints were imposed by the dimensions of the target holders (FIG. 1) and the overall station size (FIG. 3). A receiving station would be inside a hot cell and, up to three sending stations would be located in the confined vault space under the solid target irradiation units. In addition, safety and budget requirements demanded a fully automated, easy to maintain STTS. The target holders are of various geometries with the 99mTc having the maximum dimension of 46.65 mm along its diagonal. Pseudo carriers with diameters ranging from 41 to 49.5 mm (no wear band) and lengths from 50.8 to 102 mm were tested on 50.8 mm inner diameter Kuriyama Tigerflex™ and Goodyear Nutriflex™ tubing. Smaller diameter and length test samples became wobbly, slow, and were getting stuck on occasion. Lengths in the upper limits became stuck in turns with radii close to the minimum radius of the tubing. The necessary negative pressure was achieved by employing a 2.5pHP Ridgid WD06250 blower. The transparent Goodyear Nutriflex™ tubing was chosen for the further STTS development. A carrier capable of loading and unloading regardless of its axial orientation was constructed. This novel design allows for a relatively compact station W 112 × H 220 × L 300, which reduce the dependence on the location of the tube openings in the walls of the hot cell (BqSv, Taiwan). As a result the station can be conveniently placed in areas not typically occupied by processing modules or used by chemists, e.g. close to the upper left corner. To avoid reliance on expensive proprietary parts, all components were designed or chosen to insure reliability with minimal maintenance. The enclosure and opening mechanism are 3D-printable using ABS plastic, and can be made in-house on demand. “Platform sharing” between hot cell and vault stations further simplifies support and maintenance. As with the mechanical hardware, the electronic components and boards were selected to minimize the dependency on a single supplier. The main controller board is based on Atmel\'s AVR series of microcontrollers, which are known to be largely backward compatible, well documented and have an extensive user support base. A single “brick” controls up to three stations. Bricks can be daisy chained with one functioning as a master. The control software takes advantage of the rapid development capabilities of National Instrument\'s LabView graphical language. It is intended to work on Unix-like and Windows operating systems as well as to allow control from hand-held devices. Password security, interlocks and traceability follow the accepted safety standards for radioisotope handling. Results and Conclusion The Symmetric STTS has proven characteristics of reliability, ease of use and safety over hundreds of runs. Given that no convenient carting path exists, it is the ideal means for bringing solid target holders from the underground cyclotron vault to the chemistry processing hot cells at ground level. Transported activities are less than 37.0 GBq (1.0 Ci) for 64Cu and 3.7 GBq (100 mCi) for 89Zr. Carrier velocity is about 4.7m/s minimizing the time activity is present between cyclotron and hot cell. No human interaction with the irradiated target is needed during transport. The carrier does not need to be taken out of the STTS. Even though the BqSv hot cells are equipped with teletongs, they are not needed to recover the target when it arrives at the hot cell; the target is directly dropped into the processing module, e.g. the dissolution vessel for 64Cu processing. The software is engineered in a manner that gives the operator full control of the states of the sending and receiving stations. At the same time, it avoids graphically dense and overloaded GUI in order to reduce the probability of human error. Currently the control program runs on a PC/Laptop and communicates with the controller over USB. LabView provides add-ons that allow control with a tablet or other hand-held (under development). The fully automated symmetric STTS is ideal for isotope production facilities that are being envisioned, conceptualized or are in their planning stage. Its versatility, low initial and operating costs might even justify deployment in facilities which already employ a less optimal solid target transport. Invention application for the Symmetric STTS was filed with the Office of Technology Management of Washington University in Saint Louis, Missouri, USA.

Introduction The Comecer ALCEO Metal system is intended to be a comprehensive solid targetry system, capable of all steps necessary to produce copper isotopes (60Cu, 61Cu & 64Cu) from enriched nickel: plating, transfer to/from cyclotron, irradiation, and dissolution/purification. To develop plating and chemistry methods, we plate natural nickel, and irradiate with deuterons to produce 61Cu. This alleviates the need for expensive enriched nickel isotopes, but gives a lower activity yield. We report a few issues with the ALCEO system, and some of our modifications. Material and Methods BRIEF DESCRIPTION OF SYSTEM: The ALCEO system uses cylindrical shuttles (dia 28 mm, height 35 mm) comprised of an Al body with a Pt well, onto which the Ni is plated. Shuttles are transferred pneumatically from the hot cell to the irradiation module, on the end of the cyclotron beamline. The plating and dissolution are both done at the electrochemical cell, located in the hot cell. This cell is connected by capillary tubes to the electrolytic solution reservoir (for plating), or the acid reservoir (for dissolution). These tubes form a recirculation loop, through which the fluid is propelled by an inline micropump throughout plating and dissolution. The platinum well is 16 mm in diameter, while an O-ring is used to plate only the center (6 mm in diameter). A constant DC voltage is applied. PLATING: We dissolve natural nickel nitrate (99.999% pure) into an electrolytic solution comprised of deionized water, ammonium hydroxide and ammonium chloride (pH = 9.3). We use 30–100 mg of natNi in a 10mg/mL solution. We have varied the ALCEO electrochemical cell voltage between 2.25–3 VDC, and tried to maintain a low pump flow rate between 1–2 mL/min. The electrochemical cell uses a fixed metal tube as the anode (~3mm above the plating surface). This tube also delivers the electrolytic plating solution to the Pt surface, forming part of the recirculating loop. The Pt surface is in contact with a gold-plated cathode. Due to issues discussed below, we have built a custom plating rig for the ALCEO shuttles, which does not use the pump/recirculation loop, but leaves the reservoir of electrolytic solution in place, atop the plating surface. A graphite rod is used for the anode, rotating offcenter ~2mm above the plating surface. We use the same size O-ring to plate only the center 6 mm of the Pt surface, and apply a constant DC voltage. TRANSFER TO/FROM CYCLOTRON: The pneumatic transfer tube is 50 ft long between the hot cell and the cyclotron vault, and has a rise of 14 ft from under the floor to the ceiling of the cyclotron vault. IRRADIATION: The ALCEO irradiation module holds the plating surface orthogonal to the beam path. The module has a 10-mil-thick (0.010”) Al front foil, supported by a hex-grid. Once we realized the thickness, we replaced this with a 1-mil-thick Al foil, followed by a 1-mil-thick Havar foil. The foil is cooled by a flow of helium, while the shuttle and grid are cooled by a flow of water. The helium and water are cooled in heat ex-changers by chilled water. As initially plumbed, the chilled water flowed through the heat ex-changers in series, cooling the helium first, then the water. After initial runs, we plumbed the heat exchangers in parallel, teeing the chilled water to the supply of each heat exchanger, and teeing the returns together. Irradiation is performed with a PETtrace 800 accelerating deuterons to 8.4 MeV on target. The beam current limit is 20 μA for the ALCEO Metal target. A set point of 19 μA is used to avoid the system tripping off. DISSOLUTION/PURIFICATION: The ALCEO system circulates 5 mL of 6M HCl, while heating the shuttle to 100 ⁰C for 40 min. This solution is loaded onto a column containing 10 g of 200–400 mesh chromatographic resin in chloride form. A separation is performed yielding three solutions: The column is washed with 40 mL of 6M HCl to obtain the Recovered Nickel Solution, then 20 mL of 4M HCl to obtain the Cobalt Solution, then 10 mL of 0.5M HCl to obtain the Cop-per Product Solution. Results and Conclusion PLATING: Using the ALCEO method, the platings obtained had a tendency to mound, (up to 0.75 mm thick for 50 mg) giving a lower density of 3–4 g/cm3. This was attributed to the anode tube being fixed in place over the center of the plating surface. Using the custom rig, almost no mounding was observed, (0.25mm thick for 50 mg) giving a density of 7 g/cm3, closer to nickel’s nominal density of 8.9 g/cm3. FIGS. 1 and 2 attempt to show the mounding from the ALCEO method, and relative flatness from the custom rig. Both methods give a rough, or “fuzzy” plated surface. FIG. 2 shows that the custom rig exaggerates this “fuzziness”. Using the ALCEO method, a slower pump speed (~1 mL/min) gives a smoother plating surface, but the pump has a tendency to lock up at this lower set point, stalling the plating. Using the ALCEO method, slight increases in the voltage (2.65 V instead of 2.25 V), can form thin stalagmites of nickel, electrically connecting the anode and the plating surface, ending the chance for a useable plating. Using the custom rig, no stalagmites are seen, adjusting the voltage from 2.3 to 3.0 V. This leads to the potential for a faster plating. Both the ALCEO method and the custom rig have obtained plating efficiencies of 95 %. TRANSFER TO/FROM CYCLOTRON: The shuttle typically transfers without issue in < 15 seconds. Once or twice it has remained in the transfer tube, but been retrieved by cycling the com-pressed air/vacuum a couple of times. IRRADIATION: During initial testing, the temperature of the return water rose rapidly during irradiation. This was attributed to the chilled water already gaining heat from the helium heat exchanger. Once the parallel chilled water plumbing was implemented, the water temperature rose much more slowly. Initial testing with the 10-mil Al foils gave a very poor activity yield. The 1-mil Al foil ruptured under the 20 psi helium pressure before beam was applied. The 1-mil Havar foil produced 1.57 mCi of 61Cu at EOB, giving an activity yield of 0.308 mCi/μAh (results summarized in TABLE 1). This compares to yields of 1.4 obtained by [1], and 0.29 obtained by [2] for deuterons on natNi. DISSOLUTION/PURIFICATION: The dissolution in 6M HCl is close to 100% efficient by weight. After purification, the three solutions were assayed by dose calibrator as summarized in TABLE 2. The purification is very efficient at removing the starting material, and long-lived Co isotopes from the Copper Product Solution, as seen with the 57-hour EOB measurements. However, much of the desired 61Cu is removed as well, with only 32% remaining in the product. The lack of nuclide impurities in the Copper Product Solution was confirmed by gamma spectroscopy using a HP-Ge detector.

Rhenium-186 has a half-life (t1/2 = 3.72 days) and emission of both gamma and beta particles that make it very attractive for use as a theranostic agent in targeted radionuclide therapy. 186Re can be readily prepared by the 185Re(n,γ)186Re reac-tion1. However, that reaction results in low specific activity, severely limiting the use of reactor produced 186Re in radiopharmaceuticals. It has previously been shown that high specific activity 186Re can be produced by cyclotron irradiations of 186W with protons and deuterons2,3. In this investigation we evaluated the 186W(d,2n)186Re reaction using thick target irradiations at higher incident deuteron energies and beam currents than previously reported. We elected not to use copper or aluminum foils in the preparation of our 186W targets due to their activation in the deuteron beam, so part of the investigation was an evaluation of an alternate method for preparing thick targets that withstand μA beam currents. Irradiation of 186W. Initial thick targets (~600-1100 mg) were prepared using 96.86% enriched 186W by hydraulic pressing (6.9 MPa) of tungsten metal powder into an aluminum target support. Those thick targets were irradiated for 10 minu-tes at 10 µA with nominal extracted deuteron energies of 15, 17, 20, 22, and 24 MeV. Isolation of 186Re. Irradiated targets were dissolved with H2O2 and basified with (NH4)2CO3 prior to separation using column(s) of ~100–300 mg Analig Tc-02 resin. Columns were washed with (NH4)2CO3 and the rhenium was eluted with ~80˚C H2O. Gamma-ray spectroscopy was per-formed to assess production yields, extraction yields, and radionuclidic byproducts. Recycling target material. When tested on a natural abundance W target, recovery of the oxidized WO4- target material from the resin was found to proceed rapidly with the addition of 4M HCl in the form of hydrated WO3. The excess water in the WO3 was then removed by calcination at 800 °C for 4 hours. This material was found to undergo reduction to metallic W at elevated temperatures (~1550 °C) in a tube furnace under an inert atmosphere (Ar). Quanti-fication of % reduction and composition analyses were accomplished with SEM, EDS, and XRD and were used to characterize and compare both the WO3 and reduced Wmetal products to a sample of commercially available material. Structural enhancement by surface annealing. In some experiments ~1 g WO3 pellets were prepared from Wmetal that had been chemically treated to simulate the target material recovery process described above. Following calcination, the WO3 was allowed to cool to ambient temperature, pulverized with a mortar and pestle and then uniaxially pressed at 13.8 MPa into 13 mm pellets. Conversion of the WO3 back to Wmetal in pellet form was accomplished in a tube furnace under flowing Ar at 1550 °C for 8 hours. Material characterization and product composition analyses were conducted with SEM, EDS, and XRD spectroscopy. Graphite-encased W targets. Irradiations were conducted at 20 μA with a nominal extracted deuteron energy of 17 MeV using thick targets (~750 mg) of natural abundance tungsten metal powder uniaxially pressed into an aluminum target support between layers of graphite pow-der (100 mg on top, 50 mg on the bottom). Targets were then dissolved as previously described and preliminary radiochemical isola-tion yields obtained by counting in a dose calibrator. Although irradiations of W targets were possible at 10 μA currents, difficulties were encountered in maintaining the structural integrity of the full-thickness pressed target pellets under higher beam currents. This led to further investigation of the target design for irradiations conducted at higher beam currents. Comprehensive target material characterization via analysis by SEM, EDS, XRD, and Raman Spectroscopy allowed for a complete redesign of the target maximizing the structural integrity of the pressed target pellet without impacting production or isolation. At the 10 A current, target mass loss following irradiation of an enriched 186W target was < 1 % and typical separation yields in excess of 70 % were observed. Saturated yields and percent of both 183Re (t½ = 70 days) and 184gRe (t½ = 35 days) relative to 186gRe (decay corrected to EOB) are reported in TABLE 1 below. The reason for the anomalously low yield at 24 MeV is unknown, but might be explained by poor beam alignment and/or rhenium volatility during irradiation. Under these irradiation conditions, recovery yields of the W target material from the recycling process were found to be in excess of 90% with no discernable differences noted when compared to commercially available Wmetal and WO3. Conceptually, increasing the structural integrity of pressed WO3 targets by high temperature heat treatment under an inert atmosphere is intriguing. However, the treated pellets lacked both density and structural stability resulting in disintegration upon manipulation , despite the initially encouraging energy dispersive X-ray spectroscopy (EDS) determination that 94.9% percent of the WO3 material in each pellet had been reduced to metallic W. The use of powdered graphite as a target stabi-lizing agent provided successful irradiation of natural abundance W under conditions where non-stabilized targets failed (20 µA at 17 MeV for 10 minutes). Target mass loss following irradiation of a natW target was < 1 % and a separation yield in excess of 97 % was obtained. In conclusion, the theranostic radionuclide 186Re was produced in thick targets via the 186W(d,2n) reaction. It was found that pressed W metal could be used for beam currents of 10 μA or less. For deuteron irradiations at higher beam currents, a method involving pressing W metal between two layers of graphite provides increased target stability. Both target configurations allow high recovery of radioactivity from the W target material, and a solid phase extraction method allows good recovery of 186Re. An effective approach to the recycling of enriched W has been developed using elevated temperature under an inert atmosphere. Further studies are underway with 186W targets sandwiched by graphite to assess 186Re production yields, levels of contaminant radiorhenium, power deposition, and enriched 186W material requirements under escalated irradiation conditions (20 µA and 17 MeV for up to 2 hours).

Introduction The COSTIS system is a commercially available target station for the irradiation of solid targets. Up to 3 targets can be provided for irradiation by a slot system. In standard setup the target can be ejected via a pneumatically driven piston system. The target is then allowed to drop down into an open lead container, which can be closed remotely afterwards. The described procedure is well established and reliable. But the concept is limited to low dose targets and environments. The required entering of the cyclotron vault for manual pick up of the container at the cyclotron and the light 18 mm Pb lead shielding of the container itself cause exposure risk for the personnel after long term irradiations with highly activated cyclotron parts and target. The purpose of this work was the design of an alternative for the pickup and the transport of irradiated targets to minimize the radiation dosage of the personnel during manual handling of the COSTIS-lead container. Principle The new designed transport system still uses the software controlled target ejection function of the COSTIS/IBA-system. With ejection the target capsule is allowed to fall into a PTFE-container. To assure a safe target drop into the PTFE container, the gap between the target guiding plate and the PTFE container is smaller than d/2 of the target capsule. After target ejection the PTFE-container can be transferred remotely from target ejection position (1) to the loading station (2) with a target slide. The loading station allows the transfer of the PTFE container remotely into a lead container (60 mm Pb). Now the vault door is used as carrier of the Pb-container. For this purpose a proper fixture for the Pb-container is mounted at the front side of the vault door and via opening the vault door the container is safely transported out of the vault. Outside the container will be finally closed with a lid and transferred to a trolley for further handling. Due to positioning of the container at a certain altitude together with the deep positioning of the target coin inside of the container, the subsequent closing of the container does not cause significant dosage, a more complicated automatic closing system is not mandatory. After replacement of the lead container further transfers can be executed without entering the vault. For this purpose the exchanged Pb-container is placed at the loading station by closing the vault door and a new PTFE-container will be transferred remotely from a magazine onto the target slide, which again can be re-motely positioned at target ejection position. The magazine of PTFE-Containers holds two replacements in accordance with the maximal capacity of the target slot system of the COSTIS station. The remote system of the transport unit uses redundant feedback signals for a reliable and safe operation. Results and Conclusion The newly implemented transport system allows a significant reduction of the radiation dose during pickup and transport of the irradiated solid targets. No entering of the vault is needed after irradiation. The system is highly reliable due to its redundant and straightforward design (2-fold position switches and photoelectric barriers). Due to fixed attachment points in the vault and at the BTL the mobile unit can be easily removed or mounted. The system is maintenance free and all parts easy accessible. For further handling of the targets lead containers were design to fit in the transfer locks of hot cells. The transfer can be carried out directly from the trolley. Container lid and PTFE container are suited for manipulator handling in hot cells.

Introduction Solid targets for PET and SPECT radionuclides are getting popular. For radiohalogens the limiting factor, beside the high cost of enriched target material is beam current due to poor heat conductivity of the target material(s). We have designed a honeycomb solid target which has advantages over the traditional circular hole de-sign: 1) Even distribution of target material, 2) it takes higher beam current, 3) less target material loss during distillation (1) and 4) no “creeping” (surface tension phenomena) of the target material during distillation. Material and Methods The target (see FIG. 1.) consists of 19 hexagonal 0.3 mm deep openings (see FIG. 2.) thus having 84% transparency/transmission, in a 24×2 mm platinum disk. There is a 10mm circular cavity on the reverse side giving a 200µm thickness of the platinum. The irradiations were performed on an IBA twin 18/18 Cyclon equipped with a Costis sold target system. The target material thickness was ~300mg/cm2 124TeO2 (> 99.9% I.E., Isoflex) with 5% w/w Al2O3 (99.99%, Sigma-Aldrich). The target was irradiated with 14.8MeV protons (18 MeV degraded by 500µm aluminium). Results and Conclusion The target was able to take beam current up to ~35 µA (higher BCs have not yet been investigated); our “traditional” target (10mm circular hole) has a limit of ~ 20 µA. This means that the effective yield is ~ 50 % higher with the honeycomb as compared with the “traditional” target design.

Introduction A new high current (up to 50 kW) solid target irradiation system is being built. While retaining the same beam power capability of the previous target generation, the system is a totally new design with many improvements, simplified constriction, more reliable operation and a novel approach to target handling, beam collimation and beam diagnostic. Unlike the previous, three-part soldered target, the new target is fabricated from a single piece of metal. Material and Methods The target (or rather the target-material holder) is a single metal plate (usually copper or silver) incorporating the seals and the cooling channels (FIG. 1). The target is placed in the beam at 7°. Depending on target material and coolant flow the target can handle beam powers up to 50 kW (FIG. 2). Target transfer (utilizing a special shuttle) is pneumatic. Part of the transfer pipe is shown above the target station. Except the target o-rings (a part of each target) there are no elastomer seals in the system; all is of soldered/welded construction and metal seals. Sectional view (FIG. 3.) shows that target in place in the chamber. The target and the chamber are electrically insulated from the rest of the system, thus forming a Faraday cup for accurate current measurement. The collimator is formed of a two part silver casting. It is designed to handle up to 10 kW of beam power. Four-sector silver mask in front of the collimator allows precise beam cantering. The collimator parts were cast using 3D printed wax patterns. This allowed to create a complex pattern of cooling channels that are difficult to produce by machining (FIG. 4.) All the actions of target shuttle landing and the target placing are performed by three air cylinders. All three are fitted with Vespel SP22 (Du Pond) seals. Unlike previous systems that used mechanical grabbers to manipulate the target, low vacuum is employed to hold the target during removal from the shuttle and placing in the irradiation chamber. This greatly simplifies the operation and is more reliable. The pneumatic transfer system is using two vacuum producer to transfer the target shuttle between the target station and the hotcell. Both landing terminals in the target station and hotcell, as well as the transfer line itself, are under negative pressure preventing any spread of contamination. The hotcell landing terminal incorporates a fully automatic target-material dissolution system. After landing, the target is removed from the shuttle and the active face pressed against a reaction vessel where the dissolution takes place (FIG. 5.) All the functions of target transfer, placing and manipulations are controlled by a simple PLC (FMD88-10 PLC, Triangle Research) Results and Conclusion While intended mostly for cladding with metallic target materials, a special version of the target was designed to handle salts or oxides that can be fused and retained in grooves on the target face (FIG. 6.) Despite the poor thermal conduc-tivity of most of those materials, this target can handle high beam currents. FIGURE 7 shows a thermal modelling of the cen-tral 10×25 mm segment of the target (highest heat flux region under a Gaussian beam). Copper target with rubidium chloride fused in 0.8 mm wide and 1.7 mm deep grooves and spaced by 0.5 mm (60% coverage). Beam of 70 MeV energy and 400 μA intensity is collimated 20 % (320 μA on target). Cooling-water flow is set to 25 l/min. Cladding the target face with a thin metallic layer can help containing the target material. This process is currently under development. Most aspects of the system operation and con-striction were successfully used in the previous “generations” of targets in the last 30 years. The new system will provide improved performance with a simpler and more reliable design, lower maintenance and lower consumables cost. FIGURE 8 shows the “4th generation” system and target (2005). Dozens variants of this design are in use all over the world.

Introduction Temperature modeling using Finite Element Analysis (FEA) is widely used by particle beam-line designers as a useful tool to determine the thermal performance of an irradiated target system. A comparison study was performed between FEA calculated temperatures on platinum with experimental results using direct thermocouple measurements. The aims are to determine the best beam model for future solid target design, determine the maximum target current for different target materials and the temperature tolerance for any modification to our existing solid targetry system. Material and Methods The theoretical temperature of the target sys-tem was determined using SolidWorks 2013 with Flow Simulation Analysis (FSA) module. The FSA module determines the maximum temperature inside the target material given the global conditions (material specification, flow rates, boundary conditions, etc.) for a given target current. The proton beam was modeled as a volumetric heat source inside the target material based on the distribution of energy loss in the material along the beam axis. The method used by Comor, et al1 was used in this study. The method segmented the target material into five individual layers, each layer being 50 m thick. The energy lost per layer was calculated using SRIM3 and converted into the power lost per layer. A thickness of 250 μm of platinum completely stops the impinging proton beam at 11.5 MeV with the highest deposition of power per layer corresponding to the Bragg peak. The target material used in the simulation reflects the physical target disk used for temperature measurements (platinum, dia. 25.0 mm, thickness 2.0 mm) with two K-type thermocouples (dia. 0.5 mm, stainless steel sheath) embedded in the platinum disk. One thermocouple is located in the geometric center, while the other is located at a radial position 8 mm from center. The outer thermocouple is to determine the peripheral temperature near the o-ring seal. Temperature was maintained below the melting point for the material (Viton®, melting point 220 °C) during the irradiation to ensure the integrity of the water cooling system. The solid targetry system used in this study is an in-house built, significantly modified version2 of a published design1. The solid target system is mounted onto an 18/18MeV IBA Cyclotron with dual ion source, on a 300mm beam-line with no internal optics or steering magnets. A graphite collimator reduces the beam to 10mm in diameter and a degrader is used to reduce the proton beam energy to 11.5 MeV, considered suitable for production of radiometal PET isotopes 89Zr and 64Cu. Temperature was measured with and without the 300 mm beam-line to compare the effects of beam divergence on the solid target (FIGS. 1 and 2). The experiment was conducted using both H− ion sources with different ion-to-puller extraction gaps (ion source 1 is 1.55 mm with ion source 2 at 1.90 mm). The setting of the ion-to-puller gap changes the focusing of the accelerated beam inside the cavity. Results and Discussion The segmented beam model was used to calculate the temperature on and within the target, as well as the maximum temperature of the bulk material. The first segment is the leading segment of the material irradiated by the incident proton beam. Results are shown in TABLE 2. Target temperatures were measured experimentally under two different conditions; target attached at the end of a 300mm beam-line and target attached directly to the cyclotron. The temperature was measured experimentally using the platinum disk with 2 thermocouples inside the bulk target material irradiated on the end of a 300mm beam-line. The measured temperature is shown in TABLE 2. The variation between ion source 1 and 2 for the temperature measured in the center was 11–15 %, while the variation on the radial position was 2–6 %. A smaller ion-to-puller extraction distance (ion source 1) reduces the cross-sectional area of the accelerated beam; the consequent high proton current density (10mm diameter collimated beam) increases the temperature inside the bulk material for a fixed target current. The highest observed radial temperature was 93 °C, with target current of 50 μA using ion source 1. This is well below the melting point for the o-ring seal. The temperature measured experimentally using the same platinum disk with no beam-line is shown in TABLE 4. A temperature difference of up to 7 % was measured between ion source 1 and 2 at the exit port without the beam-line, while the maximum variation on the radial position was 3 %. A comparison between the calculated theoretical and measured temperatures is shown in FIGS. 3 to 6. The temperatures calculated by the FEA model underestimate the temperature regardless of target position (with or without the beam-line) and for both ion sources. The temperature difference between the FEA model and the experimental results increases with increasing target currents. As shown in Figure 3, at the target center the FEA model underestimated the temperature by 22–32 % for ion source 1 and 13–22 % for ion source 2. This is consistent with the difference between the two ion sources due to the difference in the ion-to-puller gap size. With the target mounted at the exit port the theoretical and measured temperature for the center of the platinum disk is shown in FIGURE 4. The FEA model underestimates the temperature at the center of the platinum disc by 2–10 % for both ion sources. As shown with the previous experiment, the margin of error increases with increasing target current. Comparison between FIGS. 3 and 4 shows the measured temperature at the center of the platinum disk is significantly lower when the target is attached to exit port of the cyclotron. Localised area of high current density (hot spots) is not registered as higher temperature in the bulk material. True temperature inside the bulk material is highly dependent on the thermal conductivity of the target material and the resolution of the thermocouple. The cross-sectional area of the beam ‘hot-spot’ will be greater due to beam divergence at the end of the beam line compared with the exit port. The ‘hot’ area of the expanded beam becomes a significant portion of the overall collimated beam (collimator dia. 10.0 mm). A more uniform beam profile (less heterogeneity) evenly distributed the area of high current density across the disk surface, effectively increasing the temperature of the bulk material while decreasing the sensitivity required to measure the true temperature. As observed from this comparative study it appears that a more homogeneous current density leads to a higher temperature measurement at the target center. With the solid target at the end of the beam-line, target current lost on the collimator and beam-line was >55%. The effect of beam divergence is clearly observed in TABLE 5. With the target mounted directly at the exit port the current lost was reduced to < 40 %. Although the average proton current density is the same for any set target current, irrespective of target position, the contribution of the peripheral beam to the total target current should not be underestimated. A loss of ~40 μA on the collimator and beam-line places greater reliance on the center of the ‘hot’ beam to maintain the same target current. The temperature at the radial position (FIG. 5) observes the same trend as for the temperature measured in the center. The error increases for higher target currents and the FEA model underestimated the temperature by 19–40 %. The error at this location is due partly to the model’s assumption of a uniform heat source, applied to the material on a single axis (perpendicular to the material surface) and does not account for any scattering or divergence of the incident proton beam. FIGURE 6 shows that the FEA model underestimated the radial temperature by 16–37 %, when the target is connected to the exit port, for reasons discussed previously. Comparison with FIG. 5 (target on the beam-line) shows the same margin of error between the FEA and the experimental results (19–40 %). The temperature difference between the FEA model and measured temperature at the radial position is independent of the beam profile and beam divergence. The FEA model underestimated the temperature at the radial location with or without the beam-line and for both ion sources. The significance difference in temperature between the FEA model and the experimental is due to our model assumption that the maximum radial temperature is on the irradiated surface and not inside the material corresponding to the layer with the maximum energy lost. In addition, the FEA model does not ac-count for the divergence of the proton beam as it travels through the material. Given the temperature at 50 μA target current is > 90 °C (TABLES 3 and 4) we have capped the experi-ment below this point to prevent any damage the o-ring seal. Conclusion The segmented FEA model was inadequate in determining the temperature for the target at the end of a 300mm beam-line (> 30 % difference). A combination of beam divergence and greater uniform coverage of high current density beam resulted in a higher than predicted temperature reading. However, the segmented FEA model provides a good estimation (< 10 % difference) for the observed temperature of the bulk material at the exit port. The simplistic FEA model was unable estimate the temperature at the radial position (~ 40 % difference) regardless of ion source or target position. A comparison between the two ion sources with different ion-to-puller extraction gap, leading to different focusing of the accelerated beam yield minimal temperature difference. Although a 15% difference was observed between the ion sources at the end of the beam-line, a major contributing factor is beam divergence beyond the magnetic field rather than the beam size of the accelerated beam. Further studies are underway to determine the beam profile (quantitatively using radiographic film), quantify the contribution of the peripheral beam to the total beam current by comparing different size collimators and to investigate other FEA models by applying different beam models (heterogeneous and homogeneous beam) and different heat sources (surface vs. volumetric). Currently the RAPID Lab solid targetry is placed at the end of the beam-line for easy loading and unloading, since multiple target irradiations are performed per month2. However, RAPID is presently developing a new solid targetry sys-tem which eliminates the need for a beam-line and will be able to manage a maximum extracted target current of 150 μA.