Isotope Production Target Research Articles

Design of the 590 MeV proton beamline for the proposed TATTOOS isotope production target at PSI

IMPACT (Isotope and Muon Production with Advanced Cyclotron and Target Technologies) is a proposed initiative envisaged for the high-intensity proton accelerator facility (HIPA) at the Paul Scherrer Institute (PSI). As part of IMPACT, a radioisotope target station, TATTOOS (Targeted Alpha Tumour Therapy and Other Oncological Solutions) will allow the production of terbium radionuclides for therapeutic and diagnostic purposes. The proposed TATTOOS beamline and target will be located near the UCN (Ultra Cold Neutron source) target area, branching off from the main UCN beamline. In particular, the beamline is intended to operate at a beam intensity of 100 μA, requiring a continuous splitting of the main beam via an electrostatic splitter. Realistic beam loss simulations to verify safe operation have been performed and optimised using Beam Delivery Simulation (BDSIM), a Geant4 based tool enabling the simulation of beam transportation through magnets and particle passage through the accelerator. In this study, beam profiles, beam transmission and power deposits are generated and studied.

First Simultaneous Acceleration of Multiple Charge States of Heavy Ion Beams in a Large-Scale Superconducting Linear Accelerator.

Experimental studies of the simultaneous acceleration of three-charge-state ^{129}Xe^{49+,50+,51+} beam from 17 to 180 MeV/nucleon in a superconducting linear accelerator are presented. The beam parameters for each individual- and multiple-charge-state beam were measured and compared with the particle tracking simulations. Detailed measurements were performed to characterize the multiple-charge-state beam's recombination after a second-order achromat and isopath 180° bending system. As a result of the recombination of three charge states in the six-dimensional phase space, the xenon beam intensity was increased by 2.5-fold compared to the single-charge-state beam. The results presented in the Letter fully validate the possibility to produce and utilize high-quality multiple-charge-state heavy-ion beams in a large-scale superconducting linac to increase the available beam power on an isotope production target.

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes.

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of this review presents description of the cyclotron targets properties, especially physicochemical characterization of irradiated elements. The second part is devoted to description of the electrodeposition procedures leading to obtain elements or their alloys coatings (e.g., nickel, uranium) as the targets for cyclotron and reactor generation of the radioisotopes. This review provides an evaluation of the role ILs can have in the production of isotopes.

Fiber-Optic Bragg Gratings for Temperature and Pressure Measurements in Isotope Production Targets for Nuclear Medicine

A Bragg grating inscribed into an inorganic optical fiber was tested in proton and neutron fields up to doses of 472 Gy. Observation showed that radiation had no effect on the performance of the Fiber Bragg Grating (FBG) used as a gauge measuring temperature and pressure. The FBG sensor was subsequently employed to measure the temperature and pressure inside a liquid isotope production target for nuclear medicine. The fiber Bragg grating measured the temperature and pressure of a water target as a 12 MeV proton beam impinged on it in real time and was tested with beam currents of up to 20 µA.

Ce- and B-Doped Silica Fibers for Monitoring Low-Energy Proton Beams on a Medical Cyclotron

Many medical isotopes can be produced on a small cyclotron. The alignment and profiles of low-energy proton beams from cyclotrons used for medical radioisotope production, such as the TR13 cyclotron at TRIUMF, Canada, cannot be directly quantified during dose delivery with simultaneous constant feedback and sharp spatial resolutions. Doped silica fibers are a potential solution that has been tested at TRIUMF. To measure the effects of irradiation inside an isotope production target, we attached fibers to the outside of an 18O gas target and measured the light output during irradiation. Different dopants, fiber diameters, and target materials were investigated. It was found that 200 µm diameter Ce- and B-doped fibers produce signals linearly proportional to the beam current. This only deviated when the target was moved such that the beam was steered into the target wall, increasing the production of prompt radiation and causing the beam current to decrease but the fiber signal to increase. With the technique described here, the beam can be monitored on the target, including its steering and its overall alignment with the target.

An isotope harvesting beam blocker for the National Superconducting Cyclotron Laboratory

Harvesting isotopes from beam stops and other activated materials at accelerator facilities is a promising source of environmentally, scientifically and socially important radionuclides. At the Facility for Rare Isotope Beams (FRIB), a multitude of short- and long-lived radionuclides will be collected in a synergistic manner by dumping unused beams into a flowing-water beam stop. Ongoing exploratory research at the National Superconducting Cyclotron Laboratory (NSCL) with an analogous beam blocker aims towards obtaining the necessary radiochemical expertise for this endeavor.Herein we present a beam blocker and an isotope harvesting system which allows collection of a wide variety of aqueous and gaseous radionuclides. The water which flows through the beam blocker functions as an isotope production target and concurrently transports the newly formed radionuclides to collection sites. The system includes analytical instruments for online measurements of conductivity, dissolved oxygen, temperature, pressure and for detection of radiolytic products. To limit the levels of radiolytically produced hydrogen peroxide, a stainless-steel based degradation system was designed and implemented. The suitability of the constructed system for the anticipated radionuclide harvesting project was demonstrated by offline tests and under irradiation with 140 MeV/u 48Ca20＋ ions at the NSCL Coupled Cyclotron Facility.

Production possibility of 161Tb utilizing secondary neutrons generated by protons from a low-energy cyclotron onto an isotope production target

The production possibility of the medically relevant radioisotope 161Tb using a 9Be + p (Ep = 18 MeV) neutron source was investigated at the MGC cyclotron of ATOMKI. The 161Tb is formed via the 160Gd(n,γ)161Gd → 161Tb nuclear process. The available EOB yield was about 8000 Bq C−1 g−1. Predictions based on Monte Carlo calculations in conjunction with TENDL-2017 cross-section data overestimate the experimental results. These preliminary results indicate that secondary neutrons generated in a high-intensity medical radioisotope production target station could be useful for research-scale 161Tb production.

Two-way multi-physics coupling for modeling high power RbCl isotope production targets

Abstract This work shows successful first application of two-way multi-physics coupling to model RbCl targets in a three-stacked target configuration used at Los Alamos National Laboratory’s (LANL) Isotope Production Facility (IPF). Targets are known to melt at production level beam currents and as in-beam monitoring of the targets in this configuration is not possible, high-fidelity simulation has been utilized to gain insight into target thermal behavior. Thermal hydraulic modeling was performed with ANSYS CFX and particle transport with the Monte Carlo N-Particle (MCNP) code. Multi-physics coupling of these two codes was employed to fully capture the highly coupled nature of the problem physics. Both transient and equilibrium thermal hydraulic results were obtained using this process. The equilibrium thermal hydraulic results were then employed to predict measured 82Sr yields in molten RbCl targets. This technique demonstrates promise as a tool to investigating, understanding, and enhancing high power targetry behavior and limitations.

Thermal, mechanical and fluid flow aspects of the high power beam dump for FRIB

The Facility for Rare Isotope Beams (FRIB) under construction at Michigan State University is based on a 400kW heavy ion accelerator and uses in-flight production and separation to generate rare isotope beams. The first section of the fragment separator houses the rare isotope production target, and the primary beam dump to stop the unreacted primary beam. The experimental program will use 400kW ion beams from 16O to 238U. After interaction with the production target, over 300kW in remaining beam power must be absorbed by the beam dump. A rotating water-cooled thin-shell metal drum was chosen as the basic concept for the beam dump. Extensive thermal, mechanical and fluid flow analyses were performed to evaluate the effects of the high power density in the beam dump shell and in the water. Many properties were optimized simultaneously, such as shell temperature, mechanical strength, fatigue strength, and radiation resistance. Results of the analyses of the beam dump performance with different design options will be discussed. For example, it was found that a design modification to the initial water flow pattern resulted in a substantial increase in the wall heat transfer coefficient. A detailed evaluation of materials for the shell is in progress. The widely used titanium alloy, Ti–6Al–4V (wt%), is presently considered as the best candidate, and is the subject of specific tests, such as studies of performance under heavy ion irradiation.

Tailoring medium energy proton beam to induce low energy nuclear reactions in 86SrCl2 for production of PET radioisotope 86Y

This paper reports results of experiments at Brookhaven Linac Isotope Producer (BLIP) aiming to investigate effective production of positron emitting radioisotope 86Y by the low energy 86Sr(p,n) reaction. BLIP is a facility at Brookhaven National Laboratory designed for the proton irradiation of the targets for isotope production at high and intermediate proton energies. The proton beam is delivered by the Linear Accelerator (LINAC) whose incident energy is tunable from 200 to 66MeV in approximately 21MeV increments. The array was designed to ensure energy degradation from 66MeV down to less than 20MeV. Aluminum slabs were used to degrade the proton energy down to the required range. The production yield of 86Y (1.2+/−0.1mCi (44.4+/−3.7) MBq/μAh) and ratio of radioisotopic impurities was determined by assaying an aliquot of the irradiated 86SrCl2 solution by gamma spectroscopy. The analysis of energy dependence of the 86Y production yield and the ratios of radioisotopic impurities has been used to adjust degrader thickness. Experimental data showed substantial discrepancies in actual energy propagation compared to energy loss calculations.

A new beam loss detector for low-energy proton and heavy-ion accelerators

The Facility for Rare Isotope Beams (FRIB) to be constructed at Michigan State University shall deliver a continuous, 400kW heavy ion beam to the isotope production target. This beam is capable of inflicting serious damage on accelerator components, e.g. superconducting RF accelerating cavities. A Beam Loss Monitoring (BLM) System is essential for detecting beam loss with sufficient sensitivity and promptness to inform the machine protection system (MPS) and operations personnel of impending dangerous losses. Radiation transport simulations reveal shortcomings in the use of ionization chambers for the detection of beam losses in low-energy, heavy-ion accelerators. Radiation cross-talk effects due to the folded geometry of the FRIB LINAC pose further complications to locating specific points of beam loss. We propose a newly developed device, named the Loss Monitor Ring (LMR11Loss Monitor Ring.), to be implemented upstream of each FRIB cryomodule, as part of the direct loss monitoring system to fulfill the needs of machine protection.

Cyclotrons with fast variable and/or multiple energy extraction

We discuss the principle possibility of stripping extraction in combination with reverse bends in isochronous separate sector cyclotrons (and/or FFAGs). If one uses reverse bends between the sectors (instead of drifts) and places stripper foils at the sector exit edges, the stripped beam has a reduced bending radius and it should be able to leave the cyclotron within the range of the reverse bend - even if the beam is stripped at less than full energy. We are especially interested in $H_2^+$-cyclotrons, which allow to double the charge to mass ratio by stripping. However the principle could be applied to other ions or ionized molecules as well. For the production of proton beams by stripping extraction of an $H_2^+$-beam, we discuss possible designs for three types of machines: First a low-energy cyclotron for the simultaneous production of several beams at multiple energies - for instance 15 MeV, 30 MeV and 70 MeV - thus allowing to have beam on several isotope production targets. In this case it is desired to have a strong energy dependence of the direction of the extracted beam thus allowing to run multiple target stations simultaneously. Second we consider a fast variable energy proton machine for cancer therapy that should allow extraction (of the complete beam) at all energies in the range of about 70 MeV to about 250 MeV into the same beam line. And third, we consider a high intensity high energy machine, where the main design goals are extraction with low losses, low activation of components and high reliability. The price that has to be paid for these advantages is an increase in size and/or in field strength compared to proton machines with standard extraction at the final energy.

High power density targets

In the context of new generation rare isotope beam facilities based on high-power heavy-ion accelerators and in-flight separation of the reaction products, the design of the rare isotope production targets is a major challenge. In order to provide high-purity beams for science, high resolution is required in the rare isotope separation. This demands a small beam spot on the production target which, together with the short range of heavy ions in matter, leads to very high power densities inside the target material.This paper gives an overview of the challenges associated with this high power density, discusses radiation damage issues in targets exposed to heavy ion beams, and presents recent developments to meet some of these challenges through different projects: FAIR, RIBF and FRIB which is the most challenging. Extensive use of Finite Element Analysis (FEA) has been made at all facilities to specify critical target parameters and R&D work at FRIB successfully retired two major risks related to high-power density and heavy-ion induced radiation damage.

Commissioning the TRIUMF/ISAC electron cyclotron resonance ion source for radioactive ion beams

A radiation hard 2.45 GHz ECR source has been installed in the ISAC target station. The ion source with its 8–60 kV extraction system is coupled to the radioactive isotope production target via a short transfer tube. The volatile radioactive isotopes produced by bombarding a target with a 500 MeV proton beam, are ionized and accelerated at the ECR source system. The source is reengineered to withstand a dose rate of 105 Gy/h from the activation of the target by the 500 MeV, 100 mA proton beam. The whole assembly is located beneath a 2 m thick steel shielding structure. Design aspect of the source and the initial results obtained during the commissioning at the ISAC terminal, as well as preliminary results obtained at the test stand are presented.

A radioactive ion beam facility using photofission

Abstract Use of a high-power electron linac as the driver accelerator for a Radioactive Ion Beam (RIB) facility is proposed. An electron beam of 30 MeV and 100 kW can produce nearly 5×1013 fissions/s from an optimized 235 U target and about 60% of this from a natural uranium target. An electron beam can be readily transmitted through a thin window at the exit of the accelerator vacuum system and transported a short distance through air to a water-cooled Bremsstrahlung-production target. The Bremsstrahlung radiation can, in turn, be transported through air to the isotope-production target. This separates the accelerator vacuum system, the Bremsstrahlung target and the isotope-production target, reducing remote handling problems. The electron beam can be scanned over a large target area to reduce the power density on both the Bremsstrahlung and isotope-production targets. These features address one of the most pressing technological challenges of a high-power RIB facility, namely the production of high yields of neutron-rich ions with reasonable power density in the target. The cost of an electron linac of the required specifications, including the facility shielding, is significantly less than the cost of any other primary-beam accelerator that could produce a comparable fission yield. A high-power electron linac could also be used with a multifoil helium-jet target. A large number of thin uranium foils could be irradiated with the scanned Bremsstrahlung beam and the fission fragments captured in aerosol-loaded helium and transported to an ion source that is well removed from the intense radiation fields of the primary target. The fission yield would be less than 1% of that available from a thick target, but this approach might be the easiest technical solution to obtain useable yields with manageable radiation-safety problems.

Target and ion source development at the TISOL facility at TRIUMF

This paper presents recent developments on the TISOL (test on-line isotope separator) facility at TRIUMF with details on the ongoing work with the surface ion source as well as the newly developed ECR (electron cyclotron resonance) ion source. First measurements using the ECR ion source on-line with a thick-target isotope separator are presented. Release properties of several targets for isotope production have been measured and will be reported.

Non-linear behavior of gas targets for isotope production

Gas targets have been used for production of many isotopes, especially for use in nuclear medicine. (1) We have recently used this technique to produce 81Rb, (2) and have observed that the yields of this isotope were not proportional to the beam current of gas pressure. An investigation of this effect has shown it to be present both when the target was used for preparation of 81Rb and 15O, and presumably for any other product. Therefore it was considered important to investigate the effect in detail.

Cyclotron isotopes and radiopharmaceuticals— XXI. Fabrication of 122TeAu targets for isotope production

An apparatus and technique are described for the preparation of tellurium metal targets. Isotopically enriched 122Te was melted to a thickness of 0.125 mm on to a high-purity gold foil in a hydrogen reduction furnace. The physical characteristics of the TeAu interface were investigated with a scanning electron microscope.