Production Of Radioactive Ion Beams Research Articles

An overview of the shielding optimization studies for the TRIUMF-ARIEL facility

The Advanced Rare IsotopE Laboratory (ARIEL) facility, dedicated to Radioactive Ion Beam (RIB) production via the Isotope Separation On-Line (ISOL) technique, is currently under construction at TRIUMF. The facility is to host dual target stations that will operate simultaneously, including a 500 MeV proton beam from the main TRIUMF cyclotron and a 50 MeV electron beam from an Electron Linear Accelerator (e-linac). The proton target station will operate a symbiotic medical target in series with the ISOL target.The ARIEL facility features a compact shielding envelope and as a result its optimization relied extensively on simulations generated using the Monte Carlo particle transport and interaction code FLUKA. Dose rate maps were produced of prompt radiation associated with beam losses and expected normal operations. Maps of transient fields were also generated considering radiation sources requiring transport within the facility which include radioactive waste generated in the course of normal operations. Activation studies were also conducted to estimate the amount of residual radioactivity contained in shielding materials at the time of decommissioning. Simulation results are primarily used to inform the ongoing design and construction of ARIEL; at present, the entirety of the proposed facility shielding has been validated by FLUKA simulation data. The specification of shielding geometry and the selection of materials relied extensively on engineering support through verification of CAD models and material sampling to optimize solutions for design simplicity and economy. Normal operation and failure scenarios were both evaluated, with optimized shielding materials and thicknesses selected considering the nature of the radiation fields present and their impact on room occupancy. Finally, a decommissioning plan has been defined based on the anticipated ARIEL lifetime, the characterization of structural activation, and a general disposal strategy.While ARIEL is still under construction and significant progress has been made, the ongoing radiation modelling has enabled validation of the current shielding design for nominal operation. Moreover, the systematic studies performed were paramount in defining the optimal strategies to adopt from target storage to that for decommissioning of the facility.

The SPES target production and characterization

The target sits at the core of each facility for the production of radioactive ion beams for nuclear physics research. The materials which constitutes it must withstand extremes conditions of temperature and pressure, being bombarded by intense beams of light particles for several days. This is particularly important in high-power facilities such as SPES (Selective Production of Exotic Species) in which the targets are subjected to strong thermal gradients. Accurate choice and design of materials are therefore crucial. On recent years, several studies have been carried out in the framework of the SPES target research and development. An overview of recently exploited production techniques and a selection of synthesized materials are presented.

The performance of the commissioned Notre Dame multi-reflection time-of-flight mass spectrometer

The future N=126 factory at Argonne National Laboratory is aimed to produce neutron-rich elements around the N=126 peak of the rapid-neutron capture process using multi-nucleon transfer reactions. However, this radioactive ion beam production method will entail the delivery of contaminant ions. To remove the isobar contaminants from the beam, a multi-reflection time-of-flight mass spectrometer has been built and successfully commissioned at the University of Notre Dame, reaching a resolving power of 70,000, with an efficiency of 10%. According to stability study conducted, the resolving power is potentially limited to 83,000 by the power supply stability, however it can be mitigated by the addition of RC filtration as done for other MR-TOFs. The commissioned MR-TOF has been transported to Argonne National Laboratory to be used in the N=126 factory.

Charge breeding at GANIL: Improvements, results, and comparison with the other facilities

The 1+/n+ method, based on an ECRIS charge breeder (CB) originally developed at the LPSC laboratory, is now implemented at GANIL for the production of Radioactive Ion Beams (RIBs). Prior to its installation in the middle of the low energy beam line of the SPIRAL1 facility, the 1+/n+ system CB has been modified based on the experiments performed on the CARIBU Facility at Argone National Laboratory. Later, it has been tested at the 1+/n+ LPSC test bench to validate its operation performances. Charge breeding efficiencies as well as charge breeding times have been measured for noble gases and alkali elements. The commissioning phase started at GANIL in the second half-year of 2017. It consisted of a stepwise process to test the upgrade of the SPIRAL1 facility from simple validation [operation of Charge Breeder (CB) as a stand-alone source] up to the production of the first 1+/n+ RIB. Thus, this year, a 38mK/38K RIB has been successfully delivered to a physics experiment over a period of 1 week. The yields on the physics target were in the range of ∼2-4 × 106 pps at 9 MeV/u. The target ion source system (TISS) was made of a FEBIAD ion source connected to a hot graphite target. This is the first time a RIB is accelerated with a cyclotron with the 1+/n+ method. Moreover, a production test with the FEBIAD TISS has confirmed the yields measured previously, which validates the extension of the GANIL/SPIRAL1 catalog for a number of isotopes. In parallel, R&D is being performed on new TISSs (e.g., a fast release one, using surface ionization source). Targets are also a subject of ongoing R&D for yield and release time optimization. This contribution will present the new acceleration scheme of the SPIRAL1 facility, which largely extends the palette of RIBs available for nuclear physicists. It will be compared to the ones used at similar ISOL facilities. This facility is more than a simple ISOL facility, and an overview of the new opportunities offered by the upgraded installation will be also discussed.

Production and Separation of Radioactive Ion Beams

Radioactive nuclei play an important role in many astrophysical scenarios,from the Big-Bang Nucleo-synthesis to the standard solar model, from quiescent burning to the most explosive events that can occur in our universe. A huge effort has been made for more than thirty years to construct facilities able to deliver beams of radioactive nuclei with increasing intensity and better quality. This contribution revises the different mechanisms and the separation techniques employed for the production of Radioactive Ion Beams.

The ISOLPHARM project: ISOL-based production of radionuclides for medical applications

Radionuclides for radiopharmaceuticals can be produced in cyclotrons or nuclear reactors. Each of these production modes has serious issues, such as high target costs, production of long-lived wastes and contaminants, expensive separation. For this reason, new methods are under consideration for the production of highly pure radionuclides. The ISOL (Isotope Separation On-Line) method is the major technique for the production of radioactive ion beams for nuclear physics applications. The SPES-ISOLPHARM project at INFN-LNL (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro) is a feasibility study for the production of medical isotopes exploiting the ISOL method. The ongoing activities concerning a recent experiment focused on 111Ag, a study performed in collaboration with Padova and Trento Universities, is presented.

BRIF: From the first proton beam to RIB production

Various technologies for high current compact H– cyclotron have been developed since 1990s [1,2]. The energy of compact style machines was firstly elevated up to 100 MeV [3,4] for Radioactive Ion Beam production. The project, BRIF, Beijing Radioactive Ion-beam Facility was approved to start the construction in 2011, and the first proton beam was extracted from the 100 MeV compact cyclotron CYCIAE-100 on July 4, 2014. This paper will present the progress on the BRIF after the first proton beam, including the cyclotron improvements for the stable operation and beam intensity increasing, the RIB production and the implementation for mass resolution of 24,460, and the future development etc.

Production of a 15C radioactive ion beam based on 18O(n,alpha)

.In the context of the SPIRAL2 radioactive beam facility the production rate of the neutron-rich 15C nucleus by 18O(n,alpha) has been investigated. In a water target of 20 cm3, enriched in 18O and placed behind the neutron converter, a rate of a few 1010 nuclei per second can be reached with 1mA of 40MeV deuterons. A 18O(n,alpha) cross-section based on the activation method is proposed. It is intermediate between the highest and lowest evaluations available to date.

Shielding analysis of the SPES targets handling system and storage area using the Monte Carlo code FLUKA

The SPES project (Selective Production of Exotic Species) is currently under advanced construction phase at the INFN-LNL (Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro) for the production of Radioactive Ion Beams. Several typologies of target systems will be used in different SPES production phases. The irradiated target system has a limited lifetime and has to be regularly replaced. As a consequence, the handling and the temporary storage of exhausted radioactive targets are a major concern for the management of the entire facility. Monte Carlo simulation codes as FLUKA and MCNPX are used for shielding design. Results of shielding simulations are here presented, realized using a complete FLUKA model of the system and multi-step simulations. In particular, two case studies are discussed, referring to the management of different phases of the SPES project which require human intervention. The results allow some conclusions about the safe design of shieldings to be drawn.

High-power target development for the next-generation ISOL facilities

The production of high-purity radioactive ion beams (RIB) through the isotope separation online (ISOL) method makes possible unique research programmes in several fields of science. The demand for beam time continues to be high, while the study of more and more exotic isotopes, difficult to produce in sufficient quantities, is of primary interest for many of the currently defined research projects. At the same time, the growing interest from the medical field cannot pass unnoticed, where the ISOL technique gives access to the most innovative medical isotopes, with extremely-high specific activity. Increasing the RIBs intensity is therefore of primary interest, and it is carefully addressed through several R&D programmes worldwide. In this paper, we aim to discuss the increase of primary-beam power as a means to increase the RIB intensity. Next to the improvement of in-target production yields, target-material development for efficient isotopes release, compact-target systems and highly-efficient ion sources represent other possibilities to improve the isotopes-extraction efficiency and therefore the increase in RIBs intensity.

Atom beam emersion from hot cavity laser ion sources

Ion sources exploiting laser resonance ionization offer efficient and element-selective radioactive ion beam production at the leading isotope separation on-line facilities worldwide. Most commonly, laser resonance ionization takes place inside a resistively heated atomizer tube directly coupled to the production target, where the element of interest is evaporated and provided as atomic vapor. While naturally the majority of atoms is ionized inside this hot cavity, a fraction of the neutrals effuses towards the high voltage beam extraction system of the subsequent mass separator.We report on several systematic investigations on this phenomenon regarding its significance and implications on the operation of resonance ionization laser ion sources. Experiments suggest a less sharply directed atom cone than expected from theoretical model, up to a lateral opening angle of 45°. Inside the tubular volume defined by the laser beam diameter around the central axis behind the source exit, more than 90% of potentially ionizable atoms are found within the first 2 cm. Geometrical constraints for the construction of devices based on ionization in the effusing atom beam directly downstream of the hot cavity are derived, and causes for cross-mass beam contamination are identified. Counter measures using laser repetition rate synchronized beam gating by fast electrostatic beam deflection to overcome these problems are presented.

Development of compact 2.45 GHz ECR ion source for generation of singly charged ions

2.45 GHz ECR ion sources are widely used for production of single charged heavy ions and secondary radioactive ion beams. This paper describes the development of a compact ECR ion source based on coaxial quarter wave resonator. The first results of extracted current measurements at different resonator configuration as a function of UHF frequency, power and gas flow are presented. At the extraction voltage about of 10 kV and UHF power about of 100 W more than 500 μA of He+ ions were produced with the extraction hole of 3 mm in diameter that corresponds to the current density of 7.5 mA/cm2.

DERICA Project: Dubna Electron-Radioactive Isotope Collider Facility

The study of radioactive ion beams (RIBs) is currently the main direction in the development of low-energy nuclear physics. In this work, consideration is given to the concept and the research agenda of the promising accelerator–storage ring complex for RIB research, which is a proposed international megaproject on the basis of the Flerov Laboratory of Nuclear Reactions (FLNR), JINR [1]. The motivation of the new project is described and the RIB production characteristics of the complex are briefly presented, which are comparable in some aspects with the characteristics of advanced world centers known as RIB factories. In this project, emphasis is placed on investigating short-lived RIBs in storage rings. One unique feature of the project is the possibility of studying the interaction between electrons and radioactive isotopes in a collider experiment for determining fundamental properties of nuclear matter such as electromagnetic form factors of exotic nuclei.

Heating factors of gas targets for radioactive ion beam production

At low-energy nuclear physics facilities, the in-flight fragmentation method is often employed to produce radioactive ion beams. This technique often involves a stable ion beam at high intensity and a gas cell target. Since the parameters for the production reaction are usually chosen to take advantage of a large cross section of the resonance reaction, a slight change in the center-of-mass energy due to the reduced target density may significantly affect the rare isotope production rate. Therefore, to estimate the heating effect due to beam particles on the target thickness, a new and more comprehensive semi-empirical model is developed by employing a heating factor function. The estimated heating factors were consistent with experimental data, which were obtained from various reaction measurements at wide ranges of heat densities.

STUDY OF NEUTRON RADIATION FIELD AT THE FIRST RADIOACTIVE ION BEAM LINE IN LANZHOU.

The first Radioactive Ion Beam Line in Lanzhou was a projectile fragment separator located in the HIRFL. The process of production and separation of radioactive ion beams can induce a strong and complex radiation field. The neutron dose equivalent rates were measured in four positions with a 70 MeV/u 40Ar18+ beam. The results were compared with that simulated by the FLUKA code. New shielding walls were installed to reduce the neutron background for spectroscopy measurement in the experimental terminal. In addition, the induced radioactivity of accelerator components and corresponding residual dose rates were analyzed for the radiation safety of accelerator workers. The airborne radioactivity as well as occupational exposure due to immersion in and inhalation of activated air were also estimated. This work aims to provide a valuable experience for the radiation study in the future fragment separator HFRS at HIAF.

Experimental testing and numerical simulations for life prediction of gate valve O-rings exposed to mixed neutron and gamma fields

EPDM O-rings of gate valves employed for the construction of a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams were studied in order to assess their sealing performance both during the facility service time and the post-service storage phase. Several O-ring specimens were at first exposed to different dose levels of mixed neutron and gamma radiations. Correspondent modifications of physical and mechanical properties of the material were investigated by means of uniaxial tensile tests, dynamic mechanical analyses, aging, compression set and vacuum leak tests. A hyperelastic strain energy function was adopted to fit the mechanical response of the material as a function of the absorbed dose. The minimum squeeze degree that guarantees O-ring sealing efficiency at different irradiation levels was determined by varying the interference between O-rings and grooves. A finite element model of the vacuum leak test was then set up to assess the contact pressure level required to ensure sealing. Numerical simulations of the gate valve main O-ring were subsequently carried out. By comparison of the predicted contact pressure and strain levels with experimental results, a life prediction map, as function of the service time, the storage time and the O-ring squeeze degree, was proposed.

The RIB facility EXOTIC and its experimental program at INFN-LNL

In this contribution, I will present a review about the EXOTIC facility and the research field accessible by using its Radioactive Ion Beams. The EXOTIC facility, installed at the INFN-Laboratori Nazionali di Legnaro, is devoted to the in-flight production of light Radioactive Ion Beams in the energy range between 3-5 MeV/nucleon. The scientific activity performed at EXOTIC concerns different aspects of nuclear physics and nuclear astrophysics, such as, the investigation of reaction mechanisms and nuclear structure, resonant scattering experiments and measurements of nuclear reaction cross sections of astrophysical interest.

Spes: An intense source of Neutron-Rich Radioactive Beams at Legnaro

The Isotope Separation On-Line (ISOL) method for the production of Radioactive Ion Beams (RIB) is attracting significant interest in the worldwide nuclear physics community. Within this context the SPES (Selective Production of Exotic Species) RIB facility is now under construction at INFN LNL (Istituto Nazionale di Fisica Nucleare Laboratori Nazionali di Legnaro). This technique is established as one of the main techniques for high intensity and high quality beams production. The SPES facility will produce n-rich isotopes by means of a 40 MeV proton beam, emitted by a cyclotron, impinging on a uranium carbide multi-foil fission target. The aim of this work is to describe the most important results obtained by the study of the on-line behavior of the SPES production target assembly. This target system will produce RIBs at a rate of about 1013 fissions per second, it will be able to dissipate a total power of up to 10 kW, and it is planned to work continuously for 2 week-runs of irradiation. ISOL beams of 24 different elements will be produced, therefore a target and ion source development is ongoing to ensure a great variety of produced isotopes and to improve the beam intensity and purity.

RIB production and related experiments at EXOTIC

Radioactive nuclei have a very deep relevance in many astrophysical scenarios, from the Big Bang nucleo-synthesis to supernova explosions. Several Nuclear Physics laboratories around the world have been constructing large-scale facilities for the production of Radioactive Ion Beams (RIBs). The main production techniques, i.e. In-Flight and Isotope Separation On Line, which will be reviewed in this contribution. In particular, we will concentrate on the production of light weakly-bound RIBs at the facility EXOTIC, located at INFN-LNL (Italy) and we will describe the most recent experiments.

Production of negatively charged radioactive ion beams**This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this

Beams of short-lived radioactive nuclei are needed for frontier experimental research in nuclear structure, reactions, and astrophysics. Negatively charged radioactive ion beams have unique advantages and allow for the use of a tandem accelerator for post-acceleration, which can provide the highest beam quality and continuously variable energies. Negative ion beams can be obtained with high intensity and some unique beam purification techniques based on differences in electronegativity and chemical reactivity can be used to provide beams with high purity. This article describes the production of negative radioactive ion beams at the former holifield radioactive ion beam facility at Oak Ridge National Laboratory and at the CERN ISOLDE facility with emphasis on the development of the negative ion sources employed at these two facilities.