The planned rare isotope accelerator facility RIA in the US would become the most powerful radioactive beam facility in the world. RIA's driver accelerator will be a device capable of providing beams from protons to uranium at energies of at least 400 MeV per nucleon, with beam power up to 400 kW. Radioactive beam production relies on both the in-flight separation of fast beam fragments and on the ISOL technique. In both cases the high beam power poses major challenges for target technology and handling and on the design of the beam production areas. This paper will give a brief overview of RIA and discuss aspects of ongoing conceptual design work for the RIA target areas.

The Rare Isotope Accelerator (RIA) facility, planned to be built in the USA, will be capable of delivering diverse beams, from protons to uranium ions, with energies from 1GeV to at least 400MeV per nucleon to rare isotope-producing targets. High beam power—400kW—will allow RIA to become the most powerful rare isotope beam facility in the world; however, it also creates challenges for the design of the isotope-production targets. This paper focuses on the isotope-separator-on-line (ISOL) target work, particularly the radiation transport aspects of the two-step fission target design. Simulations were performed with the PHITS, MCNPX, and MARS15 computer codes. A two-step ISOL target considered here consists of a mercury or tungsten primary target in which primary beam interactions release neutrons, which in turn induce fissions—and produce rare isotopes—in the secondary target filled with fissionable material. Three primary beams were considered: 1-GeV protons, 622-MeV/u deuterons, and 777-MeV/u 3He ions. The proton and deuterium beams were found to be about equivalent in terms of induced fission rates and heating rates in the target, while the 3He beam, without optimizing the target geometry, was less favorable, producing about 15% fewer fissions and about 50% higher heating rates than the proton beam at the same beam power.

Neutronics simulations and activation evaluations are currently in progress as part of the pre-conceptual research and development effort for the Rare Isotope Accelerator (RIA). The RIA project involves generating heavy element ion beams with powers up to 400kW for use in a fragmentation target line to produce selected ion beams for physics research experiments. Designing a fragmentation beam dump for RIA is one of the most critical challenges for such a facility. Here, we present the results from neutronics and radiation field assessments for various beam dump concepts that can meet requirements for the RIA fragmentation line. Preliminary results from heavy ion transport including radiation damage evaluations for the RIA fragmentation beam dump are also presented. Initial neutronics and activation studies will be incorporated with other target area considerations to identify important challenges and explore possible solutions.

The Department of Energy’s Office of Nuclear Physics, within the Office of Science (SC), has given high priority to consider and analyze design concepts for the target areas for the production of rare isotopes via the ISOL technique at the Rare-Isotope Accelerator (RIA) Facility. Key criteria are the maximum primary beam power of 400 kW, minimizing target change-out time, good radiological protection, flexibility with respect to implementing new target concepts, and the analysis and minimization of hazards associated with the operation of the facility. We will present examples of on-going work on simulations of radiation heating of targets, surrounding components and shielding, component activation, and levels of radiation dose, using the simulation codes MARS, MCNPX, and PHITS. These results are important to make decisions that may have a major impact on the layout, operational efficiency and cost of the facility, hazard analysis, shielding design, civil construction, component design, and material selection overall layout, and remote handling concepts.

The development of high-power beam dumps and catchers, and pre-separator layouts for proposed fragment separators of the Rare-Isotope Accelerator (RIA) Facility are important in realizing how to handle the 400 kW in the primary beam. Examples of pre-conceptual designs of the pre-separator area and components, along with examples of ongoing radiation simulations with results characterizing the secondary radiation are given. These initial studies will yield insight into the impact of the high-power dissipation on fragment separator design, remote handling concepts, nuclear safety and potential facility hazard classification, shielding design, civil construction design, component design, and material choices. Furthermore, they will provide guidance on detailed radiation analyses as designs mature.