Design of high-power ISOL targets for radioactive ion beam generation

In this report, we provide lists of refractory oxides, carbides and refractory metals suitable for use as targets for producing short-lived, proton-rich isotopes of elements (He through Pu) and neutron-rich isotopes of elements (As through Dy) for potential use at high-energy, ISOL-based radioactive ion beam facilities. Complex structure, highly permeable C matrices are described for coating with optimum thicknesses of any type of refractory target material (metal, carbide or oxide). Prescriptions are given for the design and fabrication of custom-engineered targets with diffusion lengths compatible with the release of isotopes of interest within their lifetimes. Computationally derived thermal analysis information is presented for selected low-density, fibrous, highly permeable targets, subjected to direct irradiation with 1 GeV, 100–400 kW proton beams. From these studies, internal thermal radiation is reconfirmed as an important heat transfer (cooling) mechanism within low-density, fibrous and composite targets. By utilization of the radiation cooling effect and beam manipulation techniques, in combination with placement of additional heat shielding on the exit end of targets, beam power depositional densities can be controlled and temperatures homogenized to acceptable levels within fast diffusion release, fast effusive-flow ISOL targets subjected to irradiation with 400 kW proton beams, as required at next-generation radioactive ion beam facilities.