In this report, we provide results of simulation studies for the design of fast diffusion-release high-power targets for RIB generation at high energy ISOL based facilities. Processes that lead to target heating (e.g., primary beam energy deposition, energy release through nuclear reactions and beam scattering effects) are accounted for in the simulations. From these studies, we find that internal thermal radiation is an important mechanism for heat redistribution in the low-density, small-dimensioned fibrous targets used in viable target designs and therefore, must be carefully taken into account. Such fragile, low thermal conductivity targets must withstand irradiation with 100 kW beams for extended periods of time and therefore, care must be taken to avoid exceeding the limiting temperature of the target material while ensuring homogeneous temperature distribution over the volumes of these targets. Thermal radiation of high-temperature fibers to surrounding surfaces is an effective means for cooling targets subjected to high power beam irradiation, especially for materials with poor intrinsic thermal conductivities. Focus-through and scanning techniques, used in combination with additional heat shielding placed on the exit end of the target, are found to be effective means for reducing beam power deposition density to manageable levels, homogenizing the temperature distributions within such targets while avoiding devastating primary beam scattering losses during transit. Results derived from simulation studies of fibrous (e.g., ZrO_2 and HfO_2) and composite (e.g., BeO/W/RVCF, NbC/RVCF, Ta/RVCF and UC_2/RVCF) targets subjected to irradiation with 1 GeV proton beams with power levels up to 400 kW, are presented in this report.
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