Influence of grain size and porosity on the release of radioactive isotopes from target materials with high open porosity

For the Radioactive Ion Beam facilities of next generation the release efficiency of radionuclide from porous targets is one of the crucial parameters limiting the performances of the facility itself. The efficiency of which a nucleus is released from a target is mainly defined by its diffusion from the grain of the target material and its effusion inside the target itself. Understanding of these processes can help optimize release efficiency of target materials. Advance of diffusion–effusion model is performed by description of effusion process from open porosity of target material in terms of Knudsen diffusion. It allows describe and predict release properties of powder target materials with high open porosity and well sorted grain size distribution. Release process from pill or rod like target is described analytically. Dependence of the release efficiency on target grain size and material porosity is discussed.