Deuterium release from plasma-exposed beryllium during thermal desorption

An analytic solution is obtained for the thermal desorption spectrum of deuterium released from beryllium samples containing a mixed-material surface layer following exposure to a steady-state, high flux plasma. The analytical results are used to interpret experimental data that showed two separate deuterium release peaks. By comparing the calculations and measurements, the activation energy for diffusion of deuterium in beryllium is estimated and found to be higher than values previously reported in the literature. It is also found that the desorption spectrum is determined by the temperature ramping rate, the deuterium diffusion depth, and the material diffusivity. The fact that the analytical model agrees well with large-scale TMAP4 calculations suggests that desorption in this case is not strongly dependent on boundary conditions or recombination-limited surface kinetics. (orig.)