Improved scaling law for the prediction of deuterium retention in beryllium co-deposits

Abstract

Hydrogen isotope co-deposition with Be eroded from the first wall is expected to be the main fusion fuel retention mechanism in ITER. Since good fuel accounting is crucial for economic and safety reasons, reliable predictions of hydrogen isotope retention are needed. This study builds upon the well-established empirical De Temmerman scaling law De Temmerman et al (2008 Nucl. Fusion 48 075008) that predicts D/Be ratios in co-deposited layers based on deposition temperature, deposition rate, and deuterium particle energy. Expanding the data used in the original development of the scaling law with an additional dataset obtained with more recent measurements using a different technique to the original De Temmerman approach, allows us to obtain new values for free parameters and improve the prediction capabilities of the new scaling law. In an effort to improve the model even further, scaling with D2 background pressure was included and a new two-term model derived, describing D retention in low- and high-energy traps separately.