Calculation and understanding of the nitrogen doping process in niobium for superconducting radio frequency accelerator

A computational model is developed to predict the nitrogen concentration profile within Nb utilized in superconducting radio-frequency (SRF) accelerators. This model incorporates variations in the sticking coefficient of nitrogen during the adsorption process on the Nb surface, along with the impact of nitride formation resulting from the reaction between Nb and nitrogen. The conclusions drawn from this model are compared with the outcomes of vertical test experiments. The computed results indicate that exhibiting a significant nitrogen doping effect is achieved when the nitrogen concentration is approximately 1E25 atom/m3 under various nitrogen doping recipes. This study enhances the understanding of the nitrogen doping process and enables the rapid determination of the optimal subsequent material removal thickness for various experimental recipes. [Display omitted] •Calculation of nitrogen depth profile in nitrogen-doped Nb with a new theoretical model.•Correction of the nitrogen sticking coefficient on the surface of Nb was considered.•Reveal that the optimal nitrogen concentration of different doping recipes falls within the same range.•Enables rapid determination of the material removal thickness required for various recipes.