An improved O diffusion model for the Nb-oxide system was proposed in order to explain the benefit of low-temperature baking on the Q-drop in Nb superconducting radio-frequency cavities. The model showed that baking (120C, 48h) allowed O to diffuse away from the surface, and therefore increased the lower critical field towards the value for pure Nb.

Improved Oxygen Diffusion Model to Explain the Effect of Low-Temperature Baking on High Field Losses in Niobium Superconducting Cavities. G.Ciovati: Applied Physics Letters, 2006, 89[2], 022507 (3pp)