Temperature-dependent near-surface interstitial segregation in niobium

Abstract Niobium’s superconducting properties are affected by the presence and precipitation of impurities in near-surface region. A systematic wide-temperature range x-ray diffraction study is presented addressing effect low temperatures (108 K–130 K) annealing treatments (523 K nitrogen atmosphere, 400 UHV) on region a hydrogen-loaded Nb(100) single-crystal. Under these conditions, response natural surface oxides (Nb 2 O 5 , NbO NbO) changes subsurface concentration interstitial species Nb explored, thereby including cryogenic temperature regime relevant for device operation. The formation suppression niobium hydrides such conditions also investigated. These shown to result in: (i) an increase (oxygen nitrogen) occupying octahedral sites bcc lattice at room temperature, both bulk. (ii) decrease interstitials within first 10 nm from 130 K. (iii) Hydride as results show that mild atmosphere can suppress superconducting-detrimental hydrides, while atoms tend segregate towards K, therefore altering local RF penetration depth Nb. processes discussed context improvement radio-frequency cavities next-generation particle accelerators.