Mainz 2022 – scientific programme

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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 14: Posters

AKBP 14.3: Poster

Thursday, March 31, 2022, 16:00–17:30, P

Nitrogen-doping of niobium for SRF cavities — •Márton Major, Lambert Alff, Michaela Arnold, Jens Conrad, Stefan Flege, Ruben Grewe, and Norbert Pietralla — Technische Universität Darmstadt, Darmstadt, Germany

Niobium is the standard material for superconducting radio-frequency (SRF) cavities for particle acceleration. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram, the cubic δ-phase of NbN has the highest critical temperature.

Niobium samples were annealed and doped with nitrogen in the high-temperature furnace at TU Darmstadt and investigated at its Materials Research Department with respect to structural modifications. X-ray diffraction (XRD) confirmed the appearance of Nb₄N₃ and Nb₂N phases on the surface of the samples. A single cell cavity was annealed under optimized doping conditions. The test samples treated together with the cavity showed almost single Nb₄N₃ phase. XRD pole figures also showed grain growth during sample annealing.

The work was supported by the German Federal Ministry for Education and Research (BMBF) through grant 05H18RDRB2 and the German Research Foundation (DFG) via the AccelencE Research Training Group (GRK 2128).