Nitrogen and argon doping of niobium for superconducting radio frequency cavities: a pathway to highly efficient accelerating structures

• Published in: Superconductor science & technology 2013-10, Vol.26 (10), p.102001-6
• Main Authors: Grassellino, A, Romanenko, A, Sergatskov, D, Melnychuk, O, Trenikhina, Y, Crawford, A, Rowe, A, Wong, M, Khabiboulline, T, Barkov, F
• Format: Article
• Language: English
• Subjects: Annealing; Argon; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Holes; Materials science; Microwaves; Niobium; Physics; Quality factor; Radio frequencies; Superconductivity; Surface resistance; Surface treatments; Treatment of materials and its effects on microstructure and properties
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/26/10/102001

We report a surface treatment that systematically improves the quality factor of niobium radio frequency cavities beyond the expected limit for niobium. A combination of annealing in a partial pressure of nitrogen or argon gas and subsequent electropolishing of the niobium cavity surface leads to unprecedented low values of the microwave surface resistance, and an improvement in the efficiency of the accelerating structures up to a factor of 3, reducing the cryogenic load of superconducting cavities for both pulsed and continuous duty cycles. The field dependence of the surface resistance is reversed compared to standardly treated niobium.