Analysis of Nb3Sn surface layers for superconducting RF cavity applications

Abstract

We present an analysis of the Nb3Sn surface layers grown on a bulk niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 meV and superconducting critical temperature (Tc) up to 16.3 K. Scanning Electron microscopy (STEM) performed on cross section of the sample's surface region shows a 2 microns thick Nb3Sn surface layer. The elemental composition map exhibits a Nb over Sn ratio of 3 and reveals the presence of buried sub-stoichiometric regions that have a ratio f 5. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanism occurring during RF tests of Nb3Sn-coated cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

arXiv comment4 pages, 4 figures

References in corpus (4)

• A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State
• Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity
• Tunneling study of cavity grade Nb: possible magnetic scattering at the surface
• Improvement and protection of niobium surface superconductivity by Atomic Layer Deposition and heat treatment

Cited by in corpus (16)

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• Atomic scale analysis of Nb3Sn on Nb prepared by a vapor-diffusion process for superconducting radiofrequency cavity applications
• Analysis of Magnetic Vortex Dissipation in Sn-Segregated Boundaries in Nb${}_3$Sn Superconducting RF Cavities
• Effects of nonmagnetic impurities and subgap states on the kinetic inductance, complex conductivity, quality factor and depairing current density
• Performance-defining properties of Nb${}_3$Sn coating in SRF cavities
• Tuning microwave losses in superconducting resonators
• $\text{Ab Initio}$ Study of Antisite Defects in Nb${}_3$Sn: Phase Diagram and Impact on Superconductivity
• Smooth, homogeneous, high-purity Nb3Sn superconducting RF resonant cavity by seed-free electrochemical synthesis
• Analysis of RF losses and material characterization of samples removed from a Nb3Sn-coated superconducting RF cavity
• Surface impedance measurements on Nb${}_3$Sn at high magnetic fields
• Photocathode Quantum Efficiency of Ultra-Thin Cs2Te Layers On Nb Substrates
• A Time-Dependent Ginzburg-Landau Framework for Sample-Specific Simulation of Superconductors for SRF Applications
• Nonequilibrium nonlinear response theory of amplitude-dependent dissipative conductivity in disordered superconductors
• Microscopic Investigation of rf Vortex Nucleation in Nb3Sn Films Using a Near-Field Magnetic Microwave Microscope