Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

Journal Article · Tue Apr 21 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4918272· OSTI ID:22402881

Kwon, J.; Zuo, J. -M. ^[1]; Zasadzinski, J. F. ^[2]

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1. Materials Science and Engineering Department, University of Illinois, Urbana, Illinois 61801 (United States)
2. Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

Nanoscale defect structure within the magnetic penetration depth of ∼100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120 °C baking. Furthermore, we demonstrate that adding 800 °C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120 °C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120 °C bake.

• OSTI ID: 22402881
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 15; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
77 NANOSCIENCE AND NANOTECHNOLOGY
CHEMICAL POLISHING
DEGASSING
ELECTRONS
ENERGY-LOSS SPECTROSCOPY
GRAIN BOUNDARIES
HYDRIDES
HYDROGEN
MODIFICATIONS
NANOSTRUCTURES
NIOBIUM
NIOBIUM OXIDES
PENETRATION DEPTH
PERFORMANCE
RADIOWAVE RADIATION
SURFACES
TRANSMISSION ELECTRON MICROSCOPY
VISIBLE RADIATION