Integrated Surface Topography Characterization of Variously Polished Niobium for Superconducting Particle Accelerators

Conference · Fri May 01 04:00:00 EDT 2009

OSTI ID:1021840

As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro-and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents flow. Interior surface chemical polishing (BCP/EP) to remove mechanical damage leaves surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely-used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is being used to distinguish the scale-dependent smoothing effects. The topographical evolution of the Nb surface as a function of different steps of EP is reported, resulting in a novel qualitative and quantitative description of Nb surface topography.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1021840
• Report Number(s): JLAB-ACC-09-979; DOE/OR/23177-0732
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
ATOMIC FORCE MICROSCOPY
CAVITIES
CHEMICAL POLISHING
FOURIER ANALYSIS
MAGNETIC FIELDS
NIOBIUM
PERFORMANCE
QUENCHING
ROUGHNESS
SPECTRAL DENSITY
SUPERCONDUCTIVITY
TOPOGRAPHY