Author: Böhnel, M.
Paper Title Page
WEPRB017 Operational Experiences with X-Ray Tomography for SRF Cavity Shape and Surface Control 2838
  • H.-W. Glock, J. Knobloch, A. Neumann, Y. Tamashevich
    HZB, Berlin, Germany
  • M. Böhnel, N. Reims
    Fraunhofer IIS EZRT, Fürth, Germany
  • J. Kinzinger
    X-RAY LAB, Sachsenheim, Germany
  X-ray tomography has established as a non-destructive three-dimensional analysis tool, commercially offered by industrial vendors. Typical applications cover shape control and failure detection (voids, cracks) deep inside of complicated bulk pieces like engine blocks, bearings, turbine blades etc. We evaluated the applicability of the process for superconducting radio frequency cavities, in particular the 1.4-cell 1.3 GHz BERLinPro electron gun cavity and the 1.5 GHz single-cell VSR cavity prototype. The former experienced severe shape modifications during its tuning process and features a complicated internal stiffening construction. Thus it is a demanding challenge to measure its actual internal cavity surface shape after the complete preparation process with a resolution, sufficiently high (better than 0.2 mm) to serve as input for meaningful comparative field simulations. First tests with a vendor’s on-site X-ray source, operating at X-ray energies up to 590 keV revealed an insufficient resolution of the inner surface, attributed to the unfavorable X-ray damping characteristics of niobium. This was overcome with the aid of an accelerator-based source (X-ray spectrum up to 9 MeV), operated by Fraunhofer IIS, Fürth, Germany. Results both show significant, while understood, shape changes and indicate partial inner surface modifications of the gun cavity. Further the data evaluation process, which was needed to provide input for field simulations, raised issues because of the data set size and complexity, which are discussed in the paper.  
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About • paper received ※ 17 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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