VSR Demo Cold String: Recent Developments and Manufacturing Status
N. Wunderer, V. Dürr, A. Frahm, H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples-Milne, A.V. Tsakanian, A. Veléz
HZB, Berlin, Germany
M. Bonezzi, A. D’Ambros, R. Paparella
INFN/LASA, Segrate (MI), Italy
J. Guo, J. Henry, R.A. Rimmer
JLab, Newport News, Virginia, USA
University of Siegen, Siegen, Germany
Technical University Dortmund, Dortmund, Germany
The BESSY VSR project aims to demonstrate the possibility to simultaneously run both long (15ps) and short bunches (1.7ps) within BESSY II storage ring. To achieve this, a new SRF cavity system with higher harmonic cavities (3 and 3.5 harm.) needs to be installed. The combined cavity SRF beating allows for stable bunch shortening for half of the buckets while standard lengths remaining for the other half. These SRF cavities will be equipped with waveguide-connected HOM absorbers and will be controlled with a blade tuner plus piezos. To demonstrate the feasibility of this complex system the VSR DEMO cold string consists of two 1.5 GHz cavities, each featuring five waveguides and a higher power coupler, plus all interconnecting elements coupled to the beam vacuum. For most of these components the fundamental development work is completed and has been reported in the past. This paper summarizes recent enhancements, component detailing and manufacturing status. The key cold string components such as cavities, higher power couplers and blade tuners have already entered the manufacturing phase. All other cold string components will be ready for purchase at the latest beginning of 2022.
Industrial X-Ray Tomographie as a Tool for Shape and Integrity Control of SRF Cavities
H.-W. Glock, J. Knobloch, A. Neumann, A. Veléz
HZB, Berlin, Germany
Industrial X-ray tomography offers the possibility to capture the entire inner and outer shape of an SRF cavity, providing also insights in weld quality and material defects. As a non-contact method this is especially attractive to investigate shape properties of fully processed and closed cavities. A drawback is the inherently strong X-ray damping of niobium, which causes the demand for intense hard X-rays, typically beyond the capabilities of dc-X-ray-tubes. This also limits the accuracy of material borders found by the tomographic inversion. To illustrate both capabilities and limitations, results of X-ray tomography investigations using three different cavities are reported, also describing the fundamental parameters and the hard- and software demands of the technology. We also discuss the non-trivial transferring of tomography data into RF simulation tools.
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