Keyword: photon
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MOPCAV010 Design of a HOM-Damped 166.6 MHz Compact Quarter-Wave β=1 Superconducting Cavity for High Energy Photon Source cavity, HOM, superconducting-cavity, niobium 278
 
  • X.Y. Zhang, J. Dai, L. Guo, T.M. Huang, Z.Q. Li, Q. Ma, F. Meng, Z.H. Mi, P. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
Superconducting cavities with low RF frequencies and heavy damping of higher order modes (HOM) are desired for the main accelerator of High Energy Photon Source (HEPS), a 6 GeV synchrotron light source promising ultralow emittance currently under construction in Beijing. A compact 166.6 MHz superconducting cavity was proposed adopting a quarter-wave β=1 geometry. Based on the successful development of a proof-of-principle cavity, a HOM-damped 166.6 MHz compact superconducting cavity was subsequently designed. Ferrite damper was installed on the beam pipe to reduce HOM impedance below stringent threshold of coupled-bunch instabilities. Being compact, RF field heating on the cavity vacuum seal was carefully examined against quenching the NbTi flange. The cavity was later dressed with helium vessel and the tuning mechanism was also realized. Excellent RF and mechanical properties were eventually achieved. Finally, the two-cavity string was designed to ensure smooth transitions among components and proper shielding of synchrotron light. This paper presents a complete design of a fully dressed HOM-damped low-frequency β=1 superconducting cavity for HEPS.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV010  
About • Received ※ 20 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 14 April 2022  
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WEPFAV005 Design Optimization of the 166-MHz and 500-MHz Fundamental Power Couplers for Superconducting RF Cavities at High Energy Photon Source cavity, multipactoring, simulation, cryogenics 544
 
  • T.M. Huang, Chang, Z.Z. Chang, L. Guo, H.Y. Lin, Q. Ma, W.M. Pan, P. Zhang, X.Y. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Funding: Supported in part by High Energy Photon Source, a major national science and technology infrastructure in China, and in part by the National Natural Science Foundation of China under Grant 12075263.
Five 166-MHz quarter-wave ß=1 cavities have been chosen for the fundamental srf system while two 500-MHz single-cell elliptical cavities for the third-harmonic system for High Energy Photon Source (HEPS). Each cavity will be equipped with one fundamental power coupler (FPC) capable of delivering 250-kW continuous-wave rf power. For the 166-MHz FPC, two prototypes were developed and excellent performances were demonstrated in the high-power operations. However, the inner air part was observed to be warmer than predictions. Therefore, an innovative cooling scheme was adopted. In addition, the Nb extension tube has been elongated to solve the overheating in the cavity-coupler interface region. Concerning the 500-MHz FPC, several improvements were proposed. First, a doorknob adopting WR1800 instead of WR1500 waveguide was chosen to better match the operating frequency; Second, the window position was optimized to ensure multipacting-free on the window; Third, the cryogenic heat load was estimated carefully to obtain an optimum helium gas cooling. The main parameters and the design optimizations of the 166-MHz and 500-MHz FPCs are presented in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPFAV005  
About • Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 20 January 2022  
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THOTEV07 Industrial X-Ray Tomographie as a Tool for Shape and Integrity Control of SRF Cavities cavity, detector, electron, radiation 725
 
  • H.-W. Glock, J. Knobloch, A. Neumann, A.V. Vélez
    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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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THOTEV07  
About • Received ※ 30 June 2021 — Revised ※ 03 January 2022 — Accepted ※ 03 March 2022 — Issue date ※ 08 April 2022
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