Author: Mi, Z.H.
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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 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.
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About • Received ※ 20 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 14 April 2022  
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WEPCAV012 Research and Development of 650 MHz Cavities for CEPC 616
  • P. Sha, C. Dong, F.S. He, S. Jin, Z.Q. Li, B.Q. Liu, Z.H. Mi, W.M. Pan, J.Y. Zhai, X.Y. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
  Funding: This work was supported by the National Key Programme for S&T Research and Development (No. 2016YFA0400400), the Platform of Advanced Photon Source Technology R&D.
650 MHz 2-cell superconducting cavities are proposed for the main ring of the Circular Electron Positron Collider (CEPC). The design, fabrication, surface treatment (buffered chemical polishing) and vertical tests of the cavities with HOM couplers were conducted. The performance of the cavity at 2 K is not affected by the HOM coupler. The maximum intrinsic quality factor of the cavity with the HOM coupler reached 3.1·1010 at 20 MV/m. The vertical test results showed that the fundamental mode external quality factor of all HOM couplers is an order of magnitude larger than quality factor of the cavity. The HOM damping results for the 650 MHz 2-cell cavity were also measured at cryogenic temperature and compared with the simulated and measured results at room temperature. Two 650 MHz 2-cell cavities jacketed have been integrated into a test cryomodule for CEPC. Another 650 MHz 2-cell cavity reached 6·1010 at 22 MV/m after nitrogen infusion. In addition, two 650 MHz 1-cell cavities reached 2.7·1010 at 35 MV/m (fine grain) and 3.6·1010 at 32 MV/m (large grain) after electro-polishing, respectively. In future, electro-polishing will be applied to 650 MHz 2-cell cavity soon.
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DOI • reference for this paper ※  
About • Received ※ 21 June 2021 — Accepted ※ 07 December 2021 — Issue date; ※ 02 May 2022  
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Development and Vertical Tests of a 166.6-MHz Proof-of-Principle Superconduting β = 1 Quarter-Wave Cavity for HEPS  
  • P. Zhang, J. Dai, L. Guo, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, Q.Y. Wang, X.Y. Zhang
    IHEP, Beijing, People’s Republic of China
  Funding: This work was supported by the High Energy Photon Source - Test Facility (HEPS-TF) project, HEPS project and Chinese Academy of Sciences.
Low-frequency superconducting cavities are needed in main accelerators for storage ring light sources with ultralow emittance. Therefore, a compact 166.6-MHz superconducting proof-of-principle cavity was designed for the High Energy Photon Source (HEPS) in China by adopting a quarter-wave geometry with β=1*. The cavity is compact in size yet possessing a low resonant frequency. The nearest higher order mode is significantly separated from the fundamental mode, making the cavity attractive for high-current accelerators such as HEPS. The achieved accelerating voltage of 3.0 MV is well beyond the designed 1.5 MV and high surface electromagnetic fields were reached with excellent RF and mechanical performances. Multipacting barriers were easily processed. This constitutes the first demonstration of a compact low-frequency β=1 superconducting cavity for HEPS. The design, fabrication, surface preparation, and cryogenic tests of the cavity will be presented.
* P. Zhang, et al., Review of Scientific Instruments 90, 084705 (2019).
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