Development of a low-loss magnetic-coupling pickup for 166.6-MHz quarter-wave beta $$=$$ = 1 superconducting cavities
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Development of a low-loss magnetic-coupling pickup for 166.6MHz quarter-wave beta ¼ 1 superconducting cavities Tong-Ming Huang1,2,3 • Pei Zhang1,2,3 • Zhong-Quan Li1,2,3 • Xin-Ying Zhang1,2 Hai-Ying Lin1,2 • Qiang Ma1,2,3 • Fan-Bo Meng1,2 • Wei-Min Pan1,2,3
•
Received: 13 June 2020 / Revised: 15 July 2020 / Accepted: 21 July 2020 Ó China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd. 2020
Abstract 166.6-MHz quarter-wave b ¼ 1 superconducting cavities have been adopted for the High Energy Photon Source, a 6-GeV diffraction-limited synchrotron light source currently under construction. A large helium jacket was required to accommodate the enlarged cavity beam pipe for the heavy damping of higher-order modes; the original electric-probe pickup thus becomes inevitably long with unfavorable mechanical properties. Relocated to an existing high-pressure-rinsing port, a magnetic-loop pickup was designed, characterized by low radio-frequency and cryogenic losses and being multipacting-free and insensitive to manufacturing and assembly tolerances. The consequent removal of the original pickup port from the cavity largely simplified the helium jacket fabrication and may also reduce cavity contamination. This paper presents a comprehensive design of a low-loss magnetic-coupling pickup for quarter-wave b ¼ 1 superconducting cavities. The design can also be applied to other non-elliptical structures. Keywords Pickup Magnetic coupling Quarter-wave cavity Superconducting cavity Low loss Synchrotron light source
& Pei Zhang [email protected] 1
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2
Key Laboratory of Particle Acceleration Physics and Technology, IHEP, CAS, Beijing 100049, China
3
School of Nuclear Sciences and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
1 Introduction High Energy Photon Source (HEPS) is a 6-GeV diffraction-limited synchrotron light source with a kilometer-scale storage ring [1–3]. The project is currently under construction in a Beijing suburb and will be completed in 2025. The fundamental radio-frequency (RF) system is of 166.6-MHz, adopting superconducting technologies [4]. During the R&D phase of HEPS [5], a proofof-principle (PoP) 166.6-MHz superconducting quarterwave b ¼ 1 cavity was developed with excellent RF and mechanical performances [6–8]. Based on the success of the PoP cavity as shown in Fig. 1a, a higher-order mode (HOM)-damped 166.6-MHz cavity was subsequently designed. The cavity beam pipe was enlarged to 500 mm in diameter to realize strong HOM damping with a required loaded quality factor (QL ) of merely a few hundreds. The corresponding helium jacket became consequently larger with an increased diameter from 485 mm to 576 mm as shown in Fig. 1b. This, however, makes the original electric-probe pickup inevitably long w
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