Development of a low-loss magnetic-coupling pickup for 166.6-MHz quarter-wave beta $$=$$ 1 superconducting cavities

• DOI: 10.1007/s41365-020-00795-6
• Publication Date: 2020-08-28T00:03:00Z
• Authors: Tong-Ming Huang; Pei Zhang; Zhong-Quan Li; Xin-Ying Zhang; Hai-Ying Lin; Qiang Ma; Fan-Bo Meng; Wei-Min Pan
• Keywords: Pickup; Port (circuit theory); BETA (programming language); Synchrotron light source

166.6-MHz quarter-wave $$\beta =1$$ 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 $$\beta =1$$ superconducting cavities. The design can also be applied to other non-elliptical structures.