Structural design of 648 MHz single spoke resonator prototype at CSNS

Purpose Superconducting radio frequency (SRF) cavities are adopted to upgrade the CSNS Linac energy from 80 to 300 MeV in phase II. A 648 MHz single spoke resonator (SSR) prototype has a compact size and low cost, which is a good pre-research cavity for CSNS to learn SRF technology. In this paper, the sequential approach of analysis and optimization performed for the structural design of 648 MHz SSR prototype are presented. Methods The COMSOL Multiphysics is used to perform the multiphysics analysis of jacketed cavity. Firstly, the mechanical performance of bare cavity is estimated, and then, several stiffeners are added to strengthen the cavity. After that, the Lorentz coefficient and helium fluctuation d f /d p of jacketed cavity are optimized. At last, the tuning sensitivity and mechanical performance of maximum allowable working pressure are calculated. Results The final results of Lorentz coefficient and d f /d p are − 5.06 Hz/(MV/m) 2 and 0.3 Hz/mbar, respectively, and the tuning range of jacketed cavity is larger than ± 1000 kHz at 2 K. Conclusion The structural design of a 648 MHz SSR prototype is performed in this paper. The Lorentz coefficient and d f /d p are carefully optimized. The simulation result shows all mechanical performance satisfies the design goals very well.