RF design for a quadrupole resonator with a fundamental frequency of 325 MHz at IMP

Abstract The Quadrupole Resonator (QPR), originally developed at CERN, is a dedicated radio-frequency characterization equipment for evaluating superconducting material. It employs the calorimetric compensation technique and has a surface resistance resolution of less than 1 nOhm, operating over a wide range of parameters, including temperatures, resonant frequencies and magnetic fields. As a part of R&D work of superconducting material for SRF application in particle accelerators, a QPR with operating frequency of 325 MHz has been developing at Institute of Modern Physics (IMP), CAS. In this paper, we present the detailed electromagnetic design of the QPR, the design focuses on reducing the risk of multipacting, field emission and mode overlapping, enhancing the attainable peak magnetic field. The electromagnetic simulation results indicate that the optimized structure has good electromagnetic performance. Additionally, the coupler design compatible with four QPR modes will be introduced. The cavity will be fabricated soon.