Development of the double spoke cavity prototype for CSNS-II

The China Spallation Neutron Source (CSNS), located in Dongguan city, Guangdong Province, is the country's first and only spallation neutron source. It is also the fourth spallation neutron source in the world. Meanwhile, it is one of the core large-scale scientific facilities of the Guangdong-Hong Kong-Macao Greater Bay Area Comprehensive National Science Center. The China Spallation Neutron Source phase II (CSNS-II) upgrade design will increase the total beam power from 100 kW to 500 kW and boost the beam energy from 80 MeV to 300 MeV in the linac by adding a superconducting linear accelerator to the existing accelerator complex. The double spoke resonator is used in the energy range of 80 MeV to 165 MeV. At present, the double spoke resonator (DSR) prototypes have been designed, fabricated and tested. The two prototypes underwent vertical testing five times, resulting in a maximum accelerating gradient of 15 MV/m. Additionally, the value of Q0 exceeded 4x 1010 at an Ea,, of 7.3 MV/m.