中国散裂中子源二期双spoke超导腔设计

中国散裂中子源是中国第一台、世界第四台脉冲型散裂中子源，其已于2020年2月达到100 kW功率的设计指标，运行稳定高效，供束效率位于国际前列。中国散裂中子源二期升级方案中总束流功率将升级到500 kW，其中直线加速器段将采用超导加速腔结构，束流能量由80 MeV提高到300 MeV。其中在80～165 MeV能量段采用324 MHz双spoke超导腔，在165～300 MeV能量段采用648 MHz 6-cell椭球超导腔。采用CST、COMSOL等仿真软件完成324 MHz双spoke超导腔的电磁、机械设计及优化，达到实际运行指标要求。为了提高腔运行的稳定性，在腔的设计中对E_P/E_acc着重进行了优化，使其尽量降低。

Design of the China Spallation Neutron Source phase II double spoke resonator

The China Spallation Neutron Source (CSNS), located in Dongguan city, is the country's first and only spallation neutron source. It is also the fourth spallation neutron source in the world. It achieved the design index of 100 kW power in February 2020, and its operation is reliable and efficient. The total beam power will be increased to 500 kW in the CSNS phase II upgrade design, where the linac beam energy will be boosted from 80 MeV to 300 MeV and the peak current intensity will be increased from 15 mA to 50 mA by incorporating a superconducting linear accelerator. The double spoke resonator (DSR) will be used in the energy range of 80 MeV to 165 MeV. In the energy range of 165 MeV to 300 MeV, 6-cell ellipsoidal cavity will be used. DSR has many advantages, such as large velocity acceptance, which allows the spoke cavity to be used for a wider range of velocities, small size, high shunt impedance and a high coupling degree, which allows the production error requirements to be relaxed and the frequency bandwidth to be broadened from neighboring modes, among others. The DSR performance, including electromagnetic properties and machine parameters, was simulated and optimized using CST, COMSOL and other simulation software, and it achieved the requirement of CSNS phase II upgrade project. To improve the operating stability of the cavity, the design focused on minimizing E_p/E_acc.