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作为直线加速器的前级聚焦加速部分,RFQ(射频四极场)在束流动力学和运行稳定性上都应表现良好,需要保持电场平整和电磁强耦合。为实现这两个目标,提出并研究了窗耦合结构。针对工作频率为81.25MHz的1 m长模型腔,利用三维电磁仿真软件CST MWS微波工作室对传统的四翼型、四杆型高频结构进行了仿真,并重点研究了窗耦合型结构。对开窗的对称方式、开窗的个数和大小等进行了分析,发现合适的窗耦合结构能保持较为紧凑的横向尺寸同时能耗适中,同四翼型结构相比二极模频率也远离了运行频率。为验证模拟结果,建造了一个铝模型腔,并对模型腔进行了冷模测试,实测频率为81.41 MHz,相邻模频率差为10.74 MHz,与模拟结果接近。仿真模拟和模型腔测试的结果表明,窗耦合四翼型结构可作为较低频率RFQ的一种设计。
As a pre-focus acceleration part of the linear accelerator, the RFQ (Radio Frequency Quadrupole) should perform well both in beam dynamics and in operational stability, requiring the maintenance of electric field smoothing and electromagnetic strong coupling. To achieve these two goals, the window-coupled structure is proposed and studied. Aiming at the 1 m long mold cavity with the operating frequency of 81.25 MHz, the traditional four-wing and four-bar high-frequency structure was simulated by the CST MWS microwave studio with three-dimensional electromagnetic simulation software. The window-coupled structure was emphatically studied. The symmetry of the window, the number and size of the windows were analyzed. It was found that the appropriate window-coupled structure can maintain a more compact horizontal size and moderate energy consumption. Compared with the four-wing structure, the diode mode frequency is also far The operating frequency. In order to verify the simulation results, an aluminum cavity was built and the cavity of the cavity was tested. The measured frequency was 81.41 MHz and the difference between adjacent modes was 10.74 MHz, which was close to the simulation result. The results of the simulation and model cavity tests show that the window-coupled four-airfoil structure can be used as a design for the lower frequency RFQ.