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RFQ(射频四极透镜)是直线加速器中最重要的前级聚焦加速结构,其工作模式下束流孔中的电场四极对称性是保证束流品质及加速效率的关键。为了解决其各自存在的工作模式下四极场的不对称问题,分别对四杆型RFQ和四翼型RFQ的结构和模式谐振特性做了研究。针对四翼型RFQ,模拟显示双端口对称耦合的方式从抵消二极模式和提高结构对称性两方面来达到削弱工作模式下的场分布中二极量的目的,对一个1 m段四翼RFQ模型腔的测量证实了双端口对称耦合抵消腔内二极模式的有效性;针对四杆型RFQ的二极场,以SSC-Linac项目的RFQ为原型,利用三维模拟计算软件CST-MWS进行模拟,通过改进支撑板的结构并调整参数,完全地消除了工作模式下的极间二极场,且理论上此种改进方法对支撑板结构的四杆型RFQ均有效。
RFQ (Radio Frequency Quadrupole Lens) is the most important pre-focus acceleration structure in linear accelerator. The quadrupole symmetry of the electric field in the beam hole under operating mode is the key to ensure beam quality and accelerate efficiency. In order to solve the problem of the asymmetry of the quadrupole field in their respective working modes, the resonance characteristics of the quadrupole RFQ and quadrifilar RFQ are studied respectively. For the quadrifilar RFQ, the simulation shows that the dual-port symmetric coupling method achieves the goal of reducing the amount of dipole in the field distribution in the working mode from offsetting the two-pole mode and improving the structural symmetry. A 1 m-section quadrifilar RFQ The measurement of the cavity of the model confirms the effectiveness of the dual-port symmetric coupling to cancel the mode of the cavity. For the quadrupole quadrupole RFQ, based on the RFQ of the SSC-Linac project, the three-dimensional simulation software CST-MWS is used to simulate , The dipole field in working mode is completely eliminated by improving the structure of the supporting plate and adjusting the parameters, and in theory, this improved method is effective on the four-bar RFQ of the supporting plate structure.