Background: A dual-mode congeneric mid-energy accelerating waveguide for medical electron linac is a crucial device in imaging guided radiation therapy (IGRT) technology.Purpose:To ensure the linac producing stable and high quality beam bunches for both imaging and treatment beams, a 14-MeV side-coupled standing wave waveguide accelerator structure for medical accelerator based on a novel microwave energy switch technology was developed in Shanghai United Imaging Healthcare Co., Ltd (UIH).Methods:First of all, the designs on the transverse focusing and the longitudinal bunching for the linac accelerating structure were generated using the beam dynamics simulation code Parmela to certify the optimization goal of the accelerating cavity structure which can be used in both dual-photon mode and multi-energy electron mode. Then the accelerating structure was designed and the optimized microwave parameters were obtained by using the electromagnetic code Superfish and the commercial software CST (Computer Simulation Technology).Results:A 1.3-m longp/2 mode standing-wave bi-periodic side-coupled accelerating wave-guide resonating at 2.998GHz was obtained. The accelerating structure can be adjusted to output both 3-MV imaging photon beam and dual-mode treatment photon beams, including 6-MV and 10-MV electron beam. In addition, multi-energy electron beams with maximum electron beam energy of 14MeV can be achieved.Conclusion: So far, the accelerating waveguide was machined and brazed completely. It is found that the numerical design shows very good agreement with the microwave cold test result. Recently, the frequency tuning is achieved accurately and the RF conditioning is in progress.%医用同源双模中能电子直线加速管是影像引导放射治疗技术(Image Guide Radiation Therapy, IGRT)中的核心部件，为确保放射治疗直线加速器能够提供稳定和高品质的成像射束、双光子模式治疗射束以及多档电子射束，上海联影医疗科技有限公司研制了基于一种新型的能量开关技术的14 MeV医用双模驻波加速管。采用束流动力学程序Parmela对加速管整管的横向聚焦和纵向聚束进行了动力学设计分析，为优化加速管腔体几何结构提供了指标要求，最终利用电磁场仿真软件Superfish及CST (Computer Simulation Technology)优化腔体结构设计并得到了最优的微波参数。模拟计算结果表明，该加速管总长1.3 m，采用边耦合双周期p/2驻波结构，工作频率2.998 GHz，其输出束流能量可以实现多档可调，成像模式可输出低于3 MV的光子，治疗束可输出具有6 MV和10 MV两档的光子及4档能量电子束（最高能量可达14 MeV）。完成加工后，冷测结果与设计值符合得比较好，下一步将进行高功率微波老练。
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