1.3GHz高功率输入耦合器样机设计

Design Optimization of Prototyped 1.3GHz/14kW Input Coupler: A Simulation Study

本文研究的课题是1.3 GHz高功率输入耦合器模拟仿真,是基于2018年启动的上海光源硬X射线自由电子激光器大科学装置项目。该项目采用9-cell超导腔加速粒子,在每个超导腔和功率源之间连接一个输入耦合器,负责将功率源的能量传输到超导腔中加速粒子。本文设计是基于同轴线结构的高功率输入耦合器,其结构大致可分为四个部件:冷端、热端、同轴转换波导和内导体调节驱动。其中冷端和热端各包含一个圆柱形陶瓷窗,分别称为冷窗和热窗。冷端外导体和热端内外导体采用波纹管结构设计,通过内导体调节驱动调节耦合杆可以控制波纹管的伸缩,以改变内导体天线插入腔体的深度,从而实现耦合度可调以匹配不同的束流负载。同轴转换波导通过实现矩形波导到同轴波导的过渡,从而实现TE10模到TEM模的模式变换。本文就高功率耦合器的RF仿真方面阐述耦合器的设计过程。

The prototyped 1.3 GHz/14 kW input-coupler was designed via CST simulation,to couple the hard X-ray free-electron laser-beam for Shanghai Light Source(SSRF)project.The newly-designed coupler mainly comprises the cold/warm assemblies,waveguide-to-coaxial transition adaptor and inner conductor adjustment drive.The ceramic cylinder in cold(warm)assembly maintains UHV-condition;depending on the coupling degree and/or beam load,the antenna penetration depth into the cavity can be regulated by adjusting bellows’lengths.In rectangular to coaxial waveguide transition,the waveguide-to-coaxial transition adaptor converted TE10 mode into TEM mode.The simulated results show that the new prototyped coupler meets the design requirements.For instance,operating at 1.3 GHz/14 kW,the power transmission coefficient S11 was-24.73 dB;meanwhile,when it comes to newly-optimized rectangular waveguide connected to the coupler,S11 was-47.29 dB at 1.3 GHz,and the bandwidth was 118 MHz for an S11 below-20 dB.