SXFEL与SHINE高功率X波段干负载研制

Design and test of high power X-band dry load for SXFEL and SHINE

上海软X射线自由电子激光装置(Shanghai soft X-ray Free Electron Laser,SXFEL)与上海硬X射线自由电子激光装置(Shanghai High repetition rate XFEL and Extreme light facility,SHINE)需要使用许多大功率微波元件,例如行波加速管、偏转腔、脉冲压缩器等。为了满足这些元件的高功率测试与运行的需求,研发了两台高功率不锈钢吸收负载,在X波段两台负载的工作频率分别为11.424 GHz和11.988 GHz。通过模拟仿真的方法,设计了负载的初步模型,并优化了其微波参数。模拟结果显示两台负载在中心频率附近-20 dB以下的带宽达到百兆赫兹以上。通过理论计算的方法计算了水路中的对流换热系数,并基于此对负载的机械模型进行了热分析,计算了其工作状态下的温度分布。两台负载模型均具有周期性凹槽的类波导结构,在完成负载的加工制造后,使用矢量网络分析仪对两种负载在装夹状态和焊接完成后的射频参数进行了测量。实验测试的结果与模拟计算的结果吻合较好,达到了设计要求。

[Background]The Shanghai soft X-ray Free Electron Laser(SXFEL)and the Shanghai High repetition rate XFEL and Extreme light facility(SHINE)are equipped with various high-power microwave components,including traveling wave accelerating tubes,deflection cavities,pulse compressors,etc.[Purpose]This study aims to develop two high-power stainless steel absorbing loads,so as to meet the testing and operational requirements of these components at high power levels.[Methods]Firstly,an initial load model was designed through simulation methods,and the microwave parameters were optimized.Then,the convection heat transfer coefficient in the waterway was calculated using theoretical calculations.Based on this information,thermal analysis was conducted on the mechanical model of the load to determine its temperature distribution under working conditions.Finally,the loads were manufactured and their RF parameters were measured using a vector network analyzer both in the clamping state and after welding.[Results]The two X-band loads feature a waveguide structure with periodic grooves,and are operated at 11.424 GHz and 11.988 GHz respectively.The simulation results show that the bandwidth of two loads below -20 dB near the center frequency reaches over 100 MHz.The experimental test results are in good agreement with the simulation calculation results,meeting the design requirements.[Conclusions]The developed high power X-band dry loads described in this study satisfy operating requirements for SXFEL and SHINE.