一种波荡器段间四极铁支撑平台的机械稳定性

Dynamic performance of a support system for quadrupole in undulator segment

自由电子激光(Free Electron Laser,FEL)是一种以相对论高品质电子束作为工作介质,在周期磁场中以受激发射方式放大电磁辐射的新型激光源。束流稳定性的好坏是影响FEL性能的关键指标。波荡器段关键元件运行过程中的位置稳定性是影响束流位置稳定性的关键因素之一,其中上海软X射线自由电子激光(Soft X-ray FEL,SXFEL)和大连极紫外相干光源(Dalian Coherent Light Source,DCLS)科学研究装置中波荡器段间四极铁的位置稳定性要求较高。波荡器段间四极铁支撑平台为四极铁等关键元件提供支撑、定位及位置调节,从而间接地要求其具有高的稳定性。本文通过对一种平台的支撑方式进行模态和地基随机振动响应的有限元分析和测试,得到平台的结构动态特性,并进行稳定性分析,为段间平台的工程设计提供理论依据。

Background： The electron beam stability is very important for Free Electron Laser （FEL） equipment. The increasing demands of beam position stability result in the higher position stability requirement of the FEL key parts such as undulator and quadruple magnet. Since the mechanical support system for the FEL provides supporting, location and position adjustment, the high mechanical stability of the supports is indirectly expected. Purpose： This work focuses on the research of the dynamic performance of a mechanical support system composed of three dimensional adjustments and a granite block mounted on. It will be applied to the quadrupole in undulator segment for the Soft X-ray FEL （SXFEL） and the Dalian Coherent Light Source （DCLS） project in China. Methods： The Finite-element （FE） calculations of the model characteristics were carried out to guide the subsequent model and vibration experiments. Results： First natural frequency of the support is about 28 Hz. Ratio of the root-mean-square （RMS） displacement （1-100 Hz） between the ground and the top is close to 1. Conclusion： Small RMS ratio illustrates good mechanical stability of the granite adopted by this work. First natural frequency is smaller than the required frequency, which indicates that the further structural optimization is necessary.