基于谐波运行的中等能量X射线自由电子激光研究

In recent decades, there has been an increasing interest in the development of x-ray free electron laser (FEL), known as the fourth generation light source, capable of enabling new areas of science. The presently existing x-ray FEL facilities are working with an electron beam of 5.8-17GeV, which mean large machines with substantial cost, time, and effort requirement. Recently, an x-ray FEL oscillator with intermediate energy electron beam was proposed, where fully coherent FEL radiation with megawatt peak power, in the spectral region of 10-25keV, can be generated with a 3.5GeV electron beam. As a new approach, there are still several issues needs to be addressed, such as thermal loading effects, undulator errors and other imperfections. Therefore, intensive studies of the intermediate energy x-ray FEL oscillator are expected in this grant, by theoretical analysis and numerical simulation. Moreover, new mechanism such as the intermediate energy x-ray FEL amplifier will be developed. It is hoped that our study will be useful for the future x-ray FEL projects in China.

基于先进加速器的X射线自由电子激光（FEL），具有极高的时间、空间分辨率和峰值亮度，被誉为第四代先进光源，国际上已经运行、在建和设计中的X射线FEL，电子束能量范围为5.8-17GeV。2012年，本项目申请人提出了中等能量X射线FEL振荡器概念[Phys. Rev. Lett 108, 034802 (2012)]，即基于FEL的谐波运行，利用3.5GeV的中等能量电子束团，产生光子能量范围在10-25keV的时间空间全相干辐射。本项目将通过理论分析和数值模拟，对基于谐波运行的中等能量X射线FEL振荡器进行全面系统的探索，完善细化其中的物理环节和技术问题，并结合国际上FEL的最新进展，发展基于谐波运行的中等能量X射线FEL放大器等新机理，为我国未来的X射线FEL装置的建设奠定良好的理论基础和提供充分的设计依据。

目前，国际上已经运行、在建和设计的X 射线自由电子激光（FEL），电子束能量范围为5.8-17GeV，装置规模和造价都比较巨大。本项目以理论分析和数值模拟为研究手段，全面地研究基于谐波运行的中等能量（3-4GeV）电子束团驱动的X射线FEL振荡器，并深入分析了误差以及热负载的影响；提出了基于谐波运行的中等能量X射线FEL放大器原理，用于脉冲型直线加速器；在更紧凑的全光学X射线自由电子激光方面，提出了提升光源性能的新原理。对于上海软X射线FEL装置，初步设计了基于PEHG的谐波运行方案，并成功研制国内首台具有横向磁场梯度的波荡器样机。本项目顺利完成了各项研究目标，发表文章19篇，其中SCI文章17篇。