面向基于腔的X射线自由电子激光：里程碑与挑战
Towards Cavity-Based X-ray Free-Electron Lasers: Milestones and Challenges
AI总结：
该综述梳理了CBXFELs的理论进展、全球研发与技术挑战，基于欧洲XFEL实验成果，指出其在多领域的应用潜力及未来研究方向。
AI中文摘要：
基于腔的X射线自由电子激光（CBXFELs）可输出完全相干、高光谱亮度且脉冲控制增强的辐射，突破传统自放大自发辐射范式的局限，推动X射线科学发展。欧洲XFEL近期实验已实现光谱窄化并验证多程放大概念，首次观测到相对论电子束、FEL增益动力学与高精细度布拉格腔间紧密耦合三体相互作用的实验特征。本综述整合了基于该框架的CBXFEL理论进展、全球研发工作及耦合系统带来的突出技术挑战。CBXFELs可应用于X射线光谱学、量子光学和精密计量学，未来研究方向聚焦于CBXFEL稳定化、X射线光梳生成及核跃迁相干量子控制应用。
英文摘要：
Cavity-based X-ray free-electron lasers (CBXFELs) could advance X-ray science by delivering fully coherent radiation with high spectral brightness and enhanced pulse control, addressing the limitations of conventional self-amplified spontaneous emission paradigms. Recent experiments at the European XFEL have demonstrated spectral narrowing and proof-of-concept multi-pass amplification, marking the first experimental signature of the tightly coupled three-body interaction between relativistic electron beams, FEL gain dynamics, and high-finesse Bragg cavities. This review consolidates advances in CBXFEL theory built on this framework, global R$\&$D efforts, and outstanding technical challenges arising from the coupled system. CBXFELs support applications in X-ray spectroscopy, quantum optics, and precision metrology. Future directions prioritize CBXFEL stabilization, X-ray comb generation, and applications in coherent quantum control of nuclear transitions.
