A Trade-Off between Pulse Energy and Stability in Seeded Free-Electron Lasers

Over the last decade, external seeded free-electron lasers (FELs) have achieved significant advancements across various disciplines, progressively establishing themselves as indispensable tools in fields ranging from fundamental science to industrial applications. The performance of seeded FELs is critically dependent on the quality of the frequency up-conversion process. Optimized conditions for seeded FELs are typically considered as the maximization of the bunching factor. This article discusses alternative perspectives on the optimization criteria for seeded FELs by analyzing the impact of dispersion strength on their overall performance. This study investigates the differences among the required dispersion strength for achieving the maximum bunching factor, maximum pulse energy, optimal energy stability through theoretical analysis, simulation calculations, and experimental explorations. The direct observation in experiments emphasizes the consideration of trade-off between pulse energy and energy stability in seeded FELs. These results provide valuable insights and practical guidance for controlling the pulse characteristics of seeded FELs, contributing to the tuning and optimization of FEL facilities.