Abstract
The generation of femtosecond soft x-ray free-electron laser (XFEL) pulses with an energy of hundreds of microjoules has been demonstrated at the Linac Coherent Light Source (LCLS) based on fresh-slice multistage amplifications. In this paper, we present a comprehensive simulation analysis and methods to improve fresh-slice multistage XFELs. A time-dependent transverse kick along the bunch is generated by two passive corrugated structures. The resulting oscillating orbit is controlled by downstream kickers, enabling different slices of the bunch to lase. The simulations reproduce the LCLS experimental results in terms of the pulse energy, bandwidth, and statistics of spectral spikes. The simulations reveal time-domain pulse profile properties, such as the pulse duration and structure, that were unavailable experimentally. We discuss possible issues connected with the accelerator setup and propose a simpler and more robust variation of the scheme to generate XFEL pulses shorter than 3 fs.
Highlights
X-ray free-electron lasers (XFELs) [1,2,3,4,5,6], whose peak brightness is approximately 10 orders of magnitude higher than the third-generation light sources, are cutting-edge scientific instruments in chemistry, biology, atomic physics, material science, and other disciplines [7]
The development of advanced operational modes of XFELs has become an active field of investigation in order to satisfy requirements of various scientific applications
We focus on the fresh-slice method based on a time-dependent kick imparted by passive wakefields of a corrugated metal jaw and reproduce the multistage amplification scheme in a simulation
Summary
X-ray free-electron lasers (XFELs) [1,2,3,4,5,6], whose peak brightness is approximately 10 orders of magnitude higher than the third-generation light sources, are cutting-edge scientific instruments in chemistry, biology, atomic physics, material science, and other disciplines [7]. The highest-power soft x-ray FEL pulses are produced with dechirper-based multistage amplifications [8]. This method relies on the wakefield-induced timedependent dipole kick within dechirpers. We focus on the fresh-slice method based on a time-dependent kick imparted by passive wakefields of a corrugated metal jaw and reproduce the multistage amplification scheme in a simulation. In this scheme, an x-ray pulse produced on the bunch tail is further amplified on fresh electrons in multiple stages. IV, we propose a variation on the initial scheme that allows more robust performances with a simpler setup
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