Simulation analysis and optimization of fresh-slice multistage free-electron lasers

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.

Correlation Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule

“…An x-ray transverse RF cavity streaking method (X band transverse deflecting cavity; XTCAV) [53] diagnostic could be used to monitor the pulse duration and jitter from the nominal delay settings, although for the shorter pulse series it had insufficient temporal resolution and so was used primarily to determine that the jitter was comparable to the pulse durations in the longer pulse series data. Simulation for parameters of this series indicates that the pulses are approximately 2.5 fs in duration [54]. The observed temporal jitter from the XTCAV analysis was ±2 fs for the short pulse data series, permitting us to use the chicane delay setting as the primary tool for timing the delay.…”

Observation of site-selective chemical bond changes via ultrafast chemical shifts

“…The experiment was carried out at the AMO endstation of the Linac Coherent Light Source (LCLS) free electron laser 27 . The “Fresh slice" operation mode was used to generate a pair of collinear time-delayed femtosecond x-ray pulses 16 , 28 . The time delay between the pump and probe pulses was scanned between −5 and 40 fs at discrete steps and with a jitter of 3 fs.…”