High brightness and fully coherent x-ray pulses from XFELO seeded high-gain FEL schemes

TL;DR

This paper proposes and investigates high-gain, seed-injected x-ray FEL schemes seeded by an XFELO to produce high-brightness, fully coherent, and stable x-ray pulses, addressing fluctuations seen in previous self-seeding experiments.

Contribution

It introduces novel high-gain FEL schemes seeded by XFELO radiation, with models analyzing pulse structures and options for using synchronized accelerators.

Findings

Schemes can generate high-brightness, fully coherent x-ray pulses.

Models predict stable pulse structures in XFELO-seeded FELs.

Options for using one or two accelerators are feasible.

Abstract

The successful operation of the hard x-ray self-seeding experiment at the LCLS opens the era of fully coherent hard x-ray free electron lasers (FELs). However, the shot-to-shot radiation fluctuation is still a serious issue. In this paper, high-gain, single-pass x-ray FEL schemes seeded by the narrow bandwidth radiation signal from an x-ray FEL oscillator were proposed and investigated, which are expected to generate high brightness, fully coherent and stable x-ray pulse. A simple model has been developed to figure out the temporal and the spectral structures of the output pulses in x-ray FEL oscillator. And options using two synchronized accelerators and using one accelerator were considered, respectively.