High-Power Femtosecond Soft X Rays from Fresh-Slice Multistage Free-Electron Lasers

Abstract

We demonstrate a novel multistage amplification scheme for self-amplified spontaneous-emission free electron lasers for the production of few femtosecond pulses with very high power in the soft x-ray regime. The scheme uses the fresh-slice technique to produce an x-ray pulse on the bunch tail, subsequently amplified in downstream undulator sections by fresh electrons. With three-stages amplification, x-ray pulses with an energy of hundreds of microjoules are produced in few femtoseconds. For single-spike spectra x-ray pulses the pulse power is increased more than an order of magnitude compared to other techniques in the same wavelength range.

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

“…In this section, we perform FEL simulations based on ELEGANT [24] and GENESIS version 4 [25,26] to reproduce experimental data in Ref. [11]. We start from a particle distribution simulated with IMPACT [27] at the end of the injector and propagate it to the undulator entrance with ELEGANT.…”

“…Therefore, in Fig. 2, we consider a single metal jaw for each dechirper module as it was used in the LCLS experiment [11]. Parameters of single-jaw dechirpers are listed in Table I.…”

“…The recent demonstration of fresh-slice lasing control [8] enhanced the power performance and delay control for multicolor operation over the basic split undulator concept [9], improved the power for self-seeded operation [10], and enabled production of high-power single spectral spike femtosecond pulses in the soft x rays [11].…”

“…III, we simulate the multistage experiment reported in Ref. [11] using the Linac Coherent Light Source (LCLS) parameters. Effects of delays in chicanes and on-axis slice positions on XFELs are discussed.…”

Postsaturation dynamics and superluminal propagation of a superradiant spike in a free-electron laser amplifier

“…At 1 Å, with a beam energy of 17 GeV and a peak current I p ¼ 4 kA (roughly the peak values for LCLS and XFEL), we have n ph ≈ 3.6 × 10 9 , i.e., about two orders of magnitude lower than the requirement for time resolved x-ray diffraction imaging of isolated molecules [12]. Several schemes to obtain femtosecond or sub-fs pulses were proposed and in some cases demonstrated [14][15][16][17][18][19][20][21]. Regardless of the generation method, the challenge of increasing the FEL peak power of an isolated spike beyond the saturation limit P s requires a full understanding of saturation and post saturation dynamics.…”