Generating isolated terawatt-attosecond x-ray pulses via a chirped-laser-enhanced high-gain free-electron laser

A feasible method is proposed to generate isolated attosecond terawatt x-ray radiation pulses in high-gain free-electron lasers. In the proposed scheme, a frequency chirped laser pulse is employed to generate a gradually varied spacing current enhancement of the electron beam, and a series of spatiotemporal shifters are applied between the undulator sections to amplify a chosen ultrashort radiation pulse from self-amplified spontaneous emission. Three-dimensional start-to-end simulations have been carried out, and the calculation results demonstrated that 0.15 nm x-ray pulses with a peak power over 1 TW and a duration of several tens of attoseconds could be achieved by using the proposed technique.

Figure 1

Schematic layout of the proposed technique.

Figure 2

(a) Longitudinal phase space at the end of the linac. (b) Longitudinal phase space and the corresponding current distribution at the end of the ESASE section. The bunch head is to the right.

Figure 3

XFEL radiation structure evolutions along the undulator beam line at the end of (a) the 1st, (b) the 2nd, (c) the 3rd, (d) the 5th, (e) the 8th, and (f) the 10th undulator section.

Figure 4

FEL peak power gain curves for normal SASE (blue dashed line) and the proposed scheme (red solid line).

Figure 5

Comparisons of the single shot radiation pulse (a) and corresponding spectra (b) from the proposed scheme with an initial electron beam peak current of 3 (blue dashed line) and 1 kA (red solid line).