Application of a modified chirp-taper scheme for generation of attosecond pulses in extreme ultraviolet and soft x-ray free electron lasers

Typically, in self-Amplified spontaneous emission free electron laser (SASE FEL) based short-pulse schemes, pulse duration is limited by FEL coherence time. For hard x-ray FELs, coherence time is in a few hundred attosecond range while for XUV and soft x-ray FELs it is in the femtosecond regime. In this paper the modification of so-called chirp-taper scheme is developed that allows to overcome the coherence time barrier. Numerical simulations for XUV and soft x-ray FEL user facility FLASH demonstrate that one can generate a few hundred attosecond long pulses in the wavelength range 2–10 nm with peak power reaching hundreds of megawatts. With several thousand pulses per second this can be a unique source for attosecond science.

Figure 1

Conceptual scheme for generation of attosecond pulses. Dashed rectangle illustrates a particular realization of suppression (separation) of a radiation background from the SASE undulator.

Figure 2

Energy modulation induced by the laser. Bunch head is on the left side.

Figure 3

Bunching factor at the entrance to the radiator (upper plot) and power at its exit (lower plot) for a single shot. Bunch head is on the left side.

Figure 4

Spectrum of the radiation pulse presented on Fig. 3.

Figure 5

Radiation power for four representative shots at 4.7 nm. Bunch head is on the left side.

Figure 6

Radiation power for three representative shots at 2.4 nm. Bunch head is on the left side.

Figure 7

Radiation power for four representative shots at 9.3 nm. Bunch head is on the left side.