Triple modulator–chicane scheme for seeding sub-nanometer x-ray free-electron lasers

Dao Xiang,Gennady Stupakov

doi:10.1088/1367-2630/13/9/093028

Abstract

We propose a novel triple modulator–chicane (TMC) scheme to convert external input seed into shorter wavelengths. In this scheme, high-power seed lasers are used in the first and the third modulator, while only a very-low-power seed is used in the second modulator. By properly choosing the parameters of the lasers and chicanes, we show that ultrahigh harmonics can be generated in the TMC scheme while simultaneously keeping the energy spread growth much smaller than the beam’s initial slice energy spread. As an example, we show the feasibility of generating significant bunching at 1 nm and below from a low-power (∼100 kW) high harmonic generation seed at 20 nm assisted by two high-power (∼100 MW) UV lasers at 200 nm while keeping the energy spread growth within 40%. The supreme up-frequency conversion efficiency of the proposed TMC scheme, together with its unique advantage in maintaining beam energy spread, opens up new opportunities for generating fully coherent x-rays at sub-nanometer wavelength from external seeds.

Highlights

We propose a novel triple modulator-chicane (TMC) scheme to convert external input seed to shorter wavelengths
One Free electron lasers (FELs) working in the spontaneous emission (SASE) mode has been successfully operated at hard x-ray wavelengths [3], which marks the beginning of a new era of x-ray sciences [4,5,6]
While the radiation from a SASE FEL has excellent transverse coherence, it typically has rather limited temporal coherence and relatively large statistical fluctuations because a SASE FEL starts from electron beam shot noise

Summary

Introduction

We propose a novel triple modulator-chicane (TMC) scheme to convert external input seed to shorter wavelengths. These techniques typically use seeds at UV wavelength where high power lasers are available together with dispersive elements (i.e. chicanes) to generate density modulation at a shorter wavelength in electron beam.

Results

Conclusion