%0 Journal Article
%A Ferrari, Eugenio
%T Twin Echo Enabled Harmonic Generation with Frequency Down-Conversion for Unprecedented Coherent Bunching at Short Wavelengths
%J Physical review accelerators and beams
%V 27
%N 11
%@ 2469-9888
%C College Park, MD
%I American Physical Society
%M PUBDB-2024-05328
%P 110705
%D 2024
%X Harmonic up-conversion schemes represent the most successful approach in externally seeded free-electron lasers (FELs) for obtaining radiation with laser-like properties at short wavelengths. They are however limited in the shortest achievable wavelengths, as the harmonic conversion efficiency decreases with increasing harmonic number, even for echo-enabled harmonic generation (EEHG). In the following, we introduce a novel externally seeded cascaded FEL scheme based on two EEHG stages, the second of which working in harmonic down-conversion, i.e. going towards (slightly) longer wavelengths, capable of obtaining unprecedented bunching fraction that is independent on the final FEL wavelength.Its performance at 4 nm and shorter is investigated, demonstrating the ability to achieve multi-GW level, fully coherent pulses with laser-like properties and paving the way for externally seeded radiation at 1 nm and beyond.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:001371913100003
%R 10.1103/PhysRevAccelBeams.27.110705
%U https://bib-pubdb1.desy.de/record/612376