Scientists propose novel self-modulation scheme in seeded free-electron lasers

Scientists propose novel self-modulation scheme in seeded free-electron lasers
The self-modulation scheme together with the electron-beam longitudinal phase spaces at various positions. Credit: SARI

Seeded free-electron lasers (FELs), which use frequency up-conversion of an external seed laser to improve temporal coherence, are considered ideal for supplying stable, fully coherent, soft X-ray pulses. However, the requirement for an external seed laser with sufficient peak power to modulate the electron beam can hardly be met by the present state-of-the-art laser systems, it remains challenging for seeded FELs to operate at high repetition rate, e.g., MHz repetition rate.

Motivated by such a challenge, researchers at the Shanghai Advanced Research Institute and the Shanghai Institute of Applied Physics of the Chinese Academy of Sciences reported a novel self-modulation method to enhance -induced modulation, thereby significantly reducing the requirement of an external laser system.

Based on the Shanghai soft X-ray FEL test facility, the self-amplification of coherent energy modulation in a seeded FEL is experimentally verified. The peak power requirement of an external seed laser is demonstrated to be relaxed by a factor of 10 to 25 when utilizing the proposed scheme.

Moreover, the high harmonic generation in a seeded FEL is realized by using an unprecedentedly small energy modulation. A 795 MeV with a laser-induced energy modulation amplitude as small as 1.8 times the slice energy spread is used for lasing at the 7th harmonic of a 266-nm seed laser in a single-stage high-gain harmonic generation (HGHG) and the 30th harmonic of the laser in a two-stage HGHG.

The results pave a way for a high-repetition-rate seeded FEL, which is expected to show great promise for multidimensional coherent spectroscopies, far beyond what has been demonstrated to date.

Furthermore, the self- scheme proposed in this work is also promising to solve other critical problems of seeded FELs such as reaching shorter wavelengths and improving stability.


Explore further

Researchers propose novel dichroic laser mirror design with mixture layers and sandwich-like-structure interfaces

More information: Jiawei Yan et al. Self-Amplification of Coherent Energy Modulation in Seeded Free-Electron Lasers, Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.126.084801
Journal information: Physical Review Letters

Citation: Scientists propose novel self-modulation scheme in seeded free-electron lasers (2021, March 11) retrieved 20 June 2021 from https://phys.org/news/2021-03-scientists-self-modulation-scheme-seeded-free-electron.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
0 shares

Feedback to editors

User comments