Observation of harmonic lasing in the Angstrom regime at European X-ray Free Electron Laser

E.a Schneidmiller ,D Noelle,F Wolff-Fabris,J Liu,S Karabekyan,L Froehlich,H Sinn,Jan Gruenert ,M.v Yurkov ,Liubov Samoylova ,Joakim Laksman ,Natalia Gerasimova ,T Maltezopoulos ,Matthias Scholz ,Svitozar Serkez ,I D Petrov ,Gianluca Geloni ,Naresh Kujala ,Winfried Decking ,Igor Zagorodnov ,Frank Brinker ,Marc Guetg

doi:10.1103/physrevaccelbeams.24.030701

E.a Schneidmiller , D Noelle + Show 20 more

Open Access

https://doi.org/10.1103/physrevaccelbeams.24.030701

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Abstract

Harmonic lasing provides an opportunity to extend the photon energy range of existing and planned x-ray free electron laser (FEL) user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can generate a much more intense, stable, and narrow-band FEL beam. Another interesting application is harmonic lasing self-seeding that allows to improve the longitudinal coherence and spectral power of a self-amplified spontaneous emission FEL. This concept was tested at the soft x-ray FEL user facility FLASH in the range of 4.5--15 nm and at Pohang accelerator laboratory X-ray Free Electron Laser (XFEL) at 1 nm. In this paper we present recent results from the European XFEL where we successfully demonstrated harmonic lasing at 5.9 Angstrom and 2.8 Angstrom. In the latter case we obtained both third and fifth harmonic lasing and, for the first time, operated a harmonic lasing cascade (fifth-third-first harmonics of the undulator). These results pave the way for reaching very high photon energies, up to 100 keV.

Highlights

Successful operation of x-ray free electron lasers (FELs) down to the Angstrom regime opens up new horizons for photon science
In this paper we report on recent results from the European X-ray Free Electron Laser (XFEL) [12], where we successfully demonstrated operation of the HLSS scheme at 5.9 Angstrom and at 2.8 Angstrom
The European XFEL can greatly outperform the specifications [13] in terms of the highest possible photon energy: it can reach the 60–100 keV range for the third harmonic lasing. It was shown [14] that one can keep the sub-Angstrom range of operation of the European XFEL after CW upgrade of the accelerator, even with a reduction of the electron energy from 17.5 to 7 GeV

Summary

INTRODUCTION

Successful operation of x-ray free electron lasers (FELs) down to the Angstrom regime opens up new horizons for photon science. A possible way to extend the photon energy range of high-gain x-ray FELs is to use harmonic lasing, which is the FEL instability at an odd harmonic of the planar undulator [1,2,3,4,5] developing independently from the lasing at the fundamental Another option, proposed in [5], is the possibility to improve spectral brightness of an x-ray FEL by the combined lasing on a harmonic in the first part of the undulator (with an increased undulator parameter K) and on the fundamental in the second part of the undulator. We observed for the first time the fifth harmonic lasing in a high-gain FEL and operation of a harmonic lasing cascade

HARMONIC LASING

Harmonic lasing self-seeded FEL

Harmonic lasing cascade

EXPERIMENTS AT THE EUROPEAN XFEL

CONCLUSION AND OUTLOOK