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Latest Trends in Free Electron Lasers

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 28017

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Dr. Emiliano Principi

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Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy
Interests: condensed matter under nonequilibrium conditions; electronic processes in light-activated functional materials; matter in extreme conditions; solid-density plasma; nonlinear interactions between extreme ultraviolet light and matter; ultrafast chemical reactions

Special Issue Information

Dear Colleague,

I invite you to submit an original research paper, a review, or a perspective article to this Special Issue on “Trends in Free Electron Lasers” in Applied Sciences.

After about 10 years of intense development and necessary commissioning, the free electron laser (FEL) technology is reaching maturity and can provide ultrashort intense coherent X-ray and extreme ultraviolet pulses for innovative investigations on matter. Following a natural adaptation period, an interdisciplinary scientific community routinely working on FEL facilities has grown, incorporating synchrotron and table-top fs-laser know-how. Stimulated by experimental findings, theoretical scientists have begun to simulate FEL-driven ultrafast dynamics in matter and develop new nonequilibrium theoretical methods. Meanwhile, a novel class of FEL sources experts, the “FEL physicists”, have become crucial to the proper operation and improvement of FELs.

Today, people involved in the amazing rise of FELs can be proud of the work done and look to future advances. FEL users, aware of both the limits and the potential of FEL experimental methods and techniques, can now formulate ideas for breakthrough experiments and identify future scientific challenges with the assistance of advanced numerical calculations perfected by theoreticians. FEL physicists have the crucial role of further developing FEL sources, improving their performance and flexibility, and pursuing original FEL light generation schemes.

It is important to understand in what new directions the young FEL community is moving and inform both present and potential future members about promising opportunities.

The aim of this Special Issue is to anticipate and highlight scientific and technological trends involving FELs, facilitate the dissemination of new ideas in the field, and contribute to the consolidation of the FEL community. Topics of interest include:

frontier FEL science;
challenging FEL experiments to be attempted;
novel experimental methods, instrumentation, and techniques;
numerical calculations on nonequilibrium matter;
simulation of ultrafast dynamics;
breakthrough FEL technologies and devices;
new FEL light generation schemes; and
future developments of FEL facilities.

Your contribution to this Special Issue is welcome.

Dr. Emiliano Principi
Guest Editor

Manuscript Submission Information

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Keywords

free electron lasers
FEL sources
FEL light generation schemes
relativistic linear accelerators
FEL experimental methods
ultrafast phenomena
nonequilibrium matter
sub-picosecond dynamics
nonlinear x-ray/matter interaction
high-energy and density matter
coherent control
ab initio theoretical calculations

Published Papers (12 papers)

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Editorial

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3 pages, 182 KiB

Open AccessEditorial

Special Issue on Latest Trends in Free Electron Lasers

by Emiliano Principi

Appl. Sci. 2022, 12(21), 11215; https://0-doi-org.brum.beds.ac.uk/10.3390/app122111215 - 05 Nov 2022

Viewed by 947

Abstract

In the last decade, free electron laser (FEL) sources operating from the extreme ultraviolet (EUV) up to the hard X-ray photon energy range [...] Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

Research

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12 pages, 1963 KiB

Open AccessArticle

Approaching the Attosecond Frontier of Dynamics in Matter with the Concept of X-ray Chronoscopy

by Wojciech Błachucki, Anna Wach, Joanna Czapla-Masztafiak, Mickaël Delcey, Christopher Arrell, Rafał Fanselow, Pavle Juranić, Marcus Lundberg, Christopher Milne, Jacinto Sá and Jakub Szlachetko

Appl. Sci. 2022, 12(3), 1721; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031721 - 08 Feb 2022

Cited by 2 | Viewed by 2867

Abstract

X-ray free electron lasers (XFELs) have provided scientists opportunities to study matter with unprecedented temporal and spatial resolutions. However, access to the attosecond domain (i.e., below 1 femtosecond) remains elusive. Herein, a time-dependent experimental concept is theorized, allowing us to track ultrafast processes in matter with sub-fs resolution. The proposed X-ray chronoscopy approach exploits the state-of-the-art developments in terahertz streaking to measure the time structure of X-ray pulses with ultrahigh temporal resolution. The sub-femtosecond dynamics of the saturable X-ray absorption process is simulated. The employed rate equation model confirms that the X-ray-induced mechanisms leading to X-ray transparency can be probed via measurement of an X-ray pulse time structure. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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8 pages, 2588 KiB

Open AccessArticle

Investigating Coherent Magnetization Control with Ultrashort THz Pulses

by Xuan Liu, Emmanuelle Jal, Renaud Delaunay, Romain Jarrier, Gheorghe Sorin Chiuzbaian, Grégory Malinowski, Torsten Golz, Ekaterina Zapolnova, Rui Pan, Nikola Stojanovic, Jan Lüning and Boris Vodungbo

Appl. Sci. 2022, 12(3), 1323; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031323 - 26 Jan 2022

Cited by 6 | Viewed by 2292

Abstract

Coherent terahertz control of magnetization dynamics is an area of current interest due to its great potential for the realization of magnetization control on ultrafast timescales in commercial devices. Here we report on an experiment realized at the THz beamline of the free electron laser FLASH at DESY which offers a tunable terahertz radiation source and spontaneously synchronized free-electron laser X-ray pulses to resonantly probe the magnetization state of a ferromagnetic film. In this proof-of-principle experiment, we have excited a thin Permalloy film at different THz wavelengths and recorded the induced magnetization dynamics with photons resonantly tuned to the Ni

M_{2, 3}

absorption edge. For THz pump pulses including higher orders of the undulator source we observed demagnetization dynamics, which precise shape depended on the employed fundamental wavelength of the undulator source. Analyzing the shape in detail, we can reconstruct the temporal profile of the electric field of the THz pump pulse. This offers a new method for the realization of an in-situ terahertz beamline diagnostic which will help researchers to adjust the pulse characteristics as needed, for example, for future studies of THz induced coherent control of magnetization dynamics. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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16 pages, 1354 KiB

Open AccessArticle

Perspectives towards Sub-Ångström Working Regime of the European X-ray Free-Electron Laser with Low-Emittance Electron Beams

by Ye Chen, Frank Brinker, Winfried Decking, Matthias Scholz and Lutz Winkelmann

Appl. Sci. 2021, 11(22), 10768; https://0-doi-org.brum.beds.ac.uk/10.3390/app112210768 - 15 Nov 2021

Cited by 5 | Viewed by 1684

Abstract

Sub-ångström working regime refers to a working state of free-electron lasers which allows the generation of hard X-rays at a photon wavelength of 1 ångström and below, that is, a photon energy of 12.5 keV and above. It is demonstrated that the accelerators of the European X-ray Free-Electron Laser can provide highly energetic electron beams of up to 17.5 GeV. Along with long variable-gap undulators, the facility offers superior conditions for exploring self-amplified spontaneous emission (SASE) in the sub-ångström regime. However, the overall FEL performance relies quantitatively on achievable electron beam qualities through a kilometers-long accelerator beamline. Low-emittance electron beam production and the associated start-to-end beam physics thus becomes a prerequisite to dig in the potentials of SASE performance towards higher photon energies. In this article, we present the obtained results on electron beam qualities produced with different accelerating gradients of 40 MV/m–56 MV/m at the cathode, as well as the final beam qualities in front of the undulators via start-to-end simulations considering realistic conditions. SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz-repetition 0.65 ms-long bunch train energized to 14 GeV and 17.5 GeV. Millijoule-level SASE intensity is obtained at a photon energy of 25 keV at 14 GeV electron beam energy using a gain length of about 7 m. At 17.5 GeV, half-millijoule lasing is achieved at 40 keV. Lasing at up to 50 keV is demonstrated with pulse energies in the range of a few hundreds and tens of microjoules with existing undulators and currently achievable electron beam qualities. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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14 pages, 3873 KiB

Open AccessArticle

Complex Attosecond Waveform Synthesis at FEL FERMI

by Praveen Kumar Maroju, Cesare Grazioli, Michele Di Fraia, Matteo Moioli, Dominik Ertel, Hamed Ahmadi, Oksana Plekan, Paola Finetti, Enrico Allaria, Luca Giannessi, Giovanni De Ninno, Alberto A. Lutman, Richard J. Squibb, Raimund Feifel, Paolo Carpeggiani, Maurizio Reduzzi, Tommaso Mazza, Michael Meyer, Samuel Bengtsson, Neven Ibrakovic, Emma Rose Simpson, Johan Mauritsson, Tamás Csizmadia, Mathieu Dumergue, Sergei Kühn, Harshitha Nandiga Gopalakrishnan, Daehyun You, Kiyoshi Ueda, Marie Labeye, Jens Egebjerg Bækhøj, Kenneth J. Schafer, Elena V. Gryzlova, Alexei N. Grum-Grzhimailo, Kevin C. Prince, Carlo Callegari and Giuseppe Sansone Show full author list Hide full author list

Appl. Sci. 2021, 11(21), 9791; https://0-doi-org.brum.beds.ac.uk/10.3390/app11219791 - 20 Oct 2021

Cited by 5 | Viewed by 2380

Abstract

Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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18 pages, 736 KiB

Open AccessFeature PaperArticle

Flexible and Coherent Soft X-ray Pulses at High Repetition Rate: Current Research and Perspectives

by Lucas Schaper, Sven Ackermann, Enrico Allaria, Philipp Amstutz, Karolin Baev, Martin Beye, Christopher Gerth, Ingmar Hartl, Wolfgang Hillert, Katja Honkavaara, Mehdi Mohammad Kazemi, Tino Lang, Pardis Niknejadi, Fabian Pannek, Juliane Rönsch-Schulenburg, Dmitrii Samoilenko, Evgeny Schneidmiller, Siegfried Schreiber, Markus Tischer, Mathias Vogt, Mikhail Yurkov and Johann Zemella Show full author list Hide full author list

Appl. Sci. 2021, 11(20), 9729; https://0-doi-org.brum.beds.ac.uk/10.3390/app11209729 - 18 Oct 2021

Cited by 6 | Viewed by 2157

Abstract

The successful realization of high gain free-electron lasers has opened new possibilities to X-ray scientists for investigating matter in different states. The availability of unprecedented photon properties stimulated the development of new experimental techniques capable of taking full advantage of these options and has started a virtuous collaboration between machine experts and photon users to improve further and optimize the generated X-ray pulses. Over the recent years, this has led to the development of several advanced free-electron laser (FEL) schemes to tailor the photon properties to specific experimental demands. Presently, tunable wavelength X-ray pulses with extremely high brilliance and short pulse characteristics are a few of the many options available at FELs. Few facilities can offer options such as narrowband or extremely short pulses below one fs duration and simultaneous pulses of multiple colors enabling resonant X-ray pump—X-ray probe experiments with sub fs resolution. Fully coherent X-ray radiation (both spatial and temporal) can also be provided. This new option has stimulated the application of coherent control techniques to the X-ray world, allowing for experiments with few attoseconds resolution. FELs often operate at a relatively low repetition rate, typically on the order of tens of Hz. At FLASH and the European XFEL, however, the superconducting accelerators allow generating thousands of pulses per second. With the implementation of a new seeded FEL line and with an upgrade at FLASH linac, all the new features will become available in the soft X-ray spectral range down to the oxygen K edge with unprecedented average photon flux due to the high repetition rate of pulses. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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7 pages, 1175 KiB

Open AccessArticle

Resonant X-ray Emission Spectroscopy with a SASE Beam

by Wojciech Błachucki, Yves Kayser, Anna Wach, Rafał Fanselow, Christopher Milne, Jacinto Sá and Jakub Szlachetko

Appl. Sci. 2021, 11(18), 8775; https://0-doi-org.brum.beds.ac.uk/10.3390/app11188775 - 21 Sep 2021

Cited by 2 | Viewed by 2035

Abstract

Aqueous iron (III) oxide nanoparticles were irradiated with pure self-amplified spontaneous emission (SASE) X-ray free-electron laser (XFEL) pulses tuned to the energy around the Fe K-edge ionization threshold. For each XFEL shot, the incident X-ray pulse spectrum and Fe Kβ emission spectrum were measured synchronously with dedicated spectrometers and processed through a reconstruction algorithm allowing for the determination of Fe Kβ resonant X-ray emission spectroscopy (RXES) plane with high energy resolution. The influence of the number of X-ray shots employed in the experiment on the reconstructed data quality was evaluated, enabling the determination of thresholds for good data acquisition and experimental times essential for practical usage of scarce XFEL beam times. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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11 pages, 3355 KiB

Open AccessArticle

Frequency-Mixing Lasing Mode at European XFEL

by Gianluca Geloni, Frank Brinker, Winfried Decking, Jan Grünert, Marc Guetg, Theophilos Maltezopoulos, Dirk Noelle, Svitozar Serkez, Sergey Tomin, Mikhail Yurkov and Evgeny Schneidmiller

Appl. Sci. 2021, 11(18), 8495; https://0-doi-org.brum.beds.ac.uk/10.3390/app11188495 - 13 Sep 2021

Cited by 1 | Viewed by 1405

Abstract

We demonstrate generation of X-ray Free-Electron Laser (XFEL) pulses in frequency mixing mode at the SASE3 line of the European XFEL. The majority of the SASE3 FEL segments are tuned at two frequencies

ω_{1}

and

ω_{2}

following an alternate pattern. Leveraging [...] Read more.

ω_{1}

and

ω_{2}

following an alternate pattern. Leveraging on non-linearities generated through longitudinal dispersion in the system, we obtain electron bunching at a frequency difference

ω_{F M} = ω_{2} - ω_{1}

. FEL amplification at

ω_{F M}

follows in a few last radiator segments. We report on the generation of frequency mixing at photon energies between 500 eV and 1100 eV with pulse energies, depending on the length of the radiator, in the mJ level. This method allows generating low photon energies in cases where the FEL runs at high electron energy and the target photon energy cannot be reached in the main undulator, with the simple addition of a short, custom-made afterburner. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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11 pages, 494 KiB

Open AccessArticle

Limitations of Structural Insight into Ultrafast Melting of Solid Materials with X-ray Diffraction Imaging

by Victor Tkachenko, Malik M. Abdullah, Zoltan Jurek, Nikita Medvedev, Vladimir Lipp, Mikako Makita and Beata Ziaja

Appl. Sci. 2021, 11(11), 5157; https://0-doi-org.brum.beds.ac.uk/10.3390/app11115157 - 02 Jun 2021

Cited by 12 | Viewed by 2204

Abstract

In this work, we analyze the application of X-ray diffraction imaging techniques to follow ultrafast structural transitions in solid materials using the example of an X-ray pump–X-ray probe experiment with a single-crystal silicon performed at a Linac Coherent Light Source. Due to the spatially non-uniform profile of the X-ray beam, the diffractive signal recorded in this experiment included contributions from crystal parts experiencing different fluences from the peak fluence down to zero. With our theoretical model, we could identify specific processes contributing to the silicon melting in those crystal regions, i.e., the non-thermal and thermal melting whose occurrences depended on the locally absorbed X-ray doses. We then constructed the total volume-integrated signal by summing up the coherent signal contributions (amplitudes) from the various crystal regions and found that this significantly differed from the signals obtained for a few selected uniform fluence values, including the peak fluence. This shows that the diffraction imaging signal obtained for a structurally damaged material after an impact of a non-uniform X-ray pump pulse cannot be always interpreted as the material’s response to a pulse of a specific (e.g., peak) fluence as it is sometimes believed. This observation has to be taken into account in planning and interpreting future experiments investigating structural changes in materials with X-ray diffraction imaging. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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Review

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17 pages, 5434 KiB

Open AccessEditor’s ChoiceReview

Recent Progress of the PAL-XFEL

by Intae Eom, Sae Hwan Chun, Jae Hyuk Lee, Daewoong Nam, Rory Ma, Jaehyun Park, Sehan Park, Sang Han Park, Haeryong Yang, Inhyuk Nam, Myung Hoon Cho, Chi Hyun Shim, Gyujin Kim, Chang-Ki Min, Hoon Heo, Heung-Sik Kang and Changbum Kim

Appl. Sci. 2022, 12(3), 1010; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031010 - 19 Jan 2022

Cited by 10 | Viewed by 2942

Abstract

The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding FEL, and trials of two-color operation. In the beamline, new instruments or endstations have been added or are being prepared. Overall, beamline operation has been stabilized since its initiation, which has enabled excellent scientific results through efficient user experiments. In this paper, we describe details of the recent progress of the PAL-XFEL. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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Other

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12 pages, 931 KiB

Open AccessPerspective

Potential of Time-Resolved Serial Femtosecond Crystallography Using High Repetition Rate XFEL Sources

by Raphaël de Wijn, Diogo V. M. Melo, Faisal H. M. Koua and Adrian P. Mancuso

Appl. Sci. 2022, 12(5), 2551; https://0-doi-org.brum.beds.ac.uk/10.3390/app12052551 - 28 Feb 2022

Cited by 10 | Viewed by 2472

Abstract

This perspective review describes emerging techniques and future opportunities for time-resolved serial femtosecond crystallography (TR-SFX) experiments using high repetition rate XFEL sources. High repetition rate sources are becoming more available with the European XFEL in operation and the recently upgraded LCLS-II will be available in the near future. One efficient use of these facilities for TR-SFX relies on pump–probe experiments using a laser to trigger a reaction of light-responsive proteins or mix-and-inject experiments for light-unresponsive proteins. With the view to widen the application of TR-SFX, the promising field of photocaged compounds is under development, which allows the very fast laser triggering of reactions that is no longer limited to naturally light-responsive samples. In addition to reaction triggering, a key concern when performing an SFX experiment is efficient sample usage, which is a main focus of new high repetition rate-compatible sample delivery methods. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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12 pages, 20144 KiB

Open AccessProject Report

The SXFEL Upgrade: From Test Facility to User Facility

by Bo Liu, Chao Feng, Duan Gu, Fei Gao, Haixiao Deng, Meng Zhang, Sen Sun, Si Chen, Wei Zhang, Wencheng Fang, Zhen Wang, Qiaogen Zhou, Yongbin Leng, Ming Gu, Lixin Yin, Qiang Gu, Guoping Fang, Dong Wang and Zhentang Zhao

Appl. Sci. 2022, 12(1), 176; https://0-doi-org.brum.beds.ac.uk/10.3390/app12010176 - 24 Dec 2021

Cited by 26 | Viewed by 2757

Abstract

The Shanghai soft X-ray Free-Electron Laser facility (SXFEL), which is the first X-ray FEL facility in China, is being constructed in two phases: the test facility (SXFEL-TF) and the user facility (SXFEL-UF). The test facility was initiated in 2006 and funded in 2014. The commissioning of the test facility was finished in 2020. The user facility was funded in 2016 to upgrade the accelerator energy and build two undulator lines with five experimental end-stations. The output photon energy of the user facility will cover the whole water window range. This paper presents an overview of the SXFEL facility, including considerations of the upgrade, layout and design, construction status, commissioning progress and future plans. Full article

(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)

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