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Auteur : Grafiati
Publié le 11 mars 2023

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1

Dattoli, Giuseppe, Emanuele Di Palma, Silvia Licciardi et Elio Sabia. « Free Electron Laser High Gain Equation and Harmonic Generation ». Applied Sciences 11, no 1 (24 décembre 2020) : 85. http://dx.doi.org/10.3390/app11010085.

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The FEL integral equation is reviewed here and is studied under different contexts, accounting for diverse physical regimes. We include higher order harmonics and saturation effects, and explain the origin of scaling relations, widely exploited to describe either FEL dynamics or nonnlinear harmonic generation.
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2

Zhukovsky, K. V. « Comparative theoretical analysis of harmonic generation in free electron lasers with various beam parameters ». Izvestiya vysshikh uchebnykh zavedenii. Fizika, no 9 (2022) : 34–41. http://dx.doi.org/10.17223/00213411/65/9/34.

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We theoretically study the generation of odd and even harmonics in particular in free electron lasers (FELs). The comparative analysis is held for the spectral properties of SPARC and LEUTL FEL radiation. We analyze several different theoretical approaches to the harmonic power computation, in particular with regard to even harmonics. We compare the results with available data for SPARC and LEUTL FELs. The influence of such FEL parameters as the finite beam section, emittance and originating from it betatron oscillations on the harmonic generation and radiation is analyzed.
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3

Zhukovsky, K. V. « Analytical account for off-axis effects in X-ray radiation of free electron lasers ». Izvestiya vysshikh uchebnykh zavedenii. Fizika 64, no 1 (2021) : 21–28. http://dx.doi.org/10.17223/00213411/64/1/21.

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We give analytical description of generation of harmonics of the undulator radiation (UR) with account for the finite electron beam size, emittance, off-axis beam deviation and electron energy spread, as well as for the constant magnetic components and field harmonics effects. We give exact analytical expressions for the generalized Bessel and Airy functions, which describe the spectrum line shape and intensities in the two-frequency bi-harmonic undulator with account for the above factors. The obtained analytical formulae distinguish contributions of each field component and every undulator and beam parameter on the harmonic radiation in free electron lasers (FEL). The effect of the field on the harmonic radiation is analyzed with account for the beam finite size and its off-axis deviation. The phenomenological model is employed for the FEL modeling; with its help we study the harmonic generation, including even ones, in the experiments LCLS and LEUTL. We demonstrate analytically that strong second FEL harmonic in X-ray FEL at the wavelengths λ = 0.75nm in the LCLS experiment is caused by the deviation of the electron trajectories off the axis in 15 μm on the gain length 1.6 m, which is comparable with the beam size; the strong second FEL harmonic in the LEUTL experiment at the wavelength λ = 192nm can be attributed to interaction of the electrons in wide, ~ 0.2 mm, beam with the photon radiation at the gain length 0.87 m. The modeling results fully agree with the measurements. The developed formalism allows the analysis of projected and built FELs and their radiation, helps minimizing losses and correcting magnetic fields; it also shows physical background and reasons for each harmonic radiated power in the FEL.
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4

Zhukovsky, K., et I. Potapov. « Two-frequency undulator usage in compact self-amplified spontaneous emission free electron laser in Roentgen range ». Laser and Particle Beams 35, no 2 (12 avril 2017) : 326–36. http://dx.doi.org/10.1017/s0263034617000180.

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AbstractThe generation of harmonics in two-frequency undulator in a self-amplified spontaneous emission free electron laser (SASE FEL) is studied in order to produce Roentgen radiation in a relatively compact sized installation. The dynamics of SASE FEL is analyzed with the help of the phenomenological model to obtain the maximum of the X-ray high-harmonic power. The model accounts for the properties of the undulator magnetic field and of the electron beam and includes the major sources of losses, such as the electron energy spread, etc. It is compared and calibrated with the existing data on a FEL experiment. The advantages of the two-frequency undulator for Roentgen SASE FEL are demonstrated and the possibility to generate powerful mild Roentgen radiation at already ~25 m length is shown. The evolution of the bunching coefficients for high harmonics is studied together with the evolution of the FEL-induced energy spread. The linear and non-linear regimes are explored for common and for two-frequency undulators The usage of the two-frequency undulator for cascade SASE FEL with high X-ray harmonic power and high-harmonic bunching coefficients with low-induced energy spread is proposed.
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5

Zhukovsky, K., et A. Kalitenko. « Phenomenological and numerical analysis of power evolution and bunching in single-pass X-ray FELs ». Journal of Synchrotron Radiation 26, no 1 (1 janvier 2019) : 159–69. http://dx.doi.org/10.1107/s1600577518012444.

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The harmonic power and bunching evolution in X-ray single-pass free-electron lasers (FELs) is modelled and the harmonic generation in a phase-shifted two-frequency FEL is explored. The advanced phenomenological FEL model, which is validated numerically and experimentally, is employed. The model accounts for major losses for each harmonic individually; it is compared with reported experimental data and with PERSEO numerical simulations, which are performed here for a variety of experiments. The latter cover the radiation wavelength range 0.15–300 nm. The phenomenological description is based on a few key FEL parameters: electron beam section, current, energy and its spread and divergence. The model is employed for modelling harmonic bunching and power evolution in a phase-shifted X-ray FEL with a two-frequency undulator, where lower harmonics with numbers less than nth are suppressed by the electron–photon phase shift of kπ/n, k = 2, 4, …, between the undulator sections. The benefits of the two-frequency phase-shifted FEL are highlighted. FEL-induced energy spread is shown to be three times lower than in a FEL without the phase-shift. The high-power harmonic and sub-harmonic radiation in such a FEL is demonstrated. In particular, powerful ∼14 GW X-ray radiation at λ5 = 0.15 nm from electrons with energy of 5.47 GeV and beam current ∼3.66 kA is possible in a two-frequency phase-shifted FEL at 30 m; this constitutes half of a FEL length where a common planar undulator radiates the same wavelength and power at the fundamental harmonic. Moreover, about a three times lower energy spread is induced by the dominant fifth harmonic, and the harmonic power can be thousands of times higher than in a common planar undulator FEL.
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6

Жуковский, К. В. « Генерация мягкого рентгеновского излучения в компактном лазере на свободных электронах с умножением гармоник ». Журнал технической физики 89, no 3 (2019) : 426. http://dx.doi.org/10.21883/jtf.2019.03.47180.2600.

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AbstractSingle-pass free-electron lasers (FELs) with harmonic multiplication in the X-ray range are studied theoretically with the objective of producing intense radiation with the minimum possible FEL length, beam energy, and seed laser frequency. A cascade FEL with a two-frequency undulator for electron bunching at wavelengths of higher harmonics is proposed. The dynamics of radiation power in a FEL with harmonic multiplication cascades is investigated based on a well-proven phenomenological FEL model that covers all major losses for each harmonic in each FEL cascade. The effect of the beam quality on X-ray generation in a FEL is examined. It is demonstrated that electron beams with energy spread σ_ e ≤ 0.0002 are required for efficient use of harmonics in a cascade X-ray FEL. The evolution of power of harmonics in several cascade FELs at wavelengths of ~2–3 nm with multiplication of seed harmonics at a wavelength of 13.51 nm (Mo/Si reflection peak) and 11.43 nm (MoRu/Be reflection peak) is studied. It is demonstrated that the power increases to ~1 GW at a FEL length up to 40 m. In addition, the operation of multicascade FELs with a seed F _2 excimer 157-nm UV laser and harmonics of lasers with CO_2 and C_2H_2 at 30 nm with a beam of electrons with an energy of ~0.6 GeV and a current of ~1 kА is studied. The power of the modeled X-ray radiation of these FELs at λ = 2.5 and 3.3 nm increases to ~0.5 GW at ~30 m.
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7

Abo-Bakr, M., K. Goldammer, T. Kamps, J. Knobloch, B. Kuske, T. Leitner et A. Meseck. « Nonlinear harmonic generation in the STARS FEL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 593, no 1-2 (août 2008) : 6–10. http://dx.doi.org/10.1016/j.nima.2008.04.052.

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8

Zhukovsky, K. « High harmonic generation in undulators for FEL ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 369 (février 2016) : 9–14. http://dx.doi.org/10.1016/j.nimb.2015.10.041.

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9

Knobloch, Jens, et Markus Sauerborn. « STARS : A Cascaded High-Gain Harmonic-Generation FEL ». Synchrotron Radiation News 20, no 6 (23 novembre 2007) : 16–19. http://dx.doi.org/10.1080/08940880701744741.

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10

Zhang, Kaiqing, Tao Liu, Zheng Qi, Xiaoxi Fu, Chao Feng, Haixiao Deng et Bo Liu. « Extending the Photon Energy Coverage of a Seeded Free-Electron Laser via Reverse Taper Enhanced Harmonic Cascade ». Photonics 8, no 2 (9 février 2021) : 44. http://dx.doi.org/10.3390/photonics8020044.

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External seeded free-electron lasers (FELs) hold promising prospects for producing intense coherent radiation at high harmonics of a conventional laser. The practical harmonic up-conversion efficiencies of current seeding techniques are limited by various three-dimensional effects on the electron beam. In this paper, a novel method is proposed to extend the wavelength coverage of a seeded FEL by combining the reverse taper undulator with the echo-enabled harmonic generation. The proposed technique can significantly enhance the bunching at ultra-high harmonics and preserve the electron beam qualities from degradation by deleterious effects. Theoretical analysis and numerical simulation are performed, and the results demonstrate that stable, intense, nearly fully coherent FEL pulses with photon energy up to 1 keV can be generated. The proposed technique may open up new opportunities to obtain laser-like pulses at sub-nanometer wavelength.
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11

Kalitenko, A. M. « Numerical study of the second harmonic generation in FELs ». Journal of Synchrotron Radiation 28, no 3 (22 mars 2021) : 681–87. http://dx.doi.org/10.1107/s1600577521002538.

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A numerical study of the effect of betatron oscillations on the second harmonic generation in free-electron lasers (FELs) is presented. Analytical expressions for the effective coupling strength factors are derived that clearly distinguish all contributions in subharmonics and each polarization of the radiation. A three-dimensional time-dependent numerical FEL code that takes into account the main FEL effects and the individual contribution of each electron to the second harmonic generation is presented. Also, the X- and Y-polarizations of the second harmonic are analyzed. The second harmonic was detected in experiments at the Advanced Photon Source (APS) Low Energy Undulator Test Line (LEUTL) and Linac Coherent Light Source (LCLS) in the soft X-ray regime. The approach presented in the article can be useful for a comprehensive study and diagnostics of XFELs. In the paper, the LCLS and Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) experiments are modeled. The simulation results are in a good agreement with the experimental data.
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12

McNeil, B. W. J., J. A. Clarke, D. J. Dunning, G. J. Hirst, H. L. Owen, N. R. Thompson, B. Sheehy et P. H. Williams. « An XUV-FEL amplifier seeded using high harmonic generation ». New Journal of Physics 9, no 4 (3 avril 2007) : 82. http://dx.doi.org/10.1088/1367-2630/9/4/082.

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13

Jia, Qi-ka. « Optimization of optical klystron for coherent harmonic generation FEL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 407, no 1-3 (avril 1998) : 246–50. http://dx.doi.org/10.1016/s0168-9002(98)00023-0.

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14

Ben-Zvi, I., A. Friedman, C. M. Hung, G. Ingold, S. Krinsky, K. M. Yang, L. H. Yu, I. Lehrman et D. Weissenburger. « Design of a harmonic generation FEL experiment at BNL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 318, no 1-3 (juillet 1992) : 208–11. http://dx.doi.org/10.1016/0168-9002(92)91052-b.

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15

Hajima, Ryoichi. « Few-Cycle Infrared Pulse Evolving in FEL Oscillators and Its Application to High-Harmonic Generation for Attosecond Ultraviolet and X-ray Pulses ». Atoms 9, no 1 (24 février 2021) : 15. http://dx.doi.org/10.3390/atoms9010015.

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Generation of few-cycle optical pulses in free-electron laser (FEL) oscillators has been experimentally demonstrated in FEL facilities based on normal-conducting and superconducting linear accelerators. Analytical and numerical studies have revealed that the few-cycle FEL lasing can be explained in the frame of superradiance, cooperative emission from self-bunched systems. In the present paper, we review historical remarks of superradiance FEL experiments in short-pulse FEL oscillators with emphasis on the few-cycle pulse generation and discuss the application of the few-cycle FEL pulses to the scheme of FEL-HHG, utilization of infrared FEL pulses to drive high-harmonic generation (HHG) from gas and solid targets. The FEL-HHG enables one to explore ultrafast science with attosecond ultraviolet and X-ray pulses with a MHz repetition rate, which is difficult with HHG driven by solid-state lasers. A research program has been launched to develop technologies for the FEL-HHG and to conduct a proof-of-concept experiment of FEL-HHG.
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16

Sabia, Elio, Emanuele Di Palma et Giuseppe Dattoli. « Two-Beam Free-Electron Lasers and Self-Injected Nonlinear Harmonic Generation ». Applied Sciences 11, no 14 (13 juillet 2021) : 6462. http://dx.doi.org/10.3390/app11146462.

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The possibility of extending the tunability of Free-Electron Lasers towards short wavelengths has been explored through the design of devices conceived to enhance the mechanisms of nonlinear harmonic generation. In this respect, different schemes of operation have been suggested in the past, such as harmonic seeding, bi-harmonic undulators, and two-beam self-seeding devices. In this paper, we discuss how these methods can be merged into a tool, extending the performance of FEL devices.
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17

Zeng, Ling, Weilun Qin, Gang Zhao, Senlin Huang, Yuantao Ding, Zhirong Huang, Gabriel Marcus et Kexin Liu. « Self-seeded FEL wavelength extension with high-gain harmonic generation ». Chinese Physics C 40, no 9 (septembre 2016) : 098102. http://dx.doi.org/10.1088/1674-1137/40/9/098102.

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18

Goloviznin, V. V., et P. W. van Amersfoort. « Ultrahigh harmonic generation in a FEL with a seed laser ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 375, no 1-3 (juin 1996) : 309–10. http://dx.doi.org/10.1016/0168-9002(95)01345-8.

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19

Жуковский, K. В. « Генерация гармоник в экспериментах с лазерами на свободных электронах в рентгеновском диапазоне --- теоретический анализ ». Журнал технической физики 91, no 3 (2021) : 495. http://dx.doi.org/10.21883/jtf.2021.03.50529.243-20.

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Analytical description of the generation of harmonics of the undulator radiation (UR) in free electron lasers (FELs) is given for various FEL experiments in the X-ray band. The expressions for the spectral line shape and intensity are written explicitly in terms of the generalized Bessel and Airy functions with account for the electron energy spread, beam sizes and emittances, spectral line split and non-periodic magnetic fields. The presented theory describes well the radiation spectral properties and harmonic intensities in all studied FEL experiments: SACLA, LCLS, PAL-XFEL, SwissFEL et al., in various conditions with the radiation in wide range of frequencies, covering hard X-rays.
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20

Allaria, E., L. Badano, S. Bassanese, F. Capotondi, D. Castronovo, P. Cinquegrana, M. B. Danailov et al. « The FERMI free-electron lasers ». Journal of Synchrotron Radiation 22, no 3 (21 avril 2015) : 485–91. http://dx.doi.org/10.1107/s1600577515005366.

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FERMI is a seeded free-electron laser (FEL) facility located at the Elettra laboratory in Trieste, Italy, and is now in user operation with its first FEL line, FEL-1, covering the wavelength range between 100 and 20 nm. The second FEL line, FEL-2, a high-gain harmonic generation double-stage cascade covering the wavelength range 20–4 nm, has also completed commissioning and the first user call has been recently opened. An overview of the typical operating modes of the facility is presented.
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21

Zhao, Zhouyu, Heting Li et Qika Jia. « Phase-merging enhanced harmonic generation free-electron laser with a normal modulator ». Journal of Synchrotron Radiation 24, no 5 (29 juillet 2017) : 906–11. http://dx.doi.org/10.1107/s1600577517008402.

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A phase-merging enhanced harmonic generation free-electron laser (FEL) was proposed to increase the harmonic conversion efficiency of seeded FELs and promote the radiation wavelength towards the X-ray spectral region. However, this requires a specially designed transverse gradient undulator (TGU) as the modulator to couple the transverse and longitudinal phase space of the electron beam. In this paper, the generation of the phase-merging effect is explored using the natural field gradient of a normal planar undulator. In this method, a vertical dispersion on the electron beam is introduced and then the dispersed beam travels through a normal modulator in a vertical off-axis orbit where the vertical field gradient is selected properly in terms of the vertical dispersion strength and modulation amplitude. The phase-merging effect will be generated after passing through the dispersive chicane. Theoretical analysis and numerical simulations for a seeded soft X-ray FEL based on parameters of the Shanghai Soft X-ray FEL project are presented. Compared with a TGU modulator, using the natural gradient of a normal planar modulator has the distinct advantage that the gradient can be conveniently tuned in quite a large range by adjusting the beam orbit offset.
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22

Jian-Hui, Chen, Deng Hai-Xiao, Gu Qiang, Li Dong-Guo, Wang Dong, Zhang Meng et Zhao Zhen-Tang. « Operating the SDUV-FEL with the echo-enabled harmonic generation scheme ». Chinese Physics C 33, no 8 (28 juillet 2009) : 706–10. http://dx.doi.org/10.1088/1674-1137/33/8/021.

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23

Nakao, N., M. Kokubo, K. Imasaki, M. Fujita, K. Ohkubo, A. Moon, P. K. Roy et al. « FEL experiment of the 5th harmonic generation with a modified wiggler ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 407, no 1-3 (avril 1998) : 374–79. http://dx.doi.org/10.1016/s0168-9002(98)00053-9.

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24

Graves, W. S., L. Solomon et I. Lehrman. « End fields in the harmonic generation superconducting FEL at BNL-NSLS ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 358, no 1-3 (avril 1995) : 414–17. http://dx.doi.org/10.1016/0168-9002(94)01338-1.

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25

Liu, Tao, Chao Feng, Dao Xiang, Jiansheng Liu et Dong Wang. « Generation of ultrashort coherent radiation based on a laser plasma accelerator ». Journal of Synchrotron Radiation 26, no 2 (6 février 2019) : 311–19. http://dx.doi.org/10.1107/s1600577518018209.

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A laser plasma accelerator (LPA) has the potential to realize compact free-electron laser (FEL) radiation at the regular laboratory scale. However, large initial angular divergence and energy spread dramatically hinder ways to transport the beam and realize FEL radiation. Although methods have been proposed to solve these problems, the relatively large jitter, including transverse position jitter and energy jitter, still limits the advance of these experiments. In this paper a simple method to realize coherent harmonic generation based on a LPA beam is proposed. The scheme is very compact, adopting a high-power laser split from the driver laser, a short modulator and a short radiator which has a great tolerance to these typical types of jitter. Numerical simulations indicate that coherent third-harmonic radiation with gigawatt-level power and single spike spectra can be obtained, verifying the feasibility of the scheme and indicating the capability to generate ultrashort fully coherent radiation.
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26

HANAMURA, EIICHI, et YUKITO TANABE. « NONLINEAR OPTICAL RESPONSES OF ANTIFERROMAGNETIC INSULATORS ». Journal of Nonlinear Optical Physics & ; Materials 11, no 01 (mars 2002) : 99–123. http://dx.doi.org/10.1142/s0218863502000821.

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Firstly, we show how to resolve the observed mystery in the resonance-enhancement of two-magnon Raman scattering in antiferromagnetic (AFM) insulators La2CuO4 and YBa2Cu3O6 in terms of the excitonic cluster model. Secondly, we refer to the strong third-harmonic generation (THG) in visible region from La2CuO4, and explain how we are able to understand the fine structures as quantum interference among two-photon and three-photon resonant THG. Ferroelectric (FEL)-AFM crystals RMnO3 (R=Y, Ho, Er) with a hexagonal structure show interesting two-photon resonant second-harmonic generation (SHG). Two lowest-energy excitons in the visible region are found to contribute to SHG constructively in YMnO3 and destructively in ErMnO3 depending upon the AFM spin-configuration. It is also found that the clamping of two order-parameters FEL and AFM must be introduced to explain the observation.
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Biedron, S. G., R. J. Dejus, Z. Huang, S. V. Milton, V. Sajaev, W. Berg, M. Borland et al. « Measurements of nonlinear harmonic generation at the Advanced Photon Source's SASE FEL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 483, no 1-2 (mai 2002) : 94–100. http://dx.doi.org/10.1016/s0168-9002(02)00430-8.

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Hayakawa, Y., I. Sato, K. Hayakawa, T. Tanaka, K. Yokoyama, K. Kanno, T. Sakai, K. Ishiwata, K. Nakao et E. Hashimoto. « Characteristics of the fundamental FEL and the higher harmonic generation at LEBRA ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 507, no 1-2 (juillet 2003) : 404–8. http://dx.doi.org/10.1016/s0168-9002(03)00954-9.

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Yoshida, Kyohei, Heishun Zen, Motoharu Inukai, Kensuke Okumura, Kenta Mishima, Kyohei Shimahashi, Marie Shibata et al. « RETRACTED : Observation of High Harmonic Generation from SiC by MIR-FEL Irradiation ». Energy Procedia 34 (2013) : 932–36. http://dx.doi.org/10.1016/j.egypro.2013.06.831.

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30

Wang, Xiaofan, Chao Feng, Bart Faatz, Weiqing Zhang et Zhentang Zhao. « High-repetition-rate seeded free-electron laser with direct-amplification of an external coherent laser ». New Journal of Physics 24, no 3 (1 mars 2022) : 033013. http://dx.doi.org/10.1088/1367-2630/ac5492.

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Abstract Various scientific and industrial researches such as spectroscopy and advanced nano-technologies have been demanding high flux and fully coherent extreme ultraviolet (EUV) and x-ray radiation. These demands can be commendably satisfied with a MHz-level repetition-rate seeded free-electron laser (FEL). Dictated by the seed laser system, seeded FELs have faced obstacles for the realization of MHz repetition rate. Reducing the required peak power of an external coherent seed laser can effectively increase the repetition rate of a seeded FEL. This paper presents a novel technique that employs a long modulator as a carrier for laser amplification and electron modulation, which is quite different from nominal seeded FELs. Applications of the proposed technique into high-gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) are investigated. Simulation results demonstrate that seed laser power is reduced by about three orders of magnitude and the FEL radiation possesses consistently high coherence and power stability with respect to the nominal HGHG or EEHG. The proposed technique paves the way for the realization of fully coherent EUV and soft x-ray FELs with a repetition rate of MHz and an average power of about 100 W.
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Troß, Jan, Shashank Pathak, Adam Summers, Dimitrios Rompotis, Benjamin Erk, Christopher Passow, Bastian Manschwetus et al. « High harmonic generation in mixed XUV and NIR fields at a free-electron laser ». Journal of Optics 24, no 2 (7 janvier 2022) : 025502. http://dx.doi.org/10.1088/2040-8986/ac4318.

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Abstract We present the results of an experiment investigating the generation of high-order harmonics by a femtosecond near-infrared (NIR) laser pulse in the presence of an extreme ultraviolet (XUV) field provided by a free-electron laser (FEL), a process referred to as XUV-assisted high-order harmonic generation (HHG). Our experimental findings show that the XUV field can lead to a small enhancement in the harmonic yield when the XUV and NIR pulses overlap in time, while a strong decrease of the HHG yield and a red shift of the HHG spectrum is observed when the XUV precedes the NIR pulse. The latter observations are in qualitative agreement with model calculations that consider the effect of a decreased number of neutral emitters but are at odds with the predicted effect of the correspondingly increased ionization fraction on the phase matching. Our study demonstrates the technical feasibility of XUV-assisted HHG experiments at FELs, which may provide new avenues to investigate correlation-driven electron dynamics as well as novel ways to study and control propagation effects and phase matching in HHG.
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Petrillo, Vittoria, Michele Opromolla, Alberto Bacci, Illya Drebot, Giacomo Ghiringhelli, Alberto Petralia, Ezio Puppin et al. « High Repetition Rate and Coherent Free-Electron Laser in the X-Rays Range Tailored for Linear Spectroscopy ». Instruments 3, no 3 (9 septembre 2019) : 47. http://dx.doi.org/10.3390/instruments3030047.

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Fine time-resolved analysis of matter—i.e., spectroscopy and photon scattering—in the linear response regime requires fs-scale pulsed, high repetition rate, fully coherent X-ray sources. A seeded Free Electron Laser (FEL) driven by a Linac based on Super Conducting cavities, generating 10 8 – 10 10 coherent photons at 2–5 keV with 0.2–1 MHz of repetition rate, can address this need. Three different seeding schemes, reaching the X-ray range, are described hereafter. The first two are multi-stage cascades upshifting the radiation frequency by a factor of 10–30 starting from a seed represented by a coherent flash of extreme ultraviolet light. This radiation can be provided either by the High Harmonic Generation of an optical laser or by an FEL Oscillator operating at 12–14 nm. The third scheme is a regenerative amplifier working with X-ray mirrors. The whole chain of the X-ray generation is here described by means of start-to-end simulations.
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33

Zhang, X., I. Ben-Zvi, G. Ingold, S. Krinsky et L. H. Yu. « Analysis of the superconducting wiggler magnets for the ATF harmonic generation FEL experiment ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 331, no 1-3 (juillet 1993) : 689–94. http://dx.doi.org/10.1016/0168-9002(93)90137-7.

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NAM*, Soon-Kwon. « Effect of Electron Beam Quality on Nonlinear Harmonic Generation in the X-FEL ». New Physics : Sae Mulli 63, no 10 (31 octobre 2013) : 1144–48. http://dx.doi.org/10.3938/npsm.63.1144.

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35

Solomon, L., W. S. Graves et I. Lehrman. « Magnetic field measurements of the harmonic generation FEL superconducting undulator at BNL-NSLS ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 358, no 1-3 (avril 1995) : 411–13. http://dx.doi.org/10.1016/0168-9002(94)01336-5.

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36

Meister, Severin, Hannes Lindenblatt, Florian Trost, Kirsten Schnorr, Sven Augustin, Markus Braune, Rolf Treusch, Thomas Pfeifer et Robert Moshammer. « Atomic, Molecular and Cluster Science with the Reaction Microscope Endstation at FLASH2 ». Applied Sciences 10, no 8 (24 avril 2020) : 2953. http://dx.doi.org/10.3390/app10082953.

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The reaction microscope (REMI) endstation for atomic and molecular science at the free-electron laser FLASH2 at DESY in Hamburg is presented together with a brief overview of results recently obtained. The REMI allows coincident detection of electrons and ions that emerge from atomic or molecular fragmentation reactions in the focus of the extreme-ultraviolet (XUV) free-electron laser (FEL) beam. A large variety of target species ranging from atoms and molecules to small clusters can be injected with a supersonic gas-jet into the FEL focus. Their ionization and fragmentation dynamics can be studied either under single pulse conditions, or for double pulses as a function of their time delay by means of FEL-pump–FEL-probe schemes and also in combination with a femtosecond infrared (IR) laser. In a recent upgrade, the endstation was further extended by a light source based on high harmonic generation (HHG), which is now available for upcoming FEL/HHG pump–probe experiments.
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37

Dattoli, G., L. Giannessi et P. L. Ottaviani. « Energy phase correlation effects on FEL dynamics and coherent harmonic generation : a critical review ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 432, no 2-3 (août 1999) : 501–4. http://dx.doi.org/10.1016/s0168-9002(99)00485-4.

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38

Karbushev, N. I., V. D. Sazhin et P. V. Mironov. « Higher harmonic generation in a FEL with an axisymmetric undulator of the induction type ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 358, no 1-3 (avril 1995) : 467–70. http://dx.doi.org/10.1016/0168-9002(94)01333-0.

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ALESINI, D., S. BERTOLUCCI, M. E. BIAGINI, R. BONI, M. BOSCOLO, M. CASTELLANO, A. CLOZZA et al. « The SPARC/X SASE-FEL Projects ». Laser and Particle Beams 22, no 3 (juillet 2004) : 341–50. http://dx.doi.org/10.1017/s0263034604223199.

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SPARC and SPARX are two different initiatives toward an ItalianFreeElectronLaser (FEL) source operating in theSelfAmplifiedSpontaneousEmission (SASE) mode, in which several national research institutions are involved. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting the SASE mechanism. An advanced Photo-Injector system, emittance compensating RF-gun plus a 150 MeV Linac, will inject a high quality e-beam into the undulator to generate high brilliance FEL radiation in the visible region at the fundamental wavelength, (∼500 nm). The production of flat top drive laser beams, high peak current bunches, and emittance compensation scheme will be investigated together with the generation of higher harmonic radiation in the VUV region. SPARX is the direct evolution of such a high gain SASE FEL toward the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. To get the required value for the bunch peak current, Ipeak≈ 2.5 kA, the “hybrid” scheme, RF-compression stage plus magnetic chicane, is analyzed and compared with the more standard double stage of magnetic compression. The two options are reviewed considering the tolerance to the drive laser pulse phase jitter.
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40

Paraskaki, Georgia, Sven Ackermann, Bart Faatz, Gianluca Geloni, Tino Lang, Fabian Pannek, Lucas Schaper et Johann Zemella. « Advanced Scheme to Generate MHz, Fully Coherent FEL Pulses at nm Wavelength ». Applied Sciences 11, no 13 (29 juin 2021) : 6058. http://dx.doi.org/10.3390/app11136058.

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Current FEL development efforts aim at improving the control of coherence at high repetition rate while keeping the wavelength tunability. Seeding schemes, like HGHG and EEHG, allow for the generation of fully coherent FEL pulses, but the powerful external seed laser required limits the repetition rate that can be achieved. In turn, this impacts the average brightness and the amount of statistics that experiments can do. In order to solve this issue, here we take a unique approach and discuss the use of one or more optical cavities to seed the electron bunches accelerated in a superconducting linac to modulate their energy. Like standard seeding schemes, the cavity is followed by a dispersive section, which manipulates the longitudinal phase space of the electron bunches, inducing longitudinal density modulations with high harmonic content that undergo the FEL process in an amplifier placed downstream. We will discuss technical requirements for implementing these setups and their operation range based on numerical simulations.
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41

Samoilenko, D., W. Hillert, F. Pannek, S. Ackermann, E. Ferrari, N. Mirian, P. Niknejadi et al. « Sensitivity of EEHG simulations to dynamic beam parameters ». Journal of Physics : Conference Series 2420, no 1 (1 janvier 2023) : 012024. http://dx.doi.org/10.1088/1742-6596/2420/1/012024.

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Abstract Currently, the Free electron laser user facility FLASH at DESY is undergoing a significant upgrade involving the complete transformation of one of its beamlines to allow external seeding. With the Echo-Enabled Harmonic Generation (EEHG) seeding method, we aim for the generation of fully coherent XUV and soft X-ray pulses at wavelengths down to 4 nm. The generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile imprinted either deliberately or by collective effects such as Coherent Synchrotron Radiation (CSR). In dedicated particle tracking simulations, one usually makes certain assumptions concerning the beam properties and the collective effects to simplify implementation and analysis. Here, we estimate the influence of some of the common assumptions made in EEHG simulations on the properties of the output FEL radiation, using the example of FLASH and its proposed seeding beamline. We conclude that the inherent properties of the FLASH1 beam, namely the negatively chirped energy profile, has dominant effect on the spectral intensity profile of the radiators output compare to that of the CSR induced chirp.
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42

Gullans, M., J. S. Wurtele, G. Penn et A. A. Zholents. « Performance study of a soft X-ray harmonic generation FEL seeded with an EUV laser pulse ». Optics Communications 274, no 1 (juin 2007) : 167–75. http://dx.doi.org/10.1016/j.optcom.2007.02.014.

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43

Biedron, S. G., H. P. Freund et L. H. Yu. « Parameter analysis for a high-gain harmonic generation FEL using a recently developed 3D polychromatic code ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 445, no 1-3 (mai 2000) : 95–100. http://dx.doi.org/10.1016/s0168-9002(00)00120-0.

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44

Hooper, Brett A., Stephen V. Benson, Antonello Cutolo et John M. J. Madey. « Experimental results of two stage harmonic generation with picosecond pulses on the Stanford Mark III FEL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 272, no 1-2 (octobre 1988) : 96–98. http://dx.doi.org/10.1016/0168-9002(88)90202-1.

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45

Alieva, E. V., G. Beitel, L. A. Kuzik, A. A. Sigarev, V. A. Yakovlev, G. N. Zhizhin, A. F. G. van der Meer et M. J. van der Wiel. « Linear and Nonlinear FEL-SEW Spectroscopic Characterization of Nanometer-Thick Films ». Applied Spectroscopy 51, no 4 (avril 1997) : 584–91. http://dx.doi.org/10.1366/0003702971940657.

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The conditions of the existence and transformations of surface electromagnetic waves (SEWs) on metals (surface plasmons) and dielectrics (phonon-polaritons) are discussed. Interferometric SEW experiments provide the possibility for the direct determination of the real and imaginary parts of the dielectric constants at the frequencies in the tuning range of a free electron laser (FEL) without any preliminary models. The important role of the outstanding facilities of FEL—namely, the broad tuning range, high power, narrow bandwidth of emission, and well-collimated beam—in SEW experiments is outlined. It is demonstrated by the examples of the infrared absorption spectra of a Langmuir-Blodgett film on metal, of a metal oxide film, and of polymeric films of nanometer thicknesses on metals. Free surfaces of single-crystal CaF2 and the thin polymeric film were studied by an interferometric experiment for the optical constant determination. Nonlinear spectroscopic applications of the SEW-FEL technique to studies of a second harmonic generation (SHG)—the frequency dependence of efficiency, the angle dependence of SHG, and the influence of a thin-film deposition on a quartz surface—are described.
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46

Ogawa, H., K. Yamada, N. Sei, M. Yasumoto et T. Mikado. « Simulation study on the coherent harmonic generation at the NIJI-IV FEL with a hole-coupled resonator ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 528, no 1-2 (août 2004) : 301–4. http://dx.doi.org/10.1016/j.nima.2004.04.075.

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47

Xiao, Yaozong, Chao Feng et Bo Liu. « Generating Isolated Attosecond X-Ray Pulses by Wavefront Control in a Seeded Free-Electron Laser ». Ultrafast Science 2022 (30 juillet 2022) : 1–8. http://dx.doi.org/10.34133/2022/9812478.

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We proposed a simple method based on the seeded free-electron laser (FEL) to generate fully coherent X-ray pulses with durations at dozens of attosecond level. The echo-enabled harmonic generation technique is utilized to generate the fully coherent laser pulse covering the water-window range. A wavefront rotation laser is adopted as the seed to tailor the longitudinal contour of the radiation pulse. Due to the sensitivity of seeded FEL to external lasers, this method can effectively inhibit the bunching of the adjacent regions while preserving an isolated bunching in the middle. Sending such an electron beam into a short undulator, simulation results show that ultrashort X-ray pulses with peak power of GW level and pulse duration as short as 86 attoseconds can be generated. The proposed scheme can make it possible to study the electronic dynamic of the valence electrons of which the time scale is about 100 attoseconds and may open up a new frontier of ultrafast science.
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48

Wang, Xiaofan, Chao Feng, Tao Liu, Zhen Zhang, Cheng-Ying Tsai, Juhao Wu, Chuan Yang et Zhentang Zhao. « Angular dispersion enhanced prebunch for seeding ultrashort and coherent EUV and soft X-ray free-electron laser in storage rings ». Journal of Synchrotron Radiation 26, no 3 (12 avril 2019) : 677–84. http://dx.doi.org/10.1107/s1600577519002674.

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Prebunching is an effective technique to reduce the radiation saturation length and to improve the longitudinal coherence and output stability in storage-ring-based free-electron lasers (FELs). A novel technique is proposed which uses angular dispersion to enhance the high-harmonic bunching with very small laser-induced energy spread. This technique can effectively reduce the radiation saturation length without significantly reducing the peak power of the FEL. Numerical simulations demonstrate that this technique can be used for the generation of 100 MW scale level, fully temporal coherent femtosecond extreme-ultraviolet and soft X-ray radiation pulses through a 10 m-long undulator based on a diffraction-limited storage ring.
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49

Zhukovsky, K. « Generation of coherent soft X-ray radiation in short FEL with harmonic multiplication cascades and two-frequency undulator ». Journal of Applied Physics 122, no 23 (21 décembre 2017) : 233103. http://dx.doi.org/10.1063/1.5001794.

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Huang, Ruixuan, Weiwei Li, Zhouyu Zhao, Heting Li, Jigang Wang, Tian Ma, Qiuping Huang et al. « Design of a Pre-Bunched THz Free Electron Laser ». Particles 1, no 1 (19 novembre 2018) : 267–78. http://dx.doi.org/10.3390/particles1010021.

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Terahertz (THz) radiation has attracted much attention in new scientific and industrial applications. There has been significant recent progress in generating THz with accelerators. To investigate the collective behavior of electron dynamics, we have proposed a new high throughput material characterization system, which supplies a multiple light source. The system includes a pre-bunched THz free electron laser (FEL), which is a high-power narrow-band THz source with a wide tuning range of frequency. The physical design with the main components of the facility is introduced, and the simulation results are illustrated. Radiation of 0.5–3.0 THz is obtained by the fundamental wave of the pre-bunched beam, and radiation covering 3.0–5.0 THz is realized by second harmonic generation. As the simulation shows, intense THz radiation could be achieved in a frequency from 0.5–5.0 THz, with a peak power of several megawatts (MWs) and a bandwidth of a few percent.
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