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- 摘要
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Editorial: Lasers in Accelerator Science and Secondary Emission Light Source Technology
摘要： Unifying laser and accelerator physics holds great promise for the development of future particle accelerators, light sources, and other scienti?c instruments due to increasingly synergistic advances at the cross section between these two ?elds. Their combined action has recently ushered in advanced accelerator facilities around the world that have enabled unique scienti?c and technological breakthroughs: from advanced electron and ion sources for high-energy physics to the ultrabright x-ray pulses to study ultrafast phenomena at elemental spatio-temporal scales [1–4]. The progress of ultra-intense femtosecond lasers, now attaining multi PetaWatt peak power, has recently enabled the demonstration of GeV electron beams in centimeter scale plasma accelerating section [5, 6], with the recent world record reaching 8 GeV in 20 cm [7]. As for ultrafast x-ray science, in their relatively short time since their advent, x-ray free electron lasers [8, 9] (FEL) have demonstrated the capacity to answer grand fundamental questions in a diverse set of areas in physics, chemistry, and biology, such as revealing vibration coherence in molecules [10], molecular bond formation, charge migration, and dissociation dynamics [11, 12], or ultrafast isomerization in biomolecules [13, 14], among many others. Further advances in facilities—such as augmented brightness, attosecond duration, or seeded emission—are poised to creating new scienti?c frontiers in atomic-scale correlated systems and ultrahigh resolution inner shell spectroscopies.
关键词： free electron laser (FEL),ultrafast optics,X-ray emission,non-linear optics,laser accelerated particles,secondary emission and photoemission
更新于2025-09-16 10:30:52
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Analytical Description of Nonlinear Harmonic Generation Close to the Saturation Region in Free Electron Lasers
摘要： The phenomenological modeling of nonlinear harmonic generation in single-pass free electron laser (FEL) experiments was performed. The gradual saturation of the harmonic power and its evolution around the saturated regime was modeled. The model includes all major losses for each harmonic with account for the fact that the undulator radiation (UR) and the electron-wave interaction at higher harmonic wavelengths are more sensitive to the beam energy spread, divergence, and other factors. The results of the phenomenological modeling are compared with the experimental data of the corresponding FELs and with the numerical simulation. The proposed description of nonlinear harmonic generation appears to be in good agreement with the FEL experiments SALCA, LEUTL, LCLS, and others under various conditions. The results also match their numerical simulations; in contrast to the latter, our phenomenological model allows rapid, still, and accurate modeling of the FEL harmonic power and bunching evolution with a PC or even an engineering calculator. The model permits studying FEL radiation from undulators with arbitrary magnetic field configuration. Using the analytical FEL model, we demonstrate that, in contrast to the helical undulator, in whose spectrum the fundamental and the second harmonics prevail, the FEL radiation from the elliptical undulator with the third field harmonic has a distinct fifth UR harmonic as well as the fundamental one, whereas other harmonics can be ignored even close to the saturation length.
关键词： undulator,harmonic generation,free electron laser
更新于2025-09-16 10:30:52
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Virus Structures by X-Ray Free-Electron Lasers
摘要： Until recently X-ray crystallography has been the standard technique for virus structure determinations. Available X-ray sources have continuously improved over the decades, leading to the realization of X-ray free-electron lasers (XFELs). They provide high-intensity femtosecond X-ray pulses, which allow for new kinds of experiments by making use of the diffraction-before-destruction principle. By overcoming classical dose constraints, they at least in principle allow researchers to perform X-ray virus structure determination for single particles at room temperature. Simultaneously, the availability of XFELs led to the development of the method of serial femtosecond crystallography, where a crystal structure is determined from the measurement of hundreds to thousands of microcrystals. In the case of virus crystallography this method does not require freezing of the crystals and allows researchers to perform experiments under non-equilibrium conditions (e.g., by laser-induced temperature jumps or rapid chemical mixing), which is currently not possible with electron microscopy.
关键词： structure determination,serial crystallography,XFEL,single particle imaging,virus crystallography,X-ray free-electron laser
更新于2025-09-16 10:30:52
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Multiple-Collision Free-Electron Laser Compton Backscattering for a High-Yield Gamma-Ray Source
摘要： We observed multiple-collision free-electron laser (FEL)-Compton backscattering in which a multi-bunch electron beam makes head-on collisions with multi-pulse FELs in an optical cavity, using an infrared FEL system in the storage ring NIJI-IV. It was demonstrated that the measured spectrum of the multiple-collision FEL-Compton backscattering gamma rays was the summation of the spectra of the gamma rays generated at each collision point. Moreover, it was demonstrated that the spatial distribution of the multiple-collision FEL-Compton backscattering gamma rays was the summation of those of the gamma rays generated at each collision point. Our experimental results proved quantitatively that the multiple collisions in the FEL-Compton backscattering process are effective in increasing the yield of the gamma rays. By applying the multiple-collision FEL-Compton backscattering to high-repetition FEL devices such as energy recovery linac FELs, an unprecedented high-yield gamma-ray source with quasi-monochromaticity and wavelength tunability will be realized.
关键词： Compton backscattering,multiple collision,free-electron laser,gamma ray
更新于2025-09-16 10:30:52
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Minimum Spectral Bandwidth in Echo Seeded Free Electron Lasers
摘要： This paper examines the impact of non-linear longitudinal phase distortions on the spectral bandwidth in echo seeded free electron lasers (FELs). It extends the existing theory developed in Hemsing [1] for echo-enabled harmonic generation (EEHG) to include finite laser pulse durations. An analytic expression for the shape of the optimized longitudinal bunching envelope is derived, and is used to determine the laser and electron beam pulse durations that minimize the seeded bandwidth in the presence of arbitrary phase distortions. The time-bandwidth product (TBP) is also derived, and is shown that the TBP and the bandwidth increase by no more than √2 from their transform-limited values when the bandwidth is minimized.
关键词： FEL (free electron laser),chirp,xray,seeded,nonlinear,EEHG,harmonic,echo
更新于2025-09-16 10:30:52
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[IEEE 2019 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - Saint-Petersburg, Russia (2019.6.3-2019.6.7)] 2019 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - Undulator Effect on a Bending Acoustic Wave of the Wakefield Waveguide
摘要： The possibility of creating a wake undulator on a bending acoustic wave in an accelerator structure with dielectric filling is considered. The proposed design has more flexible adjustment capabilities than traditional undulators.
关键词： wakefield accelerating structure,wakefield undulator,free electron laser,undulator
更新于2025-09-12 10:27:22
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A host dTMP-bound structure of T4 phage dCMP hydroxymethylase mutant using an X-ray free electron laser
摘要： The hydroxymethylation of cytosine bases plays a vital role in the phage DNA protection system inside the host Escherichia coli. This modification is known to be catalyzed by the dCMP hydroxymethylase from bacteriophage T4 (T4dCH); structural information on the complexes with the substrate, dCMP and the co-factor, tetrahydrofolate is currently available. However, the detailed mechanism has not been understood clearly owing to a lack of structure in the complex with a reaction intermediate. We have applied the X-ray free electron laser (XFEL) technique to determine a high-resolution structure of a T4dCH D179N active site mutant. The XFEL structure was determined at room temperature and exhibited several unique features in comparison with previously determined structures. Unexpectedly, we observed a bulky electron density at the active site of the mutant that originated from the physiological host (i.e., E. coli). Mass-spectrometric analysis and a cautious interpretation of an electron density map indicated that it was a dTMP molecule. The bound dTMP mimicked the methylene intermediate from dCMP to 5′-hydroxymethy-dCMP, and a critical water molecule for the final hydroxylation was convincingly identified. Therefore, this study provides information that contributes to the understanding of hydroxymethylation.
关键词： hydroxymethylation,XFEL,dCMP hydroxymethylase,X-ray free electron laser,T4dCH,hydroxylation,cytosine bases,phage DNA protection,dTMP,Escherichia coli,bacteriophage T4,methylene intermediate
更新于2025-09-12 10:27:22
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Development of a Multialkali Photocathode Dc Gun for a Smith-Purcell Terahertz Free-Electron Laser
摘要： We have developed a photocathode dc gun for a compact Smith-Purcell free-electron laser in the terahertz wavelength region. The gun system consists of an alkali antimonide photocathode preparation chamber, a dc gun with a 250 kV-50 mA Cockcroft-Walton high-voltage power supply, and a downstream beamline with a water-cooled beam dump to accommodate a beam power of 5 kW. We fabricated a Cs3Sb photocathode with quantum efficiency of 5.8% at a wavelength of 532 nm and generated a 150 keV beam with current of up to 4.3 mA with a 500 mW laser. A vacuum chamber for the Smith-Purcell free-electron laser has been installed in the downstream beamline. We describe the present status of our work.
关键词： photoemission dc gun,free-electron laser,Smith-Purcell radiation
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - High-Repetition-Rate High-Harmonic Generation Driven by Infrared Free-Electron Lasers
摘要： We present for high-harmonic-generation (HHG) driven by infrared free-electron lasers (FEL), which can be operated at MHz-repetition. Wavelength tunability of FEL enables one to explore HHG from mid-infrared pulses for higher cutoff energies above 1 keV. Plans and status of R&D are also presented.
关键词： x-ray,attosecond,free electron laser,high harmonic generation
更新于2025-09-11 14:15:04
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Controlled strong excitation of silicon as a step towards processing materials at sub-nanometer precision
摘要： Interaction of a solid material with focused, intense pulses of high-energy photons or other particles (such as electrons and ions) creates a strong electronic excitation state within an ultra-short time and on ultra-small spatial scales. This offers the possibility to control the response of a material on a spatial scale less than a nanometer—crucial for the next generation of nano-devices. Here we create craters on the surface of a silicon substrate by focusing single femtosecond extreme ultraviolet pulse from the SACLA free-electron laser. We investigate the resulting surface modification in the vicinity of damage thresholds, establishing a connection to microscopic theoretical approaches, and, with their help, illustrating physical mechanisms for damage creation. The cooling during ablation by means of rapid electron and energy transport can suppress undesired hydrodynamical motions, allowing the silicon material to be directly processed with a precision reaching the observable limitation of an atomic force microscope.
关键词： nanometer precision,ablation,extreme ultraviolet,femtosecond,silicon,free-electron laser
更新于2025-09-11 14:15:04