- 标题
- 摘要
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- 实验方案
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Wavelet Analysis and Decomposition Into Color Spaces in Researching of Human Fluorescently Labeled Images Tissues
摘要： At the Linac Coherent Light Source (LCLS) X-ray free-electron laser, a laser “heater” is used to generate an uncorrelated 20-keV energy spread on an electron beam to suppress the microbunching instability in downstream bunch compressors. Here we describe an alternative approach using emittance partitioning, where the increase in energy spread is generated by moving phase space volume from the transverse dimensions into the longitudinal dimension. For LCLS-relevant beam parameters, about a factor of six reduction in the product of both transverse emittances is feasible with the same amount of induced energy spread, with additional improvements possible with an optimized setup.
关键词： particle accelerators,electron beams,free-electron lasers,Electron accelerators
更新于2025-09-23 15:21:01
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Structural dynamics in proteins induced by and probed with X-ray free-electron laser pulses
摘要： X-ray free-electron lasers (XFELs) enable crystallographic structure determination beyond the limitations imposed upon synchrotron measurements by radiation damage. The need for very short XFEL pulses is relieved through gating of Bragg diffraction by loss of crystalline order as damage progresses, but not if ionization events are spatially non-uniform due to underlying elemental distributions, as in biological samples. Indeed, correlated movements of iron and sulfur ions were observed in XFEL-irradiated ferredoxin microcrystals using unusually long pulses of 80 fs. Here, we report a femtosecond time-resolved X-ray pump/X-ray probe experiment on protein nanocrystals. We observe changes in the protein backbone and aromatic residues as well as disulfide bridges. Simulations show that the latter’s correlated structural dynamics are much slower than expected for the predicted high atomic charge states due to significant impact of ion caging and plasma electron screening. This indicates that dense-environment effects can strongly affect local radiation damage-induced structural dynamics.
关键词： plasma electron screening,radiation damage,ion caging,structural dynamics,protein nanocrystals,X-ray free-electron lasers
更新于2025-09-23 15:21:01
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Laguerre-Gaussian Mode Laser Heater for Microbunching Instability Suppression in Free-Electron Lasers
摘要： Microbunching instability (MBI) driven by beam collective effects is known to be detrimental to high-brightness storage rings, linacs, and free-electron lasers (FELs). One known way to suppress this instability is to induce a small amount of energy spread to an electron beam by a laser heater. The distribution of the induced energy spread greatly affects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. Here, we present the first experimental demonstration of effective MBI suppression using a LG01 transverse laser mode and compare the improved results with respect to traditional Gaussian transverse laser mode at the Linac Coherent Light Source. The effects on MBI suppression are characterized by multiple downstream measurements, including longitudinal phase space analysis and coherent radiation spectroscopy. We also discuss the role of LG01 shaping in soft x-ray self-seeded FEL emission, one of the most advanced operation modes of a FEL for which controlled suppression of MBI is critical.
关键词： Free-electron lasers,Microbunching instability,LG01 mode,Laser heater,Soft x-ray self-seeded FEL,Gaussian mode,MBI suppression
更新于2025-09-23 15:21:01
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Angular dispersion enhanced prebunch for seeding ultrashort and coherent EUV and soft X-ray free-electron laser in storage rings
摘要： 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 femtosecond generation of 100 MW scale level, fully temporal coherent extreme-ultraviolet and soft X-ray radiation pulses through a 10 m-long undulator based on a diffraction-limited storage ring.
关键词： angular dispersion,free-electron lasers,prebunching,storage rings,high-harmonic bunching,radiation saturation length,ultrashort,extreme-ultraviolet (EUV)
更新于2025-09-23 15:21:01
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Pumping Systems for Compton Free-Electron Lasers: Microwave Undulators and Powering Sources
摘要： The concept of Compton-type free-electron lasers (FELs) operating in short wavelength ranges with a high e?ciency and power level is currently underway at the IAP RAS (Nizhny Novgorod). This concept is aimed at reducing the energy of a driving relativistic electron beam and thereby increasing the e?ciency of the electron–wave interaction in FELs, as well as making the oscillator relatively compact. The basis of this concept is microwave undulators of a new type — the so-called “?ying” undulators. This paper is devoted to the results of the current studies of these undulators, their simulation, and “cold” electrodynamic tests in the Ka band. For powering microwave undulators, a spatially extended narrow-band ˇCerenkov surface-wave oscillators (SWOs) are developed in the speci?ed frequency range driven by Sinus-6, a high-current accelerator, with a particle energy of 0.5 MeV, a current of 5 kA, and a pulse duration of 25 ns. The required sub-gigawatt power level of output radiation combined with a high stability of the narrow-band oscillation regime is achieved under conditions of a strongly oversized oscillator by using two-dimensional distributed feedback provided in a 2D doubly-periodic slow-wave structure. The design parameters of a 32 GHz/0.5 GW SWO intended for powering microwave undulators are presented and the results of its simulation and reported.
关键词： flying undulators,Ka band,Cerenkov surface-wave oscillators,Sinus-6 accelerator,microwave undulators,Compton-type free-electron lasers
更新于2025-09-23 15:21:01
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Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay
摘要： the ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (feL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray feL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly fourier transform limited pulses.
关键词： spatial coherence,split-and-delay optics,speckle contrast,temporal coherence,X-ray Free Electron Lasers
更新于2025-09-23 15:19:57
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The TeraFERMI Electro-Optic Sampling Set-Up for Fluence-Dependent Spectroscopic Measurements
摘要： TeraFERMI is the THz beamline at the FERMI free-electron-laser facility in Trieste (Italy). It uses superradiant Coherent Transition Radiation emission to produce THz pulses of 10 to 100 μJ intensity over a spectral range which can extend up to 12 THz. TeraFERMI can be used to perform non-linear, ?uence-dependent THz spectroscopy and THz-pump/IR-probe measurements. We describe in this paper the optical set-up based on electro-optic-sampling, which is presently in use in our facility and discuss the properties of a representative THz electric ?eld pro?le measured from our source. The measured electric ?eld pro?le can be understood as the superimposed emission from two electron bunches of different length, as predicted by electron beam dynamics simulations.
关键词： THz spectroscopy,free-electron-lasers,nonlinear optics
更新于2025-09-23 15:19:57
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Topological edge state laser using a photonic crystal nanocavity array
摘要： In next-generation light sources, high-brightness electron beams are used in a free-electron laser configuration to produce light for use by scientists and engineers in numerous fields of research. High-brightness beams are described for such light sources as having low transverse and longitudinal emittances, high peak currents, and low slice emittance and energy spread. The optimal generation and preservation of such high-brightness electron beams during the acceleration process and propagation to and through the photon-producing element is imperative to the quality and performance of the light source. To understand the electron beam’s phase space in the accelerating section of a next-generation light source machine, we employed radio-frequency cavities operating in a deflecting mode in conjunction with a magnetic spectrometer and imaging system for both low (250 MeV) and high (1.2 GeV) electron energies. This high-resolution, high-energy system is an essential diagnostic for the optimization and control of the electron beam in the FERMI light source generating fully transversely and longitudinally coherent light in the VUV to soft x-ray wavelength regimes. This device is located at the end of the linear accelerator in order to provide the longitudinal phase space nearest to the entrance of the photon-producing beam-lines. Here, we describe the design, fabrication, characterization, commissioning, and operational implementation of this transverse deflecting cavity structure diagnostic system for the high-energy (1.2 GeV) regime.
关键词： electron beam deflection,free-electron lasers,particle beam measurements,Electron accelerators
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - High-Frequency Modulated Photoluminescence: a simulation study of cases describing the signature of carrier recombination and trap centers
摘要： At the Linac Coherent Light Source (LCLS) X-ray free-electron laser, a laser “heater” is used to generate an uncorrelated 20-keV energy spread on an electron beam to suppress the microbunching instability in downstream bunch compressors. Here we describe an alternative approach using emittance partitioning, where the increase in energy spread is generated by moving phase space volume from the transverse dimensions into the longitudinal dimension. For LCLS-relevant beam parameters, about a factor of six reduction in the product of both transverse emittances is feasible with the same amount of induced energy spread, with additional improvements possible with an optimized setup.
关键词： particle accelerators,electron beams,free-electron lasers,Electron accelerators
更新于2025-09-19 17:13:59
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Compact low-pass/band-pass filters based on quarter-mode substrate integrated waveguide and a connected network of CSRRs
摘要： At the Linac Coherent Light Source (LCLS) X-ray free-electron laser, a laser “heater” is used to generate an uncorrelated 20-keV energy spread on an electron beam to suppress the microbunching instability in downstream bunch compressors. Here we describe an alternative approach using emittance partitioning, where the increase in energy spread is generated by moving phase space volume from the transverse dimensions into the longitudinal dimension. For LCLS-relevant beam parameters, about a factor of six reduction in the product of both transverse emittances is feasible with the same amount of induced energy spread, with additional improvements possible with an optimized setup.
关键词： free-electron lasers,electron beams,particle accelerators,Electron accelerators
更新于2025-09-19 17:13:59