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Electron Beam Brightness and Undulator Radiation Brilliance for a Laser Plasma Acceleration Based Free Electron Laser
摘要： We report here on spontaneous undulator radiation and free electron laser calculations after a 10-m long transport line (COXINEL) using a Laser Plasma acceleration (LPA) source. The line enables the manipulation of the properties of the produced electron beams (energy spread, divergence, dispersion) in view of light source applications. The electron beam brightness and undulator radiation brilliance are addressed by an analytical approach enabling us to point out the influence of chromatic effects in the COXINEL case.
关键词： undulator radiation,free electron laser,electron beam brightness,laser plasma acceleration
更新于2025-09-23 15:19:57
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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) - Formation of Space Charge Wave with Wide Frequency Spectrum in Helical Electron Beam of Two-Stream FEL Transit Section with Longitudinal Electric Field
摘要： The longitudinal electric field effect on the formation of a space charge wave (SCW) with wide frequency spectrum in the helical two-stream relativistic electron beam (REB), which moves in transit section of multiharmonic two-stream superheterodyne free-electron laser, is analyzed. In the framework of cubic nonlinear approximation, it is shown that the use of the accelerating electric field makes it possible to increase the multiharmonic SCW width of the frequency spectrum. It is shown that the retarding electric field causes the increase of the amplitude level SCW harmonics, as well as the decrease of its saturation length.
关键词： three-wave parametric resonance,helical electron beam,two-stream instability,two-stream superheterodyne free-electron laser,longitudinal electric field
更新于2025-09-23 15:19:57
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Extremely high-intensity operation of a THz free-electron laser using an electron beam with a higher bunch charge
摘要： A higher intensity THz beam is generated with a free-electron laser (FEL) based on the L-band (1.3 GHz) electron linac at Osaka University by increasing the electron bunch charge four times higher from 1 nC in the conventional mode (the 108 MHz mode) to 4 nC in the new mode (the 27 MHz mode). This is realized by expanding the electron bunch intervals four times longer with the grid pulser of the electron gun, generating a series of 5 ns pulses at a repetition frequency of 27 MHz (the 48th subharmonic of 1.3 GHz), whereas the beam loading of the linac remains unchanged. The energy of an FEL macropulse comprised of many micropulses is measured in the 27 MHz mode to be approximately 28.5 mJ at a maximum of around 65 μm or 4.6 THz compared with the maximum macropulse energy of 13 mJ in the 108 MHz mode. The maximum micropulse energy in the 27 MHz mode is approximately 260 μJ using 110 micropulses, which is estimated by a macropulse duration of 4 μs and micropulse intervals of 36.9 ns. The micropulse energy is nearly 10 times higher than the micropulse energies in the conventional mode and in other FELs in the same wavelength or frequency region.
关键词： Free-electron laser (FEL),Terahertz (THz),Electron beam,High charge
更新于2025-09-23 15:19:57
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Free Electron Laser Performance within the EuPRAXIA Facility
摘要： Over the past 90 years, particle accelerators have evolved into powerful and widely used tools for basic research, industry, medicine, and science. A new type of accelerator that uses plasma wakefields promises gradients as high as some tens of billions of electron volts per meter. This would allow much smaller accelerators that could be used for a wide range of fundamental and applied research applications. One of the target applications is a plasma-driven free-electron laser (FEL), aiming at producing tunable coherent light using electrons traveling in the periodic magnetic field of an undulator. In this work, the plasma-based electron beams with the most promising qualities, designed in the framework of EuPRAXIA, are analyzed in terms of the FEL performance.
关键词： free-electron laser,undulator magnet,laser–plasma accelerator
更新于2025-09-23 15:19:57
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Ghost imaging at an XUV free-electron laser
摘要： Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a moving diffuser, which created a noncorrelated speckled beam. This beam was then split in two identical branches by introducing a beam splitter in the form of a transmission grating. In one of these branches the sample was positioned. We demonstrate the possibility of image formation, a double bar in our case, in the beam that has never interacted with the sample. With this experiment we extend the quantum optics methodology to the FEL community.
关键词： XUV free-electron laser,speckle pattern,quantum optics,ghost imaging,transmission grating
更新于2025-09-23 15:19:57
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Demonstration of Large Bandwidth Hard X-Ray Free-Electron Laser Pulses at SwissFEL
摘要： We have produced hard x-ray free-electron laser (FEL) radiation with unprecedented large bandwidth tunable up to 2%. The experiments have been carried out at SwissFEL, the x-ray FEL facility at the Paul Scherrer Institute in Switzerland. The bandwidth is enhanced by maximizing the energy chirp of the electron beam, which is accomplished by optimizing the compression setup. We demonstrate continuous tunability of the bandwidth with a simple method only requiring a quadrupole magnet. The generation of such broadband FEL pulses will improve the efficiency of many techniques such as x-ray crystallography and spectroscopy, opening the door to significant progress in photon science. It has already been demonstrated that the broadband pulses of SwissFEL are beneficial to enhance the performance of crystallography, and further SwissFEL users plan to exploit this large bandwidth radiation to improve the efficiency of their measurement techniques.
关键词： large bandwidth,SwissFEL,free-electron laser,spectroscopy,hard x-ray,x-ray crystallography
更新于2025-09-23 15:19:57
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Infrared + vacuum ultraviolet two-color ionization spectroscopy of neutral metal complexes based on a tunable vacuum ultraviolet free-electron laser
摘要： This paper describes an experimental technique for studying neutral metal complexes using infrared + vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy based on a tunable VUV free-electron laser (VUV-FEL). The preliminary IR spectroscopy results of mass-selected nickel tetracarbonyl are reported in this work. The results demonstrate that the tunable VUV-FEL light allows the selective ionization of a given neutral cluster free of confinement along with the recording of well-resolved IR spectra. As the ionization energies of many neutral clusters are accessible by a broadly tunable VUV-FEL (50–150 nm) and near-threshold ionization can be readily achieved, the proposed experimental method offers unique possibilities for the size-specific study of a wide variety of confinement-free neutral clusters.
关键词： infrared,vacuum ultraviolet,tunable VUV free-electron laser,two-color ionization spectroscopy,neutral metal complexes
更新于2025-09-23 15:19:57
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Some analyses on optimal energy-extraction efficiency in a free-electron laser
摘要： In this paper, the energy-extraction efficiencies of the electron beam are studied for several cases of free-electron laser (FEL). For an initially cold electron beam, the optimal initial detuning for the maximum energy-extraction efficiency and the corresponding saturation length are given. A scheme of the ‘top up’ is proposed to enhance the efficiency: after the electron energy being modulated somewhat, a phase shift and a step-down of the phase bucket are introduced, so that all electrons are located near the upper separatrix of the bucket in the phase space. Finally, the energy-extraction efficiency can be increased by 30% compared with that of the normal undulator case. For a linear tapering undulator with an initially cold electron beam, the simple scaling laws for the maximum energy-extraction efficiency and the corresponding optical power gain are obtained. For a tapered undulator with the pre-bunched electron beam, our analysis gives that the energy-extraction efficiency reaches the maximum when the phase bucket height of the tapered undulator is equal to the amplitude of the detuning modulation. The numerical results validated this reasoning and show that the efficiency has a large increase compared with the case of the unbunched electron beam. The single stair-step undulator is investigated, the optimal step and the corresponding saturation power and saturation length are given by analysis, they agree well with the numerical simulation results.
关键词： pre-bunched,tapered undulator,free-electron laser,energy-extraction efficiency
更新于2025-09-23 15:19:57
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Bayesian Optimization of a Free-Electron Laser
摘要： The Linac coherent light source x-ray free-electron laser is a complex scientific apparatus which changes configurations multiple times per day, necessitating fast tuning strategies to reduce setup time for successive experiments. To this end, we employ a Bayesian approach to maximizing x-ray laser pulse energy by controlling groups of quadrupole magnets. A Gaussian process model provides probabilistic predictions for the machine response with respect to control parameters, enabling a balance of exploration and exploitation in the search for the global optimum. We show that the model parameters can be learned from archived scans, and correlations between devices can be extracted from the beam transport. The result is a sample-efficient optimization routine, combining both historical data and knowledge of accelerator physics to significantly outperform existing optimizers.
关键词： Bayesian optimization,accelerator physics,free-electron laser,Gaussian process
更新于2025-09-23 15:19:57
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Water-Window X-Ray Pulses from a Laser-Plasma Driven Undulator
摘要： Femtosecond (fs) x-ray pulses are a key tool to study the structure and dynamics of matter on its natural length and time scale. To complement radio-frequency accelerator-based large-scale facilities, novel laser-based mechanisms hold promise for compact laboratory-scale x-ray sources. Laser-plasma driven undulator radiation in particular offers high peak-brightness, optically synchronized few-fs pulses reaching into the few-nanometer (nm) regime. To date, however, few experiments have successfully demonstrated plasma-driven undulator radiation. Those that have, typically operated at single and comparably long wavelengths. Here we demonstrate plasma-driven undulator radiation with octave-spanning tuneability at discrete wavelengths reaching from 13 nm to 4 nm. Studying spontaneous undulator radiation is an important step towards a plasma-driven free-electron laser. Our specific setup creates a photon pulse, which closely resembles the plasma electron bunch length and charge profile and thus might enable novel methods to characterize the longitudinal electron phase space.
关键词： femtosecond x-ray pulses,electron beam diagnostics,water-window x-ray,laser-plasma driven undulator radiation,free-electron laser
更新于2025-09-19 17:13:59