Full characterization of superradiant pulses generated from a free-electron laser oscillator

Zen, Heishun; Hajima, Ryoichi; Ohgaki, Hideaki

doi:10.1038/s41598-023-33550-z

Cited by 12 publications

(3 citation statements)

References 52 publications

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“…This upgrade enabled an increase in the extraction efficiency of KU-FEL from 5.5% to 9.4%, which is a record-high extraction efficiency [12]. Under the photocathode operation of the 4.5-cell RF gun, it was confirmed that the FEL micro-pulse energy and duration were ~100 µJ [12] and 150 fs (4.2 cycles at 10.7 µm), respectively [13]. The other upgrade was the introduction of a new photocathode RF gun dedicated to the generation of electron beams, with a bunch charge of 1 nC or even higher because of the available electron-bunch charge of the 4.5-cell RF gun being limited to ~200 pC due to the small cathode size (2 mm in diameter), the small inter-cavity irises (8 mm in diameter), the low on-cathode electric field (<30 MV/m), and the absence of a focusing solenoid.…”

Section: Introductionmentioning

confidence: 88%

The Particle-Tracking Simulation of a New Photocathode RF Gun in the Free-Electron Laser Facility, KU-FEL

2023

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A project is underway that aims to generate attosecond pulses via high-harmonic generation in rare gases, driven by extremely short and highly intense pulses from free-electron-laser oscillators. For this purpose, it has been planned that a new photocathode RF gun, dedicated to high-bunch-charge operation, will be installed at the KU-FEL (Kyoto University Free Electron Laser) oscillator facility. In this study, RF guns with two different structures (1.6-cell and 1.4-cell) were compared, from the perspective of exploring the possibility of introducing bunch-interval modulation, which is important for achieving high extraction efficiency in the FEL oscillator. As a result, it was confirmed that the introduction of bunch-phase modulation would be possible only in the case of the 1.6-cell RF gun. After the structure of the RF gun was decided on, particle-tracking simulations were performed, to study the electron-beam parameters using the 1.6-cell RF gun and 1 nC bunch charge. The results showed that we could obtain the peak current of 1 kA without a large degradation of the other parameters.

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Section: Introductionmentioning

confidence: 88%

The Particle-Tracking Simulation of a New Photocathode RF Gun in the Free-Electron Laser Facility, KU-FEL

2023

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“…Consequently, the pulse duration was evaluated as 150 fs, corresponding to 4.2 optical field cycles. 19) The LEBRA FEL is an IR light source covering wavelengths from 1 to 6 μm. [20][21][22] This range overlaps well with the solid-state lasers widely used for HHG investigations.…”

Section: Introductionmentioning

confidence: 99%

“…Interferometric first-order and SHG simultaneous autocorrelation measurements are valuable because they allow the reconstruction of a pulse shape by retrieving the spectral phase information. 19,25,26) However, it is sensitive to the alignment accuracy of the optical system and takes much effort and time to adjust. Furthermore, the step size of the optical delay scanning of interferometric measurements should be one-tenth of the fundamental wavelength.…”

Section: Introductionmentioning

confidence: 99%

Beam characterization of mid-infrared free electron laser to drive high-harmonic generation

Kawase,

Zen,

Sakai

et al. 2024

Jpn. J. Appl. Phys.

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The maximum energy of photons from high-harmonic generation (HHG) increases with the wavelength of the driving laser. A free electron laser (FEL) is a continuously tunable light source in the mid-infrared wavelength range and it is useful for investigating the extension of the accessible photon energy in HHG. Recently, the undulator magnets of the infrared FEL at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University, have been replaced, and then the output power of the FEL has increased. Here, we evaluate the pulse duration and focal beam size of the FEL and show that the LEBRA FEL with 2-μm and 3-μm laser wavelengths under a 44-MHz bunch repetition mode can drive HHG.

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Investigating structural property of human hair by using infrared free electron lasers

Kawasaki,

Nagase,

Hayakawa

et al. 2024

Discov Appl Sci

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Intense infrared (IR) rays can heat matters and evaporate waters thermally. One of the possible applications will be hair dryer, although the irradiation effects of IR rays on the hair have not been fully explored. In this study, we first examined the interaction of IR rays at various wavelengths from 3.0 µm (near IR) to 90 µm (far IR) with the surface structure of human hair by using IR free electron lasers (FELs). IR-FEL is an accelerator-based pico-second pulse laser, and the feature is the wavelength-tunability with the high-photon density. When one thread of hair was irradiated by the FEL of 6–7 mJ energy at 60 µm, the cleavage occurred, and the morphological destruction was observed on scanning-electron microscopy images after the irradiations at 70 µm and 6.1 µm (amide I). Synchrotron-radiation infrared microspectroscopy showed that those FEL irradiations decreased a shoulder band at 1710 cm−1 that corresponds to carboxyl group in melanin or fatty acids and increased absorption intensity at 500–600 cm−1. On the contrary, the FEL at 90 µm little changed either the surface morphology or the infrared absorption spectra. Interestingly, near-IR FELs at 3.0–3.5 µm induced bending of a hair, and 2D mapping of protein secondary conformations revealed that β-sheet was more increased than the other conformations on the surface of the bending area even at low pulse energy (1–3 mJ). As a result, the structural damage of the hair was least at 90 µm, which implies an ideal wavelength for drying hair mildly.

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Full characterization of superradiant pulses generated from a free-electron laser oscillator

Cited by 12 publications

References 52 publications

The Particle-Tracking Simulation of a New Photocathode RF Gun in the Free-Electron Laser Facility, KU-FEL

The Particle-Tracking Simulation of a New Photocathode RF Gun in the Free-Electron Laser Facility, KU-FEL

Beam characterization of mid-infrared free electron laser to drive high-harmonic generation

Investigating structural property of human hair by using infrared free electron lasers

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