Record high extraction efficiency of free electron laser oscillator

共振器型自由電子レーザの世界最高変換効率を達成 --長波長赤外での強光子場の実現とアト秒X線源の開発に大きく前進--. 京都大学プレスリリース. 2020-10-13.The highest extraction efficiency (9.4%) of a free electron laser (FEL) oscillator has been achieved at the midinfrared FEL facility of Kyoto University. Because of the interaction between the electron beam and FEL electromagnetic field, a maximum electron energy decrease of 16% was observed. The measured energy decrease was consistent with the measured FEL spectrum. An FEL micropulse energy of ~100 μJ with the expected few-cycle pulse duration at a wavelength of 11 μm was observed. This result is an important milestone for the high-extraction-efficiency FEL oscillator and will contribute to the strong-field physics of atoms and molecules

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

The detailed structure of few-cycle superradiant pulses generated from a free-electron laser (FEL) oscillator was experimentally revealed for the first time. As predicted in numerical simulations, the obtained pulse structures have ringing, i.e., a train of subpulses following the main pulse. Owing to the phase retrieval with a combination of linear and nonlinear autocorrelation measurements, the temporal phase was also obtained with the pulse shape, and $\pi$-phase jumps between each pulse were confirmed. This particular pulse shape with $\pi$-phase jumps is a common feature of Burnham-Chiao ringing or superradiance ringing. Using unaveraged FEL simulations, the ringing was found to originate from repeated formation and deformation of microbunches across successive bunch slices. The simulation results imply that there should be superluminal propagation of the FEL pulse due to strong gain modulation along the undulator of the FEL oscillator.Comment: Main: 16 pages, 5 figures, Supplementary material: 10 pages, 10 figures, 1 vide

Generation of primary photons through inverse Compton scattering using a Monte Carlo simulation code

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Overview of the development program

ニュースバル放射光施設において開催される核セキュリティワークショップにおいて、核セキュリティ補助金事業で実施した研究開発プログラムの概要について報告する。Workshop on demonstration of nuclear resonance fluorescence technique for detection of nuclear material hidden in a shiel

High-Repetition-Rate High-Harmonic Generation Driven by Infrared Free-Electron Lasers

We present a scheme 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