Naoyasu Hosoda

Bio: Naoyasu Hosoda is an academic researcher. The author has contributed to research in topics: SACLA & Free-electron laser. The author has an hindex of 9, co-authored 27 publications receiving 1826 citations.

A compact X-ray free-electron laser emitting in the sub-ångström region

Abstract: Researchers report sub-angstrom fundamental-wavelength lasing at the SPring-8 Angstrom Compact Free-Electron Laser in Japan. The output has a maximum power of more than 10 GW, a pulse duration of 10−14 s and a lasing wavelength of 0.634 A.

A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region

Abstract: Single-pass free-electron lasers based on self-amplified spontaneous emission1,2,3,4 are enabling the generation of laser light at ever shorter wavelengths, including extreme ultraviolet5, soft X-rays and even hard X-rays6,7,8. A typical X-ray free-electron laser is a few kilometres in length and requires an electron-beam energy higher than 10 GeV (refs 6, 8). If such light sources are to become accessible to more researchers, a significant reduction in scale is desirable Here, we report observations of brilliant extreme-ultraviolet radiation from a 55-m-long compact self-amplified spontaneous-emission source, which combines short-period undulators with a high-quality electron source operating at a low acceleration energy of 250 MeV. The radiation power reaches saturation at wavelengths ranging from 51 to 61 nm with a maximum pulse energy of 30 µJ. The ultralow emittance (0.6π mm mrad) of the electron beam from a CeB6 thermionic cathode9 is barely degraded by a multiple-stage bunch compression system that dramatically enhances the beam current from 1 to 300 A. This achievement expands the potential for generating X-ray free-electron laser radiation with a compact 2-GeV machine. Free-electron lasers can produce powerful pulses of radiation at very short wavelengths, even in the hard-X-ray region. In general, however, they comprise facilities several kilometres in length. A 55-m-long laser could open up the technology to a broader range of researchers.

Stable operation of a self-amplified spontaneous-emission free-electron laser in the extremely ultraviolet region

Abstract: We achieved stable operation of a free-electron laser (FEL) based on the self-amplified spontaneous-emission (SASE) scheme at the SPring-8 Compact SASE Source (SCSS) test accelerator in the extremely ultraviolet region. Saturation of the SASE FEL power has been achieved at wavelengths ranging from 50 to 60 nm. The pulse energy has reached $\ensuremath{\sim}30\text{ }\text{ }\ensuremath{\mu}\mathrm{J}$ at 60 nm. The observed fluctuation of the pulse energy is about 10% (standard deviation) for several hours, which agrees with the expectation from the SASE theory showing the stable operation of the accelerator. The SASE FEL has been routinely operated to provide photon beams for user experiments over a period of a few weeks. Analysis on the experimental data gave the normalized-slice emittance at the lasing part is around $0.7\ensuremath{\pi}\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$. This result indicates that the normalized-slice emittance of the initial electron beam, $0.6\ensuremath{\pi}\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ in a 90% core part, is kept almost unchanged after the bunch compression process with a compression factor of approximately 300. The success of the SCSS test accelerator strongly encourages the realization of a compact XFEL source.

High-energy electron irradiation of NdFeB permanent magnets: Dependence of radiation damage on the electron energy

Abstract: High-energy electron-beam bombardment of Nd 2 Fe 14 B-type permanent magnets induces radiation damage characterized by a drop in the magnetic field. Experiments carried out at the SPring-8 booster synchrotron, with 4, 6, and 8 GeV electrons, show that the drop in magnetic field is energy dependent. Electromagnetic shower simulations suggest that most of the radiation damage happens in a small region around the irradiation axis, and that the contribution of neutrons with large scattering angles or with low energies to the magnetic field change is small.

Timing and llrf system of japanese xfel to realize femto-second stability

Abstract: FEMTO-SECOND STABILITY Yuji Otake, Takashi Ohshima, Naoyasu Hosoda, Hirokazu Maesaka, Toru Fukui , Toru Ohata B) Mitsuru Musha, Kenji Tamasaku , Masanobu Kitamura , Kazuhiro Imai, Motonobu Kourogi , Tumoru Shintake A) A) RIKEN, XFEL Joint Project /SPring-8 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan B) JASRI, XFEL Joint Project /SPring-8 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan C) Institute of Laser Science, Univ. of Electro-communications 1-5-1 Chofugaoka, Chofu-shi, Tokyo, 182-8585, Japan D)Optical Comb Inc. 4259-3 Nagatuda-cho, Midoriku-ku, Yokohama-shi, Kanagawa, 226-8510, Japan Abstract At SPring-8, the construction of a 5712 MHz linac and undulators for XFEL is in progress. There are mainly three parts of the linac in accordance with requirements of time accuracy. One is a master signal source part. The noise level of this part affects the phase and amplitude jitter of all rf components of the linac. The next is the crest acceleration part of a sinusoidal wave. The other is an off-crest part that corresponds to a beam bunchcompressing part. To generate a stable SASE, a beam energy stability of 10 is required. To obtain this stability, an accuracy of sub-pico-seconds is required in the crest part, and several ten femto-seconds are necessary in the off-crest part. The system based on IQ control technology used in the SCSS prototype accelerator is employed to obtain sub-pico-second accuracy. An optical signal distribution system using an optical comb generator that could realize a several ten femto-second accuracy is also employed. Test results of the above-mentioned systems showed that there is big possibility to realize femtosecond time accuracy for the XFEL.

First lasing and operation of an ångstrom-wavelength free-electron laser

Abstract: The Linac Coherent Light Source free-electron laser has now achieved coherent X-ray generation down to a wavelength of 1.2 A and at a brightness that is nearly ten orders of magnitude higher than conventional synchrotrons. Researchers detail the first operation and beam characteristics of the system, which give hope for imaging at atomic spatial and temporal scales.

A compact X-ray free-electron laser emitting in the sub-ångström region

Abstract: Researchers report sub-angstrom fundamental-wavelength lasing at the SPring-8 Angstrom Compact Free-Electron Laser in Japan. The output has a maximum power of more than 10 GW, a pulse duration of 10−14 s and a lasing wavelength of 0.634 A.

Theory and Design of Charged Particle Beams

Abstract: Review of Charged Particle Dynamics. Beam Optics and Focusing Systems Without Space Charge. Linear Beam Optics with Space Charge. Self-Consistent Theory of Beams. Emittance Variation. Beam Physics Research from 1993 to 2007. Appendices. List of Frequently Used Symbols. Bibliography. Index.

Phase Retrieval with Application to Optical Imaging: A contemporary overview

Abstract: i»?The problem of phase retrieval, i.e., the recovery of a function given the magnitude of its Fourier transform, arises in various fields of science and engineering, including electron microscopy, crystallography, astronomy, and optical imaging. Exploring phase retrieval in optical settings, specifically when the light originates from a laser, is natural since optical detection devices [e.g., charge-coupled device (CCD) cameras, photosensitive films, and the human eye] cannot measure the phase of a light wave. This is because, generally, optical measurement devices that rely on converting photons to electrons (current) do not allow for direct recording of the phase: the electromagnetic field oscillates at rates of ~1015 Hz, which no electronic measurement device can follow. Indeed, optical measurement/detection systems measure the photon flux, which is proportional to the magnitude squared of the field, not the phase. Consequently, measuring the phase of optical waves (electromagnetic fields oscillating at 1015 Hz and higher) involves additional complexity, typically by requiring interference with another known field, in the process of holography.

Highly coherent and stable pulses from the FERMI seeded free-electron laser in the extreme ultraviolet

Abstract: Researchers demonstrate the FERMI free-electron laser operating in the high-gain harmonic generation regime, allowing high stability, transverse and longitudinal coherence and polarization control.