arXiv subjects

Naoto Yamamoto

Publications and source records attributed to Naoto Yamamoto.

4 recordsLinked to original sources

arXiv2021

Bulk-Sensitive Spin-Resolved Resonant Electron Energy-Loss Spectroscopy (SR-rEELS): Observation of Element- and Spin-Selective Bulk Plasmons

We have developed a spin-resolved resonant electron energy-loss spectroscopy (SR-rEELS) in the primary energy of 0.3--1.5 keV, which corresponds to the core excitations of $2p$-$3d$ absorption of transition metals and $3d$-$4f$ absorption of rare-earths, with the energy resolution of about 100~meV using a spin-polarized electron source as a GaAs/GaAsP strained superlattice photocathode. Element- and spin-selective carrier and valence plasmons can be observed using the resonance enhancement of core absorptions and electron spin polarization. Furthermore, bulk-sensitive EELS spectra can be obtained because the primary energy corresponds to the mean free path of 1--10~nm. The methodology is expected to provide us novel information of elementary excitations by resonant inelastic x-ray scattering and resonant photoelectron spectroscopy.

physics.ins-det↗

arXiv2019

High-efficiency broadband THz emission via diffraction-radiation cavity

Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broadband source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme of coherent diffraction-radiation in an optical cavity layout is proposed. The scheme's stimulated radiation process between bunches can greatly enhance the efficiency of the radiation emission. We performed an experiment with a superconducting linac constructed as an energy recovery linac (ERL) test facility. The electron beam passes through small holes in the cavity mirrors without being destroyed. A sharp THz resonance signal, which indicates broadband stimulated radiation correlated with beam deceleration, was observed while scanning the round-trip length of the cavity. This observation proves the efficient beam-to-radiation energy conversion due to the stimulated radiation process.

physics.acc-ph↗

arXiv2018

Stimulated excitation of an optical cavity by a multi-bunch electron beam via coherent diffraction radiation process

With a low emittance and short-bunch electron beam at a high repetition rate realized by a superconducting linac, stimulated excitation of an optical cavity at the terahertz spectrum range has been shown. The electron beam passed through small holes in the cavity mirrors without being destroyed. A sharp resonance structure which indicated wide-band stimulated emission via coherent diffraction radiation was observed while scanning the round-trip length of the cavity.

physics.acc-ph↗

arXiv2015

Present status of source development station at UVSOR-III

Construction and development of a source development station are in progress at UVSOR-III, a 750 MeV electron storage ring. It is equipped with an optical klystron type undulator system, a mode lock Ti:Sa Laser system, a dedicated beam-line for visible-VUV radiation and a parasitic beam-line for THz radiation. New light port to extract edge radiation was constructed recently. An optical cavity for a resonator free electron laser is currently being reconstructed. Some experiments such as coherent THz radiation, coherent harmonic radiation, laser Compton Scattering gamma-rays and optical vortices are in progress.

physics.acc-ph↗