Showing papers by "Shoji Yamamoto published in 2010"
TL;DR: Reversed-shear Alfvén eigenmodes were observed for the first time in a helical plasma having negative q₀'' (the curvature of the safety factor q at the zero shear layer).
Abstract: Reversed-shear Alfven eigenmodes were observed for the first time in a helical plasma having negative q{sub 0}{sup ''} (the curvature of the safety factor q at the zero shear layer). The frequency is swept downward and upward sequentially via the time variation in the maximum of q. The eigenmodes calculated by ideal MHD theory are consistent with the experimental data. The frequency sweeping is mainly determined by the effects of energetic ions and the bulk pressure gradient. Coupling of reversed-shear Alfven eigenmodes with energetic ion driven geodesic acoustic modes generates a multitude of frequency-sweeping modes.
44 citations
TL;DR: Several types of diagnostic system for soft X-ray radiation (SXR) have been developed and installed on the Large Helical Device (LHD). Magnetohydrodynamic (MHD) activities are studied by the fluctu...
Abstract: Several types of diagnostic system for soft X-ray radiation (SXR) have been developed and installed on the Large Helical Device (LHD). Magnetohydrodynamic (MHD) activities are studied by the fluctu...
13 citations
TL;DR: In this paper, a Peierls-Hubbard Hamiltonian-based model of a halogen-bridged transition-metal complex within a nanotube was proposed and characterized in terms of a triangular prism.
Abstract: Motivated by recent chemical attempts at assembling halogen-bridged transition-metal complexes within a nanotube, we model and characterize a platinum-halide triangular prism in terms of a Peierls– Hubbard Hamiltonian. Based on a group-theoretical argument, we reveal a variety of valence arrangements, including heterogeneous or partially metallic charge-density-wave states. Quantum and thermal phase competitions are numerically demonstrated with particular emphasis on novel insulator-tometal and insulator-to-insulator transitions under doping, the former of which is of the first order, while the latter of which is of the second order.
7 citations
TL;DR: A diagnostic of alpha particle loss, so-called alpha particle induced gamma ray spectroscopy, is proposed and carried out by the use of the Ce doped Lu(2)SiO(5) scintillator detector and an Am-Be source to detect the 4.44 MeV high energy gamma ray due to the (9)Be(α,nγ)(12)C reaction.
Abstract: We developed a lost alpha detection system to use in burning plasma experiments. The scintillators of Ag:ZnS and polycrystalline Ce:YAG were designed for a high-temperature environment, and the optical transmission line was designed to transmit from the scintillator to the port plug. The required optical components of lenses and mirrors were irradiated using the fission reactor with the initial result that there was no clear change after the irradiation with a neutron flux of 9.6×1017 nm−2 s−1 for 48 h. We propose a diagnostic of alpha particle loss, so-called alpha particle induced gamma ray spectroscopy. The initial laboratory test has been carried out by the use of the Ce doped Lu2SiO5 scintillator detector and an Am–Be source to detect the 4.44 MeV high energy gamma ray due to the B9e(α,nγ)C12 reaction.
5 citations
TL;DR: In this article, the ground-state properties of polyacene in terms of an extended Peierls-Hubbard Hamiltonian with particular emphasis on its structural instability of two types: double bonds in a cis pattern and those in a trans pattern.
Abstract: We investigate the ground-state properties of polyacene in terms of an extended Peierls-Hubbard Hamiltonian with particular emphasis on its structural instability of two types: double bonds in a cis pattern and those in a trans pattern. The two Peierls-distorted states are degenerate in their energetics but quite distinct in their optics. The trans configuration is easily photoconverted into the cis one, whereas an opposite transition, if any, is hardly completed. Domain-wall (soliton) excitations play an important role in any photoinduced phase transitions, but charged and neutral ones behave quite differently.
3 citations
TL;DR: In this article, a Peierls-Hubbard Hamiltonian was used to characterize a halogen-bridged transition-metal complex within a nanotube and reveal a variety of valence arrangements, including heterogeneous or partially metallic charge-density wave states.
Abstract: Motivated by recent chemical attempts at assembling halogen-bridged transition-metal complexes within a nanotube, we model and characterize a platinum-halide triangular prism in terms of a Peierls-Hubbard Hamiltonian. Based on a group-theoretical argument, we reveal a variety of valence arrangements, including heterogeneous or partially metallic charge-density-wave states. Quantum and thermal phase competitions are numerically demonstrated with particular emphasis on novel insulator-to-metal and insulator-to-insulator transitions under doping, the former of which is of the first order, while the latter of which is of the second order.