Japan Atomic Energy Research Institute

About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.

Observation of nonlinear coupling between small-poloidal wave-number potential fluctuations and turbulent potential fluctuations in Ohmically heated plasmas in the JFT-2M tokamak.

Abstract: Two types of electrostatic modes with small-poloidal wave numbers ($\ensuremath{\sim}1$ and $10--15\text{ }\text{ }\mathrm{kHz}$) are observed in the edge region of Ohmically heated plasmas in the JFT-2M tokamak. The envelope of the higher frequency coherent mode is modulated at the frequency of the lower frequency mode. A bispectral analysis revealed that a significant nonlinear coupling among the two types of fluctuations and the broadband background turbulent potential fluctuations occurs inside the last closed magnetic flux surface, suggesting that a nonlinear process such as the parametric-modulational instability is involved.

Hydrogels of polysaccharide derivatives crosslinked with irradiation at paste-like condition

Abstract: Polysaccharides such as cellulose, starch, chitin/chitosan and their water-soluble derivatives have been known as degradable type polymers under action of ionizing radiation. Recently, we found that water-soluble polysaccharides derivatives such as carboxymethylcellulose (CMC), carboxymethylstarch (CMS) and carboxymethylchitin (CMCT), carboxymethylchitosan (CMCTS) lead to radiation crosslinking at high concentrated aqueous solution (more than 10%, paste-like state). It was proved that the crosslinking was remarkably affected by their concentration. It was assumed that radiation formation of hydrogels of these polysaccharides derivatives were mainly due to the mobility of side chains. Side-chains radicals were formed mostly via indirect effects, by the abstraction of H atoms by the intermediate products of water radiolysis. Some important characteristics of these novel hydrogels were also investigated. These hydrogels exhibited good swelling in water and possess satisfying biodegradability. In addition, the antibacterial activity against E.coli was also found in CMCTS hydrogel.

Structural changes of ZrO2-CeO2 solid solutions around the monoclinic-tetragonal phase boundary.

Abstract: High-resolution neutron-diffraction experiments have been performed to study the structural changes of ${\mathrm{ZrO}}_{2}$ induced by ${\mathrm{CeO}}_{2}$ doping. The crystal structures of monoclinic [P${2}_{1}$/c, Z=4] and tetragonal [P${4}_{2}$/nmc, Z=2] phases for ${\mathrm{ZrO}}_{2}$--X mol % ${\mathrm{CeO}}_{2}$ (X=0, 2, 5, 8, 10, 12, and 15) have been refined by the Rietveld analysis of the diffraction patterns measured at 298 K. The unit-cell parameters change anisotropically with an increase of ${\mathrm{CeO}}_{2}$ content X. In the monoclinic phase ${\mathit{a}}_{\mathit{m}}$ and ${\mathit{c}}_{\mathit{m}}$ increase considerably while ${\mathit{b}}_{\mathit{m}}$ shows a rather small increase with increasing X where the suffix m denotes the monoclinic phase. The angle ${\mathrm{\ensuremath{\beta}}}_{\mathit{m}}$ decreases with increasing X. The thermal ellipsoids also show large anisotropies, which correlate strongly with the directions of the movements of oxygen ions during the phase transition. The unit-cell parameters and the atomic positions discontinuously change during the monoclinic-tetragonal phase change. The crystal structure of monoclinic phase approaches that of tetragonal phase with an increase of X: (1) the length of ${\mathit{a}}_{\mathit{m}}$ approaches that of ${\mathit{b}}_{\mathit{m}}$ with increasing X, (2) the angle ${\mathrm{\ensuremath{\beta}}}_{\mathit{m}}$ decreases with X, and (3) all positional parameters of the monoclinic phase approach those of the tetragonal structure.

Plasma equilibrium and confinement in a tokamak with nearly zero central current density in JT-60U.

Abstract: A high confinement equilibrium with nearly zero toroidal current in the central region (a "current hole") has been observed for the first time to persist stably for several seconds in the JT-60U tokamak. This observation indicates the possibility of stable tokamak operation without central toroidal current; the central current has previously been believed to be necessary in tokamaks. The radius of the current hole extended up to 40% of the plasma minor radius. It was observed that the current hole was formed by the increase of the off-axis noninductive current.