2,163 research outputs found
Low Temperature Symmetry of Pyrochlore Oxide Cd2Re2O7
We report the X-ray study for the pyrochlore oxide Cd2Re2O7. Two
symmetry-lowering structural transitions were observed at Ts1=200K and
Ts2=120K. The former is of the second order from the ideal cubic pyrochlore
structure with space group Fd-3m to a tetragonally distorted structure with
I-4m2, while the latter is of the first order likely to another tetragonal
space group I4122. We discuss the feature of the lattice deformation.Comment: 4 pages, 4 figure
Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas
The stability with respect to a peeling–ballooning mode (PBM) was investigated numerically with
extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI
code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift
( *w i), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear
dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively
that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into
account both the rotation and *w i effects in the numerical analysis. When deuterium poloidal rotation
is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes
the PBM because of an acceleration of rotation and a decrease in *w i. The difference in the amount of
ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with
JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the
difference in the linear stability property, due not to the rotation direction but to the plasma density
profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A
predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and *w i effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.JSPS KAKENHI 15K06656EURATOM 63305
Quasi-One-Dimensional Spin Dynamics in -Electron Heavy-Fermion Metal YScMn
Slow spin fluctuations ( s) observed by the muon spin
relaxation technique in YScMn exhibits a power law dependence
on temperature (), where the power converges
asymptotically to unity () as the system moves away from
spin-glass instability with increasing Sc content . This linear
dependence, which is common to that observed in LiVO, is in line with
the prediction of the "intersecting Hubbard chains" model for a metallic
pyrochlore lattice, suggesting that the geometrical constraints to t2g bands
specific to the pyrochlore structure serve as a basis of the -electron
heavy-fermion state.Comment: 5 pages, 4 figures, to appear in J. Phys. Soc. Jp
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