184 research outputs found
Experimental Study on Heat Flux of Divertor Plasma (Measurement of Sheath Heat Flux on the Surface of Gamma 10 Divertor Plates)
Experimental Study on Heat Flux of Divertor Plasma (Measurement of Sheath Heat Flux on the Surface of Gamma 10 Divertor Plates)
Intermittent Transport of Particle and Heat in Scrape-off Layer of Limiter and Divertor Confi gurations on CHS
Novel Density-Wave States of Two-Band Peierls-Hubbard Chains
Based on a symmetry argument we systematically reveal Hartree-Fock
broken-symmetry solutions of the one-dimensional two-band extended
Peierls-Hubbard model, which covers various materials of interest such as
halogen-bridged metal complexes and mixed-stack charge-transfer salts. We find
out all the regular-density-wave solutions with an ordering vector or
. Changing band filling as well as electron-electron and electron-phonon
interactions, we numerically inquire further into the ground-state phase
diagram and the physical property of each state. The possibility of novel
density-wave states appearing is argued.Comment: 10 pages, 6 PS figures, to appear in Phys. Lett.
Extension and its characteristics of ECRH plasma in the LHD
One of the main objectives of the LHD is to extend the plasma confinement
database for helical systems and to demonstrate such extended plasma
confinement properties to be sustained in steady state. Among the various
plasma parameter regimes, the study of confinement properties in the
collisionless regime is of particular importance. Electron cyclotron resonance
heating (ECRH) has been extensively used for these confinement studies of the
LHD plasma from the initial operation. The system optimizations including the
modification of the transmission and antenna system are performed with the
special emphasis on the local heating properties. As the result, central
electron temperature of more than 10 keV with the electron density of 0.6 x
10 m is achieved near the magnetic axis. The electron temperature
profile is characterized by a steep gradient similar to those of an internal
transport barrier observed in tokamaks and stellarators. 168 GHz ECRH system
demonstrated efficient heating at over the density more than 1.0 x 10
m. CW ECRH system is successfully operated to sustain 756 s discharge.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Superdense core mode in the Large Helical Device with an internal diffusion barrier
In reduced recycling discharges using a local island divertor in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)], a stable high-density plasma develops in the core region when a series of pellets is injected. A core region with ~5×10^20 m^?3 and temperature of 0.85 keV is maintained by an internal diffusion barrier (IDB). The density gradient at the IDB (r/a~0.6) is very high, and the particle confinement time in the core region is ~0.4 s. Because of the increase in the central pressure, a large Shafranov shift up to ~0.3 m is observed. The critical ingredients for IDB formation are a strongly pumped divertor to reduce edge recycling, and multiple pellet injection to ensure efficient central fueling. No serious magnetohydrodynamics activity and impurity accumulation have been observed so far in this improved discharge
Characteristics of confinement and stability in large helical device edge plasmas
Recent progress in the heating capability in the large helical device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] has allowed the highest average beta value (4.1%) obtained in the helical devices, and enables exploration of magnetohydrodynamics (MHD) stability in this beta region. MHD activities in the periphery are found to become stable spontaneously from the inner region to the outer region when the averaged beta value exceeds a threshold, and then a flattening of the electron temperature profile is observed around the resonant surface. Such a flattening can be formed externally by producing an m/n=1/1 magnetic island, and the complete stabilization of the m/n=1/1 mode is demonstrated by the moderate island width. In addition, attempts to control peripheral plasmas are also performed by using a limiter and a local island divertor utilizing the m/n=1/1 island, to improve plasma confinement and, especially, to stabilize pressure-driven modes in the present study. The stabilization of peripheral MHD modes is obtained with both approaches, and this indicates that these are available to the production of higher-beta plasmas without edge MHD activities
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