The electronic and optical properties of TiS2 are studied of density functional theory. A linearized and augmented by using an ab-initio calculation within the frame plane wave basis set with the generalized gradient ...The electronic and optical properties of TiS2 are studied of density functional theory. A linearized and augmented by using an ab-initio calculation within the frame plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS2, and the plots of total and partial densities of states of TiS2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant （ε（w） = ε1（w） ＋ iε2（w））, refractive index n（w）, optical reflectivity R（w）, for E / /x and E / /z are performed for the energy range of 0-.14 eV.展开更多
The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrom...The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrometer arrays,and the EUV spectrometer.The MoXV emission intensity sharply increases compared with the spectral lines of various ionization states of other elements,which implies that the dust particles are the molybdenum impurities.The radial distribution of Mo^(14+)ion simulated by a simplified 1 D transport model indicates that the molybdenum dust mainly deposits in the pedestal bottom region.Moreover,it is observed that the coherent mode(CM)appears atρ=0.94 after the molybdenum impurities enter the main plasma region.The influx of molybdenum impurities results in increasing pedestal electron density and decreasing pedestal electron temperature in contrast to that before the event of impurities dropping.It is also found that the electron density gradient in the pedestal increases when the ablation of the molybdenum impurities is observed in the pedestal region.The qualitative experimental results indicate that the onset of CM is likely related to the increase of the density gradient and edge collisionality in the pedestal.In comparison to the density gradient,the enhancement of CM amplitude largely depends on the increase of the edge collisionality.展开更多
Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradien...Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradient effects with moderate stiffness. By analyzingperiodic perturbations to an equilibrium, one canmeasure the variations in electron energy flux andelectron temperature gradient over the perturbation cycle, obtaining the flux as a function ofgradient over the range of parameters generated by the perturbation. Although time-dependenttransport analysis is very sensitive to noise in the input data, averaging over many cycles of aperiodic perturbation can provide data of sufficient quality. The analyses presented here are basedon the ECE temperature data with high spatial and temporal resolution and full profile coverage onDIII-D for sawteeth and modulated ECH heating.展开更多
A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and S...A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.展开更多
The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation ...The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation and space correlation and another approach introduced. And then, the validity of the two methods is analyzed and compared.展开更多
We first perform a two-dimensional particle-in-cell simulation of anti-parallel magnetic reconnection to verify that in the electron diffusion region the reconnection electric field is mainly balanced by the gradient ...We first perform a two-dimensional particle-in-cell simulation of anti-parallel magnetic reconnection to verify that in the electron diffusion region the reconnection electric field is mainly balanced by the gradient of the electron pressure. Then, by following typical electron trajectories in the fixed electromagnetic field of anti- parallel reconnection, we calculate the gradient of the electron pressure. We find that the resulted gradient of the electron pressure is equal to the reconnection electric field. This indicates that in the electron diffusion region the reconnection electric field is balanced by the gradient of the electron pressure, which results from the electron nongyrotropic motions. Our result gives a microphysical explanation of the balance between the reconnection electric field and the gradient of the electron pressure.展开更多
Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentati...Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentation instability in high-density region induces the local density modification. Large-scale toroidal magnetic fields confine plasma expansion in the transverse direction, resulting in the formation of a plasma jet. The plasma expansion along the target normal direction is found to scale as t1/2.展开更多
文摘The electronic and optical properties of TiS2 are studied of density functional theory. A linearized and augmented by using an ab-initio calculation within the frame plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS2, and the plots of total and partial densities of states of TiS2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant （ε（w） = ε1（w） ＋ iε2（w））, refractive index n（w）, optical reflectivity R（w）, for E / /x and E / /z are performed for the energy range of 0-.14 eV.
基金supported by Shenzhen Clean Energy Research Institutesupported by the National Key R&D Program of China (No. 2017YFE0301205)National Natural Science Foundation of China (Nos. 11875289, 11975271, 11605244, 11675211, 12075284, 12075283, 12075155 and 11875294)
文摘The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrometer arrays,and the EUV spectrometer.The MoXV emission intensity sharply increases compared with the spectral lines of various ionization states of other elements,which implies that the dust particles are the molybdenum impurities.The radial distribution of Mo^(14+)ion simulated by a simplified 1 D transport model indicates that the molybdenum dust mainly deposits in the pedestal bottom region.Moreover,it is observed that the coherent mode(CM)appears atρ=0.94 after the molybdenum impurities enter the main plasma region.The influx of molybdenum impurities results in increasing pedestal electron density and decreasing pedestal electron temperature in contrast to that before the event of impurities dropping.It is also found that the electron density gradient in the pedestal increases when the ablation of the molybdenum impurities is observed in the pedestal region.The qualitative experimental results indicate that the onset of CM is likely related to the increase of the density gradient and edge collisionality in the pedestal.In comparison to the density gradient,the enhancement of CM amplitude largely depends on the increase of the edge collisionality.
基金the US Department of Energy under grant DE-FG03-97-ER54415
文摘Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradient effects with moderate stiffness. By analyzingperiodic perturbations to an equilibrium, one canmeasure the variations in electron energy flux andelectron temperature gradient over the perturbation cycle, obtaining the flux as a function ofgradient over the range of parameters generated by the perturbation. Although time-dependenttransport analysis is very sensitive to noise in the input data, averaging over many cycles of aperiodic perturbation can provide data of sufficient quality. The analyses presented here are basedon the ECE temperature data with high spatial and temporal resolution and full profile coverage onDIII-D for sawteeth and modulated ECH heating.
基金National Natural Science Foundation of China(No.10405014)
文摘A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.
基金Supported by the National Natural Science Foundation of China(6 95 710 2 0 ) and the Research Fund for the Doctoral Program of H
文摘The electron concentration horizontal gradient vector of the ionosphere and its south-north and east-west components over Chongqing station are analyzed and calculated, using the first approximation, time correlation and space correlation and another approach introduced. And then, the validity of the two methods is analyzed and compared.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41331067,11220101002,11235009,41274144and 41121003the National Basic Research Program of China under Grant Nos 2013CBA01503 and 2012CB825602+1 种基金the Ph.D.Foundation of the Ministry of Education of China under Grant No 20123402120010the Knowledge Innovation Program of Chinese Academy of Sciences under Grant No KZZD-EW-01-4
文摘We first perform a two-dimensional particle-in-cell simulation of anti-parallel magnetic reconnection to verify that in the electron diffusion region the reconnection electric field is mainly balanced by the gradient of the electron pressure. Then, by following typical electron trajectories in the fixed electromagnetic field of anti- parallel reconnection, we calculate the gradient of the electron pressure. We find that the resulted gradient of the electron pressure is equal to the reconnection electric field. This indicates that in the electron diffusion region the reconnection electric field is balanced by the gradient of the electron pressure, which results from the electron nongyrotropic motions. Our result gives a microphysical explanation of the balance between the reconnection electric field and the gradient of the electron pressure.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 19854001 &19825110) the National High-Tech IGF Committee, the Laboratory for Laser Fusion of China Academy of Engineering Physics the Pre-research Foundation of
文摘Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentation instability in high-density region induces the local density modification. Large-scale toroidal magnetic fields confine plasma expansion in the transverse direction, resulting in the formation of a plasma jet. The plasma expansion along the target normal direction is found to scale as t1/2.
