Liu Shenye

Electronic, optical properties, surface energies and work functions of Ag8SnS6: First-principles method*

Ternary metal chalcogenide semiconductor Ag8SnS6, which is an efficient photocatalyst under visible light radiation, is studied by plane-wave pseudopotential density functional theory. After geometry optimization, the electronic and optical properties are studied. A scissor operator value of 0.81 eV is introduced to overcome the underestimation of the calculation band gaps. The contribution of different bands is analyzed by virtue of total and partial density of states. Furthermore, in order to understand the optical properties of Ag8SnS6, the dielectric function, absorption coefficient, and refractive index are also performed in the energy range from 0 to 11 eV. The absorption spectrum indicates that Ag8SnS6 has a good absorbency in visible light area. Surface energies and work functions of , , , and (112) orientations have been calculated. These results reveal the reason for an outstanding photocatalytic activity of Ag8SnS6.

Reflective-type configuration for monitoring the photobleaching procedure based on surface plasmon resonance

A new scheme to monitor the photoinduced bleaching procedure with ultraviolet light based on surface plasmon resonance (SPR) using attenuated total reflection configuration is presented. The configuration, which is very sensitive to the changes of refractive index and nonlinear optical (NLO) coefficient of polymer, can prevent the effect of the fundamental wave and can be used to determine the nonlinear coefficient d33. With the formulation in this paper, the nonlinear coefficient d33 can be measured by comparing the second harmonic generation intensity generated by SPR from the metal–nonlinear optical (NLO) polymer interface and that from the metal–quartz interface. The remaining second-order NLO coefficients are 78% and 47% for the cross-linked and side-chain polymer, respectively.

Concentric-ring structures in an atmospheric pressure helium dielectric barrier discharge ⁄

This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional difiusion{drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present difierent appearances of ring structures within difierent radii in time due to the evolvement of the fllaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric fleld strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.

Simulation and experimental research of x-ray toroidally bent crystal imaging with laser-produced plasma

Based on the Bragg law and imaging principle of bent crystal, the imaging properties of the monochromic backlighting system with a toroidally bent crystal were studied via ray-tracing simulations and experiments. Comparison experiments with both toroidally and spherically bent crystals using a Cr line as the backlighter were performed, showing that using toroidally bent crystal, a 2D image with the same magnifications in meridional and sagittal directions can be obtained with higher spatial resolution. Experiments with laser-produced plasmas using Mica crystal were carried out on the Shenguang II laser facility. Five laser beams were focused onto a Ti planar target producing a line at 4.75 keV as the backlighter and an image of a metal grid with size of 200 μm × 200 μm was recorded with an x-ray image plate. A spatial resolution of 40 μm was demonstrated with a magnification of 3 due to the restriction of the target chamber size. 10 μm spatial resolution might be possible if the detector can be located outside the chamber to enlarge the magnification.

Methods of Generation and Detailed Characterization of Millimeter-Scale Plasmas Using a Gasbag Target

Gasbag targets are useful for the research of laser-plasma interactions in inertial confinement fusion, especially in the laser overlapping regime. We report that on the Shengguang-II laser facility, millimeter-scale plasmas are successfully generated by four 0.35 μm laser beams using a gasbag target. Multiple diagnostics are applied to characterize the millimeter-scale plasmas in detail. The images from the x-ray pinhole cameras confirm that millimeter-scale plasmas are indeed created. An optical Thomson scattering system diagnoses the electron temperature of the CH filling plasmas by probing the thermal ion-acoustic fluctuations, which indicates that the electron temperature has a 600 eV flat roof in 0.7–1.3 ns. Another key parameter, i.e. the electron density of the millimeter-scale plasmas, is inferred by the spectrum of the back stimulated Raman scattering of an additional 0.53 μm laser beam. The inferred electron density keeps stable at 0.1nc in early time consistent with the controlled filling pressure and splits into a higher density in late time, which is attributed to the blast wave entering into the SRS interaction region.

Shock-Timing Experiment Using a Two-Step Radiation Pulse with a Polystyrene Target

A shock-timing experiment plays an important role in inertial confinement fusion studies, and the timing of multiple shock waves is crucial to the performance of inertial confinement fusion ignition targets. We present an experimental observation of a shock wave driven by a two-step radiation pulse in a polystyrene target. The experiment is carried out at Shen Guang III Yuan Xing (SGIIIYX) laser facility in China, and the generation and coalescence of the two shock waves, originating from each of the two radiation steps, is clearly seen with two velocity interferometers. This two-shock-wave coalescence is also simulated by the radioactive hydrodynamic code of a multi-1D program. The experimental measurements are compared with the simulations and quite good agreements are found, with relatively small discrepancies in shock timing.

Experiments and analysis of gold disk targets irradiated by smoothing beams of Xingguang II facilities with 350 nm wavelength

Gold disk targets were irradiated using focusing and beam smoothing methods on Xingguang (XG-II) laser facilities with 350 nm wavelength, 0.6 ns pulse width and 20–80 Joules energies. Laser absorption, light scattering and X-ray conversion were experimentally investigated. The experimental results showed that laser absorption and scattered light were about 90% and 10%, respectively, under focusing irradiation, but the laser absorption increased 5%–10% and the scattered light about 1% under the condition of beam smoothing. Compared with the case of focusing irradiation, the laser absorption was effectively improved and the scattered light remarkably dropped under uniform irradiation; then due to the decrease in laser intensity, X-ray conversion increased. This is highly advantageous to the inertial confinement fusion. However, X-ray conversion mechanism basically did not change and X-ray conversion efficiency under beam smoothing and focusing irradiation was basically the same.

Thomson scattering process in laser-produced plasmas

We present the evolutions of the electron temperature and plasma expansion velocity with Thomson scattering experiment. The observed time-resolved ion-acoustic image is reproduced by a numerical code which couples the Thomson scattering theory with the output parameters of the one-dimensional hydrocode MEDUSA.

Progress and plans of X-ray temporal and spatial diagnosis technology of Shenguang facilities

In the field of indirect-drive inertial confinement fusion, temporal and spatial diagnosis of X-ray is very important to the imploded process researches and the simulate procedure verification. According to the temporal, spatial and spectral characteristics of X-ray radiation, many X-ray imaging diagnosis devices were successfully developed. Along with the development of ICF research, especially the Shenguang III facility establishment, our X-ray imaging diagnosis capability has been increasingly powerful. Some of the novel diagnosis equipment even have more excellent characteristics than that kind of diagnosis equipment abroad.

Recent progress of hohlraum physics experiments in indirect-driven ICF in China

In recent years, hohlraum experiments have been performed extensively on Shenguang series laser facilities in the context of laser indirect-drive inertial confinement fusion. Multiple aspects about the hohlraumenergetics, drive symmetry and plasma condition are studied by a variety of methods resolving different photon ranges and multiple viewing areas. To improve the experimental uncertainty, several diagnostics are optimized and calibrated, also the power balance and pointing accuracy of laser beams are evaluated and improved. These works lead a rapid progress on hohlraum experimental capabilities and a series of successful experimental campaigns. In order to further optimize the hohlraum performance, other hohlraum geometry (the spherical hohlram with six LEHs and the cylindrical hohlraum with six LEHs) and hohlraum wall material (depleted Uranium and foam Au) are explored as well. Hohlraum experiments and modeling on Shenguang series laser facilities demonstrated quantitative understanding of the laser conversion, X-ray ablation and plasma motion in different regions.