Search

A study was conducted with a line-imaging velocity interferometer on sandwich targets at the Shen Guang-III prototype laser facility in China, with the goal of eliminating the preheat effect. A sandwich target structure was used to reduce the x-ray preheat limitation (radiation temperature ∼170 eV) in a radiative drive shock experiment. With a thick ablator, the preheat effect appeared before the shock arrived at the window. After adding a shield layer of high-Z material on the ablator, x-rays which penetrated the ablator were so weak that the blank-out effect could not be measured. This experiment indicates that the sandwich target may provide a valuable technique in experiments such as equation of state and shock timing for inertial confinement fusion studies. [ABSTRACT FROM AUTHOR]

Both direct and indirect drive concepts of inertial confinement fusion rely on targets with cryogenic thermonuclear fuel shells for ignition. Experiments on the Shenguang-III prototype laser facility using laser-driven gas-filled hohlraums show distinct differences between cryogenic (20 K) and warm hohlraums. Although the measured x-ray flux in the photon range from 1.6 to 4.4 keV (Au M-band) is identical between cryogenic and warm hohlraums, the cryogenic hohlraum has a much slower rate of rise and is 20% lower in peak intensity of x-ray flux in the photon range from 0.1 to 4 keV. The reasons for this drive deficit between cryogenic and warm hohlraums are investigated using a similar series of hohlraum experiments. The experiments employ three types of hohlraums to distinguish the effect of a shroud window membrane and condensates. Warm hohlraums with a shroud window membrane replicate the slower rate of rise of radiation flux of cryogenic targets. When the shroud window is present, the measured x-ray flux in the hohlraum shows a drive deficit that decreases with time. However, the measured deficit increases as the viewing angle increases. All of these results indicate that the portion of the shroud not illuminated by the lasers absorbs the outgoing x-ray flux from the hohlraum. [ABSTRACT FROM AUTHOR]

Transmissibility limitation is one of the most important barriers in the use of windows for shock experiments if optical probes are used. In this article, we focus on the widely used window material lithium fluoride (LiF) and investigate its optical response under laser-induced shock-compression conditions. A long-pulse laser is shaped to create a continuous accelerating shock wave propagating through the LiF window in the range of 100–400 GPa. The variation of measured optical transmission with shock pressure shows that the LiF window stays transparent even when the shock stress is higher than 350 GPa and transforms to a total opaque state at about 400 GPa. The present experiment exhibits an obviously higher shock stress for LiF windows to lose transparency compared with previously reported results. The discrepancy in experimental results is considered to be due to the difference in shock thickness for a typical time scale at different experimental platforms. Meanwhile, the possible reasons for the discrepancy between our experimental data and the previous ab initio calculations can be suggested by the effect of thermal relaxation between electrons and ions or the overestimation of the absorption coefficient in theoretical calculations. This finding of higher transmissibility limitation may be of importance to researchers who use LiF as a window material in future shock-compression experiments, especially at the laser platform. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A gold(I)‐catalyzed 6‐endo‐dig cyclization of aromatic 1,5‐enynes was developed to synthesize 2‐(naphthalen‐2‐yl)anilines. The functional group tolerance of this cyclization was examined systematically and a possible mechanism was proposed. The derivatization of 2‐(naphthalen‐2‐yl)aniline was carried out to facile access to benzo[α]carbazole, benzo[c,h]cinnoline and dibenzo[i]phenanthridine derivatives in a divergent way. [ABSTRACT FROM AUTHOR]

In inertial confinement fusion, quantitative and high-spatial resolution ( < 10 μ m) measurements of the X-rays self-emitted by the hotspot are critical for studying the physical processes of the implosion stagnation stage. Herein, the 8 ± 0.39-keV monochromatic X-ray distribution from the entire hotspot is quantitatively observed in 5- μ m spatial resolution using a Kirkpatrick–Baez microscope, with impacts from the responses of the diagnosis system removed, for the first time, in implosion experiments at the 100 kJ laser facility in China. Two-dimensional calculations along with 2.5% P2 drive asymmetry and 0.3 ablator self-emission are congruent with the experimental results, especially for the photon number distribution, hotspot profile, and neutron yield. Theoretical calculations enabled a better understanding of the experimental results. Furthermore, the origins of the 17.81% contour profile of the deuterium-deuterium hotspot and the accurate Gaussian source approximation of the core emission area in the implosion capsule are clarified in detail. This work is significant for quantitatively exploring the physical conditions of the hotspot and updating the theoretical model of capsule implosion. [ABSTRACT FROM AUTHOR]

In order to study the laser plasma instabilities (LPIs) in the context of some novel six-side laser-driven indirect designs like the six-cylinder-port hohlraum and the three-axis cylindrical hohlraum, where the laser beams inject in hohlraum with a large angle. LPI experiments in cylindrical hohlraum with only outer beams were designed and performed based on the current laser arrangement condition of SGIII laser facility for the first time. Stimulated Brillouin backscatter (SBS) was found to be the dominant instability with high instantaneous reflectivity in experiments. A typical feature was obtained in the time-resolved spectra of SBS, which maintained similar for different laser intensities of the interaction beam. The experimental data are analyzed by the hydrodynamic simulations combined with HLIP code, which is based on the ray-tracing model. By analysis of experimental data, it is argued that the mixture of gas and Au in the region of their interface is important to SBS, which indicates the need for the mixture model between the filled gas and the high Z plasma from hohlraum wall in the hydrodynamic simulations. Nonlinear saturation of SBS as well as the smoothed beam are also discussed here. Our effective considerations of the ions pervasion effect and the smoothed beam provide utilitarian ways for improvement of the current ray-tracing method. [ABSTRACT FROM AUTHOR]

The ultrastable encrypted storage of X-ray image with quantitative and ultrahigh-spatial resolution are crucial for a wide range of applications in radiation imaging, and it can be achieved by using the radio-photoluminescence (RPL) material, Ag-doped phosphate glass (Ag-PG), which was fabricated via the melt-quenching method. Under X-ray irradiation, Ag-PG produces a luminescence center, obvious 650 nm emission peak, which can be repeatedly excited by ultraviolet light without intensity attenuation. Quantitative X-ray image storage was realized based on the linear relationship between RPL intensity and X-ray irradiation time. X-ray image with a submicron spatial resolution of 0.7 µm was achieved, which could be stably stored without attenuation for more than 300 days. This submicron level X-ray image can be written into the Ag-PG as an encrypted information, and can only be visualized by an ultraviolet light. Additionally, heat treatment (400 °C for 2 h) could eliminate the influence of X-ray radiation on the Ag-PG, and restore the state of the Ag-PG before X-ray irradiation, which allows the recyclability and reusability of the Ag-PG. This research is of great significance for promoting the encrypted storage of X-ray images based on Ag-PG or other RPL materials. • The study demonstrated the ultrahigh-spatial-resolution and ultrastable X-ray image storage and encryption through Ag-PG. • The X-ray imaging at submicron scale is realized by using the Ag-PG, which could be stably stored for more than 300 days. • Ag-PG further realizes the anti-counterfeiting and encryption of X-ray image information with sub-micron level. • The Ag-PG exhibits important application potential in 3D X-ray imaging. [ABSTRACT FROM AUTHOR]

A highly environmentally friendly procedure was developed for the Knoevenagel condensation of aromatic aldehydes with diethyl malonate in the presence of FeCl3 and N-fluorobenzenesulfonimide as a source of electrophilic fluorine under solvent-free conditions. The scope of the reaction was explored using commercially available substrates. The reaction with substituted salicylaldehydes afforded the corresponding coumarin derivatives which attract interest due to their potential medicinal importance. [ABSTRACT FROM AUTHOR]

CsPbBr 3 nanoparticles uniformly distributed on reduced graphene oxide (rGO) to form CsPbBr 3 /rGO nanocomposites are synthesized by a facile method. Their corresponding optical and X-ray photon response are investigated. UV–visible absorption spectra and photoluminescence measurements confirm that loading CsPbBr 3 nanoparticles with an even distribution onto rGO surface can enhance the absorption and photon-generated carrier transportation. Thus, a significant enhancement in optical and X-ray photon response is demonstrated in CsPbBr 3 /rGO nanocomposites as compared with pure CsPbBr 3 nanoparticles. Clear conductive switching phenomenon with a state conversion between “on” and “off” is also observed under the intermittent x-ray exposure. These results may provide a new potential application of CsPbBr 3 /rGO nanocomposites for X-ray photon detection. [ABSTRACT FROM AUTHOR]

An ultraviolet Thomson-scattering system has been designed and implemented on the Shenguang-III laser facility, a 48-beam, 3ω (351 nm), 180 kJ-level laser driver for high energy density physics and inertial confinement fusion researches. The 4ω (263.3 nm) probe beam of the Thomson-scattering system is injected from the north pole (top) of the target chamber, with an assistant beam-pointing monitor to achieve high pointing accuracy. The Thomson-scattered light is collected by a double-Cassegrain optical transmission system, which provides an achromatic image over a wide wavelength range of 200–800 nm. A novel on-line alignment method is developed and applied to the diagnostic system, ensuring a volumetric positioning accuracy of ∼30 μm for the scattering volume. An online calibration is also conducted to provide the wavelength benchmark and the spectral resolution of the system. This Thomson-scattering system has been tested in a complicated experimental environment with gas-filled hohlraums, and a high-quality ion feature of the scattered light has been obtained. [ABSTRACT FROM AUTHOR]

The free-carrier dynamics and nonlinear refractive index in bulk polycrystalline diamond are investigated using a femtosecond ultraviolet-pump-optical-probe technique with a phase object. Normalized transmittances under open-aperture and closed-aperture conditions are simultaneously measured to determine the dynamics of nonlinear absorption and refraction in the sample. In the dynamics of nonlinear absorption, three processes are clearly observed: nondegenerate two-photon absorption, fast and slower decay components of the free-carrier dynamics. The lifetimes of the free carriers are precisely measured. In the dynamics of nonlinear refraction, we obtain the nonlinear refractive coefficient and find that the results obtained under the femtosecond regime differ from those of other semiconducting materials previously measured under the picosecond regime. [ABSTRACT FROM AUTHOR]

The utility of this method is demonstrated in the synthesis of the mycotoxin isopatulin (IV). [ABSTRACT FROM AUTHOR]

A gold(i)-catalyzed substituent-controlled strategy for the stereoselective synthesis of bicyclic furan and pyran derivatives has been developed. The mechanisms of the reactions have been studied thoroughly by deuterium labelling experiments. The applications of the methodologies were demonstrated by evaluating the preliminary anti-fungal activity of the synthetic compounds. [ABSTRACT FROM AUTHOR]

During investigating water-compatible Lewis acids catalyzed etherifications using alcohols as alkylating reagents directly, we developed Fe(III)-catalyzed trityl benzyl ether formations irradiated by microwave. Then an in situ trityl benzyl ether formation and disproportionation cascade reaction was achieved to yield the benzaldehyde products with good functional group tolerances under neat conditions at relative higher temperatures. The substituent effects of the substrates on the etherification and disproportionation were explored by changing the substitutions on benzyl alcohols and triarylmethanols using chemical kinetic plots methods and the mechanism of the transformation was studied by crossover experiments. The etherification and disproportionation cascade process could be conveniently scaled up in laboratory without losing much efficiency. [ABSTRACT FROM AUTHOR]

Quantitative evaluation of the fractions of high energy x-rays in a hohlraum is crucial to the indirect driven-drive scheme of inertial confinement fusion and many other applications in high energy density physics. Preheat of a sample due to x-rays sensitively depends on optical thin photons. Analyzing the motion of a sample due to preheat can thus provide valuable information of those x-rays. In this article, we propose a method to infer the temporal evolution of the x-ray fluxes in the bands of our interest. By matching the simulation results to the motions of an aluminum sample, we can infer the time-resolved x-ray fluxes around the aluminum K-edge and the gold M-band inside the hohlraum. [ABSTRACT FROM AUTHOR]

Detailed research on the interaction of a 0.53 μm laser pulse with millimeter-scale plasmas produced by a gasbag target on the Shengguang-II facility is presented. The x-ray pinhole images confirm that millimeter-scale plasmas are generated and the x-ray framing images show a temporal window of 0.6-1.1 ns during which the millimeter-scale plasmas exist. The electron temperature is measured with a collective Thomson scattering system, providing 0.64 keV for C5H12 and 1.8 keV for Xe plasmas. The electron density is inferred from the stimulated Raman scattering spectra. The experimental spectra show large differences for C5H12- and Xe-filled gasbags. A one-dimensional code based upon steady-state, kinetic linear theory is applied to calculate the stimulated Raman scattering spectra. Excellent agreement between the calculated and experimental results shows that the plasma parameters, especially the electron density and the temperature, dominate the disruption behavior of stimulated Raman scattering. The results also indicate that stimulated Raman scattering is probably located within specific region of the gasbag. The time-integrated reflectivity of both the stimulated Raman and Brillouin scattering is at a low level, even in the conditions of high laser intensity (1.5×1015 W/cm2) and no beam-smoothing. The experimental results are promising for future ignition experiments with a 0.53 μm laser as the driver. [ABSTRACT FROM AUTHOR]

Streak camera is widely used in continuous time diagnostics in fast physical process. To produce accurate result, it requires delicate calibration and a reliable analysis method. High quality sweep-rate data with uncertainty smaller than 0.5% are obtained over the full record area by a constrained fitting method of peak position measurement, with a short pulse laser and an etalon as the fiducial source. The temporal response is linearized by this full-screen sweep-rate data, which eliminates errors in measurement due to nonlinearity and space-distortion inherent in streak camera. [ABSTRACT FROM AUTHOR]

Abstract: Imaging VISAR is an important diagnostic tool for a variety of shock-related phenomena in laser-driven experiments. To adapt to various types of shaped driven pulse, the imaging VISAR needs an illuminating light with good shaping capability. Here, a flexible laser probe system was experimentally studied. Being generated from a 1064-nm DFB laser, the continuous wave was modulated by a waveguide amplitude modulator driven by 10GS/s arbitrary waveform generator. After being amplified by fiber amplifiers and Nd:YAG rod amplifiers, the signal pulse was frequency-converted to 532-nm green light by a thermally controlled LBO crystal with a final output energy larger than 10mJ. Finally, the green light was coupled into a 1-mm core diameter, multimode fused silica optical fiber and propagated to the imaging VISAR. The probe laser could realize accurate pulse shaping with time resolution below 100ps. Uniformity in intensity and capability of arbitrary pulse shaping provides great convenience for the analysis of experimental data. [ABSTRACT FROM AUTHOR]

In laser driven hohlraums, laser beams on the same incident cone may have different beam and plasma conditions, causing beam-to-beam backscatter difference and subsequent azimuthal variations in the x-ray drive on the capsule. To elucidate the large variation of backscatter proportion from beam to beam in some gas-filled hohlraum shots on Shenguang-III, two 28.5° beams have been measured with the Stimulated Raman Scattering (SRS) time-resolved spectra. A bifurcated fiber is used to sample two beams and then coupled to a spectrometer and streak camera combination to reduce the cost. The SRS spectra, characterized by a broad wavelength, were further corrected considering the temporal distortion and intensity modulation caused by components along the light path. This measurement will improve the understanding of the beam propagation inside the hohlraum and related laser plasma instabilities. [ABSTRACT FROM AUTHOR]

Compounds (IIIa), (IIIc), (IIIe), (Va), (Vc), (VIa), (VII), (VIIIa), and (IX) show antifungal activity. [ABSTRACT FROM AUTHOR]