We present measurements of the 2p-3d transition opacity of a hot molybdenum–scandium sample with nearly half-vacant molybdenum M-shell configurations. A plastic-tamped molybdenum–scandium foil sample is radiatively heated to high temperature in a compact D-shaped gold Hohlraum driven by ∼30 kJ laser energy at the SG-100 kJ laser facility. X rays transmitted through the molybdenum and scandium plasmas are diffracted by crystals and finally recorded by image plates. The electron temperatures in the sample in particular spatial and temporal zones are determined by the K-shell absorption of the scandium plasma. A combination of the IRAD3D view factor code and the MULTI hydrodynamic code is used to simulate the spatial distribution and temporal behavior of the sample temperature and density. The inferred temperature in the molybdenum plasma reaches a average of 138 ± 11 eV. A detailed configuration-accounting calculation of the n = 2–3 transition absorption of the molybdenum plasma is compared with experimental measurements and quite good agreement is found. The present measurements provide an opportunity to test opacity models for complicated M-shell configurations.

A self-consistent and precise method to determine the time-dependent radiative albedo, i.e., the ratio of the reemission flux to the incident flux, for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed. A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV. The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample. The results agree well owing to the symmetrical radiation in the secondary cavity. A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux, and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis, and also to agree well with the result of a simulation using the HYADES opacity.

Experiments and simulations have been carried out to study the colliding process by two lasers irradiating a gold half-hohlraum. Via analyzing the evolutionary x-ray images, radiation fluxes and self-emission spectrum of tracers, influence on the x-ray conversion efficiency and the local plasma temperature from T-e,T-i two gold-plasma plumes have been investigated deeply, which is similar as the configuration in Inertial Confinement Fusion (ICF). Experimental results confirm a region with high electron and ion temperatures T-e,T-i are induced, satisfying the strong collision condition of lambda(i) < triangle L, where lambda(i )and triangle L are respectively the ion mean-free path and the gradient length of T-e. It leads to almost increasing of M-band component compared to that from a single laser-irradiation case. Meanwhile ion temperature in this region increases more rapidly than electrons, reaching about T-i approximate to (16 +/- 4) keV (T-e approximate to (2 +/- 0.2) keV). Thus, our studies provide the experimental evidence of quantitative x-ray enhancement and a non-equilibrium evolution simultaneously due to the plasma collision for the first time. Besides, two-dimensional simulation results reveal that this process can not be precisely described by the traditional shock-heating model by dissipating the shock energy only to ions. But by distributing the viscous heating between both electrons and ions as theoretically discussed by Miller (2020 Comput. Fluids210 104672), numerical results can match experiments better. This discovery will be of great importance to improve the precision of prediction for ICF.

- A collision frequency measurement from the optical reflectivity of laser indirectdriven CH/Al/diamond on the SG-10kJ laser facility is presented. The optical reflectivity and the Al/diamond interface velocity were measured simultaneously by the velocity interferometer. The aluminum rear surface density was deduced from the interface velocity by analyzing the wave interaction. The deduced sample state was compared with the simulation and quite good agreement was found. The electron collision frequency was deduced by fitting the sample state to the optical reflectivity, and it is found that the experimental collision frequency agrees with a semi -empirical result within the error bar, but is larger than the simulated result based on the average -atom model with the hypernetted chain approximation.

A practical experimental method is proposed to investigate thermal transport by characterizing the motion of plasma flows through a x-ray spectroscopic technique using tracers. By simultaneously measuring multiple parameters, namely, the mass-ablation rate, the temporal evolution of plasma flow velocities and trajectories and the temperature, it is possible to observe a variety of physical processes, such as shock wave compression, heating by thermal waves, and plasma thermal expansion, and to determine their relative importance in different phases during the irradiation of CH and Au targets. From a comparison with hydrodynamic simulations, we find significant differences in the motion of the plasma flows between CH and Au, which can be attributed to different sensitivities to the thermal transport process. There are also differences in the ablation and electron temperature histories of the two materials. These results confirm that velocities and trajectories of plasma motion can provide useful evidence in the investigation of thermal conduction, and the approach presented here deserves more attention in the context of inertial confinement fusion and high-energy-density physics.

A high-resolution x-ray spectrometer has been designed and constructed, using a highly oriented pyrolytic graphite Bragg crystal in von Hamos geometry. The spectrometer was designed to study x-ray fluorescence emissions of Ti, and it covers a detecting energy range from 4000 eV to 5500 eV. The factors affecting the spectral resolution and efficiency of the spectrometer were discussed. In particular, the bending of the spectral lines on the image plate was also corrected, due to the detecting plane not being parallel to the axis of the cylindrically curved crystal. Its performance has been evaluated in a laser–foil interaction experiment. The experimental results indicate that the spectrometer is of good spectral resolution and relatively high efficiency, which enables it as a suitable device for the measurements of high-resolution x-ray fluorescence spectroscopy.

Great efforts have been made to create a bright K-shell source using the thin metal cylindrical cavities in the past few decades. Several metal materials such as titanium (Ti), iron, and so on have been tested for high x-ray conversion efficiency mainly at the OMEGA and NIF laser facilities. Recently, x-ray sources in Ti K-shell transition energy range were investigated at the Shenguang-III prototype laser facility with ∼5 kJ laser energy. The experiments were aimed to reproduce the previous ones at OMEGA, but with an extraordinarily small volume of cylindrical cavity and detailed characterizations of the x-ray source. The cavities were 800 μm inner diameter, 800 μm length, and 30 μm thick plastic tubes supporting 1 μm thick Ti. Seven laser beams were focused to 200 μm diameter. The combination of the small cavity volume and the focused laser spots is intended to improve the electron temperature with limited laser energy since the electron temperature is a key issue for high x-ray conversion efficiency. Thomson scattering was adopted to experimentally probe the electron temperatures at special time and space zones as well as the average temperature obtained from the Ti K-shell spectrum. The evolutions of the electron temperature and density are predicted by the radiation hydrodynamic simulation. A top view and two photon energy bands of x-ray source images provide a way to directly observe the plasma movement toward the cavity axis and distinguish the different emission mechanisms between the Ti K-shell and lower energy x rays. Six Higher-energy x-ray detectors located at different angles were used to record the Ti K-shell x-ray emission and demonstrate its isotropic feature. The characteristics of the x-ray radiate intensity including the time evolution, the angular distribution, and the total yields for both the photon energy regions above and below 4 keV are compared between the cavity and planar targets. Obviously, different behaviors were found between the two photon energy regions and the two types of targets. The x-ray conversion efficiency of the Ti cylinder was determined to be ∼4% and ∼21% in 4π sr in the Ti K-shell (4–7 keV) and <4 keV range, respectively. The Ti K-shell conversion efficiency obtained in the present experiments is between the ones driven by 13.5 and 4.5 kJ laser energy at OMEGA.

A hohlraum used to create uniform and strongly coupled warm dense matter and its radiation flux study on the SG-III prototype laser facility are described. Time evolution of the radiation temperature from laser entrance hole (LEH) and the incident radiation temperature at the target surface are obtained using flat response X-ray diode detectors. Then, a calculation of the radiation flux evolution for this hohlraum is carried out using a view-factor method, and the calculated results agree well with the experimental data within the error bar. Using the incident radiation at the target surface as a source, the validity to create uniform and strongly coupled warm dense matter by this hohlraum is verified.

We present non-collective spectrally resolved X-ray scattering measurements from isochorically heated graphite samples. The elastic and inelastic scattering spectra for the titanium He-α x-ray line at 4.75 keV yield characterization of the temperature and ionization state of the samples. It is found that the plasma theories employing a screened Coulomb potential fail to describe the ion structure of warm dense carbon plasmas and only the models accounting for the effects of the electronic configuration show good agreement with the experimental result. This agreement further suggests that the short-lived chemical bonds play an important role in determining the ion structure of warm dense graphite systems with a temperature of several electron volts.

An eight-channel x-ray flat crystal spectrometer was developed for high energy density physics research at the Shenguang-III (SG-III) laser facility. The spectrometer uses trihydroxymethylaminomethane crystals (2d = 8.78 Å) to record Ti K-shell emission in the photon energy range of 4.65-5.05 keV. The spectrometer couples to an x-ray framing camera to achieve time-resolution. This has four microstrips, and each strip records two snapshots of the emission image. Based on the intersection positioning system with a dual-charge coupled device, the alignment system is easily operated and efficient. The instrument was tested and used for Au hohlraum plasma diagnosis experiments on SG-III. The He-α line and its Li-like satellites and the Ly-α line of a Ti tracer were detected, from which the spectral resolution of the instrument was analyzed. The spectral resolution E/ΔE at the Ti He-α line ranges from about 500 to 880 and mainly limited by the x-ray source size.

The opacity of a molybdenum plasma in local thermodynamic equilibrium with open M-shell configurations was measured in the energy range from 200 eV to 800 eV, corresponding to the Δn = 1 M to N shell and Δn = 2 M to O shell transitions. The sample was heated by thermal x-ray radiation generated with a gold cavity. The electron temperature was diagnosed with the absorption spectrum of doped aluminum, giving a value of Te = (67 ± 4) eV. The density was 9.7 mg/cm3, which was deduced from the known initial area density and the plasma thickness by radiographic measurements of the expansion of the heated foil sample. The spectrally resolved transmission data were compared to a detailed-configuration-accounting model calculation and about 20% to 100% discrepancies were found.

Fluorescence imaging of surrogate Si-doped CH targets has been used to provide a measurement for drive condition of high-energy x-ray (i.e. M-band x-ray) drive symmetry upon the capsule in hohlraum on Shenguang-II laser facility. A series of experiments dedicated to the study of photo-pumping and fluorescence effect in Si-plasma are presented. To investigate the feasibility of fluorescence imaging in Si-plasma, an silicon plasma in Si-foil target is pre-formed at ground state by the soft x-ray from a half-hohlraum, which is then photo-pumped by the K-shell lines from a spatially distinct laser-produced Si-plasma. The resonant Si photon pump is used to improve the fluorescence signal and cause visible image in the Si-foil. Preliminary fluorescence imaging of Si-ball target is performed in both Si-doped and pure Au hohlraum. The usual capsule at the center of the hohlraum is replaced with a solid Si-doped CH-ball (Si-ball). Since the fluorescence is proportional to the photon pump upon the Si-plasma, high-energy x-ray drive symmetry is equal to the fluorescence distribution of the Si-ball.

Time-resolved x-ray self-emission imaging was used to study the dynamic evolution of a laser-produced gold plasma tamped by plastic (CH), and a significant plasma collapse was observed during the laser irradiation. The plasma collapse, a kind of transverse contraction, has been ascribed to the radial compression caused by the different radiative cooling rates and thus different pressures between the central high-Z gold plasma and the surrounding low-Z CH plasma, and this has been reproduced by numerical simulations using the two-dimensional radiation-hydrodynamics code Multi2D. The experimental results represent an observation of the radiative cooling induced plasma jet within a 1 ns laser pulse duration, much more quickly than those reported previously. In addition, our experiment design may offer a method to study the radiative cooling rates of high-Z plasmas. The measured cooling rate is a factor of 2 higher than the theoretical result [Post et al., At. Data Nucl. Data Tables 20, 397 (1977)], but is within the stated calculational uncertainty.

The first observation of the K-shell photoabsorption edge of strongly coupled aluminum generated by intense x-ray radiation-driven shocks is reported. By using a "dog bone" gold hohlraum as an x-ray converter, colliding shocks compression and preheating shielding are achieved to generate an unexplored state with a density of 5.5 g/cm(3) and temperature of 0.43 eV (the ion-ion coupling parameter Gii is around 240). The time-resolved K-shell photoabsorption edges are measured with a crystal spectrometer using a short x-ray backlighter. The broadenings and redshifts of the edges are studied by using the slope fitting of the edge and quantum molecular dynamics calculations. This work shows that the K-edge of aluminum driven by laser-converted radiation provides a novel capability to probe WDM at extended conditions. Copyright (C) EPLA, 2017

Transmission measurements of warm dense iron plasma are reported over the photon energy range of 400–1200 eV, including the strong 2p–3d structures. One-dimensional hydrodynamic simulation is performed to estimate the plasma conditions: temperatures of several eV and densities of about 0.1 g/cm3. By using the simulated temperature and density, the calculations of the transmission spectra are performed and compared with the time-resolved experimental results.

We report on opacity measurements of a silicon (Si) plasma at a temperature of (72 ± 5) eV and a density of (6.0 ± 1.2) mg cm−3 in the photon energy range of 1790–1880 eV. A 23 μg cm−2 Si foil tamped by 50 μg cm−2 CH layers on each side was heated to a hot-dense plasma state by X-ray radiation emitted from a D-shaped gold cavity that was irradiated by intense lasers. Absorption lines of 1s − 2p transitions of Si xiii to Si ix ions have been measured using point-projection spectroscopy. The transmission spectrum of the silicon plasma was determined by comparing the light passing through the plasma to the light from the same shot passing by the plasma. The density of the Si plasma was determined experimentally by side-on radiography and the temperature was estimated from the radiation flux data. Radiative hydrodynamic simulations were performed to obtain the temporal evolutions of the density and temperature of the Si plasma. The experimentally obtained transmission spectra of the Si sample plasma have been reproduced using a detailed term account model with the local thermodynamic equilibrium approximation. The energy levels, oscillator strengths and photoionization cross-sections used in the calculation were generated by the flexible atomic code. The experimental transmission spectrum was compared with the theoretical calculation and good agreement was found. The present experimental spectrum and theoretical calculation were also compared with the new opacities available in the Los Alamos OPLIB database.

We describe an experimental technique to measure the drive symmetry of M-band radiation on the capsule in hohlraum. M-band radiation from the corona of the laser-produced gold plasma, especially the laser spot regions in the cavity, was used to pump x-ray fluorescence of a thin layer of Si-tracer coated on a solid CH-ball. The fluorescence images were time resolvedly recorded by an x-ray framing camera and the drive asymmetry due to M-band radiation was deduced from these fluorescence images. Moreover, a Si-doped gold cavity was used with the initial purpose of maximizing the fluorescence signal through resonance transitions. Since the Si-plasma expands more rapidly than the gold-plasma, the evolution of drive asymmetry was accelerated in Si-doped hohlraum.

An extreme ultraviolet spectrometer has been developed for high-energy density physics experiments at the Shenguang-III (SG-III) laser facility. Alternative use of two different varied-line-spacing gratings covers a wavelength range of 10-260 Å. A newly developed x-ray framing camera with single wide strip line is designed to record time-gated spectra with ~70 ps temporal resolution and 20 lp/mm spatial resolution. The width of the strip line is up to 20 mm, enhancing the capability of the spatial resolving measurements. All components of the x-ray framing camera are roomed in an aluminum air box. The whole spectrometer is mounted on a diagnostic instrument manipulator at the SG-III laser facility for the first time. A new alignment method for the spectrometer based on the superimposition of two laser focal spots is developed. The approaches of the alignment including offline and online two steps are described. A carbon spectrum and an aluminum spectrum have been successfully recorded by the spectrometer using 2400 l/mm and 1200 l/mm gratings, respectively. The experimental spectral lines show that the spectral resolution of the spectrometer is about 0.2 Å and 1 Å for the 2400 l/mm and 1200 l/mm gratings, respectively. A theoretical calculation was carried out to estimate the maximum resolving power of the spectrometer.