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Thomson scattering (TS) is a powerful diagnostics for understanding the plasma conditions in high energy density experiments. With the aid of Monte Carlo simulation and statistical analysis, we demonstrated unreported high precisions of ne, Te, Ti, etc., via fitting the multiple-wavenumber spectra of ion-acoustic featured TS simultaneously. For instance, utilizing this method in the current typical conditions on SG-180kJ laser facility, the precisions of ne, Te would be better than 8% and 0.5%, respectively. We presented the fitting precisions at different cases and the chi-square trends of the single- and dual-branch TS. This diagnostic technique is found to be applicable within a wide range of plasma parameters and wavenumbers, which is practical to prompt much more precise plasma diagnostics in experiments. [ABSTRACT FROM AUTHOR]

In the experiment of indirect-drive inertial confinement fusion, hot electrons in hohlraum are usually inferred from the bremsstrahlung, measured with filter-fluoresce X-ray spectrometer. Here, we study the feasibility of measuring hot electrons by detecting the transition radiation, emitted from energetic electrons passing through the outer surface of hohlraum. With the aid of Monte Carlo simulations, it was found that the intensity of black-body radiation in optical range, due to the energy deposition of electrons, is at least one order of magnitude larger than that of optical transition radiation, but two orders of magnitude smaller than the intensity in THz range. Hence, it would be plausibly feasible to detect the transition radiation in the far infrared and THz range. Furthermore, the sensitivity of intensity versus thickness and temperature are discussed with two temperature components of hot electrons. Finally, a proposal of diagnostic for hot electrons is put forward by adopting the wedge or stepped plate. [ABSTRACT FROM AUTHOR]

Reducing hohlraum wall loss is one of the most important ways to improve hohlraum coupling efficiency in laser indirect drive inertial-confinement fusion. It is appeared that a high Z metallic foam as hohlraum wall material will reduce wall loss. By adjusting initial hohlraum wall density distribution along radial axes to ρ0(r)=kr, the numerical simulation results show that it can indeed bring best savings of ∼40% general wall loss. We conclude that absorbed energy mainly decreases by restraining rarefactions, and a proper slope k can optimize internal energy loss of low density and increased kinetic loss by subsonic. Also saved energy ratio reduces with source temperature decreasing. This approach would cut the reactor driver that needs quite substantially if experiments demonstrate it. [ABSTRACT FROM AUTHOR]

Recently, hohlraum experiments were performed at the Shenguang-II (SG-II) laser facility [Lin et al., Chin. J. Lasers B10, Suppl. IV6 (2001)]. The measured maximum radiation temperature was 170 eV for the standard hohlraum and 150 eV for a 1.5-scaled one. This paper discusses the radiation temperature and laser hohlraum coupling efficiency in terms of a theoretical model [Phys. Plasmas 8, 1659 (2001)] and numerical simulation. A 2D laser–hohlraum coupling code, LARED-H [Chin. J. Comput. Phys. 19, 57 (2002)], gives a satisfactory coincidence with the measured time-resolved radiation temperature. Upon fitting the time-resolved curve, the theoretical model obtains the hohlraum coupling efficiency and, furthermore, the parameter n+s for the hohlraum wall material (Au) can be determined simultaneously, where n, s are the power exponents of temperature for the radiation Rosseland mean-free path and specific internal energy, respectively. © 2002 American Institute of Physics. [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]

In implosion experiments, bremsstrahlung radiation ratios of broad-energy-band x-ray emission intensities (sampled by Ross pair) and narrow-energy-band x-ray emission intensities (sampled by multilayer) are typically used to extract the hotspot electron temperature. The latter method could potentially be more accurate because it does not require any additional theoretical arithmetic. However, the boundary conditions of the energy band, drastic influence on the measured electron temperature resulting from response differences of recording devices in the energy band, evident impact from uncertainties of the detector aiming, and coordinate interrelations for the two narrow-energy-band x-ray images have not been explored. These problems should be overcome to obtain the accurate hotspot electron temperature using the narrow-energy-band x-ray emission intensities method. This study solves the problems indicated above by exploring a diagnosis technique to extract the accurate hotspot electron temperature. In particular, we determine that the effect of the response differences and uncertainties could be ignored when the width of the sampled narrow energy band is approximately ±0.5 keV in the linear spectrum response regions of the imaging plate, and the reflectivity of the multilayer is uniform and constant in that energy band and the viewing field of the detector (≥±110 µm). This study is the first to consider the linear spectrum response of the imaging plate in different energy regions, eliminating the effect of the response differences. Finally, the maximal emission intensities in the two recorded-energy-band x-ray images can be used for coordinate interrelation. [ABSTRACT FROM AUTHOR]

Abstract: The orbital relaxation effect was studied in the calculations and diagnostics of the L-shell absorption spectra () of iron and bromine plasmas. A detailed level accounting model was developed to calculate the huge number of L-shell absorption lines of the two typical mid-Z plasmas. The orbital sets were generated by the optimizations according to the initial and final states, respectively. It was found that the L-shell line positions agree with the experimental iron and bromine spectra better when the orbital relaxations were included in calculations. Since experimental mid-Z spectra have few detailed line structures, calculations without considering orbital relaxations may misinterpret the spectra and consequently lead to underestimations of the plasma temperatures. [Copyright &y& Elsevier]

In inertial confinement fusion implosion experiments with the primary-neutron yield as low as 107, the method of yield ratio is proposed to diagnose the areal density <ρR> at Shenguang II laser facility. Considering the detection efficiency and the time response, a new detector for detecting the secondary-neutron signal is developed, which locates 50 cm away from the target. According to Monte Carlo N-particle simulation, 5-cm-thick lead shield was placed in front of the detector to shield x rays. In the 2004 experiments, the highest primary-neutron yield is 3.18×106, which is an order lower than expected. Inspite of this fact, a secondary-neutron signal is measured for the first time at the Shenguang II laser facility, which proves the method’s feasibility. The method will be used in the experiments at the prototype of Shenguang III laser facility. [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]

The effect of the shell mass on the hot spot pressure is investigated numerically for the Inertial Confinement Fusion (ICF) implosion. By using a simplified one-dimensional spherical model, it is found that there exists a critical shell mass that determines whether the hot spot can reach the maximum pressure. When the shell mass is larger than the critical mass, the hot spot pressure reaches the maximum value determined by the conventional scaling law P h s max ∝ Mac h 3.2 (Mach is the Mach number of the imploding shell) and is independent of the shell mass. When the shell mass is smaller than the critical mass, the hot spot pressure decreases with decreasing shell mass. The dependence of the hot spot pressure on the shell mass can be uniformly described by an analytic formula. A similar effect of the shell mass on the hot spot pressure is also found in realistic ICF implosion for both direct drive and indirect drive. The conventional ICF implosions belong to the situation that the shell mass is smaller than the critical mass. The analytic formula can also be used to quantify the shell mass effect on the hot spot pressure for realistic ICF implosion when the effective shell mass is correctly taken into account. [ABSTRACT FROM AUTHOR]

The technique of x-ray fluorescence imaging (XRFI) has been applied to the high-energy-density (HED) jet experiments on the SG-III prototype laser facility. The jet was produced by the interaction of the laser driven shock with the perturbed Ti disk. The fluorescence emission of the Ti ejecta was pumped by the V He-α emission and recorded using a Ross Pair Imager with an optimized configuration. We achieved a spatial resolution of 35 μm and a temporal resolution of 1 ns. We also developed a method to infer the density distribution of the jet from the fluorescence images and discussed the conditions under which this method was accurate. These experiments provided insight into the characteristics of a HED jet and implied that XRFI is a promising way for studying HED hydrodynamics. [ABSTRACT FROM AUTHOR]

Laser drive ramp compression is an important method to achieve an extremely high-pressure but relatively low-temperature material state. In this study, we found VISAR streaks disappearing under high pressure. To solve this problem, the mechanism of probe-laser absorption in laser drive ramp compression experiments has been studied, and X-ray preheat is found to be the main factor in this mechanism. Subsequently, target configuration optimization and code simulation were performed based on previous experiments, and laser drive ramp compression experiments were performed on the SHENGGUANG prototype facility. In the experiments, the probe-laser reflectivity was above 90% at 450 GPa, which is much higher than those in previous experiments, demonstrating that the X-ray preheat was shielded well with the optimized target configuration. [ABSTRACT FROM AUTHOR]

The first implosion tuning experiment with a shaped pulse driven was performed on the SGIII laser facility by using 2D X-ray radiography. Under the careful design, we obtained the driven symmetry both in the picket and peak. The experimental results show that the P2/P0 asymmetry can be tuned by varying the fraction energy in the inner cone both in the picket and peak. The radiation symmetry at the peak is consistent with our simulation. However, the radiation symmetry in first 0.5 ns (picket) had an unexpected negative P2/P0, which is different from the simulation; it may be caused by inner cone absorption in the tent which supported the capsule. [ABSTRACT FROM AUTHOR]

The M-band X-ray (1.6–4.4 keV) preheating and shock temperature of aluminum (Al) foil coated on a thick polystyrene (CH) layer is experimentally measured using a streaked optical pyrometer system (SOP) in the SG-III prototype laser facility for the first time. Multi-group hydrodynamic simulation captures the main characteristics of rear surface emission. Compared with the unpreheated target with bromine (Br) doped, M-band X-rays have a large impact on shock propagation inside the undoped target. Preheating changes target the initial state and generate a broader shock front, resulting in drastic variation in rear surface emission features. By comparing sensitivity analysis in the simulation and experimental uncertainty range, it is found that the SOP measurement could achieve valuable information on the shock transition time and unique emission profile, offering reliable boundary and benchmarks for simulation and analysis. Proper evaluation on the radiation source, including both the flux and the spectrum, and material opacities is essential for data interpretation. This study could promote our understanding and predictive capability required for inertial confinement fusion studies. [ABSTRACT FROM AUTHOR]

Abstract In indirectly driven inertial confinement fusion, a high-purity germanium detector is widely used in the calibration of various X-ray detectors as a quantitative spectrum detector for the irradiating X-ray. However, the intrinsic peak efficiency of the high-purity germanium detector, which is the foundation of its applications, has not been investigated in depth. In this work, an optimized data-processing method is developed to explore the intrinsic peak efficiency of the high-purity germanium detector, based on calibration experiments. The intrinsic peak efficiency of the detector is absolutely and accurately calibrated and simulated for X-ray energy in the range of 5.48–302.85 keV. The experimental and simulated results, which agree well, are analyzed and explained in detail. The efficiency curve obtained from the data reveals the rise, flat, and fall characters. In addition, the impact of the absorption edge, which is located at 11.10 keV, on the efficiency curve was found and explained in terms of the escape of the excited K α lines. This work will improve the calibration efficiency of various X-ray detectors based on the high-purity germanium detector, and help in advancing the quantitative understanding of the detection results in inertial confinement fusion. [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]

Radiation computation is very important for high energy density experiments design in the laser-driven Inertial Confinement Fusion. The view-factor based models are often used to calculate the radiation on the capsule inside a hohlraum. However, it usually takes much time to solve them when the number of equations is very large. In this paper, an efficient iteration approach GPU is presented. The core idea is: (1) guaranteed symmetry, strictly diagonally dominant, and positive definite properties underlying the models are described, (2) a preconditioned conjugate gradient iteration approach is presented to compute the radiation based on such guaranteed properties, and (3) such approach is then parallelized and implemented for GPU so that the large scale models, especially for the non-linear model, can be efficiently solved in reasonable time. Finally, two experimental targets for Shenguang laser facilities built in China are demonstrated and compared to validate the efficiency of the presented approach. The results show that, the models’ computation (1) can be speeded up with successive over-relax iteration method by eight times as compared with Cholesky factorization based direct approach, (2) can be accelerated more with the preconditioned conjugate gradient iteration approach by almost eight times, and (3) can be further accelerated about 2 to 4 times as it parallelized and run on the GPU, which enables the large scale models, can be efficiently solved in reasonable time on the usual desktop computers. [ABSTRACT FROM AUTHOR]

Space-resolving flux detection is an important technique for the diagnostic of the radiation field within the hohlraum in inertial confinement fusion, especially for the radiation field diagnostic in the novel spherical hohlraum with octahedral six laser entrance holes (LEHs), where localized measurements are necessary for the discrimination of the radiation flux from different LEHs. A novel space-resolving flux detector (SRFD) is developed at the SG-III laser facility for the radiation flux measurement in the first campaign of the octahedral spherical hohlraum energetics experiment. The principle and configuration of the SRFD system is introduced. The radiation flux from the wall of a gas-filled octahedral spherical hohlraum is measured for the first time by placing the SRFD system at the equatorial position of the SG-III laser facility, aiming at the hohlraum wall through one of the six LEHs. The absolute radiation flux from the re-emission area on the hohlraum wall is measured, and good consistency is found between the experimental data and the calculated data from a three-dimensional view factor analysis. [ABSTRACT FROM AUTHOR]

An analytical ramp compression model for condensed matter, which can provide explicit solutions for isentropic compression flow fields, is reported. A ramp compression experiment can be easily designed according to the capability of the loading source using this model. Specifically, important parameters, such as the maximum isentropic region width, material properties, profile of the pressure pulse, and the pressure pulse duration can be reasonably allocated or chosen. To demonstrate and study this model, laser-direct-driven ramp compression experiments and code simulation are performed successively, and the factors influencing the accuracy of the model are studied. The application and simulation show that this model can be used as guidance in the design of a ramp compression experiment. However, it is verified that further optimization work is required for a precise experimental design. [ABSTRACT FROM AUTHOR]

Incoherent random lasing action in flexible eggshell membranes infiltrated with rhodamine 6G laser dyes is demonstrated. Laser radiation is achieved by exciting samples with 1-ns pulses at 526 nm. A threshold of 58 μJ/pulse is measured for the samples. The minimum threshold decreases to 35 μJ/pulse after the sample is coated with gold nanoparticles using a magnetron sputtering technique. The peaks of emission spectra are observed to redshift from 576 to 596 nm as dye concentration rises from 0.03 to 0.6 wt%. A linewidth of approximately 5 nm is obtained for most samples. This study is expected to offer a new way to induce lasing emission using biological microfibrils, and enriches basic knowledge of biophotonics. [ABSTRACT FROM AUTHOR]

High-space-resolving information of hotspot electron temperature is a foundation for further research on physical processes of implosion in inertial confinement fusion. This work proposed a novel high-space-resolving electron temperature detector, which is based on the bremsstrahlung radiation mechanism of the implosion hotspot and uses two-channel Kirkpatrick–Baez microscopes. In this novel detector, an optical quasi-coaxis method was used to eliminate the strong impact of the view field difference on the high space resolution and correctness of the electron temperature diagnosis, and a compound KB microscope method was proposed to reduce the number of spherical reflectors and save space. [ABSTRACT FROM AUTHOR]

Energy levels, radiative rates, and wavelengths are calculated for all levels of 3s 2 3p, 3s3p 2 , 3s 2 3d, 3p 3 , 3s3p3d, 3p 2 3d and 3s3d 2 configurations of Al-like krypton ion (Kr XXIV). Multiconfigurational Dirac–Hartree–Fock (MCDHF) method is adopted for calculating energy levels and radiative rates. Transition probabilities are reported for E1 and M2 transitions from the ground level. The valence–valence and core–valence correlation effects are accounted for in a systematic way. Breit interactions and quantum electrodynamics effects are estimated in subsequent relativistic configuration interaction calculations. Comparisons are made with the available data in the literature and good agreement has been found which confirms the reliability of our results. [ABSTRACT FROM AUTHOR]

Physical experiment design and optimization is very essential for laser driven inertial confinement fusion due to the high cost of each shot. However, only limited experiments with simple structure or shape on several laser facilities can be designed and evaluated in available codes, and targets are usually defined by programming, which may lead to it difficult for complex shape target design and optimization on arbitrary laser facilities. A unified modeling approach for physical experiment design and optimization on any laser facilities is presented in this paper. Its core idea includes: (1) any laser facility can be flexibly defined and included with two scripts, (2) complex shape targets and laser beams can be parametrically modeled based on features, (3) an automatically mapping scheme of laser beam energy onto discrete mesh elements of targets enable targets or laser beams be optimized without any additional interactive modeling or programming, and (4) significant computation algorithms are additionally presented to efficiently evaluate radiation symmetry on the target. Finally, examples are demonstrated to validate the significance of such unified modeling approach for physical experiments design and optimization in laser driven inertial confinement fusion. [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]

Measurements of iron-plasma absorption spectrum over 150-1200 eV photon energy range were reported at temperature T = (72 ± 4) eV. The electron temperature was diagnosed with the absorption spectrum of aluminum mixed with iron. The density was not diagnosed directly but obtained from a radiative hydrodynamic simulation with the Multi-1D code. The broad photon energy range enables simultaneous observation of the L-shell and M-shell transitions that dominate the radiation transport at this temperature. The spectrally resolved transmission data were compared to the detailed-configuration-accounting model calculations and reasonable agreement was found. [ABSTRACT FROM AUTHOR]

Abstract: An X-ray framing camera using a large-format microchannel plate (MCP) is reported. The diameter of the MCP is 106mm and the width of each microstrip line cathode deposited on the MCP is 12mm. The temporal record length of the camera is about 3ns. The photocathode is driven by a gating electrical pulse having a width of 175ps and an amplitude of −2.5kV plus −300V bias, while the exposure time is about 69ps. Finally the gain uniformity of the microstrip line photocathode is measured, showing that there is a 8.9× drop in gain along the pulse propagation direction, whereas the variations in the gain transverse to the pulse propagation direction are within 16.7%. [Copyright &y& Elsevier]

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]

The opacity of a gold plasma at the temperature of 85 eV and density of 0.02 g/cm3 was measured over the energy range from 150 eV to 1200 eV. The gold sample was heated by thermal x-ray radiation generated with a foam-baffled gold cavity. The sample transmission was obtained from the backlight, absorption and self-emission spectra measured by a time-gated, spatially resolved grating spectrometer, with the backlight and absorption spectra being measured simultaneously in a single shot and the self-emission in another shot. The temperature and density of the gold absorber were determined by the hydrodynamic simulation with Multi-1D code, which was partially tested by the reemission radiative flux measurements of the heated sample. This work permits the first test of opacity models over the photon energy range that dominates the Rosseland mean opacity at the temperature of interest for the inertial confinement fusion. [ABSTRACT FROM AUTHOR]

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]

Laser interaction with a nanobrush target plasma is investigated at the SILEX-I laser facility [X. F. Wei et al., J. Phys. Conf. Ser. 112, 032010 (2008)] with a laser of intensity 7.9×1018 W/cm2. Highly collimated fast electron beams with yields of more than three times higher than that from the planar target can be produced. Two-dimensional particle-in-cell simulation confirms that a layered surface structure can increase the efficiency of laser energy absorption, and the resulting fast electrons are tightly collimated and guided by the plasma layers to a cross section of about the laser spot size. [ABSTRACT FROM AUTHOR]

The Hohlraum physics experiments performed on the SGIII-prototype laser facility are simulated by using our two-dimensional radiation hydrodynamic code LARED-H, and the influence of laser intensity on the two-dimensional Hohlraum simulations is studied. Both the temporal radiation temperature and the x-ray spectrum from the simulations agree well with the observations, except that the simulated M-band fraction (greater than 2 keV) is obviously smaller than the observation. According to our study, the coupling efficiency from laser to x-ray is around 70% for SGIII-prototype laser facility Hohlraums. [ABSTRACT FROM AUTHOR]

A technique that combines the diagnostics of electron temperature history and the measurements of ablation velocity with two-tracer x-ray spectroscopy has been developed for diagnosing the temperature profiles in the thermal conduction layers of laser-ablated plastic foils. The electron temperature in the plastic ablator was diagnosed using the isoelectronic line ratios of Al Lyα line to Mg Lyα line, emitted from a tracer layer of Al/Mg mixture buried under the ablator. The ablation velocity was inferred from the time delay between the onset time of x-ray line emissions from Al and Mg tracer layers buried at two depths in the ablator, respectively. From the measured electron temperatures and ablation velocity, the electron temperature profile in the conduction layer was inferred. The measured temperature profile was compared with the simulated one and reasonable agreement was found. [ABSTRACT FROM AUTHOR]

Abstract: Coded imaging is an important technique in high energy physics, astronomy and many other areas. However, popular image reconstruction methods are not ideal for space-invariant systems, which badly restricts their application. In this paper, we propose a method based on the maximum-likelihood method that performs image reconstruction on coded images with general space-variant degradation. A universal space-variant model is adopted, and the maximum-likelihood method is applied to a Gaussian stochastic noise model to derive an iterative deblurring formula. In practice, this method shows fine smoothness, convergence and good performance for strongly space-variant reconstructions. [Copyright &y& Elsevier]

A novel phase-type quantum-dot-array diffraction grating (QDADG) is reported. In contrast to an earlier amplitude-type QDADG [C. Wang et al., Rev. Sci. Instrum. 78, 053503 (2007)], the new phase-type QDADG would remove the zeroth order diffraction at some certain wavelength, as well as suppressing the higher-order diffractions. In this paper, the basic concept, the fabrication, the calibration techniques, and the calibration results are presented. Such a grating can be applied in the research fields of beam splitting, laser probe diagnostics, and so on. [ABSTRACT FROM AUTHOR]

A new dispersive element named as quantum-dot-array diffraction grating [L. F. Cao, China patent No. 200410081499 (August 10, 2004)] for visible light has been developed and characterized experimentally. A large number of quantum dots distributed on a substrate as sinusoidal function can be used to diffract x rays without higher-order diffraction. The experimental patterns show that the higher-order diffractions which inevitably exist in the spectrum recorded using traditional diffraction gratings can be eliminated effectively by this newly designed element. It indicates that quantum-dot-array diffraction grating could be an attractive alternative of presently used diffraction grating in soft x-ray spectroscopy application to get rid of the higher-order diffraction distortions. [ABSTRACT FROM AUTHOR]

Most Kirkpatrick–Baez (KB) microscopes for imaging monochromatic laser-produced plasma are composed of two concave multilayer mirrors; their energy resolution (Δ E ∕ E) is approximately 1 × 1 0 − 1 . In this study, a new type of monochromatic KB microscope combining a spherically bent crystal and a multilayer mirror was developed. As the spherically bent crystal features a narrow spectral bandwidth, it can attain a high energy resolution. In addition, the grazing incidence angle on the crystal is significantly larger than that on a multilayer mirror; therefore, a large collection solid angle and a high spatial resolution can be achieved. A prototype consisting of a spherically bent mica crystal and a mirror coated with Ni/C multilayers was constructed to demonstrate the feasibility and performance of the proposed KB microscope. In the backlight imaging experiment performed, the microscope achieved a spatial resolution of approximately 10 μ m throughout a 200 μ m field of view at 4.51 keV, with Δ E ∕ E = 4.9 × 1 0 − 3 . The proposed KB microscope featuring a high energy and spatial resolution is expected to be a novel experimental tool for inertial confinement fusion (ICF) diagnostics. [ABSTRACT FROM AUTHOR]

This note describes multi-updates of the novel flat-response x-ray detector in fabrication technology, experimental application, and data uncertainty evaluation. Unlike the previous design, the compound filter is combined into one piece through an improved fabrication process that greatly enhanced its self-supporting capability. A method of pinhole-array imaging is introduced into the experimental application process to stop any debris from the hohlraum and to uniformly reduce the radiation flux. The experimental results show that this method works well. Furthermore, a method of uncertainty evaluation of the radiation flux measurement by the novel flat-response x-ray detector has been developed. The influence of the radiation spectrum to the flux measurement is analyzed. The evaluation shows that the relative uncertainty of the radiation flux is about 10% in higher radiation temperature condition (Tr > 150 eV) and 16% in lower radiation temperature condition (Tr < 100 eV). [ABSTRACT FROM AUTHOR]

Laser pulse shape design is a key work in the design of indirect-laser-driven experiments, especially for long pulse laser driven quasi-isentropic compression experiments. A method for designing such a laser pulse shape is given here. What’s more, application experiments were performed, and the results of a typical shot are presented. At last of this article, the details of the application of the method are discussed, such as the equation parameter choice, radiation ablation pressure expression, and approximations in the method. The application shows that the method can provide reliable descriptions of the energy distribution in a hohlraum target; thus, it can be used in the design of long-pulse laser driven quasi-isentropic compression experiments and even other indirect-laser-driven experiments. [ABSTRACT FROM AUTHOR]

Direct intensity calibration of X-ray grazing-incidence microscopes is urgently needed in quantitative studies of X-ray emission from laser plasma sources in inertial confinement fusion. The existing calibration methods for single reflecting mirrors, crystals, gratings, filters, and X-ray detectors are not applicable for such X-ray microscopes due to the specific optical structure and the restrictions of object-image relation. This article presents a reliable and efficient method that can be performed using a divergent X-ray source and an energy dispersive Si-PIN (silicon positive-intrinsic-negative) detector in an ordinary X-ray laboratory. The transmission theory of X-ray flux in imaging diagnostics is introduced, and the quantities to be measured are defined. The calibration method is verified by a W/Si multilayer-coated Kirkpatrick-Baez microscope with a field of view of ∼95 μm at 17.48 keV. The mirror reflectance curve in the 1D coordinate is drawn with a peak value of 20.9% and an uncertainty of ∼6.0%. [ABSTRACT FROM AUTHOR]