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The phenomenon of mass ejection from shocked surface is a crucial issue in high-energy density physics and shock compression science. Ejecta from double-shock loaded metallic targets is important in some practical applications, but there are only a few research types on this aspect due to experimental difficulty. We proposed a new method of double-shock loading based on intense laser, that is, the laser is injected into a vacuum hohlraum to generate strong radiation and plasma jet simultaneously, and the target are respectively subjected to two shocks by these two different mechanisms. In the experiment, double-shock process was clearly observed by photonic Doppler velocimetry system, and the recompression of target due to the second shock was presented by x-ray photography. After the free surface was broken, the ejecta showed a unique multi-layer density structure for the first time. This work achieves effective double-shock loading with only one single laser pulse, which is valuable for understanding the metal damage under multiple shocks and the evolution of ejected materials. It also provides an experimental design for studying the material response in complex environments. [ABSTRACT FROM AUTHOR]

We present an application of short-pulse laser-generated hard x rays for the diagnosis of indirectly driven double shell targets. Cone-inserted double shell targets were imploded through an indirect drive approach on the upgraded SG-II laser facility. Then, based on the point-projection hard x-ray radiography technique, time-resolved radiography of the double shell targets, including that of their near-peak compression, were obtained. The backlighter source was created by the interactions of a high-intensity short pulsed laser with a metal microwire target. Images of the target near peak compression were obtained with an Au microwire. In addition, radiation hydrodynamic simulations were performed, and the target evolution obtained agrees well with the experimental results. Using the radiographic images, areal densities of the targets were evaluated. [ABSTRACT FROM AUTHOR]

The physics of shock-induced ejection is a crucial phenomenon in the field of shock compression science and technology. Limited by loading methods, the previous research primarily focused on the physics of ejecta induced by single shockwave, with few data available on multiple shockwave loading conditions. To solve this problem, we proposed a double shockwave production method based on the high-intensity laser facility, which allows the interval time between the shock waves to be adjusted in the nanosecond to microsecond timescale. Meanwhile, we applied loading techniques to study the ejection behavior of metal tin and integrated photonic doppler velocimetry and high-energy x-ray radiography technology to observe the ejection process. By comparing the experimental results for single and double shockwave, the multiple shock-induced ejection features have been clearly confirmed. Our experimental results provide valuable insight into the behavior of ejecta under multiple shockwave loading conditions, which is of great significance for deepening our understanding of the ejection mechanism. [ABSTRACT FROM AUTHOR]

The radiography of gamma-ray is one of the most important non-destructive testing in many fields. However, the spot size is always in millimeter scale for the generation of gamma-ray by conventional way. As the development of laser wakefield acceleration, the electron beam with small divergence and spot size can be generated easily in the experiment by tens of terawatt ultra-short laser pulse. Based on this electron beam, gamma-ray with micro spot size is generated and the properties are measured and tested in detail experimentally. The experiment demonstrates that the spot size of this gamma-ray is always smaller than 200 μm, no matter the conversion target thickness, and can be as small as about 40 μm when the conversion target thickness of 0.2 mm is used. The spatial resolution of this gamma-ray is much better than 2.5 LP/mm, the fitting temperature (which is relative to the average energy of gamma-ray) is between 5 MeV and 8 MeV, and the maximum yield per shot of the gamma-ray can be up to 9.1 × 109 photons (energy higher than 1 MeV). High-resolution radiography shows that the areal density of the gamma-ray radiography can be up to 51.3 g/cm2 (stainless steel thickness equivalent is about 6.5 cm). Such micro-spot gamma-ray can play an important role in the high-resolution radiography of high areal density objects. [ABSTRACT FROM AUTHOR]

This study is devoted to the high-energy X-ray radiography investigation on the ejecta physics of laser shock-loaded tin. The ejecta were generated via laser shock loaded tin under sequential shock-breakout pressures by high-power nanosecond lasers. A high-energy X-ray (50∼200keV) source was created to radiograph the high dense ejecta. Due to its strong penetration, high-quality radiograph images were obtained with detailed inner information and topology structure of ejecta. The areal density distribution and total mass of ejecta were further inferred. It was found that the ejecta from laser shock-loaded tin under sequential pressures show obvious difference in density distribution between the samples in a solid state and in a melt-on-release state. In addition, the total mass of ejecta was demonstrated to increase sharply when the breakout pressure is larger than the onset of melt-on-release for tin. Such increase inferred a solid-liquid phase transition of ejecta production mechanism. [ABSTRACT FROM AUTHOR]

The dynamic fragmentation of shock-loaded high-Z metal is of considerable importance for both basic and applied science. The areal density and mass-velocity distribution of dynamic fragmentation are crucial factors in understanding this issue. Experimental methods, such as pulsed X-ray radiography and proton radiography, have been utilized to obtain information on such factors; however, they are restricted to a complex device, and the spatial resolution is in the order of 100 μm. In this work, we present the high-quality radiography of the dynamic fragmentation of laser shock-loaded tin, with good two-dimensional (2D) spatial resolution. Dynamic fragmentation is generated via high-intensity ns-laser shock-loaded tin. A high-energy X-ray source in the 50–200 keV range is realized by the interaction of a high-intensity ps-pulse with an Au microwire target, attached to a low-Z substrate material. A high 2D resolution of 12 μm is achieved by point-projection radiography. The dynamic-fragmentation radiography is clear, and the signal-to-noise ratio is sufficiently high for a single-shot experiment. This unique technique has potential application in high-energy density experiments. [ABSTRACT FROM AUTHOR]