The basic properties of dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma (containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains) are investigated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.

https://iopscience.iop.org/article/10.1088/1674-1056/22/11/115202/pdf

Effects of bi-kappa distributed electrons on dust-ion-acoustic shock waves in dusty superthermal plasmas

Anomalous rise of the Hugoniot elastic limit (HEL) with increasing temperature was observed for aluminum and copper single crystals. Within the temperature range from 20°C to 650°C the HEL of aluminum single crystals increased from 0.12 to 0.96 GPa for 3 mm thick samples and to 3 GPa for ∼0.25 mm thick samples. The spall strength decreased from 2.3 GPa and 3.2 GPa at room temperature to 1.3 GPa and 2.2–3 GPa near the melting temperature for thicker and thinner samples, respectively. For copper single crystals a HEL of 2.6 GPa was recorded at 833°C; whereas the spall strength decreased from 5.4 GPa at room temperature to 4.8 GPa at 485°C.

Hugoniot elastic limit and spall strength of aluminum and copper single crystals over a wide range of strain rates and temperatures

Both direct-drive and indirect-drive inertial confinement fusion targets use temporally shaped drive pulses to optimize the target performance. The timing of multiple shock waves is crucial to the performance of inertial confinement fusion ignition targets. This paper reports an experimental study on the shock wave characteristics of laser-irradiated targets. The shock wave velocity profiles are measured using the velocity interferometer system for any reflector (VISAR). Presented are measurements of velocities from shock waves in quartz targets driven by single 120 ps pulse, two 120 ps pulses separated by 1.1 ns and a special shaped pulse. These pulses drive two shock waves that coalesce in the target, and the coalescence times and transit times are observed by VISAR.

Laser-driven shock propagation into quartz targets driven by various drive pulse configurations: experiments

The formation and propagation of nonlinear dust acoustic waves (DAWs) as solitary and solitary/shock waves in an unmagnetized, homogeneous, dissipative and collisionless dusty plasma comprising negatively charged micron sized dust grains in the presence of free and trapped electrons with singly charged non-thermal positive ions is discussed in detail. The evolution characteristics of the solitary and shock waves are studied by deriving a modified Korteweg–de Vries–Burgers (mKdV–Burgers) equation using the reductive perturbation method. The mKdV–Burgers equation is solved considering the presence (absence) of dissipation. In the absence of dissipation the system admits a solitary wave solution, whereas in the presence of dissipation the system admits shock waves (both monotonic and oscillatory) as well as a combination of solitary and shock wave solutions. Standard methods of solving the evolution equation of shock (solitary) waves are used. The results are discussed numerically using standard values of plasma parameters. The findings may be useful for better understanding of formation and propagation of waves in astrophysical plasma.

Characteristics of dust acoustic waves in dissipative dusty plasma in the presence of trapped electrons

In indirect-drive experiment, the blank effect caused by X-rays from Hohlraum will show the dark area in time scale of optical streak camera (OSC). This blank effect, which was a serious problem in indirect-drive shock wave experiments, has been explained by the semiconductor model. The X-rays cause the band to band transition and the probe laser is absorbed by the intraband transition, which leads to a dark region in time scale of the OSC image. In the experiment, the reflectivity of shock wave front was measured to be about 50% at shock wave velocity 32 km/s and was compared to the theoretical calculations with the Drude free electron model. From the experimental data, it is found that the blank effect can be avoided at radiation temperature of 170 eV if the Al layer is thicker than 60 μm.

http://iopscience.iop.org/article/10.1088/1674-1056/20/6/065202/pdf

Shock wave velocity measurement in the Al 2 O 3 under ultrahigh pressure

With the folding target and double-step target,the propagating character of shock wave driven by an inclined-incident (with angle of ～45°) laser was studied on “Shenguang-Ⅱ” high-power laser facility.The result indicated that the shock wave in the target still propagates along the vertical direction to the target surface.Also the same result was verified indirectly by another experiment based on the measurement for spatial intensity distribution of x-ray radiated from jet plasmas.

Experimental study of shock wave propagating character in targets driven by an i nclined-incident laser

Key Techniques of Velocity Interferometer for Any Reflector

High-power laser induced shocks generated by “ShenGuang II” laser facility has been used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s. The free surface velocity histories of shock-loaded samples, 150 μm thick and with initial temperature from 293 K to 873 K, have been recorded using velocity interferometer system for any reflector (VISAR). From the free surface velocity profile, spall strength and yield stress are calculated, it demonstrates that spall strength will decline and yield strength increase with initial temperature. The loaded samples are recovered to obtain samples' section and free surface metallographic pictures through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more opportunity to appear bigger voids near the spall plane and the grain size increases with temperature slowly but smoothly except the sharply change at 893 K (near melting point). Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with the increase of initial temperature.

/pdf/high-power-laser-shock-induced-dynamic-fracture-of-aluminum-e9wr11vd7l.pdf

High-power laser shock-induced dynamic fracture of aluminum and microscopic observation of samples

Line-imaging optical recording velocity interferometer at Shenguang-II laser facility and its applications

Shock compression properties of polyethylene (CH 2 ) were studied at SG-Ⅱ laser facility. The experimental results show that the self-emission is high,which emits from the shock-front in polyethylene. And the shock-front propagates through the polyethylene step almost with constant velocity. The Hugoniot equation of state (EOS) of polyethylene was measured by using the impedance-matching method with aluminum as standard material. Pressures are high up to 0.54 TPa in polyethylene, and the relative expanded uncertainties of the measured shockwave velocity are about 2% ( K =2). Moreover, the consistency of our data is good, and our data are also consistent with existing experimental data and EOS model.

Ye Junjian

Papers

Experimental study of shock wave propagating character in targets driven by an i nclined-incident laser

Key Techniques of Velocity Interferometer for Any Reflector

High-power laser shock-induced dynamic fracture of aluminum and microscopic observation of samples

Line-imaging optical recording velocity interferometer at Shenguang-II laser facility and its applications

Experimental study on shock compression properties of polyethylene