Initial Moving Mechanism of Densely-Packed Particles Driven by a Planar Shock Wave

The initial moving mechanism of densely packed particles driven by shock waves is unclear but vital for the next accurate calculation of the problem. Here, the initial motion details are investigated experimentally and numerically. We found that before particles show notable motion, shock waves complete reflection and transmission, and stress waves propagate downstream on particle skeleton. Due to the particle stress wave, particles successively accelerate and obtain an axial velocity of 6–8 m/s. Then, the blocked gas pushes the upstream particles integrally to move downstream, while the gas flow in the pores drags the downstream particles to separate dramatically and accelerate to the velocity of 60–70 m/s. This gas push-drag dual mechanism transforms densely packed particles into a dense gas-particle cloud, which behaves as the expansion phenomena of the dense particles.

Reflecting laser-driven shocks in diamond in the megabar pressure range

In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into solid multi-layered diamond samples. The target design allows shock velocity in diamond and in two metal layers to be measured as well as the free surface velocity after shock breakout. As diagnostics, we used two velocity interferometry systems for any reflector (VISARs). Our measurements show that for the pressures obtained in diamond (between 3 and 9 Mbar), the propagation of the shock induces a reflecting state of the material. Finally, the experimental results are compared with hydrodynamical simulations in which we used different equations of state, showing compatibility with dedicated SESAME tables for diamond.