ilAbstract. We measured the response of short FBGs to a weak planar shock wave. The combined effect of the Photo-Elastic effect and the FBG strain was estimated theoretically depending on its orientation with respect to shock front (for 1550 nm FBG, parallel: 0.9 nm/kbar, perpendicular: -1.4 nm/kbar). The experimental results imply that the FBG/fibre survives for more than 1 μs at 5 kbar shock stress, and that our assumptions about the FBG behaviour under dynamic loading are valid, though more work is needed to fully quantify the effect.

The recovery of metastable structures formed at high pressure has been a long-standing goal in the field of condensed matter physics. While laser-driven compression has been used as a method to generate novel structures at high pressure, to date no high-pressure phases have been quenched to ambient conditions. Here we demonstrate, using in situ x-ray diffraction and recovery methods, the successful quench of a high-pressure phase which was formed under laser-driven shock compression. We show that tailoring the pressure release path from a shock-compressed state to eliminate sample spall, and therefore excess heating, increases the recovery yield of the high-pressure ω phase of zirconium from 0% to 48%. Our results have important implications for the quenchability of novel phases of matter demonstrated to occur at extreme pressures using nanosecond laser-driven compression.

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Investigation of the dynamic properties of aluminum targets with helium bubbles is presented. The targets were obtained by melting pure aluminum with 0.15% wt. 10 B powder. The solid targets were neutron irradiated to get homogeneous helium atoms inside the aluminum boron 10 matrix according to the reaction 10 B + n → 7 Li+ 4 He. Helium atoms further accumulated into bubbles by diffusion in the bulk aluminum. Shock wave experiments were performed by accelerating the aluminum impactor into different targets: (1) pure aluminum, (2) Al-10 B, and (3) Al-10 B with different radii and concentrations of helium bubbles. The spall strength was calculated and analyzed from the free surface velocity measurements. It was found that the addition of 10 B in pure aluminum reduces the spall strength of the material by 25-32%. However, irradiated sample with helium bubbles was found to have higher spall strength compared to samples without bubbles. This finding was reconstructed by numerical simulations. The impacted targets were collected after the impact experiments and examined by TEM. These targets were compared to TEM pictures before the impact. The number of helium atoms in the bubbles was calculated from the electron energy loss spectrum (EELS).TEM comparison between the pre-impacted and the impacted targets shows bubbles coalescence and EELS measurements demonstrate a reduction of the helium atoms concentration in the bubbles from ∼ 10 28 m −3 before the impact to ∼10 27 m −3 after the impact.

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