Direct measurement technique for shock wave velocity under super high pressure

摘要

Ignition targets planned for the laser fusion require a pulse shape with a low power foot designed to send a carefully timed series of shocks through the frozen DT (deuterium-tritium) shell [1-3]. To achieve ignition, both the strength and timing of the shock and compression waves must be accurately set. To achieve optimal shock conditions, experiments using optical diagnostics will detect the shock-velocity temporal profiles, providing both the strength and timing of the various shocks within the capsule fuel. For the basic experiment, the technique which can measure the shock front directly in the transparent material has been developed in SGIIIYX of China. All insulators are expected to transform into metals at high enough compression due to closing of the energy gap in the density of states separating occupied and unoccupied states[4, 5]. Such pressure-induced gap closure will be preceded by a stage when thermal excitation can excite substantial numbers of electrons across the reduced gap into unoccupied states.