Equations of state of some standard materials and the ahsolute tigh-pressure scale

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The objectives are to obtain experimental parameters for equations of state of some standard materials at pressures of multi-terapascal and to establish the absolute high-pressure scale. We need a high-velocity acceleration facility for symmetric impact of flat-plate-shaped materials in order to generate multi-terapascal pressures. The facility is a three-stage light-gas gun which was constructed by us seven years ago and was much improved after the construction. In this study, some operational timing jitters for synchronizing quick motion of heavy mechanical parts were reduced and confirmed. Since, however, the cooling of hydrogen gas and the erosion of a gun barrel were serious, remarkable increase of acceleration was not achieved. The projectile velocity of 10 km/s for a pressure of 1 TPa was not achieved.On the other hand, some new techniques were developed for such compact gas gun to be employed for accurate and precise equation of state experiments ; one is a convenient and preci … More se timing system, and the other is a fiber-transport-type line-laser reflection system for measuring shock velocity in materials. The former is based on the pre-event pulse generator which was developed originally by the head investigator ; the system can generate a timing trigger pulse which has a few nanoseconds time-resolution by the flyer and does not need a trigger pins arrangement on the target. Therefore, the system makes it possible that the target size is as large as the flyer. The latter also makes it possible to observe flyer distortion and tilt and target deformation due to escaped acceleration-gas.The absolute error of high pressure Hugoniot parameters was +/- 0.5% upto impact velocity of 6.5 km/s in the case of copper symmetric impact, but +/-2 or 3% between impact velocities of 6.5 and 8 km/s due to the both of deformation of target and flyer. We need to improve some technical issues such as optimization of gun operation and reinforcing of target assembly in order to obtain high-pressure standard data for multi-terapascals. Less