Measurement of the Very-High-Pressure Properties of Materials using a Light-Gas Gun

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Abstract
Equation-of-state data at extremely high pressure is required for the analysis of many problems pertaining to physics, geophysics, astrophysics, etc. The conventional method used to obtain such data is to impact one flat plate of material against another flat plate at a very high velocity. A shock wave is thus produced in the target plate and the pressure can be deduced by measuring the impact velocity and the shock velocity. American, Russian, and British researchers have used explosive to propel the driver plate to velocities of about 5 km/sec; however, the Russians do not indicate how they accelerate their driver plates for their highest velocities (14–15 km/sec). The present paper describes an experimental technique in which a 20-mm light-gas gun has been used to accelerate a driver plate against a target at velocities up to 8 km/sec. Tests have been conducted using Fansteel 77 drivers, and Hugoniot data have been obtained for Fansteel 77, tungsten, and gold to about 6-Mbar pressure. The technique is very attractive in that x-ray photographs show that the driver plate is not deformed just prior to impact and has an angle of attack less than 0.5 deg. Also, an analysis of all possible errors in measurement of impact velocity, shock velocity, etc. shows that, with the present technique, Hugoniot data can be obtained to an accuracy of about 1%.