Investigation of new impactor materials for embedded electromagnetic gauge gas gun shots

Embedded electromagnetic gauging for gas gun-driven shock experiments requires that the impactor material be both non-magnetic and non-conducting to not interfere with the externally-applied magnetic field. This requirement limits the pressure range of these experiments, as most high impedance standards are metals. Single crystal c-axis sapphire is traditionally implemented as an impactor for high pressure embedded gauge experiments. However, the high sound speed (C0 = 11.19 km/s) of sapphire limits the duration of a well-defined shock state, due to the rapid arrival of edge effects and other wave interactions through the sapphire. To circumvent the inherent properties of sapphire, we have studied two new high impedance materials for use as impactors: zirconium nitride (ZrN) and hafnium oxide (HfO2). These materials have higher densities, lower sound speeds, and similar impedance compared to single crystal sapphire. ZrN and HfO2 respectively have sounds speed of 5.35 km/s and 4.5 km/s. The lower sound speed and higher densities of the two materials provides the two materials with similar impedance to sapphire. The equations of state for ZrN and HfO2 were studied by gas gun-driven transmission experiments, which explored projectile velocities from 0.1 km/s to 3.5 km/s, accessing pressures up to a 1 Mbar. Diagnostics for these experiments included photonic Doppler velocimetry (PDV) along with velocity interferometer system for any reflector (VISAR).

LA-UR-23-20949