Measurement of shock and re-shock Hugoniot data of liquid nitrogen

ABSTRACT In this work, the equation-of-state data for liquid nitrogen shock compressed to 43 GPa along the principal Hugoniot and reflected-shock data up to 91 GPa were reported. A cryogenic target was used to liquefy the gas that was then further compressed by high-speed impactors. The first- and second-shock states were observed by a high-precision Doppler pin system (DPS). Optical wavefrom of DPS resulted in the first-shock velocity from which other derivative quantities i.e. particle-velocity, specific-volume, internal-energy, and Grüneisen-parameter, were determined. Our results and published equation-of-state data were used to extrapolate the principal Hugoniot. Their comparison showed softening above 27 GPa, attributed to the absorption of thermal energy that dissociates the molecular nitrogen. Our single-shock data provided a good match to available Hugoniot data. The reduced velocity profiles allowed us to detect optical reflectance of the dissociated liquid phase, and the apparent shock-velocity was used to determine the true shock-velocity in dissociation threshold.