Measurements of equation of state of gold using two frame shadowgraphy

In this paper, a new method is discussed for estimating the equation of state (EOS) of an unknown material in laser-induced shocks by measuring the particle velocities alone by using two frames optical shadowgraphy and impedance mismatch methods together. Identical shock waves are generated simultaneously in distinct regions of aluminum (reference) and aluminum with a gold step (unknown). The particle velocities in the two corresponding regions had been simultaneously measured under identical experimental conditions at laser intensities below * 5 x 10¹³ W/cm² . The EOS coefficients of gold were obtained as * 0.33 (± 0.06) x 10⁶ cm/s and 1.50 (± 0.22) using this technique. The advantages in the present technique for estimation of EOS over shock velocity measurements using a streak camera are discussed. (author)