New physics-based analysis approaches to determine free surface velocities, and the arrival of the free surface at lithium-niobate piezoelectric pins in the presence of dense ejecta

We apply new velocimetry (PDV) and ejecta analysis techniques on a 40 mm powder-gun experiment and find exceptional timing and precision and accuracy between two independent diagnostics. The experiment studied ejecta formation from Ce at the M-9 (Shock and Detonation Physics Group) Dynamic Equation of State (DEOS) facility. The diagnostics included PDV and lithium-niobate (LN) piezoelectric pins. The 50 mm diameter and 1.5 mm thick Ce sample was affixed to a Cu plate within an environmentally controlled cell that was filled with He to an initial gas pressure of P_I = 5.25 atm. The impact was symmetric, Cu impacting the Cu plate, and the impactor velocity was U_I = 1.883±0.008 mm/ms, as determined from six PZT-pins from a pin-block diagnostic. The new PDV analysis approach observed a free-surface velocity of u_fs = 2.432±0.003 mm/ms from seven PDV probes. The new LN-pin analysis technique determined the surface arrival, at the heights z_p = 20.2 mm of three LN-pins, to be t_fs = 19.439±0.009 ms. Based relative common timing of 0.010 ms between the two diagnostics, we evaluated the precision and accuracy of the combined approaches. That is, from the observed first motion in the PDV amplitude vs. time signals a(t), the shockwave breakout time from the Ce sample was t_BO = 11.130±0.006 ms. From this, the predicted arrival time of the Ce surface at the LN-pins was 19.435±0.006 ms, in exceptional agreement with t_fs. Additional validation is the shockwave in the He gas. Based on u_fs, we calculate a gas-shockwave velocity of U_S(C) = 3.530 mm/ms, which is to be compared the LN-pin measured velocity of U_S(M) = 3.509 mm/ms. We will present full details of the two new physics approaches we developed and applied on the Ce ejecta experiment on the DEOS 40 mm powder gun.