Quantifying error in interface location in radiography of 1D shockwave experiments

Time-resolved radiography is a critical diagnostic in application-scale dynamic compression experiments, where the location of interfaces (derived from radiographs) provides essential information in the assessment of system performance. As such, error in the estimate of interface location is also critical, as are strategies to minimize the error. Here we evaluate the error in shock wavefront position through simulations of radiographs of approximately 1D shock propagation in a poly-[methyl methacrylate] (PMMA) sample. In previously published work, these simulations accurately emulated radiographs from a small-scale impact driven experiment at the Dynamic Compression Sector at the Advanced Photon Source/Argonne National Laboratory. One principal variable in radiography is the integration time for a single frame, where longer integration time obtains higher signal to noise, but also spatially smears the apparent location of the shock front due to motion of the front during the integration time (motion blur). Generally, motion blur is thought to reduce accuracy in estimating an interface position. Here, we apply established statistical methods to a parametric model of this system to evaluate errors in interface location as a function of the frame integration time. Counter to conventional wisdom, we find the error in the shock front location decreases with increasing integration time, consistent with the results from simulations. Here we will discuss this result, the analysis method, comparisons to experiments, applications, and limitations.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. Released for distribution: LLNL-ABS-872101.