Symmetrization Techniques for High Explosive Test Data

A significant fraction of high-explosive experiments involve the viewing of a nominally-axially-symmetric detonation wave breaking out of a charge surface. In such cases the emerging wave virtually always exhibits a degree of tilt. One generally wants to remove this while also quantifying its direction and magnitude. In some cases, such as front-curvature rate sticks and Onionskin (OS)-type tests, the diagnostic is a single-slit streak camera. In those instances, the tilt correction is 1D. In other cases, such as a Plane-Wave Lens characterization test or a Furball test, multiple slits or fibers provide data over parts of a surface. In those instances, the tilt correction is 2D. Our 2D technique represents the breakout time as the sum of a symmetric component and an asymmetric component (a tilted plane). The two tilt angle components are found that minimize the data scatter associated with the symmetric component. The most compelling example is the Furball test, an OS- variant for which the breakout time over the hemispherical observation surface is measured at many points using optical fibers. Here we are able to construct detonation breakout trace vs polar angle in the direction of maximum tilt, even though there are generally no fibers at that direction. This provides a distinct advantage over the traditional OS-test, for which the streak camera slit is randomly oriented with respect to the direction of maximum tilt (such that the probability of observing the worst-case tilt is very small).