Predictive Alegra MHD Simulations of the Mach Wave Concept on the Z Machine

We describe MHD modeling of the Mach Wave concept for producing dynamic high pressure shock conditions. This novel experimental platform was developed for use on the Z Machine at Sandia National Laboratories. In the Mach Wave concept, a pulsed power driver is used to implode a conical aluminum flyer onto a conical PMMA target. This creates a converging conical shock wave that forms a Mach stem at the axis, which is idealized as a planar shock traveling along the axis of the cone. Axisymmetric 2D MHD simulations in Alegra are shown to be quantitatively predictive of the flyer speed as measured in two Z shots. The simulations identified and helped address two issues with the concept: suppression of an undesirable jet from the central cathode, and control of the flyer tilt relative to the target cone at impact. Continuing development of the Mach Wave concept is aimed at increasing the maximum pressure on the sample beyond present capabilities.