Ejecta experiments at the Pegasus pulsed power facility

When a shock wave interacts at the surface of a metal sample "ejected matter" (ejecta) can be emitted from the surface at velocities larger than the sample velocity. The mass, size, shape, and velocity of ejecta varies depending on the initial shock conditions and the target's material properties. In order to understand this phenomena, diagnostics have been developed and implemented at the Pegasus Pulsed Power Facility (PPPF) located at Los Alamos National Laboratory (LANL). The facility provides both radial and axial access for making measurements. There exist optical, laser, and X-Ray paths for performing measurements on the target assembly located near the center of the machine. The facility can provide many mega-amps of current which are transported to a 5.0-cm diameter, 2.0-cm high aluminum cylinder. The current and associated magnetic field set up forces which implode the aluminum cylinder radially inward. As the aluminum cylinder reaches the appropriate velocity, it impacts a target cylinder. Due to this impact, a shock wave is set up in the target and eventually interacts at the inner surface of the target cylinder where ejecta are produced. A 1.5-cm diameter collimator cylinder located in the target cylinder is used to control the number of ejecta particles that arrive at the center region where ejecta measurements are made. Two diagnostic techniques for characterizing ejecta, inline Fraunhofer holography and visible shadowgraphy are detailed in this report.