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A line-imaging optically recording velocity interferometer system (ORVIS) has been implemented on the Veloce pulsed power generator to enable measurement of spatially resolved velocity histories of materials under dynamic compression. Interferometric windows are regularly used to maintain the high-pressure state of shock and ramp (quasi-isentropic) loaded materials. Although imaging through a shock or fast ramp (<=10 ns) loaded window material has been reasonably successful, for slower ramp loading (∼440 ns) experiments, the elastic-plastic yielding of the window has an adverse effect on return light to the line-imaging ORVIS. The results of quasi-isentropic loading experiments with various interferometric windows such as LiF, PMMA, NaCl, quartz and sapphire are presented. [ABSTRACT FROM AUTHOR]

Sharing similarities with the GEPI pulser which is dedicated to Isentropic Compression Experiments (ICE), VELOCE, an even more compact electrical pulser, has been designed and built in duplicate for SNL and WSU. This type of machine complements gun and laser facilities in the study of material response. In order to achieve a broad loading capability and fast turn around, the design is built around a solid dielectric transmission line to couple current from low inductance capacitors and electrically triggered switches. Peaking capacitors enhanced by a low inductance, multi-channel sharpening switch reduce the quarter period of the pulser to about 470 ns (0–100%). Gas mixtures in the switch cavity and inductances in parallel allow modification of the shape of the induced pressure wave. At 80 kV of charge voltage, the peak current can reach 3.5 MA. Design of the pulser, range of pressures and velocities, as well as potential applications are presented. A consistent numerical tool developed for pulsers design based on a circuit code coupled to a 1D MHD code is also introduced. [ABSTRACT FROM AUTHOR]

A series of gas-gun experiments has probed the planar (uniaxial strain) impact response of six different commercial brazing alloys that were subjected to a peak shock stress in the range of 5.5 – 7.2 GPa. The alloys studied were copper + gold (65/35 wt%), copper + gold (50/50 wt%), Cusil®, Nicusil®-3, Nicoro® + titanium (98/2 wt%), and silver zirconate. Both as-received and annealed samples of each alloy were tested under ambient (room temperature) and preheated (100 C) initial conditions. Velocity interferometer data acquired during this investigation have been evaluated to determine the dynamic yield strength (i.e., Hugoniot Elastic Limit), shock Hugoniot state, and spall strength for baseline alloy samples (i.e., unheated, as-received material) and for samples whose initial condition involved annealing and/or preheating. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present new data on the unreacted approximate isentrope of the HMX-based explosive LX-04, measured to 170 kbar, using newly developed long pulse isentropic compression techniques at the Sandia National Laboratories Z Machine facility. This study extends in pressure by 70% the previous state of the art on unreacted LX-04 using this technique. This isentrope will give the unreacted Hugoniot from thermodynamic relations using a Gruneisen equation of state model. The unreacted Hugoniot of LX-04 is important in understanding the structure of the reaction front in the detonating explosive. We find that a Hugoniot given by US = 2.95 km/s + 1.69 uP yields for an isentrope a curve which fits our LX-04 ICE data well. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have developed a general purpose cryogenic target system for precision EOS studies with the Sandia Z accelerator short-circuit current drive. Condensation of large-area cryogenic liquid samples is accomplished using a cryostat evaporation refrigerator, shielded for survivability in the Z blast environment and connected by a thermal link to an expendable sample holder with active temperature control. Accurate shock physics measurements are performed using multiple, thermally isolated, fiber-optic-coupled VISAR interferometry, active shock breakout, and time-resolved optical spectroscopy diagnostics. We describe variations of this cryogenic system currently under development for three EOS measurement applications: (1) liquid D[sub 2] shock Hugoniot experiments using magnetically driven flyer plates; (2) liquid N[sub 2] isentropic compression experiments; and (3) EOS measurements on liquid [sup 4]He at 1.5 K. [ABSTRACT FROM AUTHOR]