Nathaniel Sanchez

An equation of state for polymethylpentene (TPX) including multi-shock response

The equation of state (EOS) of polymethylpentene (TPX) is examined through both single shock Hugoniot data as well as more recent multi-shock compression and release experiments. Results from the recent multi-shock experiments on LANLs two-stage gas gun will be presented. A simple conservative Lagrangian numerical scheme utilizing total variation diminishing interpolation and an approximate Riemann solver will be presented as well as the methodology of calibration. It is shown that a simple Mie-Gruneisen EOS based on a Keane fitting form for the isentrope can replicate both the single shock and multi-shock experiments.

DETONATION WAVE PROFILES MEASURED IN PLASTIC BONDED EXPLOSIVES USING 1550 nm PHOTON DOPPLER VELOCIMETRY

We present detonation wave profiles measured in two TATB based explosives and two HMX based explosives. Profiles were measured at the interface of the explosive and a Lithium‐Fluoride (LiF) window using 1550 nm Photon Doppler Velocimetry (PDV). Planar detonations were produced by impacting the explosive with a projectile launched in a gas‐gun. The impact state was changed from shot to shot in order to produce varied distances to detonation. In this way, we tuned the support of the Taylor wave following the Chapman‐Jouget (CJ) or sonic state. Profiles from experiments with different support should be the same between the Von‐Neumann (VN) spike and CJ state and different thereafter. Comparison of profiles with differing support, therefore, allows us to estimate reaction zone lengths. For the TATB based explosive, a reaction zone length of ≈3.9 mm, 500 ns was measured in EDC‐35, and a reaction zone length of ≈6.3 mm, 800 ns was measured in PBX 9502 pre‐cooled to −55° C. The respective VN spike state was 2.25...

The Effect of Surface Heterogeneities in Exploding Metallic Foils

During the electrical explosion of bridge-wires and bridge-foils, the metal bridge undergoes rapid resistive-heating. The metal is rapidly expanded through solid, liquid, vapour and plasma phases. This study uses ALEGRA MHD, a Sandia National Laboratory magneto-hydrocode, to predict the formation of these metallic phases during the explosion process and determine the effects of surface heterogeneities on the spatial distribution of these phases. The simulations are compared against x-ray phase contrast radiographs of electrically exploded bridge-foils. From comparison of these data, it is evident that the meso-structure of the metallic foil dominates the explosion process and is something that should be controlled during the manufacturing processes for detonator designs.During the electrical explosion of bridge-wires and bridge-foils, the metal bridge undergoes rapid resistive-heating. The metal is rapidly expanded through solid, liquid, vapour and plasma phases. This study uses ALEGRA MHD, a Sandia National Laboratory magneto-hydrocode, to predict the formation of these metallic phases during the explosion process and determine the effects of surface heterogeneities on the spatial distribution of these phases. The simulations are compared against x-ray phase contrast radiographs of electrically exploded bridge-foils. From comparison of these data, it is evident that the meso-structure of the metallic foil dominates the explosion process and is something that should be controlled during the manufacturing processes for detonator designs.

Dynamic Initiator Experiments using IMPULSE (Impact system for Ultrafast Synchrotron Experiments) at the Advanced Photon Source

Submitted for the SHOCK15 Meeting of The American Physical Society Dynamic Initiator Experiments using IMPULSE (Impact system for Ultrafast Synchrotron Experiments) at the Advanced Photon Source NATHANIEL SANCHEZ, BRIAN JENSEN, KYLE RAMOS, Los Alamos Natl Lab, ADAM IVERSON, National Security Technologies, MICHAEL MARTINEZ, GARY LIECHTY, Los Alamos Natl Lab, KAMEL FEZZAA, Argonne National Laboratory, STEVEN CLARKE, Los Alamos Natl Lab — We have successfully imaged, for the first time, the operation of copper slapper initiators that are used to initiate high explosive detonators. These data will aid in model development and calibration in order to provide a robust predictive capability and as a design tool in future applications. The initiation system consists of a copper bridge fixed to a parylene flyer. The copper bridge functions when a capacitor is discharged causing current to flow through the narrow bridge. As this happens, a plasma forms due to the high current densities and ohmic heating, which launches the parylene flyer that impacts a high explosive pellet producing detonation. Unlike traditional measurements, x-ray phase contrast imaging can see “inside” the process providing unique information with nanosecond time resolution and micrometer spatial resolution. The team performed experiments on the IMPULSE system at the Advanced Photon Source to obtain high resolution, in situ images of this process in real-time. From these images, researchers can examine the formation of the plasma instabilities and their interaction with the flyer, determine the flyer velocity, and obtain crucial information on the spatial distribution of mass and density gradients in the plasma and flyer. Nathaniel Sanchez Los Alamos Natl Lab Date submitted: 29 Jan 2015 Electronic form version 1.4

Gas gun experiments to measure the shock compression behavior of high performance propellant (HPP)

Gas-gun driven plate impact experiments were performed on High Performance Propellant (HPP) to measure the shock compression behavior and Hugoniot. HPP is a proprietary blend of ammonium-perchlorate (AP), aluminum, and plastic binder. A small amount of FeO2 gives the propellant a rust color. The primary diagnostic was embedded magnetic particle velocity gauges. The Hugoniot was determined by performing multiple experiments using different impactors and a range of impact velocities. Impact stresses ranged from 0.3 GPa to 15 GPa. Even at the highest stress no reaction was observed; none was expected. At low stress HPP exhibits viscoelastic behavior with rounded wave profiles. Hugoniot data can be described using a model based on a Murnaghan isotherm with a small amount of porosity.

Shock initiation behavior of PBXN-9 determined by gas gun experiments

The shock to detonation transition was evaluated in the HMX based explosive PBXN‐9 by a series of light‐gas gun experiments. PBXN‐9 consists of 92 wt% HMX, 2wt% Hycar 4054 & 6 wtp dioctyl adipate with a density of 1.75 g/cm3 and 0.8&% voids. The experiments were designed to understand the specifics of wave evolution and the run distance to detonation as a function of input shock pressure. These experiments were conducted on gas guns in order to vary the input shock pressure accurately. The primary diagnostics were embedded magnetic gauges, which are based on Faraday’s law of induction, and Photon Doppler Velocimetry (PDV). The run distance to detonation vs. shock pressure, or “Pop plot,” was redefined as log(X) = 2.14–1.82 log (P), which is substantially different than previous data. The Hugoniot was refined as Us = 2.32+2.211 Up. This data will be useful for the development of predictive models for the safety and performance of PBXN‐9 along with providing increased understanding of HMX based expl...