Experiments Probing Fundamental Mechanisms of Energetic Material Initiation and Ignition

2012 ◽  
Vol 1405 ◽  
Author(s):  
Christopher M. Berg ◽  
Kathryn E. Brown ◽  
Rusty W. Conner ◽  
Yuanxi Fu ◽  
Hiroki Fujiwara ◽  
...  

ABSTRACTTwo fundamental processes associated with shock compression of energetic materials (EM) are initiation and ignition. Initiation occurs just behind a shock front and ignition occurs anywhere from a few nanoseconds to hundreds of nanoseconds later. Experiments are described that probe the fundamental mechanisms of these processes on relevant length and time scales: picosecond vibrational spectroscopy of nanometer thick layers of energetic materials (EM) with laser-driven shock waves, and nanosecond emission spectroscopy of micrometer thick layers of EM using laser-driven flyer plates.

1995 ◽  
Vol 418 ◽  
Author(s):  
David E. Hare ◽  
I-Y. Sandy Lee ◽  
Jeffrey R. Hill ◽  
Jens Franken ◽  
Honoh Suzuki ◽  
...  

AbstractExperimental measurements of material effects induced by the passage of sharp shock fronts require techniques which provide high temporal resolution and high spatial resolution. Since typical shock velocities are a few microns per nanosecond, sub-nanosecond probing requires sub-micron spatial resolution. In our experiments, the required temporal resolution is furnished using picosecond laser generated shock waves and picosecond spectroscopy. The spatial resolution is furnished by engineering nanometer scale structures into our shock target arrays. In one technique, absorption transients in the spectrum of a thin layer of molecules, termed an optical nanogauge, are investigated. Shock-induced molecular energy transfer processes are observed in condensed matter for the first time. In a second technique, sub-micron particles of an energetic material are shocked and probed using ps coherent Raman spectroscopy. This probing technique permits the instantaneous measurement of the temperature, pressure and composition of an energetic material under dynamic shock loading.


Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.


2021 ◽  
Vol 45 (38) ◽  
pp. 18059-18064
Author(s):  
Dongxu Chen ◽  
Jiangshan Zhao ◽  
Hongwei Yang ◽  
Hao Gu ◽  
Guangbin Cheng

Introduction of the acylamino group into energetic material compounds will contribute to balancing the sensitivity and the energy.


2007 ◽  
Vol 111 (5) ◽  
pp. 2235-2241 ◽  
Author(s):  
Eric Surber ◽  
Aaron Lozano ◽  
Alexei Lagutchev ◽  
Hackjin Kim ◽  
Dana D. Dlott

1994 ◽  
Vol 142 ◽  
pp. 797-806
Author(s):  
Jonathan Arons ◽  
Marco Tavani

AbstractWe discuss recent research on the structure and particle acceleration properties of relativistic shock waves in which the magnetic field is transverse to the flow direction in the upstream medium, and whose composition is either pure electrons and positrons or primarily electrons and positrons with an admixture of heavy ions. Particle-in-cell simulation techniques as well as analytic theory have been used to show that such shocks in pure pair plasmas are fully thermalized—the downstream particle spectra are relativistic Maxwellians at the temperature expected from the jump conditions. On the other hand, shocks containing heavy ions which are a minority constituent by number but which carry most of the energy density in the upstream medium do put ~20% of the flow energy into a nonthermal population of pairs downstream, whose distribution in energy space is N(E) ∝ E−2, where N(E)dE is the number of particles with energy between E and E + dE.The mechanism of thermalization and particle acceleration is found to be synchrotron maser activity in the shock front, stimulated by the quasi-coherent gyration of the whole particle population as the plasma flowing into the shock reflects from the magnetic field in the shock front. The synchrotron maser modes radiated by the heavy ions are absorbed by the pairs at their (relativistic) cyclotron frequencies, allowing the maximum energy achievable by the pairs to be γ±m±c2 = mic2γ1/Zi, where γ1 is the Lorentz factor of the upstream flow and Zi, is the atomic number of the ions. The shock’s spatial structure is shown to contain a series of “overshoots” in the magnetic field, regions where the gyrating heavy ions compress the magnetic field to levels in excess of the eventual downstream value.This shock model is applied to an interpretation of the structure of the inner regions of the Crab Nebula, in particular to the “wisps,” surface brightness enhancements near the pulsar. We argue that these surface brightness enhancements are the regions of magnetic overshoot, which appear brighter because the small Larmor radius pairs are compressed and radiate more efficiently in the regions of more intense magnetic field. This interpretation suggests that the structure of the shock terminating the pulsar’s wind in the Crab Nebula is spatially resolved, and allows one to measure γ1, and a number of other properties of the pulsar’s wind. We also discuss applications of the shock theory to the termination shocks of the winds from rotation-powered pulsars embedded in compact binaries. We show that this model adequately accounts for (and indeed predicted) the recently discovered X-ray flux from PSR 1957+20, and we discuss several other applications to other examples of these systems.Subject headings: acceleration of particles — ISM: individual (Crab Nebula) — relativity — shock waves


2020 ◽  
Vol 22 (43) ◽  
pp. 25284-25296
Author(s):  
Maija M. Kuklja ◽  
Roman Tsyshevsky ◽  
Anton S. Zverev ◽  
Anatoly Mitrofanov ◽  
Natalya Ilyakova ◽  
...  

Photo-stimulated chemical reactions in energetic materials can be highly controlled by selectively designing energetic material – metal oxide interfaces with tailored properties.


1974 ◽  
Vol 29 (4) ◽  
pp. 568-576 ◽  
Author(s):  
G. Meinhold ◽  
F. Demmig ◽  
W. Bötticher

The primary ionisation relaxation up to electron densities of ne = 4·1013 cm-3 is investigated by means of 4 mm - microwave - interferometry. The values of the timedependent gas temperature Ta, and gas density na behind the shock front are calculated using a gasdynamic model which strictly takes into account the instationarity of the flow. From the results it is concluded that neither the familiar two step process dominated by atom collisions nor the assumption of additional excitation processes by electron collisions can fully describe the observed ionisation rates. There is evidence that both the ionisation rates and the electron temperature are influenced by transitions between the first four excited states due to superelastic electron collisions. As a result the electron temperature may even exceed the gas temperature.


2015 ◽  
Vol 43 (12) ◽  
pp. 3999-4008 ◽  
Author(s):  
Ruoyu Han ◽  
Haibin Zhou ◽  
Qiaojue Liu ◽  
Jiawei Wu ◽  
Yan Jing ◽  
...  

Author(s):  
Dawei Sun ◽  
S. Ravi Annapragada ◽  
Suresh V. Garimella ◽  
Sanjeev Sing

This paper investigates the problem of base separation in the casting of energetic materials in a projectile. Special challenges that arise in casting high Prandtl number energetic materials in projectiles of complex geometries are addressed. A comprehensive numerical model is developed by integrating finite volume and finite element methods to analyze the thermal and flow fields as well as the residual stresses. The predictions, which are confirmed by experimental measurements, suggest that sustenance of a linear temperature profile along the projectile axis can eliminate base separation, and also reduce residual stresses in the final casting.


Sign in / Sign up

Export Citation Format

Share Document