Temperature drives energy release

Temperature determines the energy release rate of secondary high explosives. Thus, it is critical to know temperature applied an explosive predict its response impulse. However, measuring internal a heterogenous solid undergoing in detonation has many technical challenges. We will discuss several measurement techniques, their strengths, and limitations, propose alternative route assessing effective where ignition inferred from time initiation. Detonating explosives do work on surroundings primarily by releasing stored chemical as high-pressure, hot fluid. The unique feature ability potential tens nanosecond long reaction zone which supports supersonic wave. This classic example chemistry that can proceed extreme environments. initiation particular importance arises very complex shock environment. converting initial crystalline into product fluid defines resulting physics behavior these materials. exhibits famously exponential sensitivity temperature. At molecular level determined populations excited transition states lead transformation, derives dependence and, lesser extent, effect local pressure experienced molecule energies such states. complexity simulating thus due this how introduced degrees freedom, when actually real, randomly oriented macroscopic sample morphology via any number processes, e. g. passage wave through material. difficulties involved measuring, or even bounding are famous field science have resulted necessary, often effective, indirect parameterizations literature 1. With remainder editorial we describe two simultaneous efforts our laboratory, one involves direct 2, 3 another effort infer governing using constants invert data would thermal experiment 4. A specific understanding necessary either method. description above was one: scalar describing distribution within intramolecular degree freedom (e. vibration), between intermolecular phonon solid, defects point vacancies, disorder) equilibrium imperfection crystal. While experiments been used deliberately move reacting systems out 5 early theories reactivity evoked equilibration step limiting process 6, assert at rates steady there temperatures heating unreacted Indeed, combine mechanics treatment utilizing Euler's equations with first law thermodynamics generate Hugoniot 7, 8. It also condition apply Planck radiometric Importantly, intensity bright luminosity observed during likely does not arise simply function temperature, but rather emission absorption radiation changes electronic rearranging atoms. manifold yet achieved, manifolds themselves transformation no simple value for transient state. Another important definition spatial heterogeneity volumes material, each internal, subject focus significant 9-11. These regions exhibit both volume extremely different volumes. further assertion all phenomena, including physics, hottest sufficient governs physics. Measurements proceeded multiple observables 12, 13 voltage generated thermocouple junction, graybody emission, Raman neutron spectroscopies. In one, thermoelectric junction reduced size challenge descriptions achieve resolution space time. applications successful lowest, bulk shocked were made 14, 15. techniques measure runaway samples slow 16 fast laser illumination 2. second observable black body emission. case wavelength measured, recurring 13, absolute some window measured 3. Our use depends careful calibration collection light allows (nanosecond) over small surface defined focal area aperture optical fiber. considered less precise, shown they provide accuracy precision constrain models reactivity. ranging low minutes detonators 100 ns 17, 18. Recently, explored inversion data, specifically initiation, t*, determine homogeneous concept represent phenomena single crystal polycrystalline samples. enables fraction t* intersection input be approximated. leaves tign associate leading up ignition. From k(T). recently technique 1,3-propanediol-2,2-bis[(nitrooxy)methyl]-tetranitrate (PETN) full decomposition calculations based entire family 4, 19. Both ideas illustrated Figure suite diagnostics LARS radiography PETN Exploding Bridgewire Detonator (EBW) reaction, pressurization coalescence propagation done Henson-Smilowitz kinetic scheme. On left color red, overlayed simulated calculation blue. representative Foil Initiator red comparison. middle panel calculated boundary shown. right diagram height EBW trace reduction images streak image edge propagating detonator. blue lines characteristic velocities ramp P(t) panel. increase steepen proceeds. Their (x,t)=(285 μm, 1.88 μs)). Subsequent proceeds velocity approximated here maximum achieved final state compression. show may utilize timing calculate realized experiment. Comparison material heating, detonator described above. intend address variety test ideas. If what remain conditions morphology. currently investigating pressure-temperature phase states, boundaries progress dramatically improve structure physical formula simulation response. determination parameters representation dynamic simulations classical calculations, new generation highly diagnosed allow observation component isolation. result proposed simulate prediction challenges sustaining current formulations enable rational design objective properties guide decisions design. Data requested authors.