Detecting the ejection of particles from the free surface of a shock-loaded sample

Огородников, В. А.; Михайлов, А. Л.; Burtsev, V. V.; Lobastov, S. A.; Erunov, S. V.; Romanov, A. V.; Rudnev, A. V.; Kulakov, E. V.; Bazarov, Yu. B.; Глушихин, В. В.; Калашник, И. А.; Tsyganov, V. A.; Tkachenko, B. I.

doi:10.1134/s1063776109090180

Cited by 59 publications

(12 citation statements)

References 7 publications

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“…. This corresponds to particle radii of about 1-10 µm which are compatible with the first size measurements [21][22][23]. The determination of an average particle volume/size based on an energy balance principle seems therefore relevant.…”

Section: Discussionmentioning

confidence: 48%

“…Relatively few data are available [21][22][23], and ongoing and long-term developments of specific tools [14,24] have to be undertaken. Theoretically and numerically, if it seems possible to estimate a distribution of characteristic particle sizes for small sinusoidal perturbations [16,20], models and hydrocodes fail for the moment to provide correlation between size and velocity of the particles inside the cloud.…”

Section: Introductionmentioning

confidence: 99%

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Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using atomistic simulations

Durand

Soulard

2015

Journal of Applied Physics

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Abstract:The mass (volume and areal densities) versus velocity as well as the size versus velocity distributions of a shock-induced cloud of particles are investigated using large scale molecular dynamics (MD) simulations. A generic three-dimensional tin crystal with a sinusoidal free surface roughness (single wavelength) is set in contact with vacuum and shock-loaded so that it melts directly on shock. At the reflection of the shock wave onto the perturbations of the free surface, two-dimensional sheets/jets of liquid metal are ejected. The simulations show that the distributions may be described by an analytical model based on the propagation of a fragmentation zone, from the tip of the sheets to the free surface, within which the kinetic energy of the atoms decreases as this zone comes closer to the free surface on late times. As this kinetic energy drives (i) the (self-similar) expansion of the zone once it has broken away from the sheet and (ii) the average size of the particles which result from fragmentation in the zone, the ejected mass and the average size of the particles progressively increase in the cloud as fragmentation occurs closer to the free surface.Though relative to nanometric scales, our model may help in the analysis of experimental profiles.2

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Section: Discussionmentioning

confidence: 48%

Section: Introductionmentioning

confidence: 99%

Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using atomistic simulations

Durand

Soulard

2015

Journal of Applied Physics

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“…One can better understand the process that causes the formation of initial plasma and plasma front propagation without the necessity of an electric field in FCG by noting recent results on the ejection of particles from explosively shocked metallic surfaces [5]- [7]. It was experimentally demonstrated in [5]- [7] that the ejection of particles from a shocked metallic surface into an adjoining gas occurs when shock pressure is over the shock-breakout pressure (P SB ) at the surface of the metal [6].…”

Section: Imaging Of Electric-field-free Gas Breakdownmentioning

confidence: 99%

“…Electrical insulation of the FCG winding would limit electrical contact between the initial plasma and the FCG stator, and correspondingly would avoid the development of plasma formation. Nevertheless, research reports [1], [4] present puzzling evidence that even heavy insulation of windings of FCG stators does not help to solve the problem.One can better understand the process that causes the formation of initial plasma and plasma front propagation without the necessity of an electric field in FCG by noting recent results on the ejection of particles from explosively shocked metallic surfaces [5]- [7]. It was experimentally demonstrated in [5]-[7] that the ejection of particles from a shocked metallic surface into an adjoining gas occurs when shock pressure is over the shock-breakout pressure (P SB ) at the surface of the metal [6].…”

mentioning

confidence: 99%

Imaging of Electric-Field-Free Gas Breakdown

Shkuratov

Baird

Talantsev

et al. 2011

IEEE Trans. Plasma Sci.

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Images of electric-field-free gas breakdown are presented. Possible mechanism of the breakdown is proposed.Index Terms-Explosions, electric breakdown, shock waves. G AS BREAKDOWN and gas discharge have been detected in magnetic flux compressor generators (FCGs) since 1960s [1]. Recently [2], we have reported that gas breakdown in an FCG can occur without electric field. In this paper, we present a series of high-speed images of this type of gas breakdown and discuss a possible mechanism of the plasma initiation.In these studies, we used a loop flux compression generator (LFCG) [3]. The operation of an LFCG is similar to that of other types of FCGs, and it is based on magnetic flux compression inside a stator due to the explosively driven expansion of metallic armature. The unique feature of an LFCG is the opportunity to observe the processes that occur inside the generator from the very beginning until the final stage of its operation. To avoid any shock-induced glow in the atmosphere around the LFCG, we put the generator in a wooden box purged with helium to prevent afterglow from shocked nitrogen in the air. We used a Cordin 10A high-speed framing camera at 500 000 frames per second. Other experimental details are given in [2].A schematic diagram of LFCG is shown in Fig. 1. An external seed source generated the initial current of 2.6 kA before the explosive operation of the LFCG. The two detonators of the LFCG were initiated at t = 0, and one can see the light coming from the detonation of the C-4 high explosives (HE) inside a cylindrical aluminum armature of the LFCG [ Fig. 1 (t = 0 µs)]. As the LFCG armature started its expansion [a dark contour in Fig. 1 (t = 2 µs)], gas breakdown occurred within the LFCG and plasma appeared in the gap between the armature and the crowbar. Based on high-speed photograph images, the speed of the expansion of the armature was 1.6 ± 0.1 mm/µs at the initial stage and 2.9 ± 0.1 mm/µs at the Manuscript final stage. The electric field strength between the armature and the crowbar contacts was negligible during operation of the system; it did not exceed 7 V/mm. This electric field was not high enough to initiate gas breakdown and form plasma. Further expansion of the armature in Fig. 1 (t = 4 µs) was accompanied by the generation of intense plasma that filled the gap between the armature and the stator. The plasma front propagated along the inner perimeter of the stator [ Fig. 1 (6 µs) and Fig. 1 (8 µs)].The formation of plasma and the propagation of a plasma front with no electric field can cause the development of intense electric discharges in gas within the generators, even at low intensity of electric field. Electrical insulation of the FCG winding would limit electrical contact between the initial plasma and the FCG stator, and correspondingly would avoid the development of plasma formation. Nevertheless, research reports [1], [4] present puzzling evidence that even heavy insulation of windings of FCG stators does not help to solve the problem.One can better understand the pr...

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“…For example, ejecta from materials shock loaded with a laser drive were reported [32], where the researchers studied fragmentation of Sn, even capturing the fragments for post experimental reconstruction of the size and fragmentation patterns. Another sizing diagnostic, an optical microscope, was reported in [33]. Direct numerical simulation of ejecta production was first reported in 2004 using molecular dynamics calculations [34,35], and in 2007 using a continuum code [36].…”

Section: Smentioning

confidence: 99%

Foreword to the Special Issue on Ejecta

Buttler

Williams

Najjar

2017

J. dynamic behavior mater.

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A Brief History of Ejecta Physics 1950s and 1960sThere exists anecdotal evidence that ejecta research began in the 1950s, but little of this early research was documented publicly. In Russia, the ejecta phenomenon was first observed in plate impact experiments, and shown to be dependent on the initial surface roughness [1]. The Los Alamos PHERMEX radiographic facility was used to study the production and interaction of jets from shocked surfaces, starting from its very first shot in 1963 [2]. By 1969, Bristow and Hyde [3] describe the results of a mature program in the UK using photographic imaging of ejecta processes to infer whether melt had occurred at the surface of shocked materials. They showed that drive nonuniformity and subsurface fragmentation (spall/scabbing) were also contributory factors in determining the nature of ejecta produced. 1970sThe earliest published ejecta research was done by James Asay [4]. Asay went on to develop a non-radiographic ejecta diagnostic, the eponymous Asay foil [5]. Later, he developed a prescriptive model of ejecta, where he associated the amount of mass ejected from a shocked surface to the volume of surface defects, the rise time of the shock impulse, the yield strength of the material, and the phase of the material on release, i.e., liquid or solid [6]; interestingly he also observed that ejecta production was independent over broad ranges to the peak loading stress P S . Los Alamos National Laboratory (LANL) also became active in the development of ejecta diagnostics, as released by Hopson and Olinger [7].Ejecta physics is a young field, having developed over the last 60 years or so. Essentially, ejecta forms as a spray of dense particles generated from the free surface of metals subjected to strong shocks, but the detailed mechanisms controlling the properties of this particulate ejecta are only now being fully elucidated. The field is dynamic and rapidly growing, with military and industrial applications, and applications to areas such as fusion research.This Special Issue on Ejecta reports the current state of the art in ejecta physics, describing experimental, theoretical and computational work by research groups around the world. While much remains to be done, the dramatic recent progress in the field, some of it first reported here, means that this volume provides a particularly timely review.In this foreword, we provide a brief historical overview of the development of ejecta physics, to define the context for the work in the rest of this Special Issue.

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Detecting the ejection of particles from the free surface of a shock-loaded sample

Cited by 59 publications

References 7 publications

Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using atomistic simulations

Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using atomistic simulations

Imaging of Electric-Field-Free Gas Breakdown

Foreword to the Special Issue on Ejecta

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