V. M. Titov

Application of Synchrotron Radiation for Studying Detonation and Shock-Wave Processes

A new method of remote investigation of detonation and shock‐wave processes with the use of synchrotron radiation is proposed. The facility used for the first experiments with measurement of density and small‐angle x‐ray scattering in detonation of condensed explosives is described. The high time and spatial resolution of the techniques proposed allows one to determine the character and mechanism of destruction of the condensed phase and the growth dynamics of new structures, including crystalline ones, in detonation flows. The capabilities of the new technique are described.

Experience of using synchrotron radiation for studying detonation processes

Results of studying detonation processes in condensed high explosives, which are obtained by methods based on using synchrotron radiation, are summarized. Beam parameters are given, and elements of the station and measurement system are described. Data on the density distribution in the detonation front for several high explosives are presented, and values of parameters in the Neumann spike and at the Jouguet point are determined. A method used to reconstruct a complete set of gasdynamic characteristics (density fields, particle velocity vector, and pressure) from the experimentally measured dynamics of the x-ray shadow of the examined flow is described. Results of using this method for studying detonation of a charge of plastic-bonded TATB are presented. A method of measuring small-angle x-ray scattering in the course of detonation conversion is described. Based on results obtained by this method for a number of high explosives with an excess content of carbon, kinetics of condensation of free carbon and dynamics of the mean size of nanoparticles being formed thereby are analyzed.

Implementation of the capability of synchrotron radiation in a study of detonation processes

24 Modern detonation theory is based on the gas dynamic model developed by Ya.B. Zeldovich, J. von Neumann, and W. Doring. In addition to it, the reaction zone sizes and Neumann peak have been experimentally studied and simulated, the phenome nological kinetics of the detonation transformation has been constructed, attempts to describe the reac tion zone by molecular dynamics methods have been undertaken, the data on unloading adiabats have been obtained, numerous equations of state of detonation products have been constructed, and the actual curva ture of the detonation front and a number of other properties of the process have been considered. At the same time, there are new facts not complying with the commonly accepted notions and requiring experi mental studies and subsequent explanations. Among the actively studied problems are the features of the fine structure of the reaction zone, the Chapman– Jouguet surface shape, the carbon condensation kinet ics during the detonation transition, the possibility of transition without a chemical peak, and a number of other problems. Their solution is complicated by the absence of adequate experimental techniques, since the available ones are often perturbative or do not pro vide spatial and temporal resolution sufficient for unambiguous interpretation. Partial answers to some of these questions can be obtained using the technique developed and implemented by the authors, based on the use of the soft X ray component of synchrotron radiation (SR).

Observation of Compression and Failure Waves in PMMA by Means of Synchrotron Radiation

The possibility of using synchrotron radiation for density measurements in shock‐compressed polymethylmethacrylate destroyed in a failure wave is demonstrated for the first time. Parameters of the compression and failure processes are presented.

Acceleration of solid particles during cumulation of detonation products in vacuum

The possibility of increasing the velocity of solid particles accelerated by an explosion of a long tubular charge of a high explosive (HE) in vacuum is analyzed. The experimental results obtained indicate that the acceleration velocity cannot be considerably increased. The probable causes are erosion of the material from the inner surface of the HE tube and a significant decrease in the mass flow velocity when the length of the HE tube exceeds the optimum length.

On mixing of the products of detonation of composite explosives in the chemical reaction region

The problem of mixing of the products of detonation of composite explosives is of principal importance for the synthesis of ultrafine diamond from composite mixtures and also for chemistry of detonation processes as a whole. An analysis of mixing in the chemical reaction region due to molecular diffusion shows that this mechanism may be important only for grain sizes of several micrometers. If the grain sizes reach tens or hundreds of micrometers, only partial mixing on the grain boundaries is possible. Investigations of the hydrodynamic mechanism of mixing shows that it may occur owing to a nonuniform velocity field behind the detonation wave front in the mixture and to the development of turbulence and cumulative processes during pore implosion. In mixtures with grain sizes of the order of 30 μm, these processes can lead to appreciable mixing during the time of ≈0.5 μs and longer. Theoretical estimates are compared with the results of experiments performed at the Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences and at the Altai Scientific and Industrial Enterprise (Biisk) for studying the synthesis of ultrafine diamond with the use of the isotope method.

Phase transition in pyroxenite under shock loading

Shock loading of natural pyroxenite samples and synthetic pyroxene samples sintered from a mixture of oxides with stoichiometry Mg0.9Fe0.1SiO3 was investigated. X-ray analysis of the recovered material was performed. Particle velocity profiles recorded by laser interferometry indicate the existence of a phase transition at a pressure of ≈60 GPa. At this pressure, the Lagrangian sound velocity in the shock-loaded samples of natural pyroxenite is 13.9 km/s. From an evaluation of the compression, the Eulerian sound velocity is 9.4 km/s.

HYPERVELOCITY INTERACTION OF POROUS BODIES WITH PLATES

The interaction of dense and porous cylinders with incident plates is studied experimentally at collision velocities of 3.3–4.6 km/sec. Qualitative differences in the deformation mechanics of compact porous bodies are elucidated. The compression of porous samples is found to take place in two stages. These data can be invoked to explain the structural features of impact craters on planetary surfaces.