K. A. Ten

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.

Application of introduced nano-diamonds for the study of carbon condensation during detonation of condensed explosives

This paper describes experimental studies of the formation of nano-diamonds during the detonation of TNT/RDX 50/50 mixture with small-angle X-ray scattering (SAXS) method at a synchrotron radiation beam on VEPP-3 accelerator. A new experimental method with the introduction of nano-diamonds into the explosive has been applied. Inclusion of the diamonds obtained after detonation into the TNT and RDX explosives allows modelling of the case of instant creation of nano-diamonds during detonation.

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.

The growth of carbon nanoparticles during the detonation of trinitrotoluene

In this work we present experimental data on measuring distributions of small- angle X-ray scattering (SAXS) during cast trinitrotoluene (TNT) detonation of 30 and 40 mm in diameter. Dynamics of average size of condensed carbon nanoparticle inkreases has been restored from experimental SAXS data. The work was carried out at the SYRAFEEMA (Synchrotron Radiation Facility for Exploring Energetic Materials) station at accelerator complex VEPP- 4M (Budker Institute of Nuclear Physics). We observe minimal size of particles of order of 2 nm directly behind the detonation front. Later, the average size of carbon nanoparticles increases within 4-12 μs and reach values of 6 nm.

A Detector for Imaging of Explosions on a Synchrotron Radiation Beam

Synchrotron radiation (SR) offers a unique chance to study the structure of a substance in fast processes. Since SR is emitted by electron bunches in a storage ring, the SR burst corresponding to a single bunch may be very short. Should a detector capable of detecting SR from a single bunch without mixing signals from different bunches be available, it is possible to obtain information on changes in the state of the material in a sample under investigation with a very high time resolution. A detector for imaging of explosions on an SR beam—DIMEX—has been developed by the Budker Institute of Nuclear Physics (Siberian Division of the Russian Academy of Sciences, Novosibirsk). This detector is a high-pressure ion-ization chamber with a strip readout at a pitch of 0.1 mm. The electron component of primary ionization is collected within 50 ns, which is substantially shorter than the orbital period of a bunch in the VEPP-3 storage ring (250 ns). The DIMEX is filled with a Xe—CO2 mixture (3: 1) at an absolute pressure of 7 atm. The spatial resolution of the detector is ∼210 µm, and its efficiency for radiation with an energy of 20 keV is ≥50%. The dynamic range of the detector is ∼100, which allows one to measure the signal with an accuracy of ∼1%. In this case, the maximum flux of X-ray photons, at which the DIMEX operates in a linear region, is ∼1010 photons/(channel s). Today, the detector has been used in experiments aimed at studying evolution of the density in detonation waves and processes of nanoparticle production at the VEPP-3 storage ring by employing the small-angle X-ray scattering technique.

Study of the dynamics of nanoparticle sizes in trinitrotoluene detonation using the VEPP-4M synchrotron radiation

Here we present experimental data on measuring condensed carbon nanoparticle sizes in trinitrotoluene (TNT) detonation. Nanoparticle sizes were determined from measured distributions of small-angle x-ray scattering (SAXS). The work was carried out at the VEPP- 4M (BINP) accelerator complex. In this work, we also carried out a SAXS simulation with a real spectrum on the SYRAFEEMA (Synchrotron Radiation Facility for Exploring Energetic Materials) station (wiggler radiation, TNT absorption, absorption of the DIMEX-3 detector). Comparison of the calculated and measured SAXS distribution allows one to obtain the dynamics of the average sizes of carbon nanoparticles behind the detonation front using a pink synchrotron radiation (SR) beam. The measured particle sizes in the chemical reaction zone are ≈ 2 nm. Carbon nanoparticles with a maximum size of ≈ 4-5 nm are found outside the chemical reaction zone.

About works on research of stationary and non-stationary waves of burning in the hydrogen-oxygen mix on the Novosibirsk Free Electron Laser

This work presents schemes, techniques of experiments and the first results on registration of burning front of hydrogen-oxygen mixture with the use of terahertz radiation. The problems of choice of absorption lines, on which registration is carried out, are discussed. The investigation of distribution of absorption at wavelength of 166.81 microns over the cross-section of stationary hydrogen-oxygen flame above the burner is carried out. In the dynamic experiment, the diagrams of flame propagating along the pipe obtained with both pyrodetector and Shottky detectors were compared.

Investigating shock-wave transient processes in explosives by means of synchrotron radiation

The results from studying the transient processes induced by a shock in porous TATB, obtained using an original and tested method based on employing the soft X-ray component of synchrotron radiation, are presented. The method enables us to determine the parameters of a shock-wave striker, the distribution of velocity and density behind the front of the shock and detonation wave, and the characteristics of flow after a shock wave is reflected from a rigid wall, all in one experiment. Trials with charges 1.8 and 1.9 g/cm3 in density show that modes such as the absence of detonation and initiation in direct and reflected shock waves, are possible depending on the loading conditions.