Том 54, № 5 (2018)

For about 15 years, studies of fast gas-dynamic processes have been conducted at the Logunov Institute of Experimental Physics (VNIIEF) of the Russian Federal Nuclear Center using the proton radiography system developed jointly with the Logunov Institute of High Energy Physics on the basis of a U-70 accelerator. The main advantages of flash proton radiography over widely used flash x-ray radiography are high spatial resolution, multiframe mode, transmission capability, dynamic range of recording, etc. In recent years, effort has continued to extend the capabilities of the proton radiography system by increasing the total time and recording field and supplementing it with additional diagnostic techniques and new explosion-proof chambers. This paper presents the results of studies that illustrate these capabilities.

This paper describes an experimental study of isentropic compression of a VNM-3-2 heavy tungsten alloy (tungsten–nickel–copper) by a pressure of a superstrong pulsed magnetic field, induced by MC-1 magnetocumulative generator. Experimental points obtained on a p–ρ diagram of the alloy are compared with its cold compression curve, previously constructed on the basis of shock-wave experiments. The purpose of this study is to correct and clarify a equation of state of the alloy under an ultrahigh pressure and low temperature. This equation is used to analyze data obtained in experiments on isentropic compression of various substances.

Shock wave properties of porous specimens made on the basis of matrices composed of inert and chemically active media (silicon rubber and emulsion, which is an aqueous solution of ammonium nitrate with mineral oil and emulsifier) are studied. The porosity of the specimens is generated by using a filler composed of glass microspheres. The wave velocity profiles are measured by a VISAR laser Doppler interferometer. It is shown that the shock compressibility of porous silicon rubber at pressures below 0.1 GPa displays an anomalous behavior, resulting in smearing of the compression pulse front propagating over the specimen. In the emulsion matrices without microspheres, there are no noticeable chemical transformations up to the pressure of 15 GPa. Addition of microspheres drastically decreases the threshold of chemical reaction initiation and leads to the formation of a steady detonation wave.

This paper describes experimental results on using nonstationary spectrometry in a terahertz frequency range to determine the composition of gaseous products of decomposition of energy materials. Dependences of analytical signals on lines of the main products of ammonium nitrate and PETN decomposition on time are obtained.

A key issue for explaining bursts and explosions of high explosives (HEs) under low-velocity mechanical impacts with registered time delays is the formation of local high-temperature regions. It is demonstrated by an example of HMX that the required temperatures should significantly exceed the HMX melting point and can be obtained only due to the work of viscosity forces in the liquid phase. In this case, however, it is necessary to ensure HE flow velocities greater than the primary impact velocities by several orders of magnitude. A mechanism of generation of such velocities is proposed: squeezing of the HE, which is heated on shear strains and plasticized, from the shear layer under the action of the pressure difference along the layer. Conditions of fast decomposition of the HE in the shear layer and conditions of an explosion of the surrounding HE are formulated.

This paper presents the results of an experimental study of particle ejection into low (0.05 atm) vacuum from a narrow (0.2–0.8 mm) rough (Rz = 20–50 μm) surface of a lead sample subjected to a shock wave of intensity about 17 and 34 GPa. The ejecta was recorded with a video camera in the microscopic mode with short laser irradiation. Due to the small optical thickness of the ejecta, particle spectra at approximately 80% of the ejecta height measured from the front of the ejecta were obtained. It was found that when lead is in the solid state (17 GPa), jets consisting of a lot of particles are ejected from the rough surface; when the lead is in the liquid state (34 GPa), a lot of thin (from 7 μm) microcumulative jets are ejected from the metal surface, and with time they break up into particles.

This paper describes a piezoelectric method for measuring the density and mass of ejecta from the free surface of a condensed material upon arrival of a shock wave at it and the use of this method at the Institute of Physics of Explosion (Institute of Experimental Physics of the Russian Federal Nuclear Center, Sarov). Piezoelectric sensor designs and methods of recording and signal processing are presented. Results of measuring the density and mass of ejecta using piezoelectric sensors, radiography, protonography, and the method of indicator foils are compared.

The paper describes a method of simultaneous measurements of kinematic parameters of a high-speed process by a microwave radio interferometer with a 3-mm range of wavelengths and the brightness temperature of the same process by the microwave radio interferometer operating in the radiometer mode. The methods of radiometer calibration and analysis of radiometric data are described. Results of experimental investigations are reported by an example of measuring the detonation velocity and estimating the brightness temperature of the detonation front in TNT.

Currently, the computer simulation of the behavior of products containing explosives at various stages of their life cycle has become of increasingly greater importance. Computational methods have been verified by studying the propagation of detonation wave in channels of model distributors using high-speed photography. This paper focuses on the motion of a detonation wave at the bends of the channel and the formation of dark areas. The results obtained using a NANOGATE 2000 optoelectronic system based on a NANOGATE 22 high-speed camera with a shooting frequency of up to 10⁹ fps are presented. The position of the detonation front moving with rotation at an angle of 60, 90, and 120° was first visualized with an exposure time of 20 ns and an interframe interval of 80 ns.