The isentropic expansion of shock-compressed porous metals (Cu, W, Nb) are experimentally studied, and the experimental results are used to determine their thermodynamic parameters and electrical conductivity. These results allow us to conclude that some porous metals after shock compression and expansion have a two-phase structure. The presence of an additional phase at the isentropic expansion of these metals significantly changes the character of evaporation and the critical point parameters of the liquid–vapor phase transition that are estimated using experiments on the isentropic expansion of shock-compressed porous metals. In addition, the formation of the two-phase structure explains the large difference between the critical point parameters estimated by different methods for a large group of metals (U, W, V, Co, Mo, Ta, etc.).

Целью исследования являлось определение барической зависимости удельной электропроводности бора в условиях ступенчатого ударного сжатия мегабарного диапазона. Для достижения этой цели решены следующие задачи. Измерена электропроводность образцов бора в области динамических давлений, где существуют различные фазы высокого давления этого элемента. Построены уравнения состояния beta-ромбоэдрического бора и аморфного бора в мегабарном диапазоне давлений. Рассчитаны термодинамические состояния бора в условиях выполненных экспериментов, что в комплексе с результатами измерений позволило определить изменение удельной электропроводности бора при сильном ступенчатом ударном сжатии в области динамических давлений до 110 GPa. Увеличение электропроводности поликристаллического бора в области мегабарных давлений истолковано как следствие перехода неметалл-металл. Работа выполнена при поддержке Госкорпорации Росатом" в рамках контракта N Н.4х.44.9Б.16.1012 от 01.03.2016 г. DOI: 10.21883/FTT.2017.07.44603.001

The pressure dependence of the conductivity of boron under conditions of a stepwise shock compression of megabaric range is studied. With this purpose, the following problems have been solved. The conductivity of boron has been measured in the range of dynamic pressures, where boron has different high-pressure phases. The equations of state of β-rhombohedral and amorphous boron have been constructed in a megabaric pressure range. The thermodynamic states of boron in the conditions of these experiments are calculated, which, in combination with the measurement data, made it possible to determine the change in the boron conductivity in the conditions of strong stepwise shock compression at dynamic pressures to 110 GPa. The increase in the conductivity of polycrystalline boron at megabar pressures is interpreted as a result of a nonmetal–metal transition.

The physico-mechanical properties of amorphous glassy carbon are investigated under shock compression up to 10 GPa. Experiments are carried out on the continuous recording of the mass velocity of compression pulses propagating in glassy carbon samples with initial densities of 1.502(5) g/cm(3) and 1.55(2) g/cm(3). It is shown that, in both cases, a compression wave in glassy carbon contains a leading precursor with amplitude of 0.135(5) GPa. It is established that, in the range of pressures up to 2 GPa, a shock discontinuity in glassy carbon is transformed into a broadened compression wave, and shock waves are formed in the release wave, which generally means the anomalous compressibility of the material in both the compression and release waves. It is shown that, at pressure higher than 3 GPa, anomalous behavior turns into normal behavior, accompanied by the formation of a shock compression wave. In the investigated area of pressure, possible structural changes in glassy carbon under shock compression have a reversible character. A physico-mechanical model of glassy carbon is proposed that involves the equation of state and a constitutive relation for Poisson's ratio and allows the numerical simulation of physico-mechanical and thermophysical properties of glassy carbon of different densities in the region of its anomalous compressibility.

The shock-wave loading of a gradient mixture is numerically investigated in the pressure range of 20–150 GPa. The shock compression of a platelet gradient mixture of tungsten and porous copper is considered using a model which is a modification of the model of platelet porous materials supplemented with an algorithm for calculating changes in the thermodynamic and kinematic parameters of each particle and the sample as a whole. It is shown that the calculated parameters of the state of this shock-compressed mixture in the pressure–particle velocity coordinates are consistent with experimental data for a real tungsten–copper mixture.

The shock compression of a heterogeneous material is numerically simulated. The physical model used for the simulation is based on a layered model of a porous material and consists of a set of thin matrix plates with a known equation of state that are separated by filler layers also with a known equation of state. The model is intended to calculate the parameters (pressure, temperature, mass velocity) of shock compression of the matrix and the filler of heterogeneous materials during their one-dimensional shock compression in terms of a developed hydrodynamic code. The adequacy of the proposed model is tested on porous molybdenum during shock-wave loading to a pressure of 15–70 GPa and a temperature of 4000 K.

A more than twofold increase in the average multiplicity of charged particles in electromagnetic showers initiated by electrons with an energy of 26 GeV in tungsten crystals 2.7, 5.8, and 8.4 mm thick, oriented along the 〈111〉 axis, in comparison with misoriented crystals is shown. For a silicon crystal 20 mm thick, oriented along the 〈110〉 axis, at an electron energy of 28 GeV, the average multiplicity of charged particles increases by a factor of ∼1.6. The widths of the orientation dependences of the average multiplicity of charged particles in electron-induced showers in silicon and tungsten crystals are proportional to the crystal thickness and depend on the electron energy as E −1/2.

Semi-empirical equations of state (thermal and caloric) are obtained to calculate not only the kinematic parameters (shock wave velocity, particle velocity, and reverberation of waves) but also the thermodynamic parameters (temperature, pressure, and compression) of monolithic and porous polytetrafluoroethylene at high shock pressures. The equations of state are used to model wave interaction in shock-wave experiments using the developed hydrocode. The equations are verified by comparison simulation results with published results of experiments and the data of our shock compression tests of solid and porous samples of PTFE in the range of 10–170 GPa.

The experimental results of the study of the dependence of the response of a composite Cherenkov shower spectrometer with a converter made of 〈111〉 tungsten crystal 1 mm thick on the electron energy of 26, 28, and 31 GeV are presented. It is found that the cascade curve maximum position and the energy release at the maximum of the cascade curve of shower development in the spectrometer with both oriented or misoriented converters have the logarithmic and proportional dependences on electron energy.

Cooling of a 1-mm crystalline tungsten converter oriented along the 〈111〉 axis situated in front of an electromagnetic spectrometer of thickness 25X 0, recording showers of 28-GeV electrons, to a temperature of 77 K results in a decrease of the crystal radiation length by ∼30%, shifts the cascade curve of the shower development in the spectrometer by ∼7%, and improves the spectrometer energy resolution by ∼5% in comparison with similar parameters of the spectrometer at a crystal temperature of 293 K.

The design and main characteristics of combined shower spectrometers (CSSs) are presented: combined Cherenkov and lead-scintillation spectrometers that are intended for investigating shower processes in oriented crystals and that consist of ten independent lightproof counters with thicknesses of 1X0 and 1.18X0, respectively. At an electron energy E e = 26 GeV, the energy resolutions of both CSSs together with a Cherenkov spectrometer with a thickness of 15X0, which was placed behind them, were 2.4 and 4.3% for the combined Cherenkov and lead-scintillation shower spectrometers, respectively.

It is shown that the average charged particle multiplicity in electromagnetic showers induced by γ-rays with energies of 9–26 GeV in the tungsten crystal 1 mm thick (T = 77 K) oriented along the 〈111〉 axis approximately twofold increases in comparison with a misoriented crystal.

When high-energy photons, electrons, or positrons pass through a crystal, anomalous electromagnetic showers are formed, which differ from ordinary showers in an amorphous substance. Introducing the transformation coefficient β of the amplitude spectrum and the rejection coefficient R allows one to precisely determine the degree of difference of anomalous showers from ordinary ones upon changes in the particle energy, angle of crystal orientation, etc., and distinguish the specified direction of moving particles and the probability of falling of particles from other directions within this direction of particles.

A study of electrophysical and thermodynamic properties of C-60 single crystals under step shock loading has been carried out. The increase and the following reduction in specific electroconductivity of C-60 fullerite single crystals at step shock compression up to pressure 30 GPa have been measured. The equations of state for face centred cubic (fcc) C-60 fullerite as well as for two-dimensional polymer C-60 and for three-dimensional polymer C-60 (3D-C-60) were constructed. The pressure-temperature states of C-60 fullerite were calculated at step shock compression up to pressure 30 GPa and temperature 550 K. The X-ray diffraction studies of shock-recovered samples reveal a mixture of fcc C-60 and a X-ray amorphous component of fullerite C-60. The start of the formation of the X-ray amorphous component occurs at a pressure P-m approximate to 19.8 GPa and a temperature T-m approximate to 520 K. At pressures exceeding P-m and temperatures exceeding T-m, the shock compressed fullerite consist of a two-phase mixture of fcc C-60 fullerite and an X-ray amorphous component presumably consisting of the nucleators of polymer 3D-C-60 fullerite. The decrease in electroconductivity of fullerite can be explained by the percolation effect caused by the change of pressure, size and number of polymeric phase nuclei.

We present experimental data on characteristics of peculiar electromagnetic cascades initiated by 26 GeV electrons in transparent oriented crystals of artificial garnet and lead tungstate. The mean energy deposition in the crystals and its orientation dependence as a function of the crystal thickness are determined. A measurement of the transversal development of the cascades is performed. Implications for the functioning of crystalline electromagnetic calorimeters are discussed.

The orientation dependences of the energy release in showers formed in transparent garnet crystals with thicknesses of 23 and 50 mm are measured, and the influence of the orientation of the crystals on the absorption of a shower in an amorphous radiator is determined.

Characteristics of specific showers formed by 26 GeV electrons in aligned transparent crystals of an artificial garnet and lead tungstate are measured. A change of the cascade curve shape and the growth of orientation dependence width are shown for the increase of the crystal pattern thickness, A possible influence of the showers on the function of electromagnetic calorimeters are discussed. (C) 1998 Elsevier Science B,V. All rights reserved.

The dependence of protein kinase and RNA polymerase activities, and also of the synthesis of protein in nuclear chromatin, on the addition of benzylaminopurine and a cytokinin-binding protein to the incubation mixture has been investigated. It has been shown that all three processes are hormone-dependent. It has been found that the activity of protein kinase C is regulated by a cytokinin.

The structure of a composite photon-electron spectrometer based on NaI(Tl) crystals and plastic scintillators is described. A spectrometer calibration under a beam of secondary electrons with an energy of 50-150 MeV is described. At a work-load of N similar to 10(3) Hz the energy resolution is sigma/E = 0.03E(-0.25), and the time resolution is similar to 8 nsec.