[Show abstract][Hide abstract] ABSTRACT: An experimental technique for isentropic compression of solid and liquid substances up to ultrahigh pressures is discussed.
Apulsed ultrahigh magnetic field up to 1000T is produced by an explosive flux-compression generator MC-1. Asmooth shock-free
pulse of pressure in a coaxial metal chamber of few cubic centimeters is obtained. Aradio-frequency technique of conductivity
and permittivity measurement is applied. The conductivity of solid hydrogen isentropically compressed with the initial temperature
less that 14 K was estimated at about 1(Ohm m)−1 under the pressure of 3Mbar. A sharp rise of the relative permittivity as a precursor of a metal-insulator transition was
Journal of Low Temperature Physics 01/2010; 159(1):307-310. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Software, developed in RFNC-VNIIEF for x-ray images simulation using Monte-Carlo method is described. The software is a part of an x-ray method used for investigation of an equation of state (in this case hydrogen isotopes: protium and deuterium) in a megabar pressure range. Interaction of γ–quanta with a substance is considered. Effect of a scattered radiation on the x-ray images formation is estimated.
Journal of Physics Conference Series 07/2008; 121(7):072002.
[Show abstract][Hide abstract] ABSTRACT: An isentropic compression of substances using ultra-high magnetic field makes it possible to effectively reach 'cold' pressures of several megabar in a studied substance. The process is realized in a device based on magneto-cumulative generator MC-1. Arrangement of the experiments, where the isotherm of 'cold' compression of hydrogen isotopes is studied, is described in the paper. Results of preliminary data analysis obtained at solid protium and deuterium compression are also presented. Achieved densities correspond to the pressures higher than 5 Mbar. A method of zero isotherm building, taking into account gradient and thermal corrections, is described. Errors, with which positions of experimental points in P-ρ plane are determined, are associated mostly with a precision of sizes calculation of a reference and studied samples using x-ray image, obtained in the experiment. Deviations of the built points from the curve, extrapolating the experimental data on the diamond anvils to the multi-megabar range, lie within experimental errors. The zero isotherm, approximating the obtained nowadays-experimental data, is compared with several first-principles calculation results.
Journal of Physics Conference Series 07/2008; 121(7):072001.
[Show abstract][Hide abstract] ABSTRACT: The experimental data on the shock compression of liquid nitrogen in the megabar pressure range are reported. The experiments
have been performed with a spherical measuring setup in which pressure is created by the impact of a steel shell accelerated
to a velocity of 23 km/s on the samples. The density of shock-compressed nitrogen at a pressure of about 320 GPa is about
3.4 g/cm3 (compression degree of about 4.2). The experimental data are described using a model equation of state.
[Show abstract][Hide abstract] ABSTRACT: The results of experiments on determining the shock-wave compression of initially solid hydrogen (protium) in the pressure
range from 17 to 66 GPa are reported. The data have been obtained by using spherical explosive charges. Pressure in samples
is created by the impact of a steel striker accelerated to maximum velocities of 23 km/s. Gaseous protium is converted to
the solid state using a special cryogenic cooling system.
[Show abstract][Hide abstract] ABSTRACT: Hugoniot points of liquid D2 were measured at shock pressures of 107, 54, and 28 GPa using converging explosively driven systems (CSs). The two data sets measured with a laser (L) and pulsed currents (PCs) differ substantially. Our results are in excellent agreement with the PC data and the error bars of the CS-PC data are less than half those of the L data. The limiting compression obtained from the best fit to the CS-PC data is 4.30±0.10 at 100 GPa. The CS-PC data are in good agreement with path integral Monte Carlo and density functional theory calculations, which is expected to be the case at even higher shock temperatures and pressures, as well.
[Show abstract][Hide abstract] ABSTRACT: Results are presented of experimental investigations of composite material properties, based on metal powder and polymeric binding, and offered as MC-1 generator cascade material. The possibility of direct comparison of wire and powder composite properties is realized in specially performed experiments with the cascade MC-1 generator. Along with the earlier mentioned composite properties of higher initial substance density and the possibility of its control within wide limits, composite conductivity greatly depends on the condition of further liner compression after the shock wave passage. If the diameter of a composite liner is so large that the composite compression at the liner implosion is one-dimensional at first approximation, the composite conductivity is small in comparison with the wire composite. This leads to significantly greater losses of magnetic flux. This effect disappears when the cascade radius is small, when its cylindrical shape is noticeable and two-dimensional substance compression occurs.
[Show abstract][Hide abstract] ABSTRACT: Design of the MC-1 cascade generator with a cascade system of liner acceleration was predicted by calculations and proven experimentally. The most important components of the explosive liner compression system were modified and their main characteristics measured. The initial parameters of the final variant of the cascade MC-1 generator are: external diameter of the main HE-charge is 650 mm, HE-charge total weight is about 170 kg, initial internal diameter of the first cascade is 175 mm, length is 500 mm, and internal diameters of the second and the third cascades are 28 and 12 mm, respectively. In its two final tests the generator, whose initial magnetic field was about 120 kG, had a final magnetic field reaching >20 MG in the first experiment and more than 28 MG in the second, measured with optical diagnostics. This is the maximum value of magnetic fields measured directly on Earth. The volume diameter of the maximum magnetic field is ~4 mm.
[Show abstract][Hide abstract] ABSTRACT: The possibility of recording several frames on one X-ray film is investigated. This will help to reduce the number of experiments needed to obtain information on the dynamics of liner compression of cascade MC-1 generators. We developed the method to gain information on the dimensions of cylindrical structural components moving with velocities up to several km/s. We exposed the film with two or three bremsstrahlung pulses of an ironless betatron, programmable in time. The possibility of obtaining several coaxial images of a tungsten tube on one and the same film, compressed by ultra-high magnetic field pressure, is shown. Spatial resolution was good enough to determine the tube dimensions at each moment in time.
[Show abstract][Hide abstract] ABSTRACT: The Hugoniot of deuterium is important because it intersects hydrogen
isentropes at pressures and temperatures deep in the interiors of giant
planets in this and other solar systems. This Hugoniot has been
controversial because of the different results measured with a laser (L)
and with a pulsed current facility (PCF). For this reason we have
measured Hugoniot points using hemispherically converging shock waves
driven with explosives (E). We measured points at 28, 54, and 120 GPa
using 13 cryogenically cooled experiments. Our data are in excellent
agreement with the PCF results. The error bars of the E-PCF data are
˜1/3 those of the L data. The L data agree with the E-PCF data
only at the low-density end of their error bars. This apparent
controversy is resolved by the meaning of the term "error bar".
Experimental results will be compared with PIMC and ab initio
calculations. Work at LLNL was performed under the auspices of the U.S
Department of Energy by the University of California, Lawrence Livermore
National Laboratory under contract No.W-7405-ENG-48.
[Show abstract][Hide abstract] ABSTRACT: The magnetization of the high-spin metallo-organic clusters Mn12Ac (crystal and powder) has been investigated experimentally and theoretically in magnetic fields up to 800 T at the temperature T = 2 K. It is shown that in these mesoscopic clusters the transition from ferrimagnet to ferromagnet states induced by the magnetic field is of quantum nature. In the field region of 400 - 800 T it undergoes a sequence of jumps in magnetization rather than demonstrating classic, continuous behavior. These jumps are related to the intersections of the quantum energy levels of the Mn12Ac cluster with increasing magnetic field. Such events should give rise to a change in the type of the cluster ground state, manifesting themselves in sharp magnetization jumps. Based on the experimental data, the constants of the exchange interaction between Mn ions are estimated.
[Show abstract][Hide abstract] ABSTRACT: We have studied the magnetization of high-spin metal-organic clusters Fe8 in megagauss magnetic fields at low and high temperatures. It is shown that in these mesoscopic clusters the transition from the ferrimagnetic to ferromagnetic states induced by the magnetic field is quantum in nature. At low temperatures, this transition experiences a sequence of jumps in magnetization rather than demonstrating classic, continuous behavior. These jumps are related to the intersections of the quantum energy levels of a Fe8 cluster with increasing magnetic field. Such intersections should give rise to a change in the type of the cluster ground state, manifesting them as sharp jumps in magnetization.
[Show abstract][Hide abstract] ABSTRACT: The magnetic field amplified in the magnetic explosive generator MC-1 is produced by a closed ring-electric current over the cylindrical metal shell of the generator (A.D. Sakharov, Sov. UFN, vol. 88, no. 4, pp. 3-11, 1966). Values traditionally measured in experiments with MC-1 generators are the initial and amplified magnetic field derivative and integral, sometimes the diameter of an imploding shell (since these measurements are very difficult), and, very rarely, seed current of the initial magnetic field source (mainly to control the state of the power circuit and the initial field source). The paper describes an optical technique for the MC-1 shell total current measurement during initial magnetic flux generation and on its subsequent compression. A similar technique was first implemented in the first American-Russian set of experiments performed at Los Alamos late in 1993, with VNIIEF developed MC-1 cascade generator (C.M. Fowler and B.L. Freeman, LANL Report LA-UR-94-2892, 1994). These are additional measurements to those of the generator basic parameters, which also improve adequacy of the latter and contain data on evolution of the generator's shell longitudinal section shape during implosion.
[Show abstract][Hide abstract] ABSTRACT: Experimental data on the compression of solid deuterium at a pressure of ∼60 GPa are presented. The data were obtained on
a generator of powerful converging spherical shock waves. The results are compared with the data of shock experiments obtained
on a Nova laser facility and an electrodynamic EPBF-Z plant.