2008

Zenkov, D.I., Kozlov, S.G., Kuropatkin, Yu.P., Mironenko, V.D., Nizhegorodtsev, V.I., Romanov, I.N., Tkachuk, A.A., Urlin, E.V, Shamro, O.A. A G { cyrillic } I { cyrillic } H -1200 high - voltage pulse generator  // Instruments and Experimental Techniques, 2008, Volume 51, Issue 3, Pages 396 - 400

RFNC - VNIIEF, Sarov, Russian Federation

The electric circuit, design, and electric and triggering characteristics of the G { cyrillic } I { cyrillic } H - 1200 small - sized 12 - stage high - voltage pulse generator used for charging a double forming line to 1 MV for a 300 - ns period are described. The generator is mounted in a metallic housing with the transformer - oil insulation. The storages in stages of the generator are KMK 100 - 0,017 ( 100 kV, 0,017 µF ) capacitors with a 1 - kJ  total stored energy. The switches are trigatron gaps filled with a 20% SF₆ + 80% N₂  gas mixture. The gap housings are assembled into one line. The through - passing axial channel ensures spark illumination of adjacent intervals, thereby improving the triggering characteristics of the generator. The operation - time scatter of the G { cyrillic } I { cyrillic } H - 1200 generator at an 85 - kV charging voltage and 65% electric - strength margin was ≤ 10 ns, and the operation delay time was ~100 ns. The Cyrillic capital letter GHEEe Cyrillic sign H - 1200 generator operated ~2000 times and demonstrated reliable stable operation.

Lazarchuk, V.P., Muntyan, A.N., Murugov, V.M., Petrov, S.I., Senik, A.V., Taran, S.S.  Recording the time dependence of the electron temperature and absolute yield of continuous and line X - rays from flat Au targets irradiated on the Iskra - 5 facility   // Instruments and Experimental Techniques, 2008, Volume 51, Issue 2, Pages 226 - 231

RFNC - VNIIEF, Sarov, Russian Federation

Two techniques for recording the absolute yield of continuous X - rays in the spectral range > 1 keV and M - series line X - rays from flat Au targets irradiated with one channel of the Iskra - 5 facility are described. In the first and second methods, radiation is detected with a KAP - crystal - based spectrograph and an X - ray streak camera with a 50 - ps time resolution, respectively. Both techniques allow obtainment of absolute values of the yields of continuous and line X - ray radiations from laser plasma that coincide within the measurement accuracy. The time - dependent plasma electron temperature is measured with an X - ray streak camera.

Kravchenko, A.G., Lazarchuk, V.P., Muntyan, A.N., Murugov, V.M., Petrov, S.I., Senik, A.V.   A technique for measuring the difference of times of arrival of laser beams at a target based on analysis of the X - ray emission from a target on the Iskra - 5 facility   // Instruments and Experimental Techniques, 2008, Volume 51, Issue 2, Pages 237 - 239

RFNC - VNIIEF, Sarov, Russian Federation

A technique for measuring the difference of times of arrival of laser beams at a spherically irradiated target in experiments on the 12 - channel Iskra - 5 facility is described. This technique is based on detection in test experiments of X - rays from a specially designed target with a slit X - ray streak camera. The obtained information is used to perform time locking of laser pulses recorded at the output of the facility's amplifying stages with a multichannel photochronographic system. The results of recording laser pulses at the output of the amplifying stages obtained in working experiments allow determination of the difference of times of arrival of laser beams at a target with an accuracy no worse than 50 ps.

Lazarchuk, V.P., Muntyan, A.N., Murugov, V.M., Petrov, S.I., Senik, A.V.  Multiframe detection of X - rays with a 100 - ps frame duration on the Iskra - 5 facility  // Instruments and Experimental Techniques, 2008, Volume 51, Issue 2, Pages 232 - 236

RFNC - VNIIEF, Sarov, Russian Federation

Three techniques for multiframe detection of X - rays from laser targets of different types in experiments on the Iskra - 5 facility are described. The frame duration is 100 ps, the number of frames is ten, and the spatial resolution is up to 10 µm. The developed techniques allow determination of the degree of uniformity of the emission from the end of a cylindrical target; the heating time of foils made from different materials; the collapse time of spherical glass targets filled with the DT gas; and the shape, size, and time of existence of a compressed core.

Sevast'yanov, V.D.^a, Koshelev, A.S.^b, Maslov, G.N.^b   Forming a priori neutron spectra of nuclear facilities using Maxwellian spectra  // Instruments and Experimental Techniques, 2008, Volume 51, Issue 5, Pages 694 - 698

^a  All - Russia Research Institute of Physicotechnical and Radio Engineering Measurements, p/o Mendeleevo, Solnechnogorskii raion, Moscow oblast 141570, Russian Federation
^b  RFNC - VNIIEF, Sarov, Russian Federation

A technique for forming a priori neutron spectra of nuclear facilities as the superposition of fundamental Maxwellian partial spectra has been proposed and tested.

Kosyakov, B.P.   Electromagnetic radiation in even - dimensional space - times  // International Journal of Modern Physics A, 2008, Volume 23, Issue 2, Pages 4695 - 4708

RFNC - VNIIEF, Sarov, Russian Federation

The basic concepts and mathematical constructions of the Maxwell - Lorentz electrodynamics in flat space - time of an arbitrary even dimension d = 2n are briefly reviewed. We show that the retarded field strength  { F } ^{( 2n )}_{μ ν}   due to a point charge living in a 2n - dimensional world can be algebraically expressed in terms of the retarded vector potentials { A } ^(2m)_μ   generated by this charge as if it were accommodated in 2m - dimensional worlds nearby, 2 ≤ m ≤ n+1. With this finding, the rate of radiated energy - momentum of the electromagnetic field takes a compact form.

Abakumov, A.I.^a, Kvaskov, G.A.^a, Solovyev, V.P.^a, Sinitsyn, V.V.^a, Walther, H.P.^b   An experimental study of buckling of cylindrical shells subjected to static and dynamic axial impact  // International Journal of Modern Physics B, 2008, Volume 22, Issue 9 - 11, Pages 1369 - 1376

^a  RFNC - VNIIEF, Sarov, Russian Federation
^b  SNL, Albuquerque, United States

To study structure resistance to impact loads using thin - wall cylinder units, knowledge of energy absorption parameters of these test units is required, as well as evaluations of resistance force. Buckling of cylinder test units involves formation of both axisymmetric and non - axisymmetric folds. Repeatability of buckling patterns is an important parameter of the fold formation process and, eventually, of the absorbed energy magnitude. This paper discusses buckling patterns obtained for cylinder test units of three dimension types with scales relating as 1 : 2 : 10. The units were made of three materials ( steel 09G2C and two aluminum alloys, AMg6 and AMcM  ) and subjected to static and impact loading. For static loading, a test unit was fixed on a long measuring rod and subjected to an impact by a projectile moving at a speed of V₀. The experiments were performed at three loading speeds V₀ 10 m/s, 50 m/s, 100 m/s. No less than 5 - 10 tests were performed for each type of test units, i.e. for each size, material and load level, to study buckling repeatability. Impact velocity and axial compression force history were recorded in the tests. It was obtained in the testing of cylinder test units that: Repeatability of buckling patterns was observed only in the formation of the first fold, which is axisymmetric. Then buckling, in most cases, follows a non - axisymmetric path; - With test unit scale ( i.e. size ) increasing, its relative energy absorption capacity under impact loading ( in ratio to the test unit mass ) increases; -  There is clear evidence that strain rate influences the material strength properties, except for the aluminum alloy AMg6, whose strength properties depend rather weakly on strain rate. These experimental findings can be used as a benchmark for verification of computer codes, as well as to study the behaviors of cylinder test units subjected to axial impact, which involve both axisymmetric and non - axisymmetric buckling shapes.

Medvedev, A.B.   On the possibility of crater formation associated with an ascending plume  // Izvestiya, Physics of the Solid Earth, 2008, Volume 44, Issue 4, Pages 303 - 315

RFNC - VNIIEF, Sarov, Russian Federation

A hypothetical possibility of a qualitative explanation of large crater formation on the surfaces of the Moon and Mercury is discussed in terms of the concept of thermal mantle plumes. Prerequisites to this hypothesis are revealed under the assumption that the model equation of state of SiO₂ exhibiting an anomaly ( a negative coefficient of thermal expansion ) in the range of states approximately corresponding to average conditions typical of mantles of minor planets is applicable, in a first approximation, to mantle material. The anomaly reduces the buoyancy of hot plume material in such a way that, under conditions of moderate overheating, only relatively high columns comparable in size to the mantle are capable of ascending from the mantle bottom to the crust; allows cold peripheral material surrounding the hot column to be pushed away; causes compaction of the vertical zone of the contact of the column with the surrounding medium at the first stages after the plume ascent; and leads to compaction of the deep mantle due to the long - term heat supply. Such phenomena can lead to vertical craterlike deformations of the crust in areas of ascending large plumes whose presence can be supposed at early stages of the existence of minor planets. Significant implications of such an anomaly for geophysical processes can also be postulated.

Trunin, R.F., Boriskov, G.V., Bykov, A.I., Medvedev, A.B., Simakov, G.V., Shuikin, A.N.   Shock compression of liquid nitrogen at a pressure of 320 GPa  // JETP Letters, 2008, Volume 88, Issue 3, Pages 189 - 191

RFNC - VNIIEF, Sarov, Russian Federation

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.

Arinin, V.A., Mikhailova, O.L., Mochalov, M.A., Urlin, V.D.  Quasi - isentropic compression of liquid argon at pressure ≈ 1000 GPa  // JETP Letters, 2008, Volume 87, Issue 4, Pages 209 - 212

RFNC - VNIIEF, Sarov, Russian Federation

The measurement of the density of liquid argon at a pressure of about 1000 GPa in a cylindrical setup transforming shock compression to quasi-isentropic compression gives a value of about  9 g/cm³. The experimental data are compared with calculations. The results bring out clearly that no anomaly is observed in the behavior of isentropically compressed liquid argon at pressures up to about 1000 GPa.