2010

Babich L. P., Loiko T. V.   Peculiarities of detecting pulses of runaway electrons and  X - rays  generated by high - voltage nanosecond discharges in open atmosphere  //   Plasma Physics Reports. 2010. Т. 36. № 3. С. 263 - 270.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

Peculiarities of detecting pulses of high - energy runaway electrons and the accompanying  X - rays  generated by high - voltage nanosecond discharges at high over voltages in dense gases are discussed. Methods for overcoming difficulties encountered in such measurements are demonstrated. Different techniques for detecting runaway electrons and  X - rays  generated by discharges in open atmosphere are described, and typical errors that may be done when interpreting measurement results are considered. Experiments with the use of a small - size generator of nanosecond pulses with the idle - running voltage  of  250 - 270 kV  and stored energy of ~ 0,5 J   have been carried out. It is shown that, in measuring runaway electron pulses by using an experimental configuration with a grid anode, a major portion of the recorded signal is attributed to electromagnetic disturbances. It is found that  X - rays  are mainly generated due to the deceleration of runaway electrons in the anode, rather than in gas. The number of runaway electrons with energies  ~  300  keV  does not exceed 10⁹ per shot, and the  X - ray  dose is  60 - 200  μR/shot,  depending on the anode material.

Ablesimov V. E., Dolin Y. N., Pashko O. V., Tsibikov Z. S.  Correlation of the neutron yield anisotropy with the electrical characteristics of a plasma focus discharge   //   Plasma Physics Reports. 2010. Т. 36. № 5. С. 403 - 406.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The anisotropy of the yield and energy of neutrons generated in a small - size plasma focus chamber with a total neutron yield of about  4 × 10⁹  DD  neutrons per shot was investigated experimentally. The neutrons were recorded using scintillation detectors on a 3 – m - long flight base. The measurements were performed at the angles  0°  and 90°  with respect to the chamber axis. The maximum neutron energy measured by the time – of - flight method at the angles 0° and 90°  was found to be  2,8  and  2,5 MeV, respectively. The measured anisotropy of the neutron yield was in the range  1,15 – 1,88.  The integral DD neutron yield of the source was measured using the activation method ( by activating silver isotopes ). It is found that the neutron yield and the yield anisotropy depend linearly on the discharge current jump ΔI  at the instant of neutron generation.

Vatulin V. V., Zhidkov N. V., Kravchenko A. G., Kuznetsov P. G., Litvin D. N., Mis'ko V. V., Pinegin A. V., Pleteneva N. P., Senik A. V., Starodubtsev K. V., Tachaev G. V.   Measurements of plasma temperature in indirect drive targets from the shock wave velocity in aluminum in the «Iskra – 5»  facility   //  Plasma Physics Reports. 2010. Т. 36. № 5. С. 413 - 419.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

Results are presented from the development of a method for measuring plasma temperature in indirect ( X - ray  ) drive targets by recording the shock wave velocity in the  «Iskra – 5»  facility. The samples under investigation were irradiated by X - rays in a converter box, and the shock wave velocity was determined from the time at which the wave reached the back surface of the sample and the surface began to emit visible radiation. This emission, in turn, was detected by a streak camera. The results of experiments on the interaction of  X radiation with hot dense plasma, as well as the accompanying gas - dynamic processes in aluminum samples, are analyzed both theoretically and numerically. In experiments with  Al  and  Pb samples, the shock wave velocity was measured to vary in the range  U = 8 - 35 km/s,  and the range of variation of the temperature of the box walls was measured to be  T_e = 140 - 170 eV.

Kravchenko A. G., Litvin D. N., Mis'ko V. V., Senik A. V., Starodubtsev K. V., Tachaev G. V.  Optical recording of the compression dynamics of  dt - gas - filled pellets in indirect - drive targets   //   Plasma Physics Reports. 2010. Т. 36. № 5. С. 424 - 427.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The spatiotemporal dynamics of the compression region of  DT - gas  filled micropellets was recorded using an optical streak camera in experiments on micropellet implosion in the  «Iskra – 5»  high-power laser facility. The experimental data agree with calculations and results of  X - ray  measurements.

Tsarev M. V., Mokrushin V. V., Sten'Gach A. V., Tarasova A. I., Berezhko P. G., Kremzukov I. K., Zabavin E. V.   A study of the oxidation of titanium hydride powder by measurements of its electrical resistance   //   Russian Journal of Physical Chemistry A. 2010. Т. 84. № 4. С. 679 - 683.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The oxidation of titanium hydride powder by air oxygen and the influence of oxidation conditions on the degree of oxidation of hydride particles, specific gas content in the powder, and kinetics of its thermal decomposition were studied. The resistometry method was used to determine the effective activation energy of oxidation of titanium hydride by air oxygen. The content of the surface nonconducting phase formed by titanium oxide and oxohydride films under various oxidation conditions was estimated.

Lin É. É  Influence of size factors on the character of phase transformations in light actinides   //   Physics of the Solid State. 2010. Т. 52. № 1. С. 153 - 157.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The transformations of crystalline phases of light actinides have been analyzed as the processes of formation and growth of nanoparticles. The influence of size factors on the character of martensitic phase transitions and reverse phase transformations has been investigated using plutonium as an example.

Andreev S. N., Rukhadze A. A., Tarakanov V. P., Yakutov B. P.  Simulation of photon acceleration upon irradiation of a mylar target by femtosecond laser pulses   //   Quantum Electronics. 2010. Т. 40. № 1. С. 64 - 67.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

Acceleration of protons is simulated by the particle – in - cell ( PIC ) method upon irradiation of mylar targets of different thicknesses by femtosecond plane - polarised pulsed laser radiation and at different angles of radiation incidence on the target. The comparison of the results of calculations with the experimental data obtained in recent experiments shows their good agreement. The optimal angle of incidence ( 458  ) at which the proton energy achieves its absolute maximum is obtained.

Tren'kin A. A.  Numerical simulation of the dynamics of current channel microstructure formation in atmospheric nanosecond discharges in a uniform electric field   //   Technical Physics. The Russian Journal of Applied Physics. 2010. Т. 55. № 8. С. 1145 - 1149.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The results of simulation of the current channel microstructure formation in atmospheric nano - second discharges in a uniform electric field due to the development of instability of the ionization process in the avalanche stage followed by cycling breakdowns of the avalanche are considered. It is shown that the enhancement of the electric field at the ionization front due to the intrinsic field of the avalanche leads to the contraction of the path length between consecutive avalanche breakups; after several breakups, the ionized gas passes to the plasma state. The effect of small electric field perturbations on the dynamics of microstructure formation is investigated; as a result, the possibility of  «induced»  avalanche breakup at the instant of action of perturbations is established.

Pikulev A. A., Tsvetkov V. M.  Investigation of scaling laws as applied to the gas discharge in the case of a barrier - discharge - excited kr/cc l4 mixture   //   Technical Physics. The Russian Journal of Applied Physics. 2010. Т. 55. № 1. С. 44 - 52.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

The electrical and luminescent characteristics of a barrier - discharge lamp filled with a Kr/CCl4 ( 150:1  )  mixture are experimentally studied versus the value of pd, which varies in the range ( 7,6 – 14 ) × 10³  Pa cm.  When simulating the gas discharge using similarity parameters, the following relationships are fulfilled: for  pd = const  ( p is the pressure, d is the interelectrode distance ),  the pulse duration and the mean current density are  τ_j ∼ 1/p  and 〈j〉 ∼ p;  the surface charge density on the electrodes,  σ ∼ const;  the duration of the  UV  radiation pulse and the efficiency of UV radiation due to a  KrCl*  ( 222 nm ) exciplex,  τ_rad ∼ 1/p  and   η ∼ p².  The maximal radiation efficiency achieved in the experiments is about  13%. Deviations from the similarity laws for the gas discharge are related to the filamentary form of the observed discharge. Qualitative analysis indicates that similarity laws may be fulfilled for such a form of discharge as well but locally, within a single filament.

Valiulina V. K., Dubinov A. E.  Cylindrical magnetoacoustic solitons in plasma  //   Technical Physics. The Russian Journal of Applied Physics. 2010. Т. 55. № 4. С. 496 - 502.

Russian Federal Nuclear Center ( VNIIEF ), Sarov, Russia

Nonlinear cylindrical magnetoacoustic perturbations in a plasma are considered in the framework of the two - liquid collisionless electromagnetic model. The method of power expansion in a small parameter in extended space-time coordinates is used to obtain the cylindrical Kortewegde Vries equation that describes nonlinear radial cylindrical waves. An approximate solution to this equation has the form of a cylindrical magnetoacoustic compression soliton.