High-sensitive multi-pass imaging interferometry of a gas/plasma jet.

To increase the sensitivity of optical interferometry for diagnostic of gas/plasma jet density with weak refractivity, we realize several multi-pass probing setups with the visualization field. These optical setups are based on a modified Michelson interferometer with multi-pass and multi-angle propagation of the probing beam through the transparent inhomogeneity. In comparison to the standard single-pass Mach-Zehnder setup, the multi-pass interferometer allows for an increase in the measurement sensitivity of up to 8 times.

Experimental platform for investigations of high-intensity laser plasma interactions in the magnetic field of a pulsed power generator.

An experimental platform for the studying of high-intensity laser plasma interactions in strong magnetic fields has been developed based on the 1 MA Zebra pulsed power generator coupled with the 50-TW Leopard laser. The Zebra generator produces 100-300 T longitudinal and transverse magnetic fields with different types of loads. The Leopard laser creates plasma at an intensity of 10 W/cm in the magnetic field of coil loads.

Propagation of a laser-driven relativistic electron beam inside a solid dielectric.

Laser probe diagnostics: shadowgraphy, interferometry, and polarimetry were used for a comprehensive characterization of ionization wave dynamics inside a glass target induced by a laser-driven, relativistic electron beam. Experiments were done using the 50-TW Leopard laser at the University of Nevada, Reno. We show that for a laser flux of ∼2 × 10(18) W/cm2 a hemispherical ionization wave propagates at c/3 for 10 ps and has a smooth electron-density distribution.

Transformation of a tungsten wire to the plasma state by nanosecond electrical explosion in vacuum.

Experiment demonstrates the first direct transformation of a tungsten wire core to the plasma state by Joule heating during nanosecond electrical explosion in vacuum. Energy of approximately 130 eV/atom was deposited into the 12 microm W wire coated by 2 microm polyimide during the first approximately 10 ns. All the metal rapidly transformed to highly ionized plasma, while the surrounding polyimide coating remained primarily in a gaseous state.

Thermodynamical calculation of metal heating in nanosecond exploding wire and foil experiments.

A method of thermodynamical calculation of thin metal wire heating during its electrical explosion is discussed. The technique is based on a calculation of Joule energy deposition taking into account the current wave form and the temperature dependence of the resistivity and heat capacity of the metal. Comparing the calculation to a set of exploding tungsten wire experiments demonstrates good agreement up to the time of melting.

Wire initiation critical for radiation symmetry in z-pinch-driven dynamic hohlraums.

Axial symmetry in x-ray radiation of wire-array z pinches is important for the creation of dynamic hohlraums used to compress inertial-confinement-fusion capsules. We present the first evidence that this symmetry is directly correlated with the magnitude of the negative radial electric field along the wire surface. This field (in turn) is inferred to control the initial energy deposition into the wire cores, as well as any current shorting to the return conductor.

Dynamics of mass transport and magnetic fields in low-wire-number-array Z pinches.

The dynamics of mass transport were observed in a wire array implosion with multiframe laser probing. Plasma bubbles arise at breaks in the wires. Interferometry shows that the leading edge of the bubbles brings material to the axis of the array.

Direct experimental evidence for current-transfer mode operation of nested tungsten wire arrays at 16-19 MA.

Nested tungsten wire arrays (20-mm on 12-mm diam.) are shown for the first time to operate in a current-transfer mode at 16-19 MA, even for azimuthal interwire gaps of 0.2 mm that are the smallest typically used for any array experiment.

The gas-liquid phase-transition singularities in the framework of the liquid-state integral equation formalism.

The singularities of various liquid-state integral equations derived from the Ornstein-Zernike relation and its temperature derivatives, have been investigated in the liquid-vapor transition region. As a general feature, it has been found that the existence of a nonsolution curve on the vapor side of the phase diagram, on which both the direct and the total correlation functions become complex-with a finite isothermal compressibility-also corresponds to the locus of points where the constant-volume heat capacity diverges, in consonance with a divergence of the temperature derivative of the correlation functions. In contrast, on the liquid side of the phase diagram one finds that a true spinodal (a curve of diverging isothermal compressibilities) is reproduced by the Percus-Yevick and Martynov-Sarkisov integral equations, but now this curve corresponds to states with finite heat capacity.

Characteristics and scaling of tungsten-wire-array z -pinch implosion dynamics at 20 MA.

We present observations for 20-MA wire-array z pinches of an extended wire ablation period of 57%+/-3% of the stagnation time of the array and non-thin-shell implosion trajectories. These experiments were performed with 20-mm-diam wire arrays used for the double- z -pinch inertial confinement fusion experiments [M. E.

Nanosecond electrical explosion of thin aluminum wires in a vacuum: experimental and computational investigations.

Experimental and computational investigations of nanosecond electrical explosion of a thin Al wire in vacuum are presented. We have demonstrated that increasing the current rate leads to increased energy deposited before voltage collapse. The experimental evidence for synchronization of the wire expansion and light emission with voltage collapse is presented.

Corona-free electrical explosion of polyimide-coated tungsten wire in vacuum.

We present experimental evidence of corona-free electrical explosion of dielectric-coated W wire in vacuum. A fast current rise of approximately 150 A/ns and a coating of 2 microm polyimide are both needed to achieve the corona-free regime of explosion. Breakdown is absent in corona-free explosion; the wire remains resistive, and this allows anomalously high energy deposition (approximately 20 times atomization enthalpy).

Mass-profile and instability-growth measurements for 300-wire Z-pinch implosions driven by 14-18 MA.

We present the first comprehensive study of high wire-number, wire-array Z-pinch dynamics at 14-18 MA using x-ray backlighting and optical shadowgraphy diagnostics. The cylindrical arrays retain slowly expanding, dense wire cores at the initial position up to 60% of the total implosion time. Azimuthally correlated instabilities at the array edge appear during this stage which continue to grow in amplitude and wavelength after the start of bulk motion, resulting in measurable trailing mass that does not arrive on axis before peak x-ray emission.

Polarity effect for exploding wires in a vacuum.

Experimental evidence for a strong influence of the radial electric field on energy deposition into thin metal wires during their electrical explosion in vacuum is presented. Explosion of the metal wire with a positive polarity when the radial electric field "pushes" electrons into the wire results in twice as much deposited energy than with the negative polarity when the radial field "expels" electrons from the wires. Moreover, the axial structure of the deposited energy changes.

[Effect of disruption of the entopeduncular nucleus on rat behavior in simultaneous discrimination and open field tests]].

The influence of unilateral destruction of n. entopeduncularis on learning and retention of simultaneous discrimination in a T-maze and adaptation in the open filed was studied in 29 adult rats. Destruction of n.

Self-focusing, channel formation, and high-energy ion generation in interaction of an intense short laser pulse with a He jet.

Using interferometry, we investigate the dynamics of interaction of a relativistically intense 4-TW, 400-fs laser pulse with a He gas jet. We observe a stable plasma channel 1 mm long and less than 30 microm in diameter, with a radial gradient of electron density approximately 5 x 10(22) cm(-4) and with an on-axis electron density approximately ten times less than its maximum value of 8 x 10(19) cm(-3). A high radial velocity of the surrounding gas ionization of approximately 3.

Nonlinear optics in relativistic plasmas.

We review our recent work on the various nonlinear optical processes that occur as an intense laser propagates through a relativistic plasma. These include the experimental observations of electron acceleration driven by laser-wakefield generation, relativistic self-focusing, waveguide formation and laser self-channeling.

Ultrasonic approach to obtaining partial thermodynamic characteristics of solutions.

We describe a method for evaluating the thermodynamic characteristics both of pure liquids and of solutes in solutions using data derived from ultrasonic velocity measurements. The principal possibility of using ultrasound velocity lies in the fact that the velocity of ultrasound is a simple function of the adiabatic compressibility. The problem is formulated as an initial value problem for the parabolic type differential equations in partial derivatives.

[Effect of the motivation factor on the utilization by animals of prior experience in an altered learning situation].

At studying the use by the rats of previous experience in conditions of change of the dominant need and change of learning situation, data were obtained that allowed to evaluate differently the significance of drinking and defensive motivations as a factor providing for dissociated learning of animals. Significance is discussed of motivation factor during the use by the rats of one or other behavioural strategies in the process of learning.