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The characteristics of x-ray radiation of a target that is bombarded by a beam of accelerated electrons ejected by a low-power vacuum discharge with laser ignition are studied. It is shown that the maximum radiation energy exceeds the applied potential difference across the discharge gap by almost an order of magnitude and is inversely proportional to the mass of the cathode material ablated by laser radiation. The energy spectrum of x-ray radiation reconstructed from the radiation attenuation curve by filters-absorbers of various thicknesses showed that in the maximum acceleration mode the average energy of the main part of the spectrum is more than four times higher than the voltage across the discharge gap at the moment of beam emission. Possible mechanisms providing anomalous acceleration of electrons in the discharge are considered. [ABSTRACT FROM AUTHOR]

A comparative study of the characteristics of moderate-current (∼10 kA), low-energy (<=20 J) vacuum discharge triggered by multipicosecond and nanosecond duration laser pulses is performed. Temporal profiles of the x-ray emission, discharge current, and anode voltage measured in vacuum discharge created between a planar titanium cathode and a conical point-tip anode are observed to be quite different for the two regimes of the laser pulse duration. While cathode plasma jet pinching is clearly observed in the discharge created by low-energy (∼5 mJ), 27 ps full width at half-maximum (FWHM) laser pulses, a feeble pinching occurred for 4 ns (FWHM) laser pulses only above a threshold energy of ∼250 mJ. In addition to the multiple K-shell x-ray pulses emitted from the titanium anode up to 100 ns, evidence of a much harder x-ray component (hν>100 keV) is also seen in the discharge triggered by picosecond laser pulses. [ABSTRACT FROM AUTHOR]

The formation of a current-plasma shell is studied during the expansion of a laser-ignited low-power vacuum-discharge cathode plasma jet into the interelectrode gap. The shell geometry is found to be determined by the mode of laser-plasma expansion at the discharge ignition stage. It is shown that the increase in the laser-beam focal spot area on the cathode surface leads to the increase in the matter density and the decrease in the density gradient in the discharge gap and to transition from the spherical laser-plasma expansion mode to the jet mode. The latter considerably stabilizes the current transfer in the discharge plasma, even during the development of the hydrodynamic sausage instability in it. [ABSTRACT FROM AUTHOR]

The report presents the results from experimental investigation of micropinch formation in the plasma of a vacuum discharge induced by a 6 ns laser pulse of energy J=0.5-200 mJ (at a storage voltage from 4 to 15 kV and the discharge current range of 6-26 kA, respectively). The discharge gap images were obtained using a pinhole camera in the EUV and soft X-ray ranges of 15-73 eV and 80-284 eV energy. It is shown that micropinch formation in the plasma cathode jet occurs, mainly, in the matter evaporated by the laser pulse at the discharge ignition near the moment when the current derivative reaches the maximum. It is found that the cathode jet may consist of several pinched areas, and each of them has its own structure, and the improvement of the discharge and laser radiation parameters allows us to reach a stable single pinching of plasma. The parameters of the micropinch (the plasma compression ratio, size, and position of the emitting area in the interelectrode gap) as well as the current flow through the interelectrode gap, at the given storage voltage, are completely governed by the laser radiation characteristics. [ABSTRACT FROM AUTHOR]

Current studies on gender identification indicate that this personality formation is complex. It is viewed primarily as the individual's realization and experience of the position of the Self [Ia] with respect to gender images and models [3]. It has been shown that a low level of differentiation of gender models reduces the influence that gender identity has as a mechanism that influences a person's behavior, choice of values, and so forth [4; 5]. Studies on the developmental dynamic of gender identity indicate that there are two crises in its development, one between the ages of 3 and 5 and the second in adolescence [1]. [ABSTRACT FROM AUTHOR]

Laser driven high current density pulsed electron emission is observed from a lead zirconium titanate (PZT, Zr/Ti: 53/47) ferroelectric ceramic disk using second harmonic of neodium: glass laser (wavelength ∼527 nm, pulse duration ∼3 ns, laser fluence ∼5–40 mJ/cm2) in the presence of a dc extraction field. Apart from electron current pulses of ∼100 A/cm2 [full width at half maximum (FWHM) ∼400 ns] obtained from laser irradiation of the surface towards the positive end of the polarization vector, electron current pulses of ∼30 A/cm2 (FWHM ∼1.1 μs) are also emitted from laser irradiation of the opposite surface. Dependencies of various characteristics of the electron pulse on laser fluence in the two configurations are presented. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]