Search

Soft X-ray emission from nitrogen plasma of a small gas-puff Z-pinch has been studied. Multilayer mirror polychromator with time-resolved registration by PIN diodes was installed and its relatively narrow spectral windows were aligned to the important parts of nitrogen spectrum between 390 and 710 eV. The electron temperature evolution (T(sub e) is approximately equal to 400 eV in hot spots) was measured from a slope of recombination continuum of He-like nitrogen. The T(sub e) of bulk plasma (approximately equal to 100 eV) is compared with T(sub e) calculated from yields of K-shell lines. Moreover, pinhole cameras were used for better understanding the radiation phase of the pinch. Time sequences of peaks in X-ray signals corresponding to a number of bright spots on photographs, are presented.

In this paper, we reveal the feasibility of obtaining laboratory craters to investigate planetary events such as meteorite craters. Experiments were performed by using 0.44-[micro]m laser beam with energy of [less than or equal to] 15 J in 350 ps (full-width at half-maximum) on aluminum targets. We obtain simple and complex craters similar in contour that are formed due to large meteorite impacts on the terrestrial surface. Simulations performed with the 2-D radiation hydrodynamic code MULTI help in understanding the origin of the experimentally observed central uplift of complex craters. Index Terms--Complex craters, laser ablation, laser produced craters, meteorite impact, shock pressure.

Emission of several tens of mA/cm^2 currents carried by MeV-protons is reported for plasmas produced by a beam of the 3-TW kJ-class Prague Asterix Laser System (PALS) focused onto foil targets of various thicknesses. The maximum proton energy of 4.2 MeV is observed at a modest irradiance (I\lambda^2\sim 2\times 10^16~W~cm^-2\mum^2). According to the maximum ion energy scaling EM\sim (I{\lambda}^{2})^{0.4} found for picosecond lasers such a value should be reached at I\lambda^2\sim 3\times 10^18~W~cm^-2~\mum^2. Enhancement of the maximum proton energy can be explained by nonlinear interaction of the PALS laser beam with the generated plasma. Nonlinear effects also result in enhancement in the yield of fusion neutrons from CD2 plasma. The obtained yield of 4\times 10^5 DD-neutrons per laser energy is comparable to those obtained by the use of ps- and fs-lasers irradiating targets with I\lambda^2\sim 10^19~W~cm^-2~\mum^2. [ABSTRACT FROM AUTHOR]

This paper describes the investigation of the influence of target material atomic number ( Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers ( Z = 3.5 - 73), i.e. plastic ( CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging. [ABSTRACT FROM AUTHOR]