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High-resolution x-ray spectroscopy is capable of providing complex information on environmental conditions in hot dense plasmas. Benefiting from application of modern spectroscopic methods, we report experiments aiming at identification of different phenomena occurring in laser-produced plasma. Fine features observed in broadened profiles of the emitted x-ray lines and their satellites are interpreted using theoretical models predicting spectra modification under diverse experimental situations. [ABSTRACT FROM AUTHOR]

In the present work we study the effect of the laser beam energy on the properties of the plasma generated by focusing an intense laser beam on Al solid target in air at atmospheric pressure. Plasma is generated using a Nd:YAG pulsed laser at 1064 nm wavelength, 6 ns pulse duration with a maximum pulse energy of 750mJ. The emission spectrum is collected using an Echelle spectrometer equipped with ICCD camera Andor type. The measurements were performed at several delay times between 0 to 9 μs. Measurements of temperature and electron density of the produced plasmas at different laser energies and at different delay times are described using different emission spectral lines. Based on LTE assumption, excitation temperature is determined from the Boltzmann plot using O I spectral lines at 777.34, 794.93, and 848.65 nm and the electron density is determined from Stark width of Al II at 281.6 and 466.3 nm. The determined density is compared with the density determined from Hα spectral line. [ABSTRACT FROM AUTHOR]

The excitation of X-ray plasma satellites was investigated in the plasma created by subpicosecond laser pulses with various intensities. It is shown that when laser flux density is greater then 6×1016 W/cm2 strong oscillating electrical fields with ω∼(1.5–1.6)×1015 s-1 are excited in the plasma. These oscillations lead to modifications of profiles of X-Ray spectral lines observed. [ABSTRACT FROM AUTHOR]

A deconvolution analysis of ion currents, which is based on the use of shifted Maxwell-Boltzmann velocity distribution, is applied to determine the temperatures and the centre-of-mass velocities of ions emitted from polyethylene and Cu targets irradiated by pulsed laser beams. This analysis can render important details in establishing the mechanisms responsible for the ion emission. [ABSTRACT FROM AUTHOR]

Two-element plasma ions generated from porous (Ho2O3) and solid (PbMg) targets were studied depending on the target density ρ and on the fraction of light (Mg) component of the target, using a mass-spectrometer. Oxygen ions with maximal charge is observed for small values of ρ, while the heavy component of the target Ho has maximal charge for larger values of ρ. The influence of ρ to the energy spectra and intensity of plasma ions is also investigated. In the case of solid (PbMg) target the increase of the fraction of Mg leads to the widening of the energy spectra of Pb ions by more than a factor of two, while the intensity of Pb ions of all charge states does not depend on the Mg fraction. These effects are explained by the friction existing between light and heavy ions during their expansion away from the target. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A method to produce ring plasmas on a metal surface is presented. The ring plasma is produced by focusing a laser pulse into an annular shape. This is achieved by using a combination of a converging lens and an axicon. The axicon is a rotationally symmetric prism. The radius of the focused ring is determined by the base angle of the axicon, and the focal length of the converging lens. The experiments are performed on a titanium surface, using a 0.18 J, 10 ns, 1064 nm pulsed, from a Nd:YAG laser. The background gas is hydrogen, at pressures in the atmospheric range. The ring structure was measured using schlieren imaging and Mach Zehnder interferometry. The expansion velocities of the laser-produced plasma in the background gas were measured in two directions; parallel and perpendicular to the metallic surface. Characteristic values are 5–9·103 m/s, for the ring radius expansion, parallel to the surface, and 1.0–1.7·104 m/s, perpendicular to the surface. Characteristic electron densities of the order of 1018 cm-3 were measured, with hollow radial profiles. The temperature of the plasma was estimated to be between 0.1 and 0.4 eV. This ring plasma is used as precursor plasma to achieve a hollow gas embedded z-pinch. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

To achieve a higher thrust performance in the laser-driven in-tube accelerator operation, numerical analysises have been carried out. The computational code covers from the generation of the blast wave to its interactions with the projectile and the acceleration wall. The thrust history and the momentum coupling coefficient evaluated from the numerical simulation depend on the fill pressure and the projectile shape. The confinement effect can be clearly found using the projectile attached with a shroud. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The results of measurements of the multicharged ions spectra in plasma produced by moderately intense (up to 4×1017 W/cm-2) laser pulses are presented. In the first case, Nd glass laser radiation with energy 1 – 2 J and pulse duration 1.5 ps was focused on the flat solid Teflon target. In the second case, Ti:Sa laser radiation with energy ∼70 mJ and pulse duration 70 and 500 fs was focused onto an N2O gas jet, created by a high-pressure liquid nitrogen cooled, pulsed (10 Hz) nozzle. Profiles of the Lyα lines of F IX ions in Teflon target and O VIII ions in N2O clusters were recorded with a very high spectral resolution λ/δλ ∼ 3000 – 5000. The features (peaks and dips) in the Lyα line profiles were observed. They suggest the existence of intense plasma oscillations with a frequency appreciably lower than the frequency of the laser radiation. The observed X-ray spectra for the plasma satellites of the Lyα doublet of the hydrogen F IX and O VIII ions in plasma were modeled theoretically. It was shown that the resulting doublet profile have a complex structure, which depends nontrivially both on the plasma temperature, density and on the frequency and amplitude of the plasma oscillations. Experimental positions of the satellites and their separations allowed them to be associated with intense electrostatic oscillations with an amplitude E0 ∼ (4–6)×108 Vcm-1 and a frequency ω ∼ (0.7–1)×1015 s-1 for F IX ions and E0 ∼ (0.5 – 1.0)×10 9 V/cm and frequency ω ∼ (0.7–2.4)×1015 s-1 for O VIII, simultaneously. Assuming the oscillation frequency to be determined by the strength of the magnetic field B generated in the plasma, we obtained an estimate of B that is in reasonable agreement with other measurements. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]