Short-pulse laser ablation of materials at high intensities: Influence of plasma effects

AbstractThe paper is devoted to the study of plasma effects, which are present in laser ablation at relatively high intensity (I ≥ 1012 W/cm2). We start from the classical "two temperature model" of laser ablation ("cold solid approximation") and we extend it to higher intensities where laser-induced heating and laser-induced changes in the background material become relevant. The new model is also compared to experimental results on laser ablation of solid targets from short pulse lasers at high intensities (up to 1014 W/cm2). Finally, we consider the effects on laser-ablation of laser-generated fast electrons

Guest Editors' Preface: The International Conference on Ultrashort High-Energy Radiation and Matter

The International Conference on "Ultrashort High-Energy Radiation and Matter" has been held in Villa Monastero, Varenna, Italy, during October 7–10, 2003. The conference has been jointly organized by the "Piero Caldirola" International Centre for the Promotion of Science and International School of Plasma Physics, Milan, Italy, and by the FEMTO Programme of the European Science Foundation (chaired by Prof. Charles Joachain of the University of Bruxelles)

Radiation effects on shock propagation in Al target relevant to equation of state measurements

We present one-dimensional simulations performed using the multi group radiation hydro code MULTI with the goal of analyzing the target preheating effect under conditions similar to those of recent experiments aimed at studying the Equation of State (EOS) of various materials. In such experiments, aluminum is often used as reference material; therefore its behavior under strong shock compression and high-intensity laser irradiation (1013–1014 W/cm2) should be studied in detail. Our results reveal that at high laser irradiance, the laser energy available to induce shock pressure is reduced due to high X-rays generation. Simultaneously X-rays preheat the bulk of the reference material causing significant heating prior to shock propagation. Such effects induce deviations in shock propagation with respect to cold aluminum

Lasing properties and nonlinearities of dyes under high power pumping

AbstractNitrogen lasers have been used for many years to make dye solutions lase. A nitrogen laser, which transverse electrical discharge in gas at atmospheric pressure has been built in our laboratory. It has been characterized and applied to pump different dyes: Rhodamine 6G, Coumarin 440, DOTCI, and pyranine in simple "on axis" geometric configuration. It has been shown that pyranine can lase in the absence of any optical external mirror cavity, this happens at very low threshold, and in different solvents. Dyes under consideration can be grouped into two major classes according to their lasing behavior independently on their concentration in the solvent: Rhodamine 6G and DOTCI can lase both axially or transversally and Coumarin 440 and pyranine can lase only axially. Other intriguing features have been observed that span from simultaneous multiple beam generation, to super fluorescence and to distribute axial pumping of dye solutions. A preliminary basis for understanding and controlling such processes is the spatial energy distribution and the energy density of the beam

A cellular automaton model of laser-plasma interactions

This paper deals with the realization of a CA model of the physical interactions occurring when high-power laser pulses are focused on plasma targets. The low-level and microscopic physical laws of interactions among the plasma and the photons in the pulse are described. In particular, electron–electron interaction via the Coulomb force and photon–electron interaction due to ponderomotive forces are considered. Moreover, the dependence on time and space of the index of refraction is taken into account, as a consequence of electron motion in the plasma. Ions are considered as a fixed background. Simulations of these interactions are provided in different conditions and the macroscopic dynamics of the system, in agreement with the experimental behavior, are evidenced

Microscopy characterization of doped fibers

The use of the Soft X-ray Contact Microscopy technique is discussed as a possible new tool to get information on dopant distribution in the core of single-mode optical fibers with 50 nm spatial resolution

Laser-ablation and induced nanoparticle synthesis

Laser pulses are largely used for processing and analysis of materials and in particular for nano-particle synthesis. This paper addresses fundamentals of the generation of nano-materials following specific thermodynamic paths of the irradiated material. Computer simulations using the hydro code MULTI and the SESAME equation of state have been performed to follow the dynamics of a target initially heated by a short laser pulse over a distance comparable to the metal skin dept

Recent advances in laser-plasma experiments using foams

The paper discusses recent advances in the use of foams in laser–plasma experiments, concerning in particular: (1) the use of foam in order to get an efficient smoothing of laser energy deposition, (2) the problem of hydrodynamics of layered foam-payload targets, (3) the use of foam for shock pressure amplification in equation-of-state experiments, (4) the study of the equation of state of foams in the Megabar regime, and (5) the use of foams for astrophysics relevant experiments, here in particular shock acceleration experiments

Design of absolute equation of state measurements in optically thick materials by laser-driven shock waves

Abstract Some aspects of the design of a target for the absolute measurement of Equation-of-State data at pressure of tens of Mbar, in optically thick materials are discussed. In the proposed experiment, a shock wave is generated in a laser-irradiated sample, and the shock velocity and the material velocity behind the shock are simultaneously measured by the optical and X-ray diagnostics. Accurate measurements require the generation of a steady, planar shock, and the detection of the motion of a shocked fluid interface by transverse radiography. One- and two-dimensional numerical fluid simulations have been performed to optimize beam and target design, in order to fulfil such requirements

Development of the PETAL Laser Facility and its Diagnostic Tools

The PETAL system (PETawatt Aquitaine Laser) is a high-energy short-pulse laser, currently in an advanced construction phase, to be combined with the French Mega-Joule Laser (LMJ). In a first operational phase (beginning in 2015 and 2016) PETAL will provide 1 kJ in 1 ps and will be coupled to the first four LMJ quads. The ultimate performance goal to reach 7PW (3.5 kJ with 0.5 ps pulses). Once in operation, LMJ and PETAL will form a unique facility in Europe for High Energy Density Physics (HEDP). PETAL is aiming at providing secondary sources of particles and radiation to diagnose the HED plasmas generated by the LMJ beams. It also will be used to create HED states by short-pulse heating of matter. Petal+ is an auxiliary project addressed to design and build diagnostics for experiments with PETAL. Within this project, three types of diagnostics are planned: a proton spectrometer, an electronspectrometer and a large-range X-ray spectrometer