Time-resolved Studies of Colliding Laser-produced Plasmas PDF Download
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Author: Domagoj Kos
Publisher:
ISBN:
Category :
Languages : en
Pages : 118
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Book Description
Author: Domagoj Kos
Publisher:
ISBN:
Category :
Languages : en
Pages : 118
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 302
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Author: John Murdoch
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Stephen Davitt
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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When two, or more, laser produced plasma plumes are forced to collide there are two extremes in the resulting outcome, (i) the plasmas may interpenetrate, or, (ii) a layer of stagnated plasma is formed at the collision front. The degree of interpenetration (or stagnation) is determined by the so-called 'collisionality parameter' which is the ratio of the separation of the individual 'seed' plasmas to the ion-ion mean- free path. Previous work on colliding plasmas in vacuo show that when 'stagnation layers' are formed, they exhibit an enhancement in plasma emission duration and a reasonably uniform spatial distribution of electron density, electron temperature and atomic/ionic density. These characteristics have made stagnation layers of interest to the laser plasma community, however to date research has been almost exclusively in vacuo. This work concerns experimental efforts to produce similar conditions for plasmas formed on solid targets in air at atmospheric pressure. This was realised by creating plasmas on the walls of V-shaped aluminium targets irradiated by a single, defocused laser pulse. Channels of varying vertex angles (namely, 30o, 60o, 90o) were employed to alter the relative collisional velocity of the expanding plumes and thus the collisionality parameter. The formation and evolution of the plasmas were tracked using time resolved imaging and spectroscopy. It was observed that the confined plasma plumes exhibited three distinct phases. For early time delays (
Author: Colm Fallon
Publisher:
ISBN:
Category :
Languages : en
Pages : 141
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Recently prepulse techniques such as dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) have emerged as commonly used analytical techniques for qualitative and quantitative elemental investigations in various research fields and disciplines such as industrial, defense and medical applications. The performance of the DP-LIBS technique is strongly dependent on the choice of the experimental conditions. The key parameters that affect its performance are the target properties, laser wavelength, pulse duration, energy and spot-size, interpulse delay times, delay time of observations, ambient background gas pressure and geometrical setup of the optics. The DP-LIBS approach provides significant enhancement in the intensities of emission lines and their lifetimes, up to two orders of magnitude greater than conventional single pulse laser induced breakdown spectroscopy. The aim of the work presented here is to further advance prepulse techniques, as well as other methods to control species density, with a view to optimise emission in the visible wavelength range. In particular, a new technique involving reheating the stagnation layer formed at the collision front between two (or more) colliding plasmas is explored. Spatially and temporally resolved imaging and spectroscopy of the interaction region between two colliding plasmas are employed to demonstrate for the first time that pumping of an optimised stagnation layer significantly increases the intensity emission and duration of selected spectral lines. This technique offers the promise of tunable density and tunable energy (temperature) plasmas. It will potentially increase both the lifetimes and intensities of spectral lines in laser produced plasmas by creating relatively low density - high energy plasmas which can overcome the problem of flux loss due to opacity, which leads to the attenuation of discrete emission lines with a concomitant reduction in line contrast, signal-to-noise ratio (SNR) and signal-to-background ratio (SBR). The latter is a key parameter in determining the limit-of-detection (LOD) of the LIBS technique. Other applications of stagnation layers include the development of 'target fuel' for Extreme UltraViolet (EUV) and X-ray light sources with an especial emphasis on generating high repetition rate, preheated droplet-like targets that can compete with the current liquid drop targets. The latter suffer from clogging at the jet nozzle due to adiabatic expansion freezing. Also, unlike stagnation layers the basic parameters of the droplet fuel cannot be easily varied in the way that stagnation layers allow.
Author: Stefan Andrei Irimiciuc
Publisher: World Scientific
ISBN: 9811270686
Category : Science
Languages : en
Pages : 233
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Book Description
Fourteen years after the first proposal of a fractal theoretical model to understand the dynamics of laser produced plasma, a complete image of the model is projected on a wide range of empirical data related to laser produced plasmas.The book tackles the two sides of laser produced plasmas with experimental data on a wide range of materials, from metallic alloys to geological samples and the associated mathematical model is developed in the multifractal theory of motion. A new perspective is explored in analyzing and interpreting the data collected by electrical or optical methods, focusing especially on the charged particles dynamics and the nature of fractal fluctuations and their influence during measurements as well as to the scattering process and plasma splitting phenomena, all seen through the lens of multifractal physics.The book offers the best presentation of the multifractal theoretical model for the study of transient phenomena in laser produced plasmas, which focus leads to a balanced development of the model showcasing both the flexibility and the unique vision of a multifractal mathematical apparatus.
Author: J. Murdoch
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Richard M. More
Publisher: Springer Science & Business Media
ISBN: 1489915761
Category : Technology & Engineering
Languages : en
Pages : 476
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The aim of this NATO Advanced Study Institute was to bring together scientists and students working in the field of laser matter interactions in order to review and stimulate developmentoffundamental science with ultra-short pulse lasers. New techniques of pulse compression and colliding-pulse mode-locking have made possible the construction of lasers with pulse lengths in the femtosecond range. Such lasers are now in operation at several research laboratories in Europe and the United States. These laser facilities present a new and exciting research direction with both pure and applied science components. In this ASI the emphasis is on fundamental processes occurring in the interaction of short laser pulses with atoms, molecules, solids, and plasmas. In the case of laser-atom (molecule) interactions, high power lasers provide the first access to extreme high-intensity conditions above 10'8 Watts/em', a new frontier for nonlinear interaction of photons with atoms and molecules. New phenomena observed include multiphoton ionization processes, atomic collisions in the presence of a strong laser field, Coulomb explosion following rapid ionization of a molecule and the production of high harmonics of the laser source. Another important topic reviewed in this ASI is the lasercooling ofatoms.
Author:
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 912
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Author: Nichola Walsh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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During the interaction of an intense laser pulse with a solid metal target, a high temperature, high density plasma is formed. Pulsed laser ablation has attracted much interest over the past fifty years with experimental and theoretical work largely focussed on the study of laser produced plasmas in vacuum. The study of pulsed laser ablation has been largely motivated from a materials processing perspective, with the characterisation of thin films using pulsed laser deposition of particular interest. Another application resulting from the study of laser produced plasmas is the use of laser-induced breakdown spectroscopy (LIBS) for elemental composition and quantitative analysis of samples. LIBS is now a widely used technique employed in various fields including environmental analysis, forensics and biomedical applications. While much work has been carried out on pulsed ablation of materials in vacuum and gas ambient, comparatively little research has been done on ablation in liquid media. As a result, the fundamental understanding of laser produced plasmas in liquids remains insufficient. Using techniques such as time resolved imaging and spectroscopy, a full characterisation of the plasma formed in air was undertaken as a comparison to the subsequent investigation of the plasma formed in water ambient. Single pulse studies revealed information on the dynamic evolution of a laser plasma formed in the liquid phase where strong confinement and broadband emission were the main observations. Shadowgraphy measurements were performed to examine the dynamic behaviour of the cavitation bubble that eventually forms post plasma ignition. The results of time resolved optical emission measurements from within the cavitation bubble using a second laser pulse reveal for the first time the full dynamic evolution of the plasma formed in such an environment.
