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Languages : en
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Spatial and temporal coherence is a fundamental property of laser beams. This peculiar quality is a problem for laser fusion because it induces spatial non uniformities of the laser intensity in the focal spot and it generates coherent coupling between the electromagnetic laser wave and the plasma waves. In the past many years, it has been shown that laser beam smoothing using different techniques (random phase plate, smoothing by spectral dispersion, polarization smoothing ...) can reduce parametric and hydrodynamic instabilities which are detrimental processes to Inertial Confinement Fusion (ICF). More recently, it has been predicted theoretically and numerically that the laser beam coherence properties can be modified by the propagation of the laser beam through an underdense plasma. Recent experiments with the six-beam LULI laser facility demonstrate the effectiveness of this process through different diagnostics, give insight on its origin, and show some of its consequences on parametric instabilities.
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Languages : en
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The control of coherence is a critical issue for the high-power lasers used in inertial confinement fusion (ICF). The level of coherence is an important parameter for the control of the light intensity distribution as well as the growth rate of parametric instabilities. Over the past few years, experimental and theoretical studies have evidenced the ability of an underdense plasma to reduce the spatial and temporal coherence of an intense laser beam propagating through it. As any process affecting laser propagation, plasma-induced incoherence appears fundamental for ICF for it can impact on wave-coupling conditions. We present results obtained with the six-beam LULI laser facility, in the nanosecond regime, showing direct evidences of the reduction of spatial and temporal coherence of an initially RPP-smoothed laser beam after propagation through a preformed plasma. Plasma induced incoherence (PII) proceeds from several mechanisms which include self-focusing and filament instabilities and non-linear coupling between self-focusing and forward stimulated Brillouin scattering (FSBS). Part of these experiments was dedicated to the understanding of the physical mechanisms involved in PII, as the break up of a single hot spot and the existence of ion acoustic waves having small wave vectors transverse to the interaction beam which are produced in the PII processes. The spatial and temporal characteristics of these waves give a unique access to the influence of PII on stimulated Brillouin and Raman scattering.
Author: N. S. Baneesh
Publisher: Springer Nature
ISBN: 3030522644
Category : Technology & Engineering
Languages : en
Pages : 262
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This book addresses plasma modification of polyolefin surfaces. It comprises 21 chapters divided into three major sections. The first section covers the different techniques used for plasma modification of polyolefin surfaces and the effects of various gases as a surrounding medium, while the second provides a detailed analysis of the physics and chemistry of plasma modification and discusses various innovative characterization techniques, as well as ageing of the modified surface. It focuses on the analysis of changes in polymers’ surface chemistry using various spectroscopic techniques, and of changes in their surface morphology after plasma treatment using optical microscopy, electron microscopy and atomic force microscopy. In addition, it provides detailed information on the characterization of modified polymer surfaces. The book’s third and last section covers a range of applications of plasma-modified polyolefin surfaces varying from the packaging industry to the biomedical field, and shares valuable insights on the lifecycle analysis of plasma modification and modified surfaces.
Author: Vladimir Tikhonchuk
Publisher: Cambridge Scholars Publishing
ISBN: 1527552551
Category : Science
Languages : en
Pages : 361
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Book Description
Laser-plasma interaction is a continuously growing field with a broad range of applications in fundamental science, industry, and medicine. This book provides a comprehensive introduction to the physics of the interaction of intense laser pulses with high-temperature plasmas motivated by applications in high-energy-density physics and inertial confinement fusion. It combines the presentation of basic elements of the kinetics of charged particles in plasma and properties of electromagnetic waves with up-to-date developments related to nonlinear laser-plasma interactions, plasma heating, particle acceleration, excitation and mitigation of parametric instabilities. The book is based on the lectures taught by the author to students at master’s and graduate levels. It provides original material combining qualitative descriptions of physical processes with a strict but accessible theoretical background and practical exercises.
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Category : Military research
Languages : en
Pages : 854
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Category :
Languages : en
Pages : 101
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The coherence properties of a pulsed ruby, multi-mode laser were determined by recording the time-averaged effect of the radiation field on photographic emulsion. The recorded relative intensity distributions were analyzed and compared with a theoretical, single mode prediction. The laser beam was expanded to a one-inch diameter beam. Then, with the aid of a Twyman-Green interferometer, a temporal coherence length of approximately 1.27 centimeters was observed. Also, for an aperture radius of 0.51 millimeters, in conjunction with a modified Youngs experiment, a spatial coherence length of approximately 2.2 millimeters was observed.
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Category : Lasers
Languages : en
Pages : 778
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Author: Heinrich Hora
Publisher: Springer Science & Business Media
ISBN: 3540889663
Category : Science
Languages : en
Pages : 455
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"New physics" is an appealing new keyword, not yet devalued by the ravages of inflation. But what has this to do with such an ugly field as plasma physics, steeped in classical physics, mostly outworn, with all its unsolved and ambiguous technological problems and its messy and open ended numerical studies? "New physics" is concerned with quarks, Higgs particles, grand unified theory, super strings, gravitational waves, and the profound basics of cosmology and black holes. It is the field of astonishing quantum effects, demonstrated by the von Klitzing effect and high temperature superconductors. But what can plasma physicists offer, after so many years of expensive and frustrating research to solve the problem of fusion energy? One may suggest that the fascinating research ofchaos with applications to plasma, or the achievements of statistical mechanics applied to plasmas, has something to offer and should be the subject of attention. However, this is not the aim of this book. Complementing the traditional aim of physics, which is to interpret the phenomena of nature by generalizing laws such that exact predictions about new properties and effects can be drawn, this book demonstrates how new physics has been derived over the last 30 years from the state of matter which exists at high temperatures (plasma).
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Category : Nuclear energy
Languages : en
Pages : 764
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Category : Aeronautics
Languages : en
Pages : 702
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