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Author: Seppo Karttunen
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Book Description
Author: Seppo Karttunen
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Parametric instabilities excited by an intense electromagnetic wave in a plasma is a fundamental topic relevant to many applications. These applications include laser fusion, heating of magnetically-confined plasmas, ionospheric modification, and even particle acceleration for high energy physics. In laser fusion, these instabilities have proven to play an essential role in the choice of laser wavelength. Characterization and control of the instabilities is an ongoing priority in laser plasma experiments. Recent progress and some important trends will be discussed. 8 figs.
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ISBN:
Category :
Languages : en
Pages : 8
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Book Description
The study of parametric instabilities in laser plasmas is of vital importance for inertial confinement fusion (ICF). The long scale-length plasma encountered in the corona of an ICF target provides ideal conditions for the growth of instabilities such as stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and filamentation. These instabilities can have detrimental effects in ICF and their characterization and understanding is of importance. Scattering instabilities are driven through a feedback loop by which the beating between the electromagnetic EM fields of the laser and the scattered light matches the frequency of a local longitudinal mode of the plasma. Any process which interferes with the coherence of this mechanism can substantially alter the behavior of the instability. Of particular interest is the study of laser beam smoothing techniques on parametric instabilities. These techniques are used to improve irradiation uniformity which can suppress hydrodynamic instabilities. Laser beam smoothing techniques have the potential to control the scattering level from parametric instabilities since they provide not only a smoother laser intensity distribution, but also reduced coherence. Beam smoothing techniques that affect the growth of parametric instabilities include spatial smoothing and temporal smoothing by laser bandwidth. Spatial smoothing modifies the phase fronts and temporal distribution of intensities in the focal volume. The transverse intensity spectrum is shifted towards higher spatial wavenumber and can significantly limit the growth of filamentation. Temporal smoothing reduces the coherence time and consequently limits the growth time. Laser bandwidth is required for most smoothing techniques, and can have an independent effect on the instabilities as well.
Author:
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Category :
Languages : en
Pages :
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Book Description
A survey of parametric instabilities in plasma, and associated particle heating, is presented. A brief summary of linear theory is given. The physical mechanism of decay instability, the purely growing mode (oscillating two-stream instability) and soliton and density cavity formation is presented. Effects of density gradients are discussed. Possible nonlinear saturation mechanisms are pointed out. Experimental evidence for the existence of parametric instabilities in both unmagnetized and magnetized plasmas is reviewed in some detail. Experimental observation of plasma heating associated with the presence of parametric instabilities is demonstrated by a number of examples. Possible application of these phenomena to heating of pellets by lasers and heating of magnetically confined fusion plasmas by high power microwave sources is discussed. (auth).
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Category :
Languages : en
Pages :
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Book Description
The purpose of this LDRD was the study of parametric instabilities on a laser-produced plasma, addressing crucial issues affecting the coupling between the laser and the plasma. We have made very good progress during these three years, in advancing our understanding in many different fronts. Progress was made in both theoretical and experimental areas. The coupling of high-power laser light to a plasma through scattering instabilities is still one of the most complex processes in laser-plasma interaction physics. In spite of the relevance of these parametric processes to inertial confinement fusion (ICF) and all other situations where a high-power laser beam couples to a plasma, many aspects of the interaction remain unexplained, even after many years of intensive experimental and theoretical efforts. Important instabilities under study are stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and the Langmuir decay instability (LDI). The study of these instabilities is further complicated by the competition and interplay between them, and, in the case of ICF, by the presence of multiple overlapping interaction beams. Stimulated Brillouin scattering consists of the decay of the incident electromagnetic (EM) wave into a scattered EM wave and an ion acoustic wave (IAW). Similarly, SRS consists of the decay of the incident EM wave into a scattered EM wave and an electron plasma wave (EPW). Langmuir decay instability is the further decay of an EPW into a secondary EPW and an IAW. The principal areas of research covered during this three-year period were the following: a) Modeling of Parametric Instabilities in Speckles b) Langmuir Decay Instability c) Non Maxwellian Plasmas d) Multiple Interaction Beams e) SBS from Speckle Distributions.
Author: Laszlo Veisz
Publisher:
ISBN: 9783836456562
Category : Science
Languages : de
Pages : 112
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Book Description
Laser-produced plasmas play an important role in plasma physics and fusion research. Parametric instabilities are the most important processes governing the laser-plasma interaction. Some parametric instabilities as two-plasmon decay or stimulated Raman scattering were investigated in this work using an optical signal, the so called 3/2 harmonics. As this harmonic originates from the plasma its characteristics provide important information about the plasma properties. The angular, spectral and temporal structure of this 3/2 harmonics were studied. Detailed theoretical analysis was made based on a new model to explain the measured results and to gain information about the generation process and the plasma.
Author: N. C Luhmann (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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Book Description
There is currently a great interest in the mechanisms by which intense electromagnetic radiation interacts with plasmas. A major impetus for this interest has been the laser-pellet fusion program. The process whereby the incident electromagnetic wave gives up energy to the plasma can be much more complex than simple binary collisional damping by electronion collisions. (Author).
Author: Hector A. Baldis
Publisher: CRC Press
ISBN: 1000658635
Category : Technology & Engineering
Languages : en
Pages : 110
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Book Description
This book covers recent developments in laser plasma physics such as absorption, instability, energy transport and radiation from the standpoint of theory and simulation for plasma corona, showing how the elements for the high density compression depend on the interaction physics and heat transport.
Author: Jukka Heikkinen
Publisher:
ISBN: 9789516662407
Category : Plasma heating
Languages : en
Pages : 26
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Book Description
Author: D. N. Gupta
Publisher: LAP Lambert Academic Publishing
ISBN: 9783848431953
Category :
Languages : en
Pages : 104
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Book Description
With the advent of laser and maser, the wave-plasma interaction emerged as a major rich field of research. To explore the possibility of laser driven fusion, laser-plasma interaction became a subject of worldwide research, revealing many novel nonlinear phenomena including generation and saturation of plasma instabilities, electron acceleration, and ion Coulomb explosion. The work presented in this thesis is related to intense laser-plasma and electron beam-plasma interaction. The development of intense short pulse laser and high current, high-energy electron beams has allowed exploration of new regimes of laser and beam plasma interaction. Enormous progress has been made in inertial confinement fusion, plasma heating, X-ray lasers, free electron laser and charged particle accelerators. In these applications parametric instabilities, self-focusing, self phase modulation and other non-linear phenomena are important. The present thesis deals with these phenomena. This work is relevant to laser-driven fusion, charged particle acceleration, and laboratory plasma heating.
