Parametric Instabilities in Laser

Parametric Instabilities in Laser PDF Author:
Publisher:
ISBN:
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.

Parametric Instabilities in Laser

Parametric Instabilities in Laser PDF Author:
Publisher:
ISBN:
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.

Parametric Instabilities in Large Nonuniform Laser Plasmas

Parametric Instabilities in Large Nonuniform Laser Plasmas PDF Author:
Publisher:
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.

Parametric Instabilities in Picosecond Time Scales

Parametric Instabilities in Picosecond Time Scales PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 40

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Book Description
The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 1014--1015W/cm2 these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.

Investigation of Parametric Instabilities in Femtosecond Laser-Produced Plasmas

Investigation of Parametric Instabilities in Femtosecond Laser-Produced Plasmas PDF 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.

Parametric instabilities in laser heating of fusion plasmas

Parametric instabilities in laser heating of fusion plasmas PDF Author: Seppo Karttunen
Publisher:
ISBN:
Category :
Languages : en
Pages : 11

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Experimental Simulation of Parametric Instabilities in Laser-Plasma Interactions

Experimental Simulation of Parametric Instabilities in Laser-Plasma Interactions PDF 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).

The Physics Of Laser Plasma Interactions

The Physics Of Laser Plasma Interactions PDF Author: William Kruer
Publisher: CRC Press
ISBN: 1000754200
Category : Science
Languages : en
Pages : 197

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Book Description
This book focuses on the physics of laser plasma interactions and presents a complementary and very useful numerical model of plasmas. It describes the linear theory of light wave propagation in plasmas, including linear mode conversion into plasma waves and collisional damping.

Hydrodynamic and Parametric Instabilities in a Long Scalelength Laser Produced Plasma

Hydrodynamic and Parametric Instabilities in a Long Scalelength Laser Produced Plasma PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 310

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Laser Fusion and Parametric Instabilities

Laser Fusion and Parametric Instabilities PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Investigation of Parametric Instabilities in Femtosecond Laser-produced Plasmas

Investigation of Parametric Instabilities in Femtosecond Laser-produced Plasmas PDF Author: László Veisz
Publisher:
ISBN:
Category :
Languages : en
Pages : 200

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