Download or read book High energy Electron Generation and Transport in CO2 laser heated Plasmas written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary goal of the Inertial Fusion Program at Los Alamos is to demonstrate the feasibility of burning (fusing) a large fraction of a small mass (less than 1 mg) of DT fuel. A major portion of our program is devoted to examining the physics of CO2-laser-irradiated targets. In addition, projects are continuing in the development of other lasers and heavy ion accelerators, and relativistic electron beam plasma heating, as possible alternate drivers. Our objective is to provide the necessary useful energy to a fusion capsule (0.2 to 2 MJ) at the lowest cost. A review of the Los Alamos program is given.

Download or read book Impact of Pre Plasma on Electron Generation and Transport in Laser Plasma Interactions written by Jonathan Lee Peebles and published by . This book was released on 2017 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Relativistic laser plasma interactions in conjunction with an underdense pre-plasma have been shown to generate a two temperature component electron spectrum. The lower temperature component described by "ponderomotive scaling" is relatively well known and understood and is useful for applications such as the fast ignition inertial confinement fusion scheme. The higher energy electrons generated due to pre-plasma are denoted as "super-ponderomotive" electrons and facilitate interesting and useful applications. These include but are not limited to table top particle acceleration and generating high energy protons, x-rays and neutrons from secondary interactions. This dissertation describes experimental and particle-in-cell computational studies of the electron spectra produced from interactions between short pulse high intensity lasers and controlled pre-plasma conditions. Experiments were conducted at 3 laser labs: Texas Petawatt (University of Texas at Austin), Titan (Lawrence Livermore National Laboratory) and OMEGA-EP (University of Rochester). These lasers have different capabilities, and multiple experiments were carried out in order to fully understand super-ponderomotive electron generation and transport in the high intensity laser regime (I > 10^18 W/cm^2). In these experiments, an additional secondary long pulse beam was used to generate different scale lengths of "injected" pre-plasma while the pulse length and intensity of the short pulse beam were varied. The temperature and quantity of super-ponderomotive electrons were monitored with magnetic spectrometers and inferred via bremsstrahlung spectrometers while trajectory was estimated via Cu-K[alpha] imaging. The experimental and simulation data show that super-ponderomotive electrons require pulse lengths of at least 450 fs to be accelerated and that higher intensity interactions generate large magnetic fields which cause severe deflection of the super-ponderomotive electrons. Laser incidence angle is shown to be extremely important in determining hot electron trajectory. Longer pulse length data taken on OMEGA-EP and Titan showed that super-ponderomotive electrons could be created without the need for an initial pre-plasma due to the underdense plasma created during the high intensity interaction alone.

Download or read book Laser plasma Interactions and Hot Electron Generation in Inertial Confinement Fusion written by Jun Li and published by . This book was released on 2016 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies several problems related to hot (energetic) electron generation in laser-plasma interactions in inertial confinement fusion (ICF). We study laserplasma instabilities (LPI) that can generate hot electrons in direct drive ICF under a range of laser intensities relevant to both the conventional hot-spot ignition and shock ignition. We study the in uence of LPI and hot electrons on the hydrodynamic evolution of ICF targets. We study hot electron generation in intense laser-plasma interactions in fast ignition cone targets. We also study how to implement particle collisions, which are important to hot electron generation in LPI, in Particle-in-Cell (PIC) codes on Graphic Process Units (GPU's). We find that ion density modulations can turn convective two-plasmon decay (TPD) and stimulated Raman scattering (SRS) instabilities to absolute ones in the region below the quarter critical density (nc=4). In this region, our uid simulations show that when a sinusoidal density modulation is superimposed on a linear density profile, convective two-plasmon decay (TPD) and stimulated Raman scattering (SRS) instabilities can become absolutely unstable under realistic direct-drive ICF conditions. Analysis of a three-wave model with a two-slope density profile shows that a sufficiently large change of the density gradient in a linear density profile can turn convective instabilities into absolute ones. An analytical expression is given for the threshold of the gradient change, which depends on the convective gain only. Growth rates for the absolute modes are also obtained. The threshold and growth rates from the two-slope profile are found to approximate those under sinusoidal modulations. These results explain the origin of the TPD modes below the nc=4 surface that in previous research were found to be critical to hot electron generation. Combining PIC and hydrodynamics simulations, we study the LPI and hydro evolution of coronal plasmas in an OMEGA EP[J.H. Kelly et al., 2006] long-scalelength experiment[Hu et al., 2013; Haberberger et al., 2014] with planar targets. Plasma and laser conditions are first obtained in a DRACO hydro simulation with only inverse-bremsstrahlung absorption. Using these conditions, an OSIRIS PIC simulation is performed to study laser absorption and hot-electron generation caused by LPI near the nc=4 region. The obtained information from the PIC simulation is subsequently coupled back to another DRACO simulation to examine how the LPI affect the overall hydrodynamics. The results show that the LPIinduced laser absorption can increase the electron temperature due to local heating by plasma waves. But it does not significantly change the density scale length in the corona because the high heat conductivity can spread the higher energy deposited near the nc=4 region in a wider region, and the portion of the energy carried by the hot electrons going towards high density region is still deposited beyond the nc=4 region. The collisional effects can affect the hot electron generation by damping the coupling waves of TPD and SRS instabilities. We have benchmarked the collision package in OSIRIS and adapted this package to a PIC code on graphics processors (GPU) with CUDA. The collision package is based on the cumulative collision theory, which treats a succession of small-angle binary collisions as a unique binary collision with a large scattering angle. It uses the computing cell in the GPUPIC code as the collision cell, and randomly pairs the particles in each collision cell for collision. In this process, it takes advantage of the fast on-chip shared memory and gets a remarkable performance. The benchmarks show that this collision package only needs to be called every 100 steps, and has a performance of 0:07 - 0:09ns=particle - step, only a 1:4% increase over the 5:36ns=particle - step without collisions on a Nvidia GTX 680 GPU. Test problems of beam-plasma scattering and electron plasma wave damping show that the collision frequencies calculated from the simulation results are consistent with theory. Hot electron generation is also important in fast ignition where typical laser intensities are higher than the hot-spot ignition or shock ignition. We perform PIC simulations for a cone-in-shell integrated fast-ignition experiment at the Omega Laser Facility[Boehly et al., 1997] with the initial plasma density profile taken from hydrodynamic simulations of the prepulse interaction with the gold cone. Hotelectron generation from laser-pre-plasma interactions and transport up to 100nc are studied. The simulations show a mean divergence half-angle of 68 degrees and 50% absorption for the hot electrons. The results show that the hot electrons are dominated in number by low-energy electrons but in energy by multi-MeV electrons. Electron transport between 5 and 100 nc is ballistic. In the late stage of the simulation, hot electron generation is largely independent of polarization, indicating a stochastic hot-electron-generation mechanism.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Energy Research Abstracts written by and published by . This book was released on 1994-12 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Energy Research Abstracts written by and published by . This book was released on 1983 with total page 738 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes all works deriving from DOE, other related government-sponsored information and foreign nonnuclear information.

Download or read book The Effects of Pre formed Plasma on the Generation and Transport of Fast Electrons in Relativistic Laser solid Interactions written by Bhooshan S. Paradkar and published by . This book was released on 2012 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we present the dynamics of relativistic fast electrons produced in the laser-solid interactions at the intensities greater than 1018 W/cm2. In particular, the effects of pre-formed plasma in front of a solid target on the generation and transport of these fast electrons is studied. The presence of such a pre-formed plasma is ubiquitous in almost all the present short pulse high intensity laser-solid interaction experiments. First, the generation of fast electrons in the presence of pre-formed plasma of varying density scale-lengths is studied with the help of Particle In Cell (PIC) simulations. It is shown that the fast electrons energy increases with the increasing pre-formed plasma, consistent with the experimental observations. The possible mechanism of generation of such energetic electrons is studied. It is proposed that the interaction of plasma electrons with the laser in the presence of ambipolar electric field, generated due to the laser heating, can result in the electron acceleration beyond laser ponderomotive energy. The analytical and numerical studies of this heating mechanism are presented. In the second part of thesis, the influence of pre-formed plasma on the fast electrons transport is studied. Especially the physics of refluxing of these fast electrons due to the excitation of electrostatic sheath fields inside the pre-formed plasma is investigated. It is shown that this refluxing is responsible for the `annular ring shaped' copper K[alpha] x-ray emission observed in the recent high intensity laser-solid experiments.

Download or read book Electron Generation and Transport in Intense Relativistic Laser plasma Interactions Relevant to Fast Ignition ICF written by Tammy Yee Wing Ma and published by . This book was released on 2010 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reentrant cone approach to Fast Ignition, an advanced Inertial Confinement Fusion scheme, remains one of the most attractive because of the potential to efficiently collect and guide the laser light into the cone tip and direct energetic electrons into the high density core of the fuel. However, in the presence of a preformed plasma, the laser energy is largely absorbed before it can reach the cone tip. Full scale fast ignition laser systems are envisioned to have prepulses ranging between 100 mJ to 1 J.A few of the imperative issues facing fast ignition, then, are the conversion efficiency with which the laser light is converted to hot electrons, the subsequent transport characteristics of those electrons, and requirements for maximum allowable prepulse this may put on the laser system. This dissertation examines the laser-to-fast electron conversion efficiency scaling with prepulse for cone-guided fast ignition. Work in developing an extreme ultraviolet imager diagnostic for the temperature measurements of electron-heated targets, as well as the validation of the use of a thin wire for simultaneous determination of electron number density and electron temperature will be discussed.

Download or read book Fusion Energy Update written by and published by . This book was released on 1980 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Inventory of Current Energy Research and Development written by Oak Ridge National Laboratory and published by . This book was released on 1972 with total page 1464 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Interaction and Related Plasma Phenomena written by Helmut J. Schwarz and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 913 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 7th International Workshop in the series LASER INTERACTION AND RELATED PLASMA PHENOMENA continued the high standards established by the earlier meetings in this series. It was organized under the directorship of Heinrich Hora and George H. Miley at the Naval Postgraduate School in Monterey, California, with Fred Schwirzke as the local organizer. These workshops have presented many "firsts" in laser plasma interactions and especially in laser fusion. Some presentations provided continuity with the past, most represented advancements; however, in some workshops, progress did not appear to be occurring as rapidly as in others. Therefore, it was a special pleasure that in the present workshop when, on October 30, 1985, Chiyoe Yamanaka disclosed a breakthrough in the generation of fusion neutrons with laser fusion targets. The 7th Workshop also continued to represent other new fields of laser-plasma interaction. The progress reported was most pronounced in the fields of X-ray lasers, laser acceleration of particles by electrostatic double layers in plasmas, and a particle beam technique to solve the geometric problem of muon-catalyzed fusion. The development of laser-plasma interactions at medium to high laser intensities may be seen in its whole complexity from a brief review of prior conferences. At the first Workshop in 1969, a comprehensive review of the field was presented by the speakers with the opening address by N.

Download or read book Lasers Induced Plasmas and Applications written by Radziemski and published by CRC Press. This book was released on 2020-09-10 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the physics of plasma initiation and reviews the features of dissipating, propagating plasmas. It deals with advances in diagnostics for high-energy, laser-fusion plasmas. The book reviews the basic physical processes, plasma characteristics of the "continuous optical discharge".

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hot Electron Generation and Transport in Fast Ignition Relevant Plasmas written by Ian Bush and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a mixture of theoretical work and experimental results relating to the generation and transport of relativistic electrons in fast ignition inertial confinement fusion. First the theoretical work is presented, which focuses on the effect that a fast electron beam has on a background plasma. The fast electron beam drives a resistive return current in the plasma, which causes Ohmic heating, leading to a pressure gradient, and a $J \times B$ force. Both of these would be expected to cause cavitation in the background plasma. In this work an analytic model has been developed which shows that the pressure gradient is the dominant force, and predicts the significance of cavitation over a range of parameters relevant to fast ignition fusion. In addition to this the timescale on which shocks can form is considered. This work was verified by the development of a one dimensional fluid code which included the effects of a resistive return current, and was used to model shock formation when the cavitation in the plasma is strong. Some results from a two dimensional version of the code are also presented. The experimental work in this thesis focuses on an experiment which looked at the interaction of a high-powered laser with gold cone targets, similar to those that would be used in cone-guided fast ignition schemes. In this experiment, the effect of defocusing the laser upon the production of hot electrons was investigated. A copper wire was attached to the cones to act as a diagnostic for the hot electrons. A ray-tracing code was developed to better understand the change in intensity inside the cone when the laser is defocused. The results of this experiment demonstrate that the energy coupling of the laser into hot electrons is maintained when defocusing, while the spectrum of the hot electrons softens.

Download or read book Electron Generation and Transport in Intense Relativistic Laser Plasma Interactions Relevant to Fast Ignition ICF written by and published by . This book was released on 2010 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reentrant cone approach to Fast Ignition, an advanced Inertial Confinement Fusion scheme, remains one of the most attractive because of the potential to efficiently collect and guide the laser light into the cone tip and direct energetic electrons into the high density core of the fuel. However, in the presence of a preformed plasma, the laser energy is largely absorbed before it can reach the cone tip. Full scale fast ignition laser systems are envisioned to have prepulses ranging between 100 mJ to 1 J.A few of the imperative issues facing fast ignition, then, are the conversion efficiency with which the laser light is converted to hot electrons, the subsequent transport characteristics of those electrons, and requirements for maximum allowable prepulse this may put on the laser system. This dissertation examines the laser-to-fast electron conversion efficiency scaling with prepulse for cone-guided fast ignition. Work in developing an extreme ultraviolet imager diagnostic for the temperature measurements of electron-heated targets, as well as the validation of the use of a thin wire for simultaneous determination of electron number density and electron temperature will be discussed.

Download or read book Publications of Los Alamos Research written by Los Alamos National Laboratory and published by . This book was released on 1983 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Government Reports Annual Index written by and published by . This book was released on 1982 with total page 1220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.