Modeling Shortpulse Single Hot Spot Laser Plasma Interaction Experiments Using The Vpic Particle In Cell Code
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Modeling Shortpulse Single Hot Spot Laser Plasma Interaction Experiments Using The Vpic Particle In Cell Code
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Author :
language : en
Publisher:
Release Date : 2010
Modeling Shortpulse Single Hot Spot Laser Plasma Interaction Experiments Using The Vpic Particle In Cell Code written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Laser Plasma Interactions And Hot Electron Generation In Inertial Confinement Fusion
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Author : Jun Li
language : en
Publisher:
Release Date : 2016
Laser Plasma Interactions And Hot Electron Generation In Inertial Confinement Fusion written by Jun Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
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.
Integrated Kinetic Simulation Of Laser Plasma Interactions Fast Electron Generation And Transport In Fast Ignition
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Author :
language : en
Publisher:
Release Date : 2009
Integrated Kinetic Simulation Of Laser Plasma Interactions Fast Electron Generation And Transport In Fast Ignition written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We present new results on the physics of short-pulse laser-matter interaction of kilojoule-picosecond pulses at full spatial and temporal scale, using a new approach that combines a 3D collisional electromagnetic Particle-in-Cell code with an MHD-hybrid model of high-density plasma. In the latter, collisions damp out plasma waves, and an Ohm's law with electron inertia effects neglected determines the electric field. In addition to yielding orders of magnitude in speed-up while avoiding numerical instabilities, this allows us to model the whole problem in a single unified framework: the laser-plasma interaction at sub-critical densities, energy deposition at relativistic critical densities, and fast-electron transport in solid densities. Key questions such as the multi-picosecond temporal evolution of the laser energy conversion into hot electrons, the impact of return currents on the laser-plasma interaction, and the effect of self-generated electric and magnetic fields on electron transport will be addressed. We will report applications to current experiments.
Hot Electron Measurement And Modeling For Short Pulse Laser Plasma Interactions
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Author : H. Chen
language : en
Publisher:
Release Date : 2003
Hot Electron Measurement And Modeling For Short Pulse Laser Plasma Interactions written by H. Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
We measured the hot electron production from short pulse laser plasma interactions using a fiber-array-based compact electron spectrometer that uses permanent magnets for electron energy dispersion and over 100 scintillating fibers coupled to a 1024 x 1024 pixel CCD as the detection system. This spectrometer has electron energy coverage from 10 keV to 60 MeV. The whole spectrometer is compact with dimensions of 8 inch x 7 inch x 4 inch. We performed systematic measurements of electron production on the ultra short pulse laser JanUSP (with pulse width less than 100 fs) at intensity range interest to Fast Ignition scheme from 10{sup 17} Wcm{sup -2} up to 10{sup 19} Wcm{sup -2} at Lawrence Livermore National laboratory. The electron distributions were obtained at various laser energies for different solid target materials and observation angles. We determined characteristic temperature of the escaped hot electrons at various incident laser intensity which is confirmed by theoretical simulations using the ZOHAL Particle-in-cell (PIC) code.
Inertial Fusion Sciences And Applications 2003
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Author : B. A. Hammel
language : en
Publisher:
Release Date : 2004
Inertial Fusion Sciences And Applications 2003 written by B. A. Hammel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Controlled fusion categories.
Energy Research Abstracts
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Author :
language : en
Publisher:
Release Date : 1991
Energy Research Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with Power resources categories.
Investigation Of Stimulated Raman Scattering Using Short Pulse Diffraction Limited Laser Beam Near The Instability Threshold
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Author :
language : en
Publisher:
Release Date : 2008
Investigation Of Stimulated Raman Scattering Using Short Pulse Diffraction Limited Laser Beam Near The Instability Threshold written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Short pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of Stimulated Raman Scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations (> 1 kJ and> 1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the LULI (Laboratoire pour l'Utilisation des Lasers Intenses) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light respectively with 1.5-3.0 ps pulses. In both experiments, the interaction beam was focused into a pre-ionized He gas-jet plasma. Measurements of the reflectivity as a function of intensity and k[lambda]{sub D} were completed at the Trident laser facility. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC [K.J. Bowers, et at., Phys. Plasmas, 15 055703 (2008)] particle-in-cell code. Details of the experimental results are presented in this manuscript.
Electron Transport Ion Acoustic Dynamics In Laser Produced Plasmas
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Author :
language : en
Publisher:
Release Date : 2008
Electron Transport Ion Acoustic Dynamics In Laser Produced Plasmas written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
In this thesis laser-plasma processes are studied at transport and ion time scales. In order to study these processes the particle-in-cell code QNPIC with one spatial dimension and three dimensions in velocity space was developed. Collisional effects are included by a Monte Carlo procedure, and an electric field solver based on the quasineutrality condition has been implemented. This allows long time scale simulations without having to resolve the electron plasma frequency. Collisional heating of the electrons in the laser electric field is one of the major restrictions on the time step in particle-in-cell codes. We have developed a collisional heating procedure that is based on a Langevin equation. It utilizes a Fokker-Planck equation that describes heating time averaged over the laser frequency. This procedure, in conjunction with the fast field solver and procedures to represent collisions, allows simulation of long time scale in laser-plasma interactions without the need to resolve the short time scales to ensure numerical stability and suppress numerical artifacts. We have studied in detail homogeneously heated plasmas and the effects of electron-electron collisions and collisional heating on the electron distribution function. We have suggested a nonlocal, nonlinear heat transport model based on a earlier self consistent nonlocal transport theory that is formally restricted to small (linearized) temperature perturbations. Our model extends this model to the case of finite temperature perturbations. The model is tested successfully in simulations of hot spot relaxation of an initial temperature distribution that corresponds to the instantaneous release of heat into a spatially Gaussian temperature profile and Maxwellian velocity distributions of the electrons. In simulations of collisionally heated hot spots we qualitatively describe the effects of non-Maxwellian velocity distributions on the heat flux and the change of the distribution function due to transpor.
Frontiers In High Energy Density Physics
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Author : National Research Council
language : en
Publisher: National Academies Press
Release Date : 2003-05-11
Frontiers In High Energy Density Physics written by National Research Council and has been published by National Academies Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-05-11 with Science categories.
Recent scientific and technical advances have made it possible to create matter in the laboratory under conditions relevant to astrophysical systems such as supernovae and black holes. These advances will also benefit inertial confinement fusion research and the nation's nuclear weapon's program. The report describes the major research facilities on which such high energy density conditions can be achieved and lists a number of key scientific questions about high energy density physics that can be addressed by this research. Several recommendations are presented that would facilitate the development of a comprehensive strategy for realizing these research opportunities.
Continuation Of The Application Of Parallel Pic Simulations To Laser And Electron Transport Through Plasmas Under Conditions Relevant To Icf And Sbss
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Author :
language : en
Publisher:
Release Date : 2007
Continuation Of The Application Of Parallel Pic Simulations To Laser And Electron Transport Through Plasmas Under Conditions Relevant To Icf And Sbss written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
One of the important research questions in high energy density science (HEDS) is how intense laser and electron beams penetrate into and interact with matter. At high beam intensities the self-fields of the laser and particle beams can fully ionize matter so that beam -matter interactions become beam-plasma interactions. These interactions involve a disparity of length and time scales, and they involve interactions between particles, between particles and waves, and between waves and waves. In a plasma what happens in one region can significantly impact another because the particles are free to move and many types of waves can be excited. Therefore, simulating these interactions requires tools that include wave particle interactions and that include wave nonlinearities. One methodology for studying such interactions is particle-in-cell (PIC) simulations. While PIC codes include most of the relevant physics they are also the most computer intensive. However, with the development of sophisticated software and the use of massively parallel computers, PIC codes can now be used to accurately study a wide range of problems in HEDS. The research in this project involved building, maintaining, and using the UCLA parallel computing infrastructure. This infrastructure includes the codes OSIRIS and UPIC which have been improved or developed during this grant period. Specifically, we used this PIC infrastructure to study laser-plasma interactions relevant to future NIF experiments and high-intensity laser and beam plasma interactions relevant to fast ignition fusion. The research has led to fundamental knowledge in how to write parallel PIC codes and use parallel PIC simulations, as well as increased the fundamental knowledge of HEDS. This fundamental knowledge will not only impact Inertial Confinement Fusion but other fields such as plasma-based acceleration and astrophysics.