Laser-Induced Sources for Magnetic Fields PDF Download
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Author: John A. Stamper
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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Book Description
Large magnetic fields are produced near the target when a powerful laser pulse is focused onto a solid target. A discussion is given of how the laser radiation produces conditions in the laser-produced plasma which allow the conversion of thermal energy to magnetic field energy. This concept of a thermal source generating the magnetic field is illustrated by deriving the source function for a spherical plasma. It is shown that the necessary nonadiabatic conditions exist in the presence of laser radiation. At a sufficiently high intensity (approximately 10 to the 14th power W/square cm), the linear polarization of the radiation produces a corresponding anisotropy in the electron velocity distribution. Magnetic sources then exist for any spatial variation of pressure and density. Sources due to the direct action of radiation pressure are also discussed. This implies that part of the laser radiation is absorbed by direct conversion (no heating) from laser field energy to magnetic field energy. An estimate is made of the magnetic field produced in the region where laser radiation is being absorbed. Such fields can be quite large--in the megagauss range. (Author).
Author: John A. Stamper
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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Book Description
Large magnetic fields are produced near the target when a powerful laser pulse is focused onto a solid target. A discussion is given of how the laser radiation produces conditions in the laser-produced plasma which allow the conversion of thermal energy to magnetic field energy. This concept of a thermal source generating the magnetic field is illustrated by deriving the source function for a spherical plasma. It is shown that the necessary nonadiabatic conditions exist in the presence of laser radiation. At a sufficiently high intensity (approximately 10 to the 14th power W/square cm), the linear polarization of the radiation produces a corresponding anisotropy in the electron velocity distribution. Magnetic sources then exist for any spatial variation of pressure and density. Sources due to the direct action of radiation pressure are also discussed. This implies that part of the laser radiation is absorbed by direct conversion (no heating) from laser field energy to magnetic field energy. An estimate is made of the magnetic field produced in the region where laser radiation is being absorbed. Such fields can be quite large--in the megagauss range. (Author).
Author: Edward James Button (MAJ, USAF.)
Publisher:
ISBN:
Category : Ionization of gases
Languages : en
Pages :
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Author: Naval Research Laboratory (U.S.)
Publisher:
ISBN:
Category : Naval research
Languages : en
Pages : 632
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Author: Mario John-Errol Manuel
Publisher:
ISBN:
Category :
Languages : en
Pages : 233
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Spontaneous electromagnetic fields can be important to the dynamic evolution of a plasma by directing heat flow as well as providing additional pressures on the conducting fluids through the Lorentz force. Electromagnetic fields are predicted to affect fluid behavior during the core-collapse of supernovae through generation of fields due to hydrodynamic instabilities. In the coronae of stars, self-generated magnetic fields lead to filamentary structure in the hot plasma. Recent experiments by Gregori et al. investigated sources of protogalactic magnetic fields generated by laser-produced shock waves. In inertial confinement fusion experiments, self-generated electromagnetic fields can also play a role and have recently become of great interest to the community. Present day laser facilities provide a unique opportunity to study spontaneous field-generation in these extreme environments under controlled conditions. Instability-induced electromagnetic fields were investigated using a novel monoenergetic-proton radiography system. Fusion protons generated by an 'exploding-pusher' implosion were used to probe laser-irradiated plastic foils with various preimposed surface perturbations. Imaging protons are sensitive to electromagnetic fields and density modulations in the plasma through the Lorentz force and Coulomb collisions, respectively. Corresponding x-ray radiographs of these targets provided mass density distributions and Coulomb effects on protons were assessed using a Monte Carlo code written using the Geant4 framework. Proton fluence distributions were recorded on CR-39 detectors and Fourier analyzed to infer path-integrated field strengths. Rayleigh-Taylor (RT) growth of preimposed surface perturbations generated magnetic fields by the RT-induced Biermann battery and were measured for the first time. Good data were obtained during linear growth and when compared to ideal calculations, demonstrated that field diffusion near the source played an important role. At later times in the plasma evolution, 3-D cellular structures were observed for all foil types. These features were found to be analogous to previously observed filamentary field structures by Séguin et al. in laser-driven spherical targets. Face-on images of these field structures provided good data to quantitatively analyze the size of these features, not previously attainable due to the complexity of the 3-D spherical data. Work presented here demonstrates that these field structures are likely caused by the magnetothermal instability in the underdense corona.
Author:
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Category : Nuclear energy
Languages : en
Pages : 912
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Author: Edward James Button
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ISBN:
Category : Deuterium
Languages : en
Pages : 69
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A quantum-rate analysis of laser-induced breakdown in deuterium and helium gas was used to predict the dependence of the breakdown threshold intensity on gas pressure, laser pulse length, and the magnitude of an applied external magnetic field parallel to the direction of propagation of the laser beam. Diffusion, elastic and inelastic collisions, and multiphoton ionization of atomic and molecular states excited by electron impact were considered.
Author: United States. Superintendent of Documents
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ISBN:
Category : Government publications
Languages : en
Pages : 1252
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February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.
Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 1572
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Author:
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ISBN:
Category : Government publications
Languages : en
Pages : 1386
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Author: Shenghui Liang
Publisher:
ISBN:
Category : Laser beams
Languages : en
Pages : 134
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