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Raj G, Hüller S. Impact of Laser Beam Speckle Structure on Crossed Beam Energy Transfer via Beam Deflections and Ponderomotive Self-Focusing. PHYSICAL REVIEW LETTERS 2017; 118:055002. [PMID: 28211711 DOI: 10.1103/physrevlett.118.055002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Indexed: 05/16/2023]
Abstract
The role of laser speckle structure (hot spots) and its ponderomotive self-focusing (PSF), in crossed beam energy transfer (CBET), of smoothed laser beams is investigated in an inhomogeneous expanding plasma. Numerical simulations using the code harmony in two spatial dimensions, demonstrate how self-focusing of laser hot spots in crossed beams can significantly affect the transfer of energy from one beam to the other in addition to the stimulated Brillouin scattering (SBS) process. It is shown that for sufficiently intense laser beams, when the laser hot spots exceed the criterion for self-focusing in a plasma with flow, the angular spread of transmitted light beams increases considerably with the intensity, which arises in particular, in expanding plasma where significant beam deflection is observed. It is shown for the first time that besides SBS, the contribution of speckle structure, PSF, and deflections of the intense hot spots in multiple speckle beams to CBET, therefore matters.
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Affiliation(s)
- G Raj
- Centre de Physique Théorique (CPHT), Ecole Polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau, France
| | - S Hüller
- Centre de Physique Théorique (CPHT), Ecole Polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau, France
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2
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Berger RL, Suter LJ, Divol L, London RA, Chapman T, Froula DH, Meezan NB, Neumayer P, Glenzer SH. Beyond the gain exponent: Effect of damping, scale length, and speckle length on stimulated scatter. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:031103. [PMID: 25871045 DOI: 10.1103/physreve.91.031103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Indexed: 06/04/2023]
Abstract
Three-dimensional wave propagation simulations and experiments show that the gain exponent, an often used metric to assess the likelihood of stimulated Brillouin scatter, is insufficient and must be augmented with another parameter, Nr, the ratio of the resonance length, Lres, to the laser speckle length. The damping rate of ion acoustic waves, ν, and thus Lres, which is proportional to ν, are easily varied with plasma species composition, e.g., by varying the ratio of hydrogen and carbon ions. As Nr decreases, stimulated Brillouin scattering increases despite the same gain exponent.
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Affiliation(s)
- R L Berger
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - L J Suter
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - L Divol
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - R A London
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - T Chapman
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - D H Froula
- Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA
| | - N B Meezan
- Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551, USA
| | - P Neumayer
- ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Planckstrae 1, 64291 Darmstadt, Germany
| | - S H Glenzer
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 72 Menlo Park, California 94025, USA
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Langer SH, Bhatele A, Still CH. pF3D Simulations of Laser-Plasma Interactions in National Ignition Facility Experiments. Comput Sci Eng 2014. [DOI: 10.1109/mcse.2014.79] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Landge AG, Levine JA, Bhatele A, Isaacs KE, Gamblin T, Schulz M, Langer SH, Bremer PT, Pascucci V. Visualizing Network Traffic to Understand the Performance of Massively Parallel Simulations. IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2012; 18:2467-2476. [PMID: 26357155 DOI: 10.1109/tvcg.2012.286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The performance of massively parallel applications is often heavily impacted by the cost of communication among compute nodes. However, determining how to best use the network is a formidable task, made challenging by the ever increasing size and complexity of modern supercomputers. This paper applies visualization techniques to aid parallel application developers in understanding the network activity by enabling a detailed exploration of the flow of packets through the hardware interconnect. In order to visualize this large and complex data, we employ two linked views of the hardware network. The first is a 2D view, that represents the network structure as one of several simplified planar projections. This view is designed to allow a user to easily identify trends and patterns in the network traffic. The second is a 3D view that augments the 2D view by preserving the physical network topology and providing a context that is familiar to the application developers. Using the massively parallel multi-physics code pF3D as a case study, we demonstrate that our tool provides valuable insight that we use to explain and optimize pF3D's performance on an IBM Blue Gene/P system.
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Affiliation(s)
- A G Landge
- Scientific Computing and Imaging Institute, University of Utah, USA.
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Mounaix P, Divol L, Huller S, Tikhonchuk VT. Effects of spatial and temporal smoothing on stimulated brillouin scattering in the independent-hot-spot model limit. PHYSICAL REVIEW LETTERS 2000; 85:4526-4529. [PMID: 11082587 DOI: 10.1103/physrevlett.85.4526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2000] [Indexed: 05/23/2023]
Abstract
The influence of laser beam smoothing on stimulated Brillouin backscattering (SBBS) is studied analytically in the limit of the independent hot spot model. It is shown that the temporal beam smoothing can reduce the SBBS reflectivity significantly even though the laser bandwidth is smaller than the growth rate for the average intensity. The explanation of this reduction effect is given in terms of SBBS growth in the statistically significant hot spots. The minimum laser bandwidth corresponding to an important reduction of the reflectivity is thus determined properly. The dependence of this reduction effect on the acoustic damping for a given laser bandwidth is discussed.
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Affiliation(s)
- P Mounaix
- Centre de Physique Theorique, UMR 7644 du CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France
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Vidal F, Johnston TW. Electromagnetic Beam Breakup: Multiple Filaments, Single Beam Equilibria, and Radiation. PHYSICAL REVIEW LETTERS 1996; 77:1282-1285. [PMID: 10063037 DOI: 10.1103/physrevlett.77.1282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Drake RP, Watt RG, Estabrook K. Onset and Saturation of the Spectral Intensity of Stimulated Brillouin Scattering in Inhomogeneous Laser-Produced Plasmas. PHYSICAL REVIEW LETTERS 1996; 77:79-82. [PMID: 10061776 DOI: 10.1103/physrevlett.77.79] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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