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  1. Fusion Energy Sciences Exascale Requirements Review. An Office of Science review sponsored jointly by Advanced Scientific Computing Research and Fusion Energy Sciences, January 27-29, 2016, Gaithersburg, Maryland

    The additional computing power offered by the planned exascale facilities could be transformational across the spectrum of plasma and fusion research — provided that the new architectures can be efficiently applied to our problem space. The collaboration that will be required to succeed should be viewed as an opportunity to identify and exploit cross-disciplinary synergies. To assess the opportunities and requirements as part of the development of an overall strategy for computing in the exascale era, the Exascale Requirements Review meeting of the Fusion Energy Sciences (FES) community was convened January 27–29, 2016, with participation from a broad range ofmore » fusion and plasma scientists, specialists in applied mathematics and computer science, and representatives from the U.S. Department of Energy (DOE) and its major computing facilities. This report is a summary of that meeting and the preparatory activities for it and includes a wealth of detail to support the findings. Technical opportunities, requirements, and challenges are detailed in this report (and in the recent report on the Workshop on Integrated Simulation). Science applications are described, along with mathematical and computational enabling technologies. Also see for more information.« less
  2. Modeling ultrafast laser-driven ionization dynamics with Monte Carlo collisional particle-in-cell simulations

    Ionization dynamics of cold dense matter induced by ultrashort (<100 fs) laser pulses is studied for intensities at the onset of the relativistic regime by one-dimensional kinetic simulations. As a model we use a particle-in-cell code that includes field and electron collisional ionization, as well as elastic binary Coulomb collisions. As examples for the different ionization mechanisms, we give the spatial and temporal evolution of laser-induced ionization dynamics in helium gas and solid boron targets. Special attention is paid to the quasi-static electric fields at the rear surface of laser-irradiated targets that are important for laser-ion acceleration.
  3. Emittance growth mechanisms for laser-accelerated proton beams

    In recent experiments the transverse normalized rms emittance of laser-accelerated MeV ion beams was found to be <0.002 mm mrad, which is at least 100 times smaller than the emittance of thermal ion sources used in accelerators [T. E. Cowan et al., Phys. Rev. Lett. 92, 204801 (2004)]. We investigate the origin for the low emittance of laser-accelerated proton beams by studying several candidates for emittance-growth mechanisms. As our main tools, we use analytical models and one- and two-dimensional particle-in-cell simulations that have been modified to include binary collisions between particles. We find that the dominant source of emittance ismore » filamentation of the laser-generated hot electron jets that drive the ion acceleration. Cold electron-ion collisions that occur before ions are accelerated contribute less than ten percent of the final emittance. Our results are in qualitative agreement with the experiment, for which we present a refined analysis relating emittance to temperature, a better representative of the fundamental beam physics.« less

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"Kemp, Andreas"

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