

From attobeams to KelvinHelmholtz instabilities: kinetic plasma modelling at the Jülich Supercomputing Centre
报告人：Prof. Paul Gibbon（Institute for Advanced Simulation, Jülich Supercomputing Centre, Germany）
时间：2016年7月21日（周四）15:0016:00
地 点：工学院力学楼434会议室
主持人：乔宾 特聘研究员
报告简介：
Numerical modeling of plasmas often demands a kinetic approach to handle extreme nonlinearities, waveparticle interactions and other nonMaxwellian phenomena. Mathematically this requires the ab initio solution of the relativistic VlasovBoltzmann equation for the plasma constituents together with the appropriate Maxwell equations for the electromagnetic fields. Currently the model of choice is the particleincell (PIC) code, a highly versatile, robust, finitedifference discretization of the Vlasov equation for the particle distribution function f(x,p). State of the art three dimensional PIC simulations involve up to 1012 particles on 105 cores on modern supercomputers and have, for example, become an indispensable tool for exploring the complex physics behind laserbased particle beam and radiation sources.
Despite these successes, PIC simulation still has its limitations: the necessity of transferring information to and from the spatial grid makes it inherently noisy, collisional regimes are only accessible via adhoc extensions, and some form of adaptive mesh refinement is required to handle geometrically complex problems. Recently a new modeling paradigm has been established – meshfree plasma simulation – in which fast summation techniques replace the solution of the field equations on the mesh. The key innovation behind this development is the hierarchical tree algorithm, a rapid O(N log N) technique for evaluating mutual (Coulomb) forces due to an ensemble of charged particles. At JSC we have developed a parallel treecode (PEPC) capable of running on the entire 458k processors of the BlueGene/Q supercomputer JUQUEEN, a milestone which makes it feasible to perform first principles simulation of collective and collisional plasma phenomena in a variety of physical settings using well over 109 particles.
Recent work at the Jülich Supercomputing Centre on the development of the above two paradigms will be presented with regard to present and future supercomputer architectures. Examples of their respective application in various areas will also be discussed, including the generation of attosecond electron bunches with highintensity, fewcycle lasers, plasmawall interactions in ITERlike environments, and a fully kinetic treatment of the KelvinHelmholtz instability in a magnetized plasma sheath.
报告人介绍：
Paul Gibbon received the B.Sc. degree in physics from the University of Bristol, Bristol, U.K., in 1985 and a Ph.D. in plasma physics from Imperial College London, London, U.K. in 1988 under the supervision of A. R. Bell. He continued working in the field of highintensity laser–matter interactions at several European institutes, including Darmstadt University of Technology, Germany, CEA Saclay, and the University of Jena, Germany. Since 2001, he has been with Forschungszentrum Jülich GmbH, Jülich, Germany, where he now heads the Computational Science Division of the Jülich Supercomputing Centre. His current research interests are centred on the application of highperformance computing to topical challenges in plasma physics, ranging from laserdriven particle acceleration and radiation sources, to tokamak edge physics – subjects on which he has authored 2 text books and over 100 peerreviewed publications. Recently he has been appointed Associate Professor at the Katholieke Universiteit Leuven, where he teaches computational methods in physics. Since 2009 he has been Topic Speaker of the Helmholtz Association’s Supercomputing Programme. Further information about Paul Gibbon’s research group can be found here: http://www.fzjuelich.de/ias/jsc/slpp 
