Stefano Markidis

Multi-scale simulations of plasma with iPIC3D

The implicit Particle-in-Cell method for the computer simulation of plasma, and its implementation in a three-dimensional parallel code, called iPIC3D, are presented. The implicit integration in time of the Vlasov-Maxwell system, removes the numerical stability constraints and it enables kinetic plasma simulations at magnetohydrodynamics time scales. Simulations of magnetic reconnection in plasma are presented to show the effectiveness of the algorithm.

Relaxation of relativistic plasmas under the effect of wave-particle interactions

We simulate the acceleration of electrons to relativistic energies due to the interaction of electrons with waves generated by longitudinal (i.e., electrostatic) streaming instabilities in plasmas. Two equal systems undergoing a streaming instability evolve, one according to the classical Newtons law and one according to the special relativity dynamics equation. The system that obeys Newtons law relaxes to a Maxwellian equilibrium distribution. In the case of the relativistic dynamics, the equilibrium distribution exhibits peaks in the phase space at high momenta and a larger number of particles at high energies. This steady electron population at higher energies could explain power-law energy distribution in many plasma physics and astrophysical systems.

Computer experiments on the relaxation of collisionless plasmas

The relaxation of a collisionless plasma is not regulated by the usual collisional Boltzmann equation and its related H-theorem. The interactions are long range and the collisions are not instantaneous. A direct simulation approach is presented for measuring by computer experiment what the relaxed distribution is. The conclusion of the analysis is that the relaxed distribution includes both a low energy component that is well described using the usual Boltzmann distribution and a high energy tail described using a power law. The results of the simulation study are compared directly with the model recently proposed by Kaniadakis (2002 Phys.xa0Rev.xa0E 66 056125). The observed cumulative distribution function is well reproduced by the theory.

Development and performance analysis of a UPC Particle-in-Cell code

The development and the implementation of a Particle-in-Cell code written in the Unified Parallel C (UPC) language for plasma simulations with application to astrophysics and fusion nuclear energy machines are presented. A simple one dimensional electrostatic Particle-in-Cell code has been developed first to investigate the implementation details in the UPC language, and second to study the UPC performance on parallel computers. The initial simulations of plasmas with the UPC Particle-in-Cell code and a study of parallel speed-up of the UPC code up to 128 cores are shown.

A Virtual Reality Framework to Optimize Design, Operation and Refueling of GEN-IV Reactors.

many GEN-IV candidate designs are currently under investigation. Technical issues related to material, safety and economics are being addressed at research laboratories, industry and in academia. After safety, economic feasibility is likely to be the most important crterion in the success of GEN-IV design(s). Lessons learned from the designers and operators of GEN-II (and GEN-III) reactors must play a vital role in achieving both safety and economic feasibility goals.