13,166 research outputs found
Transport of charged particles under fast oscillating magnetic fields
The energy production through thermo-nuclear fusion requires the confinement
of the plasma into a bounded domain. In most of the cases, such configurations
are obtained by using strong magnetic fields. Several models exist for
describing the evolution of a strongly magnetized plasma, i.e., guiding-center
approximation, finite Larmor radius regime, etc. The topic of this paper
concerns a different approach leading to plasma confinement. More exactly we
are interested in mathematical models with fast oscillating magnetic fields. We
provide rigorous derivations for this kind of models and analyze their
properties
Eulerian and Newtonian dynamics of quantum particles
We derive the classical equations of hydrodynamic type (Euler equation and
the continuity equation) from which the Schrodinger equation follows as a limit
case. It is shown that the statistical ensemble corresponding to quantum system
and described by the Schrodinger equation, can be considered as an inviscid gas
obeying the ideal gas law with quickly oscillating sign-alternating
temperature. This statistical ensemble performs the complex movements
consisting of smooth average movement and fast oscillations. It is shown that
average movements of statistical ensemble are described by Schrodinger
equation. A model of quantum motion within the limits of classical mechanics
which corresponds to the considered hydrodynamic system is suggested.Comment: 25 page
A crude model to study radio frequency induced density modification close to launchers
The interplay between radio frequency (RF) waves and the density is discussed by adopting the general framework of a 2-time-scale multi-fluid treatment, allowing to separate the dynamics on the RF time scale from that on the time scale on which macroscopic density and flows vary as a result of the presence of electromagnetic and/or electrostatic fields. The focus is on regions close to launchers where charge neutrality is incomplete and waves are commonly evanescent. The fast time scale dynamics influences the slow time scale behavior via quasilinear terms (the Ponderomotive force for the case of the equation of motion). Electrons and ions are treated on the same footing. Also, both fast and slow waves are retained in the wave description. Although this work is meant as a subtopic of a large study-the wave induced "convective cell" physics at hand is of a 2- or 3-dimensional nature while this paper limits itself to a single dimension-a few tentative examples are presented
ASCOT: solving the kinetic equation of minority particle species in tokamak plasmas
A comprehensive description of methods, suitable for solving the kinetic
equation for fast ions and impurity species in tokamak plasmas using Monte
Carlo approach, is presented. The described methods include Hamiltonian
orbit-following in particle and guiding center phase space, test particle or
guiding center solution of the kinetic equation applying stochastic
differential equations in the presence of Coulomb collisions, neoclassical
tearing modes and Alfv\'en eigenmodes as electromagnetic perturbations relevant
to fast ions, together with plasma flow and atomic reactions relevant to
impurity studies. Applying the methods, a complete reimplementation of the
well-established minority species code ASCOT is carried out as a response both
to the increase in computing power during the last twenty years and to the
weakly structured growth of the code, which has made implementation of
additional models impractical. Also, a benchmark between the previous code and
the reimplementation is accomplished, showing good agreement between the codes.Comment: 13 pages, 9 figures, submitted to Computer Physics Communication
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