FWF - Stochastic Mapp T u N T - Stochastic Mapping Technique and Neoclassical Transport

  • Allmaier, Klaus, (Co-Investigator (CoI))
  • Kasilov, Sergei (Co-Investigator (CoI))
  • Leitold, Georg, (Co-Investigator (CoI))
  • Seiwald, Bernhard, (Co-Investigator (CoI))
  • Nyemov, Victor, (Co-Investigator (CoI))
  • Kernbichler, Winfried (Principal Investigator (PI))

Project: Research project

Description

The evaluation of neoclassical transport coefficients is an essential element
in stellarator studies. It is needed for the optimization of magnetic
configurations, and for the analysis and planning of experiments. It is also
of relevance for stellarator specific issues of fusion reactors. In an
arbitrary 3-dimensional magnetic field configuration of a stellarator this
problem has to be solved numerically. At the present time methods which
provide the most general solution are the conventional MC (Monte Carlo)
method, which has been realized in numerous codes and the DKES (Drift Kinetic
Equation Solver), a "regular" code which employs a variational principle
where the solution is expressed using a series of Fourier-Legendre test
functions. These two methods do not have principal limitation from the
geometry of the device or from the confinement regime, however, as an adverse
consequence of problem generality, these methods have low computational
efficiency in certain collisionality regimes. This low efficiency becomes a
substantial obstacle for optimization procedures where new, more effective
methods are necessary. High computational speed is desirable also for the
creation of neoclassical databases for a certain magnetic field
configuration. Such databases are used for the analysis and the planning of
experiments and are planned at the IPP Greifswald. Within the current
proposal, the stochastic mapping technique (SMT) should be applied to compute
transport coefficients, the bootstrap current, and supra-thermal particle
fluxes. All the calculations will be done in the long mean free path regime,
a regime where conventional MC methods have a very low efficiency. Up to now
SMT works for magnetic fields given in real space coordinates and therefore a
version of the code working directly with magnetic fields represented in
Boozer coordinates (the most common representaion of magnetic fields) has to
be developed. The procedure to calculate the bootstrap current, developed for
the conventional MC method, has to be implemented in SMT. This includes the
implementation of the proper orbitintegrated Coulomb collision operator into
the code. Convective transport of supra-thermal electrons can play a
significant role in the energy balance of stellarators in the presence of
high power electron cyclotron heating. Here, together with neoclassical
thermal particle fluxes, also the supra-thermal electron flux should be taken
into account in the flux ambipolarity condition, which defines the
self-consistent radial electric field. In this approach, SMT which is more
effective than the conventional MC method, will be used.
StatusFinished
Effective start/end date1/01/0430/06/07