### 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.

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.

Status | Finished |
---|---|

Effective start/end date | 1/01/04 → 30/06/07 |