Note: As always in science and research, the realization of planned
projects and tasks depends on a job in the field and proper funding.
Projects:
Classification of Magnetic Field Lines in progress
In toroidal fusion devices a magnetic field line may form either a
magnetic flux surface, magnetic islands or a stochastic zone. For
various problems (e.g. optimization of stellarators in real space
coordinates) it is of interest to classify magnetic field lines
according these three groups. The classification should be based
purely on the coordinates of the magnetic field line without any
further assumptions.
What shall I say - no funding, so it is leisure activities.
Keywords: topology, magnetic field line integration
Accurate Mapping of Vacuum Magnetic Flux Surfaces and Islands in progress
In H-1 experiments a systematic exploration of magnetic islands and
flux surfaces is of interest. For this purpose a high resolution
electron-beam wire-tomography system is installed. For numerical
treatment one needs a extreme accurate model of the experiments
magnetic system. Based on the measurements of the electron-beam
wire-tomography system the existing numerical models of the magnetic
system will be optimized.
Keywords: optimization, image processing, magnetic field line integration
Stellarator Optimization in progress
An energy optimizing method for stellarators is developed and
numerically implemented in the code SORSSA.
SORSSA is developed for optimizing stellarators with fixed coil
design. The figure of merit is the total stored energy in the plasma
volume. In the used model, the energy depends on the effective ripple
ε_{eff}, which is a measure for the
neoclassical transport. To optimize the configurations, the currents
of the magnetic field coils are varied such that the energy in the
plasma is maximized. In addition to the coil currents, it is possible
to vary, the coil positions and the angles between the coils. Thus, it
is possible to use the code for the design of simple stellarators. The
magnetic field is computed directly from the coil currents with help
of a Biot-Savart code. Because magnetic field lines are independent of
each other in vacuum magnetic fields, the computation of the field
lines has been parallelized which significantly increases the speed of
the computations. For the optimization process, the Simulated
Annealing algorithm is used.
Currently some upgrades/tasks are ongoing/planned:
automatic magnetic axis finder in progress
computation of α-particle confinement properties not started
optimization of H-1 configurations exhibiting stellarator symmetry in progress
optimization of H-1 configurations without stellarator symmetry not started
SORSSA has been successfully applied to the following fusion experiments:
TJ-II (CIEMAT, Spain), U-2M (Kharkov, Ukraine), CNT (Columbia University, New York, USA).
V. Kalyuzhnyj, S. Kasilov, W. Kernbichler, V. V. Nemov, B. Seiwald.
Neoclassical transport for URAGAN-2M in the 1/ν regime.Problems of Atomic Science and Technology, 30-32, 2005.
Finished Projects:
PRLCodeMonster - Virtual Machine finished
The PRLCodeMonster is a virtual machine hosting several programs for fusion plasma physics.
The aim of the project is to have a working system frozen in time.
The advantage is that for the programs, which are installed on the PRLCodeMonster, one has to undergo the installation process only once. This in very important as for some programs the installation process is quite time consuming.
Furthermore, PRLCodeMonster can be run on whatever host platform.
Keywords: virtual machines
Nearest Point in Complex Magnetic Field Geometry finished
To measure magnetic field fluctuations an array of Mirnov coils is
installed in H-1. Data obtained by the Mirnov coils are further
analyzed an processed in a magnetic coordinate system, in particular
in Boozer coordinates. As the Mirnov coils are located outside the
last closed magnetic flux surface (LCMS) and Boozer coordinates exist
only for magnetic flux surfaces the position of the Mirnov coils can't
be determined in Boozer coordinates. Therefore, one has to find the
points on the LCMS which are next neighbours to the corresponding
Mirnov coil.
Keywords: optimization, magnetic coordinates, inversion
Publications:
A special procedure has been designed for post-processing the output
data of the magneto hydrodynamic equilibrium code
VMEC
The code VMEC_PP post-processes the output data of the standard software named
VMEC
for computing magneto hydrodynamic equilibria
for toroidal magnetic confinement under the assumption of nested
magnetic flux surfaces. Close to the innermost flux surface VMEC
shows a bad convergence and the data cannot be used as input data in
other codes. Thus, this region is not used for several
applications. On the other hand this region is important e.g. for
Monte Carlo simulations of the plasma transport. To post-process the
data a special smoothing spline is designed. The smoothed data form
the basis for a consistent recalculation of the magnetic field data.
Keywords: MHD, curve fitting, spline, automatic smoothing of data
Publications:
Nature mostly provides nonlinear dynamics. Methods of chaos theory are used to analyze time series and to describe the dynamics.
The aim of this work is to obtain a model for sunspot numbers. Basics for reconstructing attractors like state space, delay time embedding dimension and reconstruction techniques are introduced. Here, one's attention is turned to the NARMA technique. For validation of the used code the Rössler system is used. Therefore, topological properties of the original attractor are compared to the reconstructed attractor. Finally, the NARMA technique is used to build a model for the sunspot number.