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"Bernhard Seiwald: Projects"

Note: As always in science and research, the realization of planned projects and tasks depends on a job in the field and proper funding.


  • 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 εeff, 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).

    Keywords: stochastic optimization, neoclassical transport, parallel processing (MPI)

    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

    • VMEC Post-processing finished

      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

    • Global Modeling for Sunspot Numbers finished

      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.

      Keywords: nonlinear dynamics, chaos theory, solarphysics

https://www.bernhardseiwald.com/ --- Nobody ( ) 2019-11-20 16:12:35