Joseph Daniel Kotulski

EIGER ™ : An open-source frequency-domain electromagnetics code

EIGERtrade is a general-purpose, 3D frequency-domain electromagnetics code suite consisting of a pre-processor (Jungfrau), the physics code (EIGER), and post processor (Moench). In order to better enable collaborative development, EIGERtrade version 2.0 has been approved for release as open source software under a GNU Public License. EIGERtrade is primarily an integral-equation code for both frequency-domain electromagnetics and electrostatics. This version includes the following Greens functions: 2D and 3D free space, symmetry-planes, periodic and layered media. There is a thin-wire algorithm as well as junction basis functions for attachment of a wire to a conducting surface, and also thin-slot models for coupling into cavities. The code is written in Fortran 90 using object-oriented design and has the capability to run both in parallel and serial.

Electromagnetic Analysis of Forces and Torques on the Baseline and Enhanced ITER Shield Modules due to Plasma Disruption

An electromagnetic analysis is performed on the ITER shield modules under different plasma-disruption scenarios using the OPERA-3d software. The models considered include the baseline design as provided by the International Organization and an enhanced design that includes the more realistic geometrical features of a shield module. The modeling procedure is explained, electromagnetic torques are presented, and results of the modeling are discussed.

Numerical study of a time-domain finite element method for nonlinear magnetic problems in three dimensions

In this work, numerical analysis of nonlinear ferromagnetic problems is presented using the three-dimensional time-domain flnite element method (TDFEM). Formulated with the second- order nonlinear partial difierential equation (PDE) combined with the inverse Jiles-Atherton (J-A) vector hysteresis model, the nonlinear problems are solved in the time domain with the Newton- Raphson method. To solve the ordinary difierential equation (ODE) representing the magnetic hysteresis accurately and e-ciently, several ODE solvers are speciflcally designed and investigated. To improve the computational e-ciency of the Newton-Raphson method, the multi-dimensional secant methods, aka Broydens methods, are incorporated in the nonlinear TDFEM solver. A nonuniform time-stepping scheme is also developed using the weighted residual approach to remove the requirement of a uniform time-step size during the simulation. The capability and the performance of the proposed methods are demonstrated by various numerical examples.

Two dimensional unstable scar statistics.

This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

Electromagnetic analysis and modeling of the coax-to-triplate transition for the pulse-compression section the ZR accelerator

Transverse electromagnetic (TEM) wave analysis is used to estimate the efficiencies of the coax to triplate transition in Sandias Z-20 test module. The structure of both the TEM mode and higher order TE modes in the triplate transmission line are characterized. In addition, three dimensional time domain simulations are carried out and used in conjunction with the modal analysis to provide insight into the wave structure excited in the triplate transmission line.

Parallel CARLOS-3D — an electromagnetic boundary integral method for parallel platforms

Abstract CARLOS-3D is a three-dimensional general purpose computer code for calculating the scattering from complex three-dimensional bodies. The code uses the method of moments technique with Galerkin testing, to solve the StattonChu, integral equations for the specified geometry. All of the surfaces describing the scatterer are replaced by equivalent electric and magnetic currents which are then determined via the solution of a matrix equation. The parallel implementation of this code is discussed together with the parallel in-core solver developed at Sandia National Laboratories. Results for the parallel performance of the code are presented.

Analysis of airframe-mounted antennas using parallel and hybridized finite-element time-domain methods

The application of numerical methods to electrically large, three-dimensional geometries typically requires the use of parallel-processing techniques. The distributed parallelization of the finite-element time-domain-finite-difference time-domain (FETD-FDTD) hybrid is described. An application is provided for antenna radiation on a realistic airframe. The parallelization procedure requires two domain decompositions: one for the structured, finite-difference grid, and the other for the unstructured, finite-element grid. The two grids communicate across the interface shown. The FETD method and the interface to FDTD are described, and the parallelization implementation is presented together with applications.

High-order Calderón multiplicative preconditioner for time domain electric field integral equations

Marching-on-in-time (MOT) time domain electric field integral equation (TDEFIE) solvers are often used to analyze scattering of transient electromagnetic fields from perfect electrically conducting (PEC) surfaces. Unfortunately, just like their frequency domain counterparts, MOT-TDEFIE solvers suffer from dense-mesh breakdown when the linear dimensions of the patches in a surface mesh are small compared to the space-time step and/or the order of the spatial basis functions used to expand the surface currents is high. This breakdown phenomenon manifests itself in the form of ill-conditioned MOT system matrices and slow convergence rates of the MOT iterative solver.

The analysis of the electromagnetic loads on selected ITER blanket shield modules due to induced eddy and halo currents

The prediction of electromagnetic loads on the ITER blanket modules during a plasma disruption is considered for two different blanket modules and different disruption events.

Electromagnetic Analysis of Forces and Torques on Selected Components of the ITER Blanket System due to Plasma Disruption

Abstract The ITER device is based on the tokamak concept of magnetic confinement in which the plasma is contained by the use of strong magnetic fields. The nearest structure to the plasma is the blanket system which provides shielding to the vacuum vessel and the superconducting magnets. There are potential abnormal operating environments where the plasma currents inside the tokamak are disrupted and induce eddy currents in the blanket (first wall and shield module). These currents interact with the large magnetic fields to produce forces in the blanket which could potentially cause mechanical failure in the first wall, shield module, or vacuum vessel. For this reason the design and qualification of the ITER blanket system requires appropriate high-fidelity electromagnetic simulations that capture the physics of these disruption scenarios. A number of different geometries will be discussed revealing the effect of different first wall designs and shield modules on the forces and torques experienced by these assemblies during plasma disruption. The key features of the modeling procedure will be presented including the plasma current modeling and geometric modeling of the first wall, shield modules, and vacuum vessel. The eddy current calculation is performed using the Opera-3d software.