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ABSTRACT: Cancelation of 1/R<sup>2</sup>-associated integrals in the numerical solution procedure of the time-domain magnetic field integral equations are explained to halve the computational costs of the classical marching-on-in-time (MOT) schemes in which the delay time is approximated by the barycentric electric distance of the subdomain patches. The new technique improves the accuracy of the MOT as the resulting interpolation coefficients for the calculation of the impedance matrices became independent of the electrical distance of surface elements. Additionally, the analytical closed-form expressions for the evaluation of the remaining 1/R<sup>3</sup>-associated integrals allow the fast computation of the retarded matrices on demand. The applicability of the scheme to large-scale wave scattering problems is investigated.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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ABSTRACT: In electrodynamic field computations the continuous Maxwell equations are typically discretized in the space variables, i. e the continuous space is mapped onto a finite set of discrete elements leading to a system of differential equations constituting the Maxwell grid equations. These dynamical systems can be very large. Due to limited computational, accuracy and storage capabilities, simplified models, obtained by means of model order reduction (MOR) methods, which capture the main features of the original model are then successfully used instead of the original models. Most commonly MOR via projection is used. Variation of model parameters like geometrical or material parameters give rise to multivariate dynamical systems. It is aimed that also the simplified models keep this parameter dependence. In this work, MOR methods are presented for multivariate systems based on the finite integration technique (FIT). The methods are applied to numerical examples with both geometrical and material variations.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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Y Poltoratska,
C Eckardt, W Ackermann,
K Aulenbacher,
T Bahlo,
R Barday,
M Brunken,
C Burandt,
R Eichhorn,
J Enders, [......],
C Ingenhaag,
J Lindemann,
W F O Müller,
M Platz,
M Roth,
F Schneider,
M Wagner,
A Weber,
T Weiland,
B Zwicker
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ABSTRACT: At the superconducting Darmstadt electron linac a 100 keV source of polarized electrons has been installed. Major components had been tested prior to installation at an offline teststand. Commissioning of the new source at the S-DALINAC will take place early in 2011. We report on the performance of the teststand, simulations, developments on the laser systems, new radio-frequency components for the S-DALINAC injector, and the status of the implementation of the source.
Journal of Physics Conference Series 06/2011; 298(1):012002.
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C Eckardt,
T Bahlo,
P Bangert,
R Barday,
U Bonnes,
M Brunken,
C Burandt,
R Eichhorn,
J Enders,
M Espig, [......],
M Roth,
F Schneider,
H Schusler,
M Wagner,
A Weber,
B Zwicker, W Ackermann,
W F O Müller,
T Weiland,
K Aulenbacher
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ABSTRACT: At the superconducting 130 MeV Darmstadt electron linac S-DALINAC the new source of polarized electrons uses a GaAs cathode illuminated with pulsed Ti:Sapphire and diode laser light. The electron source had been set up and commissioned at a test stand with a beam line where a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and a chopper-prebuncher system were part of the system. Upon completion of the tests, test stand and beam line were dismantled and re-installed at the S-DALINAC. The new photo injector opens up the potential for experiments with polarized electron and photon beams for nuclear structure studies at low momentum transfers. Various polarimeters will be installed at all experimental sites to monitor the beam polarization. We report on the S-DALINAC, the results from the teststand performance, the implementation of the polarized source and the polarimeter research and development.
Proceedings of the Particle Accelerator Conference, New York/N.Y., U.S.A. (2011); 01/2011
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Y Poltoratska,
C Eckardt, W Ackermann,
K Aulenbacher,
T Bahlo,
R Barday,
M Brunken,
C Burandt,
R Eichhorn,
J Enders, [......],
C Ingenhaag,
J Lindemann,
W F O Müller,
M Platz,
M Roth,
F Schneider,
M Wagner,
A Weber,
T Weiland,
B Zwicker
[show abstract]
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ABSTRACT: At the superconducting Darmstadt electron linac a 100 keV source of polarized electrons has been installed. Major components had been tested prior to installation at an offline teststand. Commissioning of the new source at the S-DALINAC will take place early in 2011. We report on the performance of the teststand, simulations, developments on the laser systems, new radio-frequency components for the S-DALINAC injector, and the status of the implementation of the source.
Journal of Physics: Conference Series 298 (2011) [Workshop on Sources of Polarized Leptons and High Brightness Electron Beams (PESP2010) Bonn, Germany]; 01/2011
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ABSTRACT: In this paper equivalent circuit models of inductive coupled radio frequency identification (RFID) antenna systems are extracted by means of the partial element equivalent circuit (PEEC) method. Each antenna impedance is analyzed separately regarding frequency dependent behavior including skin- and proximity effects as well as parasitic capacitances. On the contrary, the inductive coupling between any two coils is computed for an arbitrary 3D spatial arrangement by a filamentary mutual inductance computation technique, allowing for fast spatial sweeps. Both models are combined to a reduced equivalent circuit that maintains the topology of mutually coupled inductances. The described approach is tested with a conventional reader transponder arrangement and compared with the full PEEC models.
IEEE Transactions on Magnetics 09/2010; · 1.36 Impact Factor
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ABSTRACT: The temporal discretization of the time-domain integral equations (TDIE) is commonly accomplished by either the implicit marching-on-in-time (MOT) schemes using subdomain Lagrange polynomial interpolations or the always-stable marching on-in-order/degrees (MOD) of the entire-domain weighted Laguerre basis functions. An alternative approach for discretizing the time convolution integrals in the TDIE, competitive to the time basis expansion in the MOT or MOD recipes, is the Lubich's convolution quadrature methods (CQM), using the (first or) second order backward finite difference (BFD) approximations in the Laplace domain. The underlying physics describing the wave scattering process is time invariant, as the material properties do not change over time. The CQM are utilized to transform continuous-time representation of the time-invariant integral kernel (system transfer function) to discrete-time domain. The CQM are called finite difference delay modeling (FDDM) when the scattering analysis of arbitrarily shaped three-dimensional (3D) structures is carried out in a marching style.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In this paper, the finite volume time domain (FVTD) semi-discrete formulation, discrete in the space and continuous in the time, is derived for the electromagnetic field simulation, starting from the Maxwell's equations. The time marching schemes that can be employed to turn this into discrete system of equations are presented. The discrete formulation is used to explain variations in FVTD methods e.g., methods which differ in spatial approximation. For a given problem, numerical methods anticipate the convergence of the solutions towards the reference (analytical) solution as the grid is refined. The convergence order for various FVTD methods is presented in different scenarios and compared with that of finite integration technique (FIT) and finite element method (FEM).
Applied Electromagnetics Conference (AEMC), 2009; 01/2010
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ABSTRACT: The unconditionally stable solution of time-domain integral equations by the classical marching-on-in-order schemes demands O(N<sub>t</sub> <sup>3</sup>N<sub>s</sub> <sup>2</sup>) CPU cycles, where N<sub>t</sub> and N<sub>s</sub> are the number of temporal and spatial unknowns, respectively. Discrete fast Fourier transform (FFT)-based algorithms are proffered to expedite the recursive temporal convolution products of the Toeplitz block aggregates of the retarded interaction matrices through which the overall computational cost and memory requirements reduces to O(alpha(N<sub>s</sub>)N<sub>t</sub>log(N<sub>t</sub>)) and O(N<sub>t</sub>alpha(N<sub>s</sub>)), respectively. Simulation results for arbitrarily shaped scatterers demonstrate the accuracy and efficiency of the technique.
Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International; 07/2009
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ABSTRACT: The numerical accuracy and energy conservation are of great importance in real-life electromagnetic (EM) problems, such as tracing the influence of excited wake fields inside accelerator structures on moving charge particles over long time periods. In practice, the essential property needed for accurate time-domain simulations is the fulfillment of the energy conservation law implied by Maxwell equations. Time- domain integral equations (TDIE) are commonly solved by the marching-on-in-time (MOT) or marching-on-in-degree (MOD) methods.
Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
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ABSTRACT: Electrodynamic field simulations typically require the solution of large linear systems which may depend on several variables. Model Order Reduction Techniques offer an approach to solve these multivariate problems in a reasonable time. This paper presents an Order Reduction Method and the required system equation linearization for structures discretized by the Finite Integration Technique (FIT) depending on frequency and length variation.
IEEE Transactions on Magnetics 04/2009; · 1.36 Impact Factor
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ABSTRACT: A fast, yet unconditionally stable, solution of time-domain electric field integral equations (EFIE) pertinent to the scattering analysis of uniformly meshed conducting structures is introduced. A discrete fast Fourier transform (FFT)-based algorithm is proffered to expedite the recursive spatial convolution products of the Toeplitz-block-Toeplitz retarded interaction matrices in a new marching-without-time-variable scheme. The total computational cost and storage requirements of the proposed method scales as O(N<sub>t</sub> <sup>2</sup> N<sub>s</sub>log(N<sub>s</sub>)) and O(N<sub>t</sub>N<sub>s</sub>), respectively, as opposed to O(N<sub>t</sub> <sup>2</sup> N<sub>s</sub> <sup>2</sup>) and O(N<sub>t</sub>N<sup>2</sup> <sub>s</sub>) for classical marching-on-in-order methods, where N<sub>t</sub> and N<sub>s</sub> are the number of temporal and spatial unknowns, respectively. Simulation results for long strip, platelike, and cylindrical scatterers demonstrate the accuracy and efficiency of the technique.
Microwave Conference, 2008. EuMC 2008. 38th European; 12/2008
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T Kuerzeder,
A Araz,
M Brunken,
J Conrad,
R Eichhorn,
H.-D Graef,
M Hertling,
F Hug,
M Konrad,
M Platz,
A Richter,
S Sievers,
T Weilbach, W Ackermann,
W F O Mueller,
B Steiner,
T Weiland
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ABSTRACT: The injector section of the S-DALINAC currently delivers beams of up to 10 MeV with a current of up to 60 µA. The upgrade aims to increase both parameters to 14 MeV and 150 µA in order to allow more demanding experiments. Therefore, a modified cryostat module equipped with two new cavities is required. Due to an increase in rf power to 2 kW the old coaxial rf input couplers, being designed for a maximum power of 500 W, have to be replaced by new waveguide couplers. We review the design principles and report on the fabrication of the coupler and the whole module.
European Particle Accelerator Conference 2008, Genoa, Italy; 07/2008
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ABSTRACT: The numerical integration of electromagnetic models with sinusoidal excitation should be implemented in a special manner because standard adaptive Runge-Kutta integration methods do not work properly if the difference between the main and the embedded order of approximations is one. In this paper, a new class of adaptive time stepping schemes specially designed for the numerical integration of the electromagnetic models with sinusoidal dynamics is proposed.
IEEE Transactions on Magnetics 07/2008; · 1.36 Impact Factor
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ABSTRACT: The design process and the operation of particle accelerator machines can advantageously be assisted by fast online beam dynamics simulations because of its flexible parameter variation combined with nearly simultaneous solution responses providing a detailed insight into the actual machine status. Based on the moment approach a fast tracking code named V-Code has been implemented at TEMF. At the Superconducting DArmstädter LINear ACcelerator S-DALINAC the V-Code is used during the design process of the injector for the new 100 keV polarized electron source but is also supposed to be employed at the control system. For these purposes an implementation of fringe field alpha magnets is mandatory. In this paper a summary of issues regarding the implementation complemented with simulation results will be provided.
Linear Accelerator Conference , Victoria, B.C/Canada (2008); 01/2008
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R Eichhorn,
R Barday,
U Bonnes,
M Brunken,
C Eckardt,
J Conrad,
J Enders,
H D Gräf,
C Heßler,
T Kurzeder, [......],
Y Poltoratska,
M Roth,
S Sievers,
T Weilbach, W Ackermann,
W F O Müller,
B Steiner,
T Weiland,
K Aulenbacher,
J Fuerst
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ABSTRACT: The current upgrade for the injector mainly involves the superconducting rf part. In order to increase the maximum current from 60 μA to 150 or 250 μA the power coupler design had to be modified, resulting in major changes in the whole cryo-module. Second, an additional polarized electron source (SPIN) has been set-up at an offline test area. There, the polarized electrons are produced by photoemission at a strained GaAs cathode on a 100 kV platform. The test beamline includes a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and additional diagnostic elements. We will give an overview to the project, report on the status and present first measurement results including the proof of polarisation.
Linear Accelerator Conference, Victoria, B.C/Canada (2008); 01/2008
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ABSTRACT: To make the implicit marching-on-in-time schemes stable for practical applications, choices of appropriate temporal basis functions are investigated. The quadratic and cubic cardinal B-spline functions are introduced as new time bases for which the numerical solution of the electric field integral equation demonstrates that they can compete with the time shifted Lagrange interpolating functions in terms of accuracy and stability. It is shown that especially for small time step sizes using the analytical closed-form derivatives of the bases tremendously enhance the extension of the stable region in comparison with the results obtained using available consistent integrator-interpolator pairs.
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: Adapted from 'Computational Fluid Dynamics', Finite Volume Time Domain (FVTD) method is becoming increasingly popular in 'Computational Electromagnetics'. The focus of this paper is on the convergence analysis of different FVTD methods on tetrahedral and hexahedral meshes. Other aspects like implementation techniques, CPU time and memory are also furnished.
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: Mathematicians have proven that few specific collocation methods provide stable numerical solution for the delay differential equations provided the accuracy order of the finite difference approximation matches to that of the temporal interpolation. To adjoin this important conclusion to the development of stable time-domain field integral equation-based solvers, this paper investigates the impact of diverse proposed interpolators over conveniently usable integrators.
Electromagnetics in Advanced Applications, 2007. ICEAA 2007. International Conference on; 10/2007
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ABSTRACT: Polyhedral finite elements of lowest order are introduced in the formulation of the finite integration technique (FIT). The resulting availability of general polyhedral element shapes in the FIT facilitates e.g. consistent subgridding or consistent grids containing both hexahedral and tetrahedral elements without resorting to interpolations. To show the practical suitability of the scheme, the frequency response of a dielectric filter is calculated and compared to the results of a standard simulation tool.
Electromagnetics in Advanced Applications, 2007. ICEAA 2007. International Conference on; 10/2007
