ICAP 2006 - List of Keywords (electromagnetic-fields)

A B C D E F G H I K L M O P Q R S T U V W

electromagnetic-fields

Paper	Title	Other Keywords	Page
MOM2IS02	Large Scale Parallel Wake Field Computations for 3D-Accelerator Structures with the PBCI Code	simulation, vacuum, diagnostics, electron	29
	E. Gjonaj, X. Dong, R. Hampel, M. Kärkkäinen, T. Lau, W. F.O. Müller, T. Weiland TEMF, Darmstadt
	Funding: This work was partially funded by EUROTeV (RIDS-011899), EUROFEL (RIDS-011935), DFG (1239/22-3) and DESY Hamburg The X-FEL project and the ILC require a high quality beam with ultra short electron bunches. In order to predict the beam quality in terms of both, single bunch energy spread and emittance, an accurate estimation of the short range wake fields in the TESLA crymodules, collimators and other geometrically complex accelerator components is necessary. We have presented earlier wake field computations for short bunches in rotationally symmetric components with the code ECHO. Most of the wake field effects in the accelerator, however, are due to geometrical discontinuities appearing in fully three dimensional structures. For the purpose of simulating such structures, we have developed the Parallel Beam Cavity Interaction (PBCI) code. The new code is based on the full field solution of Maxwell equations in the time domain, for ultra-relativistic current sources. Using a specialized directional-splitting technique, PBCI produces particularly accurate results in wake field computations, due to the dispersion free integration of the discrete equations in the direction of bunch motion. One of the major challenges to deal with, when simulating fully three dimensional accelerator components is the huge computational effort needed for resolving both, the geometrical details and the bunch extensions by the computational grid. For this reason, PBCI implements massive parallelization on a distributed memory environment, based on a flexible domain decomposition method. In addition, PBCI uses the moving window technique, which is particularly well suited for wake potential computations in very long structures. As a particular example of such a structure, the simulation results of a complete module of TESLA cavities with eight cells each for a um-bunch will be given.
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MOM2IS03	Low-Dispersion Wake Field Calculation Tools	simulation, linac, vacuum, linear-collider	35
	M. Kärkkäinen, E. Gjonaj, T. Lau, T. Weiland TEMF, Darmstadt
	Funding: This work was partially funded by EUROTeV (RIDS-011899), DFG (1239/22-3) and DESY Hamburg. Extremely short bunches are used in future linear colliders, such as the International Linear Collider (ILC). Accurate and computationally efficient numerical methods are needed to resolve the bunch and to accurately model the geometry. In very long accelerator structures, computational efficiency necessitates the use of a moving window in order to save memory. On the other hand, parallelization is desirable to decrease the simulation times. Explicit schemes are usually more convenient to parallelize than implicit schemes since the implementation of a separate potentially time-consuming linear solver can thus be avoided. Explicit numerical methods without numerical dispersion in the direction of beam propagation are presented for fully 3D wake field simulations and for the special case of axially symmetric structures. The introduced schemes are validated by comparing with analytical results and by providing numerical examples for practical accelerator structures. Conformal techniques to enhance the convergence rate are presented and the advantages of the conformal schemes are verified by numerical examples.
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MOA1MP01	EM Field Simulation Based on Volume Discretization: Finite Integration and Related Approaches	simulation	41
	R. Schuhmann UPB, Paderborn
	Today's design and analysis demands for accelerator components request for reliable, accurate, and flexible simulation tools for electromagnetic fields. Amongst the widest spread approaches is the Finite Integration Technique (FIT), which has been used in electro- and magnetostatics, eddy current problems, wave propagation problems, as well as PIC codes. FIT belongs to the class of local approach in the sense, that the discrete equations are derived cell-by-cell by transforming the continuous Maxwellian equations onto the computational grid. Other representatives of local approaches are Finite Differences (FD), Finite Volumes (FV), Finite Elements (FE), and the Cell Method (CM). All these approaches are based on a volume discretization, defined by the three-dimensional mesh. Whereas the close relations between FIT and FD has been known since the beginning of both approaches in the seventies, recent research has revealed that under certain circumstances, also FIT and FE have many important properties in common. In the light of the forthcoming 30 years-anniversary of the first FIT-publication in 1977, this contribution reviews these properties as well as some still existing important differences, and their consequences for the usage of the methods in practice. It is shown that the differences between the main representatives of so-called "geometrical methods" (FIT, FD, FE, CM) are surprisingly small. Some of the recent research on this topic is presented, which has lead to new theoretical insights in computational electromagnetics. Finally the possible impact of these results on the derivation of new simulation methods is discussed.
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MOA1MP02	Geometry of Electromagnetism and its Implications in Field and Wave Analysis	background, focusing	42
	L. Kettunen, A. Tarhasaari TUT, Tampere
	Electromagnetism has a strong geometrical structure which, however, is hidden when the theory is examined in terms of classical vector analysis. Consequently a more powerful framework of algebraic topology and differential geometry is needed to view the subject. Recently, the geometric view has become rather popular among the community of computational electromagnetism, but still it has been asked, whether the more generic view truly enables one to develop new tools applicable to pragmatic field and wave analysis which could not be discovered otherwise. In other words, is the investment needed to study the new subject justified by the advantages brought by the more accurate viewpoint? Such a question is, evidently, not trivial to answer. Not because the larger framework did not have clear advantages, but rather for it takes a considerable effort to understand the difference between the "old" and "new" approach. Second, the advantages tend to be rather generic in the sense, that the geometric viewpoint tends to be more useful in building a software system to solve electromagnetic boundary value problems instead of in finding some handy techniques to solve certain specific problems. This paper makes an attempt to highlight some keypoints of the geometric nature of electromagnetism and to explain which way the geometric viewpoint is known to be useful in numerical analysis of electromagnetic field and wave problems. We start from the basics of electromagnetism and end up with more specific questions related to computing.
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MOA1MP03	A Framework for Maxwell’s Equations in Non-Inertial Frames Based on Differential Forms	vacuum, acceleration	47
	S. Kurz Robert Bosch GmbH, Frankfurt B. Flemisch, B. Wohlmuth IANS, Stuttgart
	In many engineering applications the interaction between the electromagnetic field and moving bodies is of great interest. It is natural to use a Lagrangian description, where the unknowns are defined on a mesh which moves and deforms together with the considered objects. What is the correct form of Maxwell’s equations and the material laws under such circumstances? The aim of the present paper is to tackle this question by using the language of differential forms. We first provide a review of the formulations of electrodynamics in terms of vector fields, as well as differential forms in the (1+3)- and four-dimensional setting. In order to keep both Maxwell’s and the constitutive equations as simple as possible, we set up two reference frames. In the natural material frame, the (1+3)-Maxwell’s equations have their simple form, whereas in the co-moving inertial frame, the material laws are canonical. In contrast to existing literature these frames are both retained to benefit from their individual advantages. It remains to construct transformation laws connecting the considered frames. To achieve this, we use a (1+3)-decomposition in terms of general projection operators which do primarily not depend on an underlying metric or on the choice of a spatial coordinate system [1]. The desired transformation laws are established by comparing the different decompositions of an arbitrary p-form with respect to the considered frames. We provide an interpretation in terms of vector fields, and consider the low frequency limit, which is the most relevant case for an implementation into numerical codes. For the description of low frequency electromagnetism, all rigid frames are equivalent. This goes beyond the standard principle of Galilean relativity, where only inertial frames are regarded as equivalent. The proper treatment in the general case is demonstrated by means of an example in rotating coordinates, where the classical paradox by Schiff [2] is resolved. [1] F. Hehl and Y. Obukhov, Foundations of Classical Electrodynamics. Boston: Birkhäuser, 2003. [2] L. Schiff, "A question in general relativity," Proc. Nat. Acad. Sci. USA, vol. 25, 1939.
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MOAPMP01	Coupled Transient Thermal and Electromagnetic Finite Element Simulation of Quench in Superconducting Magnets	simulation, superconducting-magnet, target, controls	70
	C. W. Trowbridge, J. Simkin, S. Taylor, E. Xu Vector Fields Ltd., Oxford
	Resistive, normal zones may propagate through the low temperature superconducting coils. The rise in temperature in the windings and the internal voltages developed during this quench process are a critical issue for magnet safety, in addition the eddy currents induced in support structures during a quench may result in large Lorentz forces that can cause damage. Approximate adiabatic models have been used to achieve good results for the time profile of the current decay. More accurate methods based on finite element simulations have also been used to obtain temperature and voltage distributions. This paper describes transient, closely coupled thermal, electromagnetic finite element and circuit simulations developed to model quenching magnets. The program was designed to be efficient for this calculation. It uses nodal finite elements for the transient thermal simulation and edge elements for the electromagnetic simulation. The two simulations can be performed on different symmetry groups so that the model size can be minimized. Circuit models are coupled to the electromagnetic simulator either using filamentary edge loops or with a full volume mesh in the coils. Accurately meshing the coils increases the model size, but it is essential if accurate fields and time derivatives of the field are required. The main source of heat in the coils during quench is resistive loss in the normal zone. However rate dependent losses caused by the changing magnetic field may cause heating and therefore trigger a quench in other coils. Having closely coupled thermal and electromagnetic simulations makes it easy to include these effects and hence greatly improves the reliability of the simulation. Calculated and measured results for a 4 coil superconducting polarized target magnet will be presented. In this system the quench spreads to another coil as a result of rate dependent losses, the calculated results change dramatically if these losses are not included. M. N. Wilson, Superconducting magnets p217ff ** S. Caspi et Al, Calculating Quench propagation with Ansys, IEEE Trans. Appl. Supperconduct. Vol 13, No2, pp1714-1717
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MOAPMP02	High-Performance Self-Consistent Electromagnetic Modeling of Beams	plasma	74
	J. R. Cary CIPS, Boulder, Colorado
	Funding: US Department of Energy This talk will review some of the recent advances of electromagnetic modeling with the inclusion of charged particles, as is important for beam physics and plasma physics. Important advances include methods for accurately treating boundaries for accelerator cavities, beam pipes, etc.; increasing the maximum stable time step; and algorithms that work well on parallel architectures. Higher-order algorithms with good properties are also of interest. Early cut-cell approaches failed to result in a symmetric linear system and, as a result, can be weakly damped or unstable. Later cut-cell approaches were shown to be symmetric, but they suffered from a reduction of the stable time step. Now available are cut-cell methods that can accurately model curvilinear boundaries with no reduction in stable time step. With Richardson extrapolation, these methods can give frequencies accurate to 1 part in 10⁶ with less than 100 cells in each direction. The use of these new algorithms in VORPAL,* a flexible, object-oriented, massively parallel modeling application, will be presented. VORPAL has been used for a number of applications** involving the self-consistent interaction of charged particles with electromagnetic fields. Finally, we will discuss the needs for improvements to self-consistent EM modeling. * C. Nieter and J. R. Cary, "VORPAL: a versatile plasma simulation code", J. Comp. Phys. 196, 448-472 (2004). ** C. G.R. Geddes, et al Nature 431, 538-541 (Sep. 2004)
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TUPPP24	Transverse Coupling Impedance of a Ferrite Kicker Magnet: Comparison between Simulations and Measurements	impedance, kicker, coupling, simulation	128
	E. Arevalo, B. Doliwa, T. Weiland TEMF, Darmstadt
	Funding: This work was partially funded by DIRACsecondary-Beams(RIDS-515873). The driving terms of instabilities in particle accelerators depend on the beam surroundings which are conveniently described by coupling impedances. In the case of critical components, for which analytical calculations are not available, direct measurements of the coupling impedances on a prototype are usually needed. However, this obvious drawback on the design of particle accelerators can be overcome by electromagnetic field simulations within the framework of the Finite Integration Technique. Here we show results from numerical evaluations of the transverse coupling impedance of a ferrite kicker. In order to excite the electromagnetic fields in the device we implement numerically the conventional twin-wire method. A good agreement with experimental measurements is observed, showing a promising way to determine coupling impedances of components of particle accelerators before construction.

TUPPP29	Charge Conservation for Split-Operator Methods in Beam Dynamics Simulations	simulation, electron, focusing, space-charge	140
	T. Lau, E. Gjonaj, T. Weiland TEMF, Darmstadt
	Funding: DFG (1239/22-3) and DESY Hamburg For devices in which the bunch dimensions are much smaller than the dimensions of the structure the numerical field solution is typically hampered by spurious oscillations. The reason for this oscillations is the large numerical dispersion error of conventional schemes along the beam axis. Recently, several numerical schemes have been proposed which apply operator splitting to optimize and under certain circumstances eliminate the dispersion error in the direction of the bunch motion. However, in comparison to the standard Yee scheme the methods based on operator splitting do not conserve the standard discrete Gauss law. This contribution is dedicated to the construction of conserved discrete Gauss laws and conservative current interpolation for some of the split operator methods. Finally, the application of the methods in a PIC simulations is shown.

TUAPMP04	Simulation of Secondary Electron Emission with CST Particle Studio(TM)	electron, simulation, vacuum, scattering	160
	F. Hamme, U. Becker, P. Hammes CST, Darmstadt
	In accelerator physics and high power vacuum electronics the secondary electron emission (SEE) has in many cases an important influence on the physical behavior of the device. Since its analytical prediction even for simple geometries is extremely cumbersome, numerical simulation is essential to get a better understanding of the possible effects and ideas to change the design. The current paper introduces the implementation of SEE within the code CST Particle Studio (TM), which is an easy to use three dimensional tool for the simulation of electromagnetic fields and charged particles. There are three basic types of secondary electrons, the elastic reflected, the rediffused and the true secondary ones. The implemented SEE model is based on a probabilistic, mathematically self-consistent model developed by Furman and includes the three kinds of secondary electrons mentioned above. The paper presents simulation results with focus to the SEE for the absorbed power within an electron collector of a high power tube. As second example the secondary emission process is studied within the superconducting TESLA cavity, which gives some hints for the understanding of multipactor effects in those cavity and filter structures.
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WEPPP02	Recent Improvements to the IMPACT-T Parallel Particle Tracking Code	space-charge, simulation, cathode, linac	185
	J. Qiang, I. V. Pogorelov, R. D. Ryne LBNL, Berkeley, California
	Funding: Supported in part by the US DOE, Office of Science, SciDAC program; Office of High Energy Physics; Office of Advanced Scientific Computing Research The IMPACT-T code is a parallel three-dimensional quasi-static beam dynamics code for modeling high brightness beams in photoinjectors and RF linacs. Developed under the US DOE Scientific Discovery through Advanced Computing (SciDAC) program, it includes several key features including a self-consistent calculation of 3D space-charge forces using a shifted and integrated Green function method, multiple energy bins for a beams with large energy spread, and models for treating RF standing wave and traveling wave structures. In this paper, we report on recent improvements to the IMPACT-T code including short-range transverse and longitudinal wakefield models and a longitudinal CSR wakefield model. Some applications will be presented including simulation of the photoinjector for the Linac Coherent Light Source (LCLS) and beam generation from a nano-needle photocathode.

WESEPP01	CST's Commercial Beam-Physics Codes	simulation, controls, emittance, impedance	228
	U. Becker CST, Darmstadt
	During the past decades Particle Accelerators have grown to higher and higher complexity and cost, so that a careful analysis and understanding of the machines' behaviour becomes more and more important. CST offers userfriendly numerical simulation tools for the accurate analysis of electromagnetic fields in combination with charged particles, including basic thermal analysis. The CST STUDIO SUITE code family is the direct successor of the code MAFIA, combining the numerical accuracy of the Finite Integration Theory and Perfect Boundary Approximation within an intuitive, easy-to-use CAD environment. Automatic Parameter Sweeping and Optimization are available to achieve and control the design goals. In this paper various solver modules of CST PARTICLE STUDIO, CST EM STUDIO and CST MICROWAVE STUDIO will be presented along accelerator-relevant examples, such as: Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis. Coupler Design, including external Q-factor Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light dispersion diagram for the analysis of periodic structures design of guns, including beam emittance studies study of secondary emission processes and dark current effects in accelerating structures.

THM1MP03	A Differential Algebraic High-Order 3-D Vlasov Solver		296
	M. Berz, K. Makino MSU, East Lansing, Michigan
	Funding: US Department of Energy, National Science Foundation We show how the differential algebraic methods for ODEs and the resulting high order map computation can be generalized for solving certain PDEs. The entire PDE solving problem is cast in the form of an implicit constraint satisfaction problem, which is solved via differential algebraic partial inversion methods. As a result, it is possible to describe the solutions of the PDE locally as a very high order expression in the independent variables. Because of the high orders, it is possible to choose the size of the finite elements to be large, which leads to a very favorable behavior in high dimensions. The approach can be parallelized, and as such allows the solution of complicated high-dimensional PDEs in a reasonably efficient way. Furthermore, utilizing remainder differential algebraic methods, it is possible to provide rigorous and reasonably sharp error estimates of the entire procedure. We apply the methods to the study of the Vlasov equation describing the evolution of a beam under internal and external electromagnetic fields. In the case of this particular PDE, it is possible to perform time stepping to arbitrary order with a similar ease as in the case of the corresponing map computation case. Various examples will be given to illustrate the practical behavior of the method.

THM2IS03	CST's Commercial Beam-Physics Codes	simulation, controls, emittance, impedance	308
	U. Becker CST, Darmstadt
	During the past decades Particle Accelerators have grown to higher and higher complexity and cost, so that a careful analysis and understanding of the machines' behaviour becomes more and more important. CST offers userfriendly numerical simulation tools for the accurate analysis of electromagnetic fields in combination with charged particles, including basic thermal analysis. The CST STUDIO SUITE code family is the direct successor of the code MAFIA, combining the numerical accuracy of the Finite Integration Theory and Perfect Boundary Approximation within an intuitive, easy-to-use CAD environment. Automatic Parameter Sweeping and Optimization are available to achieve and control the design goals. In this paper various solver modules of CST PARTICLE STUDIO, CST EM STUDIO and CST MICROWAVE STUDIO will be presented along accelerator-relevant examples, such as: Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis. Coupler Design, including external Q-factor Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light dispersion diagram for the analysis of periodic structures design of guns, including beam emittance studies study of secondary emission processes and dark current effects in accelerating structures.
	Slides