IPAC2017 - List of Authors (Nasr, M.H.)

Paper	Title	Page
TUPAB132	A Novel Dual-Mode Dual-Frequency Linac Design	1634
SUSPSIK123	use link to see paper's listing under its alternate paper code
	M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	In this paper we will present a new type of accelerator structure that operates simultaneously at two accelerating modes with two frequencies. The frequencies are not harmonically related, but rather have a common sub-harmonic. This design will use a recently developed parallel-feeding network that feeds every cavity cell independently using a distributed feeding network. This will overcome many of the practical complications of coupled cell structure. We will provide the theoretical background for our dual-mode design as well as present our optimized design that operates at C and X bands simultaneously and provides enhanced gradient and efficiency compared to single-mode designs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB132
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WEPIK111	Derivation of a Finite Element Formulation From a Lagrangian for the Electromagnetic Potentials	3208
	A.R. Vrielink, M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Conventional electromagnetic finite element solvers typically solve a weak formulation of the Helmholtz wave equation. While mathematically this approach is correct, it does not fully reflect the fundamental physics involved. We offer an alternative variational formulation which is not derived from the Helmholtz wave equation but is more fundamentally tied to the physics of the system: a Lagrangian for the electromagnetic potentials. Solving for the potentials directly allows for a natural accounting of the beam wave interaction. It could also potentially avoid the issue of deleterious spurious modes inherent when selecting the Coulomb gauge and enforcing the subsequent divergence free condition, eliminating the need for vector basis functions. Herein we present the theory and the resulting formulation including a discussion on gauge fixing. We conclude with some numerical results demonstrating the potential of this formulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK111
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WEPIK112	A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry	3211
	A.R. Vrielink, M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK112
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUPAB132

A Novel Dual-Mode Dual-Frequency Linac Design

1634

SUSPSIK123

use link to see paper's listing under its alternate paper code

M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

In this paper we will present a new type of accelerator structure that operates simultaneously at two accelerating modes with two frequencies. The frequencies are not harmonically related, but rather have a common sub-harmonic. This design will use a recently developed parallel-feeding network that feeds every cavity cell independently using a distributed feeding network. This will overcome many of the practical complications of coupled cell structure. We will provide the theoretical background for our dual-mode design as well as present our optimized design that operates at C and X bands simultaneously and provides enhanced gradient and efficiency compared to single-mode designs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB132

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK111

Derivation of a Finite Element Formulation From a Lagrangian for the Electromagnetic Potentials

3208

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Conventional electromagnetic finite element solvers typically solve a weak formulation of the Helmholtz wave equation. While mathematically this approach is correct, it does not fully reflect the fundamental physics involved. We offer an alternative variational formulation which is not derived from the Helmholtz wave equation but is more fundamentally tied to the physics of the system: a Lagrangian for the electromagnetic potentials. Solving for the potentials directly allows for a natural accounting of the beam wave interaction. It could also potentially avoid the issue of deleterious spurious modes inherent when selecting the Coulomb gauge and enforcing the subsequent divergence free condition, eliminating the need for vector basis functions. Herein we present the theory and the resulting formulation including a discussion on gauge fixing. We conclude with some numerical results demonstrating the potential of this formulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK111

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK112

A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry

3211

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK112

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)