Shape determination for deformed electromagnetic cavities

Akçelik, Volkan; Ko, K.; Lee, Lie-Quan; Li, Zenghai; Ng, Cho-Kuen; Xiao, Liling

doi:10.1016/j.jcp.2007.09.029

Cited by 21 publications

(50 citation statements)

References 20 publications

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“…Shape optimization studies have been performed with adjoint gradient information (inverse eigenvalue problems) (Akcelik et al, 2005(Akcelik et al, , 2008b. Because adjoint variables enable gradient calculation at a given design point regardless of the number of design variables, achieving a near-optimal shape in a reasonable turnaround time has become feasible (Lee, 2010;Choi et al, 2008;Xiao et al, 2011).…”

Section: Particle Accelerator Designmentioning

confidence: 99%

Multiphysics simulations: challenges and opportunities.

Keyes¹,

McInnes²,

Woodward³

et al. 2012

149

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We consider multiphysics applications from algorithmic and architectural perspectives, where "algorithmic" includes both mathematical analysis and computational complexity and "architectural" includes both software and hardware environments. Many diverse multiphysics applications can be reduced, en route to their computational simulation, to a common algebraic coupling paradigm. Mathematical analysis of multiphysics coupling in this form is not always practical for realistic applications, but model problems representative of applications discussed herein can provide insight. A variety of software frameworks for multiphysics applications have been constructed and refined within disciplinary communities and executed on leading-edge computer systems. We examine several of these, expose some commonalities among them, and attempt to extrapolate best practices to future systems. From our study, we summarize challenges and forecast opportunities.

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Section: Particle Accelerator Designmentioning

confidence: 99%

Multiphysics simulations: challenges and opportunities.

Keyes¹,

McInnes²,

Woodward³

et al. 2012

149

View full text Add to dashboard Cite

show abstract

“…In accelerator physics, it is desirable to find the cavity shape that maximizes the quality factor of a fixed accelerating mode while minimizing the quality factor of (parasitic) higher-order modes [23,24]. This design problem can be formulated as an eigensystem-constrained shape optimization problem of the form in Eq.…”

Section: Background and Related Workmentioning

confidence: 99%

Optimization of spectral functions of Dirichlet–Laplacian eigenvalues

Osting

2010

Journal of Computational Physics

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“…Then, for example, the objective functions are scalarized, i.e., the multi-objective optimization problem is converted into a single-objective optimization problem, usually with the help of some predetermined weights, and a gradient-based optimization method is applied, starting from the already found cavity shape [23]. Approaches that employ scalarization and gradient-based methods for EM shape optimization problems where the frequency of the accelerating mode has to match a given target frequency and one or a few properties of the EM field of the three-dimensional cavity shape need to be optimized are published in [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Multi-objective shape optimization of radio frequency cavities using an evolutionary algorithm

Kranjčević

Adelmann

Arbenz

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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Radio frequency (RF) cavities are commonly used to accelerate charged particle beams. The shape of the RF cavity determines the resonant electromagnetic fields and frequencies, which need to satisfy a variety of requirements for a stable and efficient acceleration of the beam. For example, the accelerating frequency has to match a given target frequency, the shunt impedance usually has to be maximized, and the interaction of higher order modes with the beam minimized. In this paper we formulate such problems as constrained multi-objective shape optimization problems, use a massively parallel implementation of an evolutionary algorithm to find an approximation of the Pareto front, and employ a penalty method to deal with the constraint on the accelerating frequency. Considering vacuated axisymmetric RF cavities, we parameterize and mesh their cross section and then solve time-harmonic Maxwell's equations with perfectly electrically conducting boundary conditions using a fast 2D Maxwell eigensolver. The specific problem we focus on is the hypothetical problem of optimizing the shape of the main RF cavity of the planned upgrade of the Swiss Synchrotron Light Source (SLS), called SLS-2. We consider different objectives and geometry types and show the obtained results, i.e., the computed Pareto front approximations and the RF cavity shapes with desired properties. Finally, we compare these newfound cavity shapes with the current cavity of SLS.cavities with resonant frequencies of 70 MHz power the cyclotron of the PROSCAN facility for cancer treatment. In the storage ring of the Swiss Synchrotron Light Source (SLS), four 500 MHz ELETTRA-type [5] cavities compensate for the energy loss due to synchrotron radiation and focus the electron bunches in longitudinal direction. A pair of passive superconducting cavities with operation frequency at the third harmonic provide bunch lengthening and Landau damping [6]. The newest accelerator at PSI is the SwissFEL facility [7], with pulsed RF cavities at operation frequencies of 3, 5.7 and 12 GHz. Compared to other PSI facilities, where standing wave cavities are used, most of the cavities of the SwissFEL LINAC are of the traveling wave cavity type. Other than for beam acceleration, RF cavities are also used for beam diagnostics, like beam current and position monitors [8,9], for bunch rotation in deflecting cavities [10], or in power amplifiers of accelerators, like klystrons, or filters.PSI is currently elaborating an upgrade proposal for SLS, called SLS-2 [11], for dramatically improved synchrotron light quality. This process is triggered by the development of distributed vacuum pumping, which allowed a reduction of the vacuum chamber dimensions, larger number and more compact magnets, and advancements in high precision machining. It is foreseen to reuse the existing main cavities, extended by a new type of absorber for the most troubling beam excited higher order modes (HOMs).In order to efficiently accelerate the beam, the RF cavity has to be optimized and engineered to satis...

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Shape determination for deformed electromagnetic cavities

Cited by 21 publications

References 20 publications

Multiphysics simulations: challenges and opportunities.

Multiphysics simulations: challenges and opportunities.

Optimization of spectral functions of Dirichlet–Laplacian eigenvalues

Multi-objective shape optimization of radio frequency cavities using an evolutionary algorithm

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