Computational Benefits Using an Advanced Concatenation Scheme Based on Reduced Order Models for RF Structures

Heller, Johann; Flisgen, Thomas; Rienen, Ursula van

doi:10.1016/j.phpro.2015.11.060

Cited by 1 publication

(3 citation statements)

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“…In order to compute the eigenmode spectrum of the chain of eight cavities with bellows and couplers, the state-space concatenation (SSC) approach [24,[27][28][29][30] is employed. The method is a combination of domain decomposition and model-order reduction.…”

Section: B Numerical Approachmentioning

confidence: 99%

“…The scheme is directly discussed hereinafter by help of the structure under study. A validation of the scheme can be found in [24,29].…”

Section: B Numerical Approachmentioning

confidence: 99%

“…The recently proposed state-space concatenation (SSC) [24,[27][28][29][30] algorithm allows for computing eigenmodes of long chains by combining a model-order reduction approach with a domain decomposition technique. The SSC approach is a further development of the coupled S-parameter calculation (CSC) [31][32][33] scheme, which has been employed in [34] to compute the scattering parameters of a four-cavity string with couplers.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Eigenmode compendium of the third harmonic module of the European X-ray Free Electron Laser

Flisgen

Heller

Galek

et al. 2017

Phys. Rev. Accel. Beams

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Chains of superconducting radio-frequency resonators are key components of modern particle accelerators such as the European XFEL, which is currently under construction in the north of Germany. In addition to the accelerating mode of the resonators, their beam excited higher order modes are of special interest, because they can harm the beam quality. In contrast to the accelerating mode, these modes are in general not confined within single resonators of the cavity string. For instance, eigenmodes can be localized between adjacent cavities or can be distributed along the entire chain of cavities. Therefore, the full chain has to be considered for a reasonable investigation of its resonant spectra. Accounting for such complex structures is computationally challenging and is therefore often avoided. In this article, the challenge is faced by using the so-called state-space concatenation approach, which is a combination of domain decomposition and model-order reduction. The technique allows for a reduction of the number of degrees of freedom by a factor of ≈ 1.471 × 10 −4. The method is employed to generate a compendium of eigenmodes in the chain of third harmonic cavities for the European XFEL. The results are discussed in detail and are compared with experimental measurements. The compendium serves as a reference for experiments (inter alia for diagnostics based on higher order modes) at the third harmonic cavity string of the European XFEL, it allows for qualitative understanding of resonant effects appearing in chains of cavities, and it is meant to be a proof of principle of the state-space concatenation approach to handle very long and complex radio-frequency structures. To the authors' knowledge, it is the first time that a modal compendium of a structure with the given complexity is generated. The article presents geometrical details of the chain, defines quantities relevant to superconducting radio-frequency cavities, and describes the employed computational approach.

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Section: B Numerical Approachmentioning

confidence: 99%

“…The scheme is directly discussed hereinafter by help of the structure under study. A validation of the scheme can be found in [24,29].…”

Section: B Numerical Approachmentioning

confidence: 99%