Modeling imperfection effects on dipole modes in TESLA cavity

Xiao, Liling; Adolphsen, C.; Akçelik, Volkan; Kabel, A.; Ko, K.; Lee, L.; Li, Z.; Ng, C.

doi:10.1109/pac.2007.4441281

Cited by 15 publications

(16 citation statements)

References 1 publication

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“…Table 1 shows that, in this cavity, the frequency of the two measured modes in the first dipole band have been shifted downwards by ∼10 MHz with respect to the frequencies predicted by a 3D simulation, while the measured modes in the second dipole band have only small downward shifts. These numbers are consistent with the shifts predicted in simulations of cavities with manufacturing imperfections [6].…”

Section: Locating Dipole Modessupporting

confidence: 89%

Investigations of the wideband spectrum of higher order modes measured on tesla-style cavities at the FLASH LINAC

Molloy

Adolphsen

Bane

et al. 2007

2007 IEEE Particle Accelerator Conference (PAC)

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Higher Order Modes (HOMs) excited by the passage of the beam through an accelerating cavity depend on the properties of both the cavity and the beam. It is possible, therefore, to draw conclusions on the inner geometry of the cavities based on observations of the properties of the HOM spectrum. A data acquisition system based on two 20 GS/s, 6 GHz scopes has been set up at the FLASH facility, DESY, in order to measure a significant fraction of the HOM spectrum predicted to be generated by the TESLA cavities used for the acceleration of its beam. The HOMs from a particular cavity at FLASH were measured under a range of known beam conditions. The dipole modes have been identified in the data. 3D simulations of different manufacturing errors have been made, and it has been shown that these simulations can predict the measured modes.

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Section: Locating Dipole Modessupporting

confidence: 89%

Investigations of the wideband spectrum of higher order modes measured on tesla-style cavities at the FLASH LINAC

Molloy

Adolphsen

Bane

et al. 2007

2007 IEEE Particle Accelerator Conference (PAC)

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“…In operation, the geometry of a particular TESLA cavity will differ from the design shown in Fig. 2b: the manufacturing process, tuning and multiphysical effects as cooling, Lorentz detuning and microphoning will introduce geometry variations [16,24,25,6]. In the simplest case, these variations can be expressed in terms of the design parameters, see Fig.…”

Section: Domain Parametrizationmentioning

confidence: 99%

Uncertainty quantification for Maxwell’s eigenproblem based on isogeometric analysis and mode tracking

Georg

Ackermann

Corno

et al. 2019

Computer Methods in Applied Mechanics and Engineering

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The electromagnetic field distribution as well as the resonating frequency of various modes in superconducting cavities used in particle accelerators for example are sensitive to small geometry deformations. The occurring variations are motivated by measurements of an available set of resonators from which we propose to extract a small number of relevant and independent deformations by using a truncated Karhunen-Loève expansion. The random deformations are used in an expressive uncertainty quantification workflow to determine the sensitivity of the eigenmodes. For the propagation of uncertainty, a stochastic collocation method based on sparse grids is employed. It requires the repeated solution of Maxwell's eigenvalue problem at predefined collocation points, i.e., for cavities with perturbed geometry. The main contribution of the paper is ensuring the consistency of the solution, i.e., matching the eigenpairs, among the various eigenvalue problems at the stochastic collocation points. To this end, a classical eigenvalue tracking technique is proposed that is based on homotopies between collocation points and a Newton-based eigenvalue solver. The approach can be efficiently parallelized while tracking the eigenpairs. In this paper, we propose the application of isogeometric analysis since it allows for the exact description of the geometrical domains with respect to common computer-aided design kernels, for a straightforward and convenient way of handling geometrical variations and smooth solutions.

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“…• Select the set of inversion variables for the deformed cavity [27]. Choose the ideal cavity as the initial guess (this is equivalent to setting d = 0).…”

Section: Outline Of the Algorithmmentioning

confidence: 99%

“…The selection of this set includes all the potential degrees of freedom that both has sensitivity the objective function, and known to have uncertainties in the manufacturing process. In general, we choose the set of unknown shape parameters such that the resulted inversion variable is a good approximation of the potential shape deformation [8,27]. We use the following measurement data in this example: The J f includes the 9 monopole frequencies and 36 HOM frequencies, and J E the field values for the 9 monopole modes.…”

Section: Shape Determination With Synthetic Datamentioning

confidence: 99%

Shape determination for deformed electromagnetic cavities

Akçelik

Lee

et al. 2008

Journal of Computational Physics

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The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using experimentally measured cavity data. The objective is to match the results of the deformed cavity model to experimental data through least-squares minimization. The inversion variables are unknown shape deformation parameters that describe perturbations of the ideal cavity. The constraint is the Maxwell eigenvalue problem. We solve the nonlinear optimization problem using a line-search based reduced space GaussNewton method where we compute shape sensitivities with a discrete adjoint approach. We present two shape determination examples, one from synthetic and the other from experimental data. The results demonstrate that the proposed algorithm is very effective in determining the deformed cavity shape.

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Modeling imperfection effects on dipole modes in TESLA cavity

Cited by 15 publications

References 1 publication

Investigations of the wideband spectrum of higher order modes measured on tesla-style cavities at the FLASH LINAC

Investigations of the wideband spectrum of higher order modes measured on tesla-style cavities at the FLASH LINAC

Uncertainty quantification for Maxwell’s eigenproblem based on isogeometric analysis and mode tracking

Shape determination for deformed electromagnetic cavities

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