Author: Brackebusch, K.
Paper Title Page
MOPWO008 Eigenmode Computation for Elliptical Cavities Subject to Geometric Variation using Perturbative Methods 900
  • K. Brackebusch, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  Funding: Work supported by Federal Ministry for Research and Education BMBF under contracts 05H09HR5 and 05K10H.
Parametric studies of geometric variations are an essential part of the performance optimization and error estimation in the design of accelerator cavities. Using common eigenmode solvers the analysis of intentional and undesired geometric perturbations tend to be very extensive since any geometric variation involves an entire eigenmode recomputation. Perturbative methods constitute an efficient alternative for the computation of a multitude of moderately varying geometries. They require a common eigenmode computation of solely one (so called unperturbed) geometry and allow for deriving the eigenmodes of similar but modified (so called perturbed) geometries from these unperturbed eigenmodes. In [*],[**] the practicability of perturbative methods was already proven by means of simple cavity geometries. In this paper we investigate the applicability and efficiency for practically relevant cavities. For this, basic geometric parameters of elliptical cavities are varied and the respective eigenmodes are computed by using perturbative as well as common methods. The accuracy of the results and the computational effort of the different methods are compared.
*K. Brackebusch, H.-W. Glock, U. van Rienen, WEPPC096, IPAC 2011
**K. Brackebusch, U. van Rienen, MOPPC062, IPAC 2012
WEPWO010 BERLinPro Seven-cell SRF Cavity Optimization and HOMs External Quality Factors Estimation 2331
  • T. Galek, K. Brackebusch, T. Flisgen, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  • B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  Funding: Work funded by EU FP7 Research Infrastructure Grant No. 227579 and by German Federal Ministry of Research and Education, Project: 05K10HRC.
The main scope of this work is the optimization of the superconducting radio frequency (SRF) accelerating cavity design for the Berlin Energy Recovery Linac Project (BERLinPro)*. BERLinPro shall serve as a demonstrator for 100-mA-class ERLs with CW LINAC technology. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. Consequently it is important, at the SRF cavity design optimization stage, to calculate the external quality factors of HOMs to avoid beam break up (BBU) instabilities. The optimization of the SRF cavity design consists of two steps. In the first step the cavities' end half-cells are tuned with respect to field flatness, effective shunt impedance and geometrical factor of the fundamental accelerating mode using robust eigenmode simulations. The second step involves frequency domain simulations and the extraction of external quality factors of HOMs from transmission S-parameter spectra using vector fitting procedure and an automated scheme to remove non-static poles **. The eigenmode,as well as the frequency domain simulations are performed using CST Microwave Studio ***.
* A. Neumann et al., Proc. of ICAP2012, pp. 278–280.
** T. Galek et al., Proc. of ICAP2012, pp. 152–154.
*** CST AG,