ICAP2012 - List of Authors (Guo, H.)

Paper	Title	Page
WEP12	Realistic 3-Dimensional Eigenmodal Analysis of Electromagnetic Cavities using Surface Impedance Boundary Conditions	161
	H. Guo, B.S.C. Oswald PSI, Villigen, Switzerland P. Arbenz ETH, Zurich, Switzerland
	Funding: The work of the first author (H. Guo) was supported in part by grant no. 200021-117978 of the Swiss National Science Foundation. The new X-ray Free Electron Laser (SwissFEL) at the Paul Scherrer Institute (PSI) employs, among many other radio frequency elements, a transverse deflecting cavity for beam diagnostics. Since the fabrication process is expensive, an accurate 3-D eigenmodal analysis is indispensable. The software package Femaxx has been developed for solving large scale eigenvalue problems on distributed memory parallel computers. Usually, it is sufficient to assume that the tangential electric field vanishes on the cavity wall. To better approximate reality, we consider the cavity wall conductivity is large but finite, and thus the tangential electrical field on the wall is nonzero. We use the surface impedance boundary conditions (SIBC) arising from the skin-effect model. The resulting nonlinear eigenvalue problem is solved with a nonlinear Jacobi–Davidson method. We demonstrate the performance of the method. First, we investigate the fundamental mode of a pillbox cavity. We study resonance, skin depth and quality factor as a function of the cavity wall conductivity. Second, we analyze the transverse deflecting cavity to assess the capability of the method for technologically relevant problems.

Paper

Title

Page

Realistic 3-Dimensional Eigenmodal Analysis of Electromagnetic Cavities using Surface Impedance Boundary Conditions

161

H. Guo, B.S.C. Oswald
PSI, Villigen, Switzerland
P. Arbenz
ETH, Zurich, Switzerland

Funding: The work of the first author (H. Guo) was supported in part by grant no. 200021-117978 of the Swiss National Science Foundation.
The new X-ray Free Electron Laser (SwissFEL) at the Paul Scherrer Institute (PSI) employs, among many other radio frequency elements, a transverse deflecting cavity for beam diagnostics. Since the fabrication process is expensive, an accurate 3-D eigenmodal analysis is indispensable. The software package Femaxx has been developed for solving large scale eigenvalue problems on distributed memory parallel computers. Usually, it is sufficient to assume that the tangential electric field vanishes on the cavity wall. To better approximate reality, we consider the cavity wall conductivity is large but finite, and thus the tangential electrical field on the wall is nonzero. We use the surface impedance boundary conditions (SIBC) arising from the skin-effect model. The resulting nonlinear eigenvalue problem is solved with a nonlinear Jacobi–Davidson method. We demonstrate the performance of the method. First, we investigate the fundamental mode of a pillbox cavity. We study resonance, skin depth and quality factor as a function of the cavity wall conductivity. Second, we analyze the transverse deflecting cavity to assess the capability of the method for technologically relevant problems.