femaxx - 3-dimensional electromagnetic eigenmodal analysis

large-scale computation of electromagnetic eigenmodes

general description

femaxx is a finite element based numerical solver that computes eigenfrequencies, quality factors and eigenmodal solutions of electromagnetic resonators. Initial code development has been a joint project between the Paul Scherrer Institute (Roman Geus, Andreas Adelmann, Stephan Adam) and ETHZ (Peter Arbenz). The package is compiled and linked with the standard GNU configure/make command chain.

CAD integration

To integrate femaxx into the workflow of commercial CAD software, preprocessor and postprocessor programs have been implemented. It is now possible to export CAD geometry from an industrial grade CAD system, e.g. CATIA, mesh the geometry and run an electromagnetic eigenmodal analysis.


The program has been designed from the ground up to run on large distributed memory compute clusters. The objective has been to allow designers to study novel cavity designs free of constraints. Such constraints are often imposed by solvers that require symmetries of different types. femaxx does not require the user to incorporate symmetries a priori into the design process. Still, symmetries can be used if required. Thus, novel concepts can be studied free of limitations. femaxx is capable to run fully 3-dimensional computations of accelerator cavities that have been discretized into meshes with millions of tetrahedra.


The numerical computation of eigenfrequencies and eigenmodal fields of large accelerator cavities, based on full-wave, three-dimensional models, has attracted considerable interest in the recent past. In particular, it is of vital interest to know the performance characteristics, such as resonance frequency, quality figures and the modal fields, respectively, of such devices prior to construction; given the fact that the physical fabrication of a cavity is expensive and time-consuming, a device that does not comply with its specifications can not be tolerated; a robust and reliable digital prototyping methodology is therefore essential. Furthermore, modern cavity designs typically exhibit delicate and detailed geometrical features that must be considered for obtaining accurate results. The finite element method is therefore the method of choice for modeling widely variable geometry.