Computer Calculations of Traveling-Wave Periodic Structure Properties

Abstract

The versatility and accuracy of programs such as LALA and specially SUPERFISH to calculate the rf properties of standing-wave cavities for linacs and storage rings is by now well established. Such rf properties include the resonant frequency, the phase shift per periodic length, the E- and H-field configurations, the shunt impedance per unit length and Q. While other programs such as TWAP have existed for some time for traveling-wave structures, the wide availability of SUPERFISH makes it desirable to extend the use of this program to traveling-wave structures as well. That is the purpose of this paper. In the process of showing how the conversion from standing waves to traveling waves can be accomplished and how the group velocity can be calculated, the paper also attempts to clear up some of the common ambiguities between the properties of these two types of waves. Good agreement is found between calculated results and experimental values obtained earlier.