CCT, a Code to Automate the Design of Coupled Cavities

Abstract

The CCT (Coupled Cavity Tuning) code automates the RF calculations and sizing of RF cavities for the CCL (Coupled Cavity Linac) structures of APT. It is planned to extend the code to the CCDTL (Coupled Cavity Drift Tube Linac). The CCT code controls the CCLFISH code, a member of the Poisson Superfish series of codes [1]. CCLFISH performs RF calculations and tunes the geometry of individual cavities, including an accelerating cavity (AC) and a coupling cavity (CC). CCT also relates the AC and CC by means of equations that describe the coupling slot between cavities. These equations account for the direct coupling, the next nearest neighbor coupling between adjacent AC's, and the frequency shifts in the AC and CC caused by the slot. Given design objectives of a coupling coefficient k, the pi/2 mode frequency, and the net frequency of the CC, the CCT code iterates to solve for the geometry of the AC and CC and the separation distance between them (this controls the slot size), satisfying the design objectives. The resulting geometry is used to automate CAD drawing preparation. The code can also be used in "as-designed" mode to calculate the frequencies and coupling of a specified configuration. An overview of the code is presented.