Special lattice computation for the CERN Compact Linear Collider

In the study of a high-energy linear collider like CLIC, there are domains of activities where analytical developments are useful guides before doing fully numerical calculations or using standard accelerator design programs. The purpose of this report is to illustrate the interest of such an approach in designing rarely used magnetic insertions, such as isochronous modules or tunable achromats, which are required in several locations of the CLIC complex. Algorithmic codes have been written in this context. They give global information or guidance among a variety of approximated solutions and they help the user in selecting the most promising one before fully numerical calculations and eventually optimisations are carried out to obtain the solution consistent with the physical model.