Chromatic index to find a working point for a 4th generation synchrotron light source

The design and tuning of a storage ring for a fourth-generation synchrotron light source is very demanding. Recently, some research groups have considered techniques based on quasi-invariants of motion to address this task. This contribution presents tools, based on a quasi-invariant of motion method, for the description and optimisation of the electron dynamics in a storage ring. An overview of this quasi-invariant formalism in the context of electron dynamics in storage rings for synchrotron light sources is presented. Quasi-invariant surface techniques to study and optimise the dynamics of a particular model are shown in detail. The relevance of the distorted chromatic index for cell tuning and for determining a working point of a machine is highlighted. These techniques are implemented to optimise the horizontal electron dynamics generated by a ring model based on a 7BA cell, with 20 cells, 81 pm rad emittance and approximately 490 m circumference, and the results are presented.