Intrabeam scattering study for longitudinal strong focusing storage rings and lattice optimization

In low and medium energy electron storage rings, intrabeam scattering (IBS) is a significant collective effect that can lead to an increase in equilibrium emittance, thereby diminishing the light source’s flux. Typically, the bunch length of the electron beam in storage rings is considered constant around the ring circumference. However, in the concept of steady-state microbunching storage rings, the bunch length can vary significantly around the ring in an effort to achieve high coherence in the longitudinal dimension. In this paper, we have extended the Bjorken and Mtingwa (B-M) model to accommodate this requirement, making it versatile enough to be used for arbitrary planar storage rings. Additionally, this paper addresses the simplification of equilibrium emittance calculations involving IBS through certain approximations, making it possible to directly calculate equilibrium emittance by a formula rather than conventional iteration method. This method reveals the physical relationship between equilibrium emittance and the IBS growth rates, and also allows for the IBS effect optimization of the ring lattice by directly using equilibrium emittance as the optimization target rather than the IBS growth rate.