# Numerical optimization of a low emittance lattice cell

## TL;DR

This paper uses numerical optimization to determine the optimal dipole and quadrupole field distributions in a storage ring lattice cell to minimize natural emittance, revealing that higher quadrupole gradients lead to cell splitting.

## Contribution

It introduces a particle swarm optimization approach to optimize dipole and quadrupole distributions for low emittance in storage ring cells, a novel application in this context.

## Key findings

- Optimized cells show specific longitudinal field variation features.
- Higher quadrupole gradients cause the cell to split into two similar cells.
- The method effectively minimizes natural emittance in lattice design.

## Abstract

In the lattice designs for the next generation storage ring light sources, longitudinal gradient bending magnets and anti-bending magnets have been adopted. A logical question raised by the trend of varying the longitudinal distribution of dipole strength is: what are the optimal distributions of the dipole and quadrupole fields in a lattice cell for the purpose of minimizing the natural emittance? We studied this problem by numerically optimizing the dipole and quadrupole distributions of the normalized cell optics using the particle swarm optimization algorithm. The results reveal the features of the longitudinal field variation of the optimized cell and show that when the quadrupole gradient is increased enough, the cell tends to split into two identical cells with similar features.