Optics tuning simulations for FCC-ee using Python Accelerator Toolbox

TL;DR

This paper explores optics correction methods for the FCC-ee collider using Python-based simulations, demonstrating improved correction schemes that enhance beam quality and luminosity in ultra-low emittance storage rings.

Contribution

It introduces a correction approach using Python Accelerator Toolbox to optimize optics correction, achieving target emittance and luminosity with improved performance over existing methods.

Findings

The RDTs + $\eta_y$ correction method outperforms LOCO in achieving target emittance.

Optimized correction scheme improves Dynamic Aperture and beam quality.

Python-based simulation effectively guides optics correction in large-scale colliders.

Abstract

The development of ultra-low emittance storage rings, such as the e+/e- Future Circular Collider (FCC-ee) with a circumference of about 90 km, aims to achieve unprecedented luminosity and beam size. One significant challenge is correcting the optics, which becomes increasingly difficult as we target lower emittances. In this paper, we investigate optics correction methods to address these challenges. We examined the impact of arc region magnet alignment errors in the baseline optics for the FCC-ee lattice at Z energy. To establish realistic alignment tolerances, we developed a sequence of correction steps using the Python Accelerator Toolbox (PyAT) to correct the lattice optics, achieve the nominal emittance, Dynamic Aperture (DA), and in the end, the design luminosity. The correction scheme has been recently optimized and better machine performance demonstrated. A comparison was conducted between two optics correction approaches: Linear Optics from Closed Orbits (LOCO) with phase advance + $\eta_x$ and coupling Resonance Driving Terms (RDTs) + $\eta_y$. The latter method demonstrated better performance in achieving the target emittance and enhancing the DA.