The first superconducting final focus quadrupole prototype of the FCC-ee study

TL;DR

This paper reports the development and testing of a superconducting CCT quadrupole prototype for FCC-ee, demonstrating excellent field quality and no training behavior, suitable for compact high-precision accelerator applications.

Contribution

It presents the first superconducting CCT quadrupole prototype for FCC-ee, with optimized conductor layout and validated performance through cryogenic testing.

Findings

No training behavior observed during initial ramp

Higher-order multipoles below 1e-4 units

Field quality matches simulations and room temperature tests

Abstract

A single aperture Canted-Cosine-Theta (CCT) quadrupole magnet, made of NbTi superconductors, has been developed for the final focus region of the FCC-ee study. The conductor layout is optimised to mitigate edge effects on one of the two sides of the magnet that typically lead to undesired higher-order multipoles. Experimental results of a prototype, including paraffin wax impregnation and cryogenic temperature measurements, are presented. The magnet exhibits no training behaviour, surpassing the nominal current during the initial ramp. Field quality is excellent, with higher-order multipoles below $1\times 10^{-4}$ units, consistent with simulations and room temperature tests. These findings confirm the potential of superconducting CCT magnets to offer compact solutions for applications demanding stringent field quality.