Generating a highly uniform magnetic field inside the magnetically shielded room of the n2EDM experiment

TL;DR

This paper describes a coil system designed to produce a highly uniform magnetic field inside a magnetically shielded room, enabling precise measurements for the n2EDM experiment.

Contribution

The paper introduces a novel coil system and characterization method that achieves unprecedented magnetic field uniformity for neutron EDM measurements.

Findings

Achieved a magnetic field uniformity with a relative RMS deviation of 3×10^{-5}.

Generated a 1 μT vertical magnetic field over a 40 cm radius and 30 cm height volume.

Surpassed the uniformity requirements for the n2EDM experiment, enabling high-sensitivity neutron EDM measurements.

Abstract

We present a coil system designed to generate a highly uniform magnetic field for the n2EDM experiment at the Paul Scherrer Institute. It consists of a main $B_0$ coil and a set of auxiliary coils mounted on a cubic structure with a side length of 273 cm, inside a large magnetically shielded room (MSR). We have assembled this system and characerized its performances with a mapping robot. The apparatus is able to generate a 1 $\mu$ T vertical field with a relative root mean square deviation $\sigma$ ($B_z$)/$B_z$ = 3 $\times$ $10^{-5}$ over the volume of interest, a cylinder of radius 40 cm and height 30 cm. This level of uniformity overcomes the n2EDM requirements, allowing a measurement of the neutron Electric Dipole Moment with a sensitivity better than 1 $\times$ $10^{-27}$ ecm.