Achieving ultra-low and -uniform residual magnetic fields in a very large magnetically shielded room for fundamental physics experiments

TL;DR

This paper reports on the development of a degaussing and magnetic field stabilization method that achieves ultra-low, highly uniform residual magnetic fields in a large shielded room, crucial for high-precision physics experiments.

Contribution

The paper introduces an optimized degaussing procedure and system configuration that significantly reduces residual magnetic fields and improves uniformity in a large MSR for neutron EDM experiments.

Findings

Residual magnetic field reduced by a factor of two.

Magnetic field uniformity below 300 pT in a 1.4 m^3 volume.

Procedure is faster and dissipates less heat, reducing thermal relaxation time from 12 h to 1.5 h.

Abstract

High-precision searches for an electric dipole moment of the neutron (nEDM) require stable and uniform magnetic field environments. We present the recent achievements of degaussing and equilibrating the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute. We present the final degaussing configuration that will be used for n2EDM after numerous studies. The optimized procedure results in a residual magnetic field that has been reduced by a factor of two. The ultra-low field is achieved with the full magnetic-field-coil system, and a large vacuum vessel installed, both in the MSR. In the inner volume of ~1.4 m^3, the field is now more uniform and below 300 pT. In addition, the procedure is faster and dissipates less heat into the magnetic environment, which in turn, reduces its thermal relaxation time from 12 h down to ~1.5 h.