The `n2EDM MSR' -- a very large magnetically shielded room with an exceptional performance for fundamental physics measurements

TL;DR

This paper describes the design, construction, and characterization of a large, highly effective magnetically shielded room (MSR) for fundamental physics experiments, achieving extremely low magnetic fields and high shielding factors.

Contribution

The paper introduces a very large MSR with exceptional magnetic shielding performance suitable for sensitive physics measurements.

Findings

Remanent magnetic field below 100pT in 1m3 volume

Shielding factor of 10^5 at 0.01Hz, increasing to 10^8 above 1Hz

Interior volume of 25m3 with multiple openings for experimental access

Abstract

We present the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute which features an interior cubic volume with each side of length 2.92m, thus providing an accessible space of 25m3. The MSR has 87 openings up to 220mm diameter to operate the experimental apparatus inside, and an intermediate space between the layers for sensitive signal processing electronics. The characterization measurements show a remanent magnetic field in the central 1m3 below 100pT, and a field below 600pT in the entire inner volume, up to 4\,cm to the walls. The quasi-static shielding factor at 0.01\,Hz measured with a sinusoidal 2muT peak-to-peak signal is about 100,000 in all three spatial directions and rises fast with frequency to reach 10^8 above 1Hz.