Minimizing magnetic fields for precision experiments

TLDR

Fundamental and applied physics experiments increasingly rely on magnetically shielded rooms that achieve sub‑nanotesla residual fields, requiring multi‑layer high‑permeability and conductive shields and precise magnetic equilibration. The authors aim to develop a magnetic equilibration scheme that reduces the equilibration time by a factor of ten while improving field homogeneity. The method employs a shortened equilibration sequence that lowers the magnetic field magnitude and enhances homogeneity. The new scheme yields a linear improvement in systematic reach and a 40 % increase in statistical reach for neutron electric dipole moment searches, and can enhance any MSR application.

Abstract

An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.