Cryogenic magnetic coil and superconducting magnetic shield for neutron electric dipole moment searches

TL;DR

This paper presents a cryogenic magnetic coil and superconducting shield prototype designed for neutron EDM experiments, achieving ultra-low magnetic gradients essential for precise neutron spin measurements at SNS.

Contribution

Introduction of a superconducting magnetic shielding and cryogenic apparatus to improve magnetic field uniformity for neutron EDM searches.

Findings

Magnetic gradients below 6 ppm/cm achieved

Stable magnetic field over several hours

Effective superconducting shielding implemented

Abstract

A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6 ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparatus, particularly the introduction of super-conducting magnetic shielding and the associated cryogenic apparatus. The magnetic gradients observed are sufficiently low for the nEDM search at SNS.