A method for controlling the magnetic field near a superconducting boundary in the ARIADNE axion experiment

TL;DR

This paper presents a comprehensive method for controlling magnetic fields near superconducting boundaries to enhance the sensitivity of the ARIADNE axion detection experiment, with potential applications in similar experimental setups.

Contribution

It introduces a superconducting magnetic shielding system, a gradient reduction technique, and a novel coil design for magnetic field control near superconductors.

Findings

Achieved magnetic shielding at the $10^8$ level.

Reduced magnetic field gradients by up to 100 times.

Developed a coil design for field generation near superconducting boundaries.

Abstract

The QCD Axion is a particle postulated to exist since the 1970s to explain the Strong-CP problem in particle physics. It could also account for all of the observed Dark Matter in the universe. The Axion Resonant InterAction DetectioN Experiment (ARIADNE) experiment intends to detect the QCD axion by sensing the fictitious "magnetic field" created by its coupling to spin. The experiment must be sensitive to magnetic fields below the $10^{-19}$ T level to achieve its design sensitivity, necessitating tight control of the experiment's magnetic environment. We describe a method for controlling three aspects of that environment which would otherwise limit the experimental sensitivity. Firstly, a system of superconducting magnetic shielding is described to screen ordinary magnetic noise from the sample volume at the $10^8$ level. Secondly, a method for reducing magnetic field gradients within the sample up to $10^2$ times is described, using a simple and cost-effective design geometry. Thirdly, a novel coil design is introduced which allows the generation of fields similar to those produced by Helmholtz coils in regions directly abutting superconducting boundaries. The methods may be generally useful for magnetic field control near superconducting boundaries in other experiments where similar considerations apply.