Characterization of magnetic field noise in the ARIADNE source mass rotor

N Aggarwal ,I Lee,Alex Brown,A Kapitulnik,E Smith,W M Snow,A Schnabel,Y H Lee,D Kim,J C Long,C Y Liu,J Shortino,Y Kim,Lutz Trahms ,Chloe Lohmeyer ,Yannis K Semertzidis ,Jens Voigt ,Yun Chang Shin ,Austin Reid ,Andrew Geraci ,Andrea Fang ,Evan Weisman

doi:10.1103/physrevresearch.4.013090

Abstract

The Axion Resonant Interaction Detection Experiment (ARIADNE) is a nuclear-magnetic-resonance-based experiment that will search for novel axion-induced spin-dependent interactions between an unpolarized source mass rotor and spin-polarized $^{3}\mathrm{He}$ nuclei placed nearby. To detect a feeble axion-mediated signal at the subattotesla level, the experiment relies on ultralow magnetic background and noise. We measure and characterize the magnetic field from a prototype tungsten rotor. We show that the field is dominantly caused by a few discrete magnetic dipoles, likely due to impurities in the rotor. This is done via a numerical optimization pipeline which fits for the locations and magnetic moments of each dipole. We find that under the current demagnetization procedure, the magnetic moment of the impurities is bounded at ${10}^{\ensuremath{-}9}$ A ${\mathrm{m}}^{2}$. We further show that a shielding factor of ${10}^{9}$ will support ARIADNE's design sensitivity with the current level of tungsten purity and demagnetization process.

Highlights

The QCD axion is a particle predicted to exist in order to explain the strong-CP problem, connected with the lack of CP violation observed in the strong interactions [1,2,3,4]
This field would have components at the same frequency as the fictitious axion field and would be completely indistinguishable from the signal; the only way forward is to reduce it below the expected axion interaction level
We measured the magnetic field in proximity to the Axion Resonant Interaction Detection Experiment (ARIADNE) rotor after demagnetizing it

Summary

Introduction

The QCD axion is a particle predicted to exist in order to explain the strong-CP problem, connected with the lack of CP violation observed in the strong interactions [1,2,3,4]. Experimental searches for a neutron electric dipole moment constrain the angle θQCD—which would be expected to be of order 1 rad—to be less than 10−10 rad [5,6]. The axion provides a dynamical mechanism to explain the unnatural smallness of this angle. The axion can mediate novel short-range spin-dependent forces between fermions.

Objectives

Methods

Findings

Conclusion