[Paper Review] Progress on the ARIADNE axion experiment

Andrew Geraci, Harry Fosbinder-Elkins+18 more|arXiv (Cornell University)|Oct 15, 2017

Atomic and Subatomic Physics Research3 citations

TL;DR

ARIADNE proposes a novel search for the QCD axion using nuclear magnetic resonance in a laser-polarized 3He gas, detecting axion-induced spin precession via a rotating tungsten sprocket that mimics a time-varying magnetic field. The experiment achieves high sensitivity through superconducting magnetic shielding and rotary stability, targeting the 0.1–10 meV mass range where existing haloscopes are ineffective.

ABSTRACT

The Axion Resonant InterAction Detection Experiment (ARIADNE) is a collaborative effort to search for the QCD axion using techniques based on nuclear magnetic resonance. In the experiment, axions or axion-like particles would mediate short-range spin-dependent interactions between a laser-polarized 3He gas and a rotating (unpolarized) tungsten source mass, acting as a tiny, fictitious "magnetic field". The experiment has the potential to probe deep within the theoretically interesting regime for the QCD axion in the mass range of 0.1-10 meV, independently of cosmological assumptions. The experiment relies on a stable rotary mechanism and superconducting magnetic shielding, required to screen the 3He sample from ordinary magnetic noise. Progress on testing the stability of the rotary mechanism is reported, and the design for the superconducting shielding is discussed.

Motivation & Objective

• To probe the QCD axion in the 0.1–10 meV mass range, a region currently inaccessible to existing axion haloscopes.
• To test a new experimental approach based on resonant spin precession driven by axion-induced effective magnetic fields.
• To achieve sensitivity to axion couplings below the standard model benchmark by leveraging spin amplification and magnetic shielding.
• To address experimental challenges such as rotary stability, magnetic noise, and vibrational background in ultra-low-noise environments.
• To validate key components including superconducting shielding, 3He polarization, and SQUID detection for future axion discovery.

Proposed method

• Utilizes laser-polarized 3He gas as a spin-sensitive detector to transduce axion-mediated spin-dependent interactions into measurable transverse magnetization.
• Employs a rotating sprocket-shaped tungsten mass to generate a time-varying effective magnetic field at the nuclear Larmor frequency, resonantly driving spin precession.
• Applies superconducting magnetic shielding to suppress ambient magnetic noise while preserving the axion-induced effective field.
• Relies on a SQUID magnetometer to detect the precessing transverse magnetization from the 3He sample.
• Uses a rotary mechanism with high speed stability (10 Hz rotation) to maintain resonance with axion Compton wavelength-dependent frequency.
• Employs metrology and finite-element simulations to model and mitigate background sources such as acoustic vibrations, trapped flux, and patch potentials.

Experimental results

Research questions

• RQ1 Can a rotating source mass generate a detectable effective magnetic field that mimics axion-mediated spin interactions in a 3He NMR system?
• RQ2 What level of rotary speed stability is required to maintain resonance and avoid signal degradation over long integration times?
• RQ3 To what extent can superconducting shielding suppress environmental magnetic noise without attenuating the axion-induced effective field?
• RQ4 What are the dominant background sources (e.g., vibrations, trapped flux, patch potentials) and can they be mitigated to reach the required sensitivity?
• RQ5 Can the experimental setup achieve the projected sensitivity to probe the QCD axion in the 0.1–10 meV mass window?

Key findings

• Rotary mechanism stability was experimentally tested and found to support the required 10 Hz rotation with sub-micron wobble, ensuring resonance fidelity.
• Acoustic vibrations were modeled to produce a magnetic field background of ~10⁻²² T at resonance, well below the expected axion signal for 10⁶ s averaging.
• Trapped flux noise was estimated at ~7×10⁻²⁰ T/√Hz at 100 Hz, depending on shield construction, but tolerable if controlled.
• Patch potential effects were modeled to induce <5 pm vibration in copper membranes and <0.5 fm in quartz walls, yielding a background field of ~5×10⁻²¹ T on resonance.
• The system can tolerate a DC field of up to 10⁻⁷ T without significant degradation, and additional shielding layers may be added if needed.
• Overall, simulations and tests indicate that key experimental requirements—rotary stability, thermal management, and magnetic noise suppression—are within reach for the full experiment.