Benchtop magnetic shielding for benchmarking atomic magnetometers

Hobson, Peter J.; Holmes, Niall; Patel, Prashant; Styles, Ben; Chalmers, James; Morley, Chris; Davis, Alister; Packer, Michael; Smith, Thomas X.; Raudonyte, Sintija; Holmes, Darragh; Harrison, Robert; Woolger, David; Sims, Dominic; Brookes, Matthew J.; Bowtell, Richard; Fromhold, Mark

Abstract

Here, a benchtop hybrid magnetic shield containing four mumetal cylinders and nine internal flexible printed circuit boards is designed, constructed, tested, and operated. The shield is designed specifically as a test-bed for building and operating ultra-sensitive quantum magnetometers. The geometry and spacing of the mumetal cylinders are optimized to maximize shielding efficiency while maintaining Johnson noise < 15 fT/ √ Hz. Experimental measurements at the shield’s center show passive shielding efficiency of (1.0 ± 0.1)×106 for a 0.2 Hz oscillating field applied along the shield’s axis. The nine flexible printed circuit boards generate three uniform fields, which all deviate from perfect uniformity by ≤ 0.5% along 50% of the inner shield axis, and five linear field gradients and one second-order gradient, which all deviate by ≤ 4% from perfect linearity and curvature, respectively, over measured target regions. Together, the target field amplitudes are adjusted to minimize the remnant static field along 40% of the inner shield axis, as mapped using an atomic magnetometer. In this region, the active null reduces the norm of the magnitudes of the three uniform fields and six gradients by factors of 19.5 and 19.8, respectively, thereby reducing the total static field from 1.68 nT to 0.23 nT.

Citation

Hobson, P. J., Holmes, N., Patel, P., Styles, B., Chalmers, J., Morley, C., …Fromhold, M. (2023). Benchtop magnetic shielding for benchmarking atomic magnetometers. IEEE Transactions on Instrumentation and Measurement, 72, Article 6007309. https://doi.org/10.1109/tim.2023.3293540

• Journal Article Type: Article
• Acceptance Date: Jun 21, 2023
• Online Publication Date: Jul 10, 2023
• Publication Date: 2023
• Deposit Date: Jul 24, 2023
• Publicly Available Date: Jul 24, 2023
• Journal: IEEE Transactions on Instrumentation and Measurement
• Print ISSN: 0018-9456
• Electronic ISSN: 1557-9662
• Publisher: Institute of Electrical and Electronics Engineers (IEEE)
• Peer Reviewed: Peer Reviewed
• Volume: 72
• Article Number: 6007309
• DOI: https://doi.org/10.1109/tim.2023.3293540
• Keywords: Analytical models, coils, demagnetization, elec- tromagnetic measurements, flexible printed circuits, Fourier transforms, magnetic shielding, magnetometers
• Public URL: https://nottingham-repository.worktribe.com/output/23005654
• Publisher URL: https://ieeexplore.ieee.org/abstract/document/10177829