A conformal array of microfabricated optically-pumped first-order gradiometers for magnetoencephalography

• Published in: EPJ quantum technology Vol. 7; no. 1
• Main Authors: Nardelli, N. V., Perry, A. R., Krzyzewski, S. P., Knappe, S. A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2020; Springer Nature B.V
• Subjects: Arrays; Gradiometers; Linearity; Magnetic fields; Magnetic measurement; Magnetic shielding; Magnetoencephalography; Magnetometers; Nanotechnology and Microengineering; Negative feedback; Noise sensitivity; Physics; Physics and Astronomy; Quantum Information Technology; Quantum Physics; Special issue on Quantum Magnetometers; Spintronics; Laser sensors; Magnetoencephalography (MEG); Optically-pumped magnetometer (OPM); Optical instruments; Spin-exchange relaxation-free (SERF); Magnetometer; Atomic; Quantum sensors; Micro-optical devices
• ISSN: 2662-4400; 2196-0763
• DOI: 10.1140/epjqt/s40507-020-00086-4

An array of 21 first-order gradiometers based on zero-field optically-pumped magnetometers is demonstrated for use in magnetoencephalography. Sensors are oriented radially with respect to the head and housed in a helmet with moveable holders which conform to the shape of a scalp. Our axial gradiometers have a baseline of 2 cm and reject laser and vibrational noise as well as common-mode environmental magnetic noise. The median sensitivity of the array is 15.4 fT/Hz 1/2 , measured in a human-sized magnetic shield. All magnetometers are operated independently with negative feedback to maintain atoms at zero magnetic field. This yields higher signal linearity and operating range than open-loop operation and a measurement system that is less sensitive to systematic and ambient magnetic fields. All of the system electronics and lasers are compacted into one equipment rack which offers a favorable outlook for use in clinical settings.