TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: NAVSEA 073, Undersea Technology

OBJECTIVE: Develop a low-noise prototype triaxial magnetometer by leveraging recent advances in atomic magnetometers.

DESCRIPTION: Advancements over the last decade in atomic vapor magnetometers have resulted in room temperature devices with sensitivities rivaling Superconducting Quantum Interference Devices (SQUIDs). At the same time, these advances have also reduced the Size, Weight, and Power (SWaP) of commercially available devices by an order of magnitude making them a good match for unmanned Navy systems. While these devices typically readout a scalar magnetic field, other work has considered methods to create atomic triaxial magnetometers such as: applying alternating current (ac) signals to scalar magnetometers in one or more vapor cells, measuring multiple resonance peaks, or using Nitrogen Vacancy (NV) centers in diamond. Creating a magnetometer that provides accurate vector readings as well as a scalar field value provides more information from these sensors thereby minimizing the number of sensors needed for Navy applications.

This STTR topic seeks a prototype atomic-based magnetometer that can simultaneously read out the orthogonal magnetic field components with an amplitude noise spectral density of less than 0.3 pT/rtHz from 1 mHz to 100 Hz, which is similar to commercially available scalar magnetometers. The magnetometer should work in real-world conditions including a dynamic range of plus or minus 100 �T on each axis, no dead zones, and an accuracy of 1 nT over the temperature range of 0-50�C. The final sensor should fit in a form factor less than 5 cm x 5 cm x 20 cm, should weigh less than 1 kg including the electronics, and use less than 20 watts of electrical power. The full vector read-out will provide more information than a scalar value, presenting additional correlations that can further improve magnetic detection. Magnetometer will be assessed for far field signature detection at the South Florida Ocean Measurement Facility (SFOMF). A device should cost less than $10k, similar to the chip scale atomic magnetometers currently being commercialized, with design considerations to reduce costs with larger production volumes. Proposals that will leverage prior atomic magnetometer development should include performance data in the frequency range required for this STTR topic.

PHASE I: Design and develop a concept for an atomic-based triaxial magnetometer. Demonstrate the ability to measure a vector magnetic field over the dynamic range of �100 �T in a bench-top sensor and report the amplitude noise spectral density from 1 mHz to 100 Hz and other requirements provided in the Description. Create models and simulations that shows the feasibility of the design. Develop a Phase II plan. The Phase I Option, if exercised, will include the design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Based upon the Phase I design and the Phase II Statement of Work (SOW), deliver, for testing and certification, four prototype triaxial magnetometers that will meet the requirements of the SOW and Description. Demonstrate that the 1 nT accuracy is independent of orientation with respect to Earth�s background field. Integrate the device components into a sensor for testing in a simulated operational environment. Identify components driving the cost and power of the device, and identify measures that could be implemented to reduce the cost and power. A Phase III plan will be required to transition.

PHASE III DUAL USE APPLICATIONS: Assist the Navy with transitioning the technology to Navy use. Ruggedize and mature the sensor and implement cost-reduction measures to provide a minimal-cost product for Navy acquisition. The technology is expected to transition to submarines.

Triaxial magnetometers are used for attitude control on satellites and for geologic exploration of deep structures in the Earth. Long-term accuracy and scalar value are of interest for both applications and an atomically stable sensor should outperform existing solid-state devices.

REFERENCES:

1. Seltzera, S. J. and Romalis, M. V. �Unshielded three-axis vector operation of a spin-exchange-relaxation-free atomic magnetometer,� Applied Physics Letters Vol. 85, No. 20 (2004); http://physics.princeton.edu/romalis/magnetometer/papers/Seltzer%20-%20Vector%20Magnetometer.pdf

2. Yudin, V. I., et al. �Measurement of the magnetic field vector using multiple electromagnetically induced transparency resonances in Rb vapor.� Physical Review A 82, 033807 (2010). http://adsabs.harvard.edu/abs/2011PhRvA..83a5801C

3. Braje, Danielle, et al. �Broadband Magnetometry and Temperature Sensing with a Light Trapping Diamond Waveguide.� Nature Physics, 11, 393-397 (2015). https://arxiv.org/abs/1406.5235

4. Wolf, Thomas, et al. �A Subpicotesla Diamond Magnetometry.� Phys. Rev. X, 5, 041001 (2015). https://arxiv.org/abs/1411.6553

5. Fang, Kejie, et al. �High-Sensitivity Magnetometry Based on Quantum Beats in Diamond Nitrogen-Vacancy Centers.� Phys. Rev. Lett. 110, 130802 (2013). http://adsabs.harvard.edu/abs/2013PhRvL.110m0802F

KEYWORDS: Magnetometry; Atomic Magnetometers; Triaxial; NV Centers in Diamond; Environmental Magnetic Fields; Orthogonal Magnetic Field Components