Optically pumped gradient magnetometer
| DWPI Title: Method for sensing magnetic field in atomic magnetometer, involves performing spin-polarizing process to host atoms with pump beam of light when, adiabatically extinguishing controlled magnetic field, and sensing ambient magnetic field components perpendicular to pump beam |
| Abstract: A method is provided for sensing a magnetic field in a magnetic gradiometer of the kind in which pump light and light constituting an optical carrier traverse first and second atomic vapor cells that contain host atoms and that are separated from each other by a known distance. According to such method, the host atoms are prepared in a coherent superposition of two quantum states that differ in energy by an amount that is sensitive to an ambient magnetic field. Modulation of the optical carrier in the respective cells gives rise to sidebands that interfere to generate a beat frequency indicative of the magnetic field gradient. The host atoms are prepared at least in a mode that allows measurement of ambient magnetic field components perpendicular to the axis of the pump light. In such mode, the host atoms are spin-polarized by pump light while subjected to a controlled magnetic field directed parallel to the pump beam, and then the controlled magnetic field is adiabatically extinguished. |
| Use: Method for sensing magnetic field in an atomic magnetometer. Uses include but are not limited to ordnance detection, geophysical mapping, navigation and detection of biomagnetic fields associated with heart and brain activity. |
| Advantage: The method enables providing non-zero beat-note output signal at zero external magnetic field for calibration and diagnosis by a gradiometer, canceling thermal effects which contaminate the output signal, thus relaxing requirement for the pump beam parallel to external magnetic fields, and hence removing dead zones i.e. pointing directions relative to the magnetic field which produce severely attenuated response, and permitting pump and probe beams to share same propagation axis without suffering dead zones. |
| Novelty: The method involves preparing host atoms in a coherent superposition of two quantum states in a first atomic vapor cell and in a second atomic vapor cell situated at distance from the first atomic vapor cell. An optical carrier in the first and second atomic vapor cells is modulated. An impinging process is performed to light comprising sidebands to a photodetector. Beat frequency generated by interference between the sidebands from the respective cells is measured. A spin-polarizing process is performed to the host atoms with pump beam of light when subjecting the host atoms to controlled magnetic field directed parallel to the pump beam. The controlled magnetic field is adiabatically extinguished. Ambient magnetic field components perpendicular to the pump beam are sensed, where the first and second atomic vapor cells are filled with nitrogen buffer gas, the host atom is rubidium-87 atom and the coherent superposition is between Zeeman sublevels of two distinct hyperfine manifolds. |
| Filed: 7/20/2021 |
| Application Number: US17380860A |
| Tech ID: SD 15309.1 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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