Noise characterization of an atomic magnetometer at sub-millihertz frequencies

• Magnetic field noise measurements in an AM-NMOR atomic magnetometer have shown values of 50 pT Hz−1/2 at 0.1 mHz.
• The electronic noise contributions do not limit the sensor performance in the low-frequency range.
• The magnetometry technique proves to be suitable for applications with demanding long-term stability like the eLISA mission.

Noise measurements have been carried out in the LISA bandwidth (0.1–100 mHz) to characterize an all-optical atomic magnetometer based on nonlinear magneto-optical rotation. This was done in order to assess if the technology can be used for space missions with demanding low-frequency requirements like the LISA concept. Magnetometry for low-frequency applications is usually limited by 1/f noise and thermal drifts, which become the dominant contributions at sub-millihertz frequencies. Magnetic field measurements with atomic magnetometers are not immune to low-frequency fluctuations and significant excess noise may arise due to external elements, such as temperature fluctuations or intrinsic noise in the electronics. In addition, low-frequency drifts in the applied magnetic field have been identified in order to distinguish their noise contribution from that of the sensor. We have found the technology suitable for LISA in terms of sensitivity, although further work must be done to characterize the low-frequency noise in a miniaturized setup suitable for space missions.