Orientation-Independent Optically Pumped Magnetometers: Total Field Sensors Without Dead Zones.

This report presents our SBIR Phase-I results demonstrating the feasibility of an improved optically pumped magnetometer without dead zones, with improved sensitivity, reduced heading errors, and reduced power consumption. Optically Pumped Magnetometers OPMs are among the most sensitive magnetometers available. In addition, OPMs are total field sensors they measure the magnitude of the ambient magnetic field rather than its vector components. The total field measurement greatly reduces noise when the magnetometer is deployed on a moving platform such as an aircraft, towed body, or divers hand. This reduced motional noise is a crucial advantage over competing technologies such as fluxgates, magnetoresistive sensors, and SQUIDs Superconducting QUantum Interference Devices. One major disadvantage of existing OPMs is that they have dead zones the noise in the magnetic measurements deteriorates badly when the OPM is oriented in the wrong way with respect to the ambient magnetic field. This orientation dependent performance restricts the way the OPM can be deployed. In some applications, multiple sensor units are required to cover the full range of platform orientations. The dead zones thus impair the utility and increase the cost of OPMs.