Integrated optically pumped magnetometer for measurements within Earth's\n magnetic field

Abstract

We present a portable optically pumped magnetometer instrument for\nultra-sensitive measurements within the Earth's magnetic field. The central\npart of the system is a sensor head operating a MEMS-based Cs vapor cell in the\nlight-shift dispersed Mz mode. It is connected to a compact, battery-driven\nelectronics module by a flexible cable. We briefly review the working\nprinciples of the device and detail on the realization of both, sensor head and\nelectronics. We show shielded and unshielded measurements within a static\nmagnetic field amplitude of 50 uT demonstrating a noise level of the sensor\nsystem down to 140 fT/\\sqrt{Hz} and a sensor bandwidth of several 100 Hz. In a\ndetailed analysis of sensor noise we reveal the system to be limited by\ntechnical sources with straightforward strategies for further improvement\ntowards its fundamental noise limit of 12 fT/\\sqrt{Hz}. We assess the\nparameters defining the sensor bandwidth by theoretical modeling based on the\nBloch equations. Finally, we compare our sensors' performance to a commercial\nSQUID system in a measurement environment typical for geomagnetic observatory\npractice and geomagnetic prospection.\n