Calibration of a magnetometer system

A method for calibrating a magnetometer system, the method comprising:

• applying a first magnetic field aligned with a first axis of three orthogonal axes in response to a first current, a second magnetic field approximately aligned with a second axis of the three orthogonal axes in response to a second current, and a third magnetic field approximately aligned with a third axis of the three orthogonal axes in response to a third current;
• providing a probe beam through the sensor cell comprising alkali metal particles and at least one nuclear spin isotope;
• monitoring a characteristic of precession of the at least one nuclear spin isotope in the sensor cell in response to at least one of the first, second, and third magnetic fields based on characteristics of a detection beam associated with the probe beam through the sensor cell;
• and
• controlling an amplitude of at least one of the first current, the second current, and the third current based on the detected characteristic of the precession of the at least one nuclear spin isotope in a feedback manner.

A combined nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) magnetometer system comprising:

• a sensor cell comprising alkali metal particles and at least one nuclear spin isotope;
• a probe laser configured to provide a probe beam through the sensor cell to generate a detection beam;
• a magnetic field system configured to generate a first magnetic field aligned with a first axis of three orthogonal axes associated with the sensor cell, a second magnetic field approximately aligned with a second axis of the three orthogonal axes, and a third magnetic field approximately aligned with a third axis of the three orthogonal axes;
• a detection system configured to implement NMR detection and EPR detection of an external magnetic field based on characteristics of the detection beam in response to precession of the alkali metal particles and the at least one nuclear spin isotope based on the plurality of magnetic fields;
• and
• a calibration controller comprising:
• a current controller configured to control a first current, a second current, and a third current that are associated with the first magnetic field, the second magnetic field, and the third magnetic field, respectively, the current controller being configured to square-wave modulate at least one of the first, second, and third currents about a DC baseline amplitude;
• and
• a frequency monitor configured to monitor the precession frequency of the at least one nuclear spin isotope at each modulated amplitude of the at least one of the first, second, and third currents to calibrate the combined EPR and NMR magnetometer system.