protonprecessionmagnetometer

A proton precession magnetometer, also known as a proton magnetometer or a total field magnetometer, is a type of magnetometer that measures the strength of a magnetic field by observing the precession frequency of protons. This technique relies on the fact that atomic nuclei with a net magnetic moment, such as protons, will precess at a specific frequency when placed in an external magnetic field. This precession frequency is directly proportional to the strength of the magnetic field.

The operation of a proton precession magnetometer involves a sensing coil filled with a proton-rich fluid, such as kerosene or water. A strong current is passed through the coil, creating a powerful magnetic field that aligns the magnetic moments of the protons within the fluid. When this polarizing current is suddenly switched off, the protons, no longer held in alignment, begin to precess around the direction of the ambient magnetic field. This precession generates a weak alternating current in the same sensing coil. The frequency of this induced signal is measured by electronic circuitry. By accurately determining this frequency, the magnitude of the total magnetic field at the sensor's location can be calculated using a known gyromagnetic ratio for protons.

Proton precession magnetometers are known for their high sensitivity and accuracy, making them suitable for a wide range of applications. These include geophysical surveys for mineral exploration and groundwater studies, archaeological investigations to detect buried structures, and in navigation systems where precise magnetic field measurements are required. They are also used in scientific research, such as studying Earth's magnetic field and its variations. Their ability to measure the absolute total magnetic field strength, independent of orientation, is a significant advantage in many of these uses.