Applications of Modern High-Precision Overhauser Magnetometers

Increased sensitivity and resolution of geophysical instruments significantly enhances the effectiveness of non-destructive investigation methods for standard geological problems and allows new experiments. We suggest to use modern highly sensitive scalar magnetometers for identification and study of geological and artificial low-contrast objects in a magnetic field. We present application results of a modern nuclear precession magnetometer POS based on the processor Overhauser sensor. The device is developed and produced by the Quantum Magnetometry Laboratory, Ural Federal University, Yekaterinburg, Russia. Experiments conducted in the laboratory and observatories allowed to determine the device absolute accuracy of 0.5 nT and sensitivity of 0.02 nT, and to confirm its operability in large magnetic field gradients. This sensitivity is sufficient for detection of magnetic field changes caused, for example, by tectonomagnetic, seismomagnetic, piezomagnetic effects and electrokinetic phenomena in the geological environment. We conducted field experiments comparing POS magnetometers metrological characteristics with similar instruments from Scintrex and Geometrics. The results confirm measurement high stability in long-term observations of the magnetic field change due to geodynamic processes. We tested POS instruments in various geophysical applications, including prospecting and exploration of minerals (placer and ore gold, hydrocarbons, kimberlites); identification of ferromagnetic objects in cover environments; archaeological sites mapping. Our latest experience adds to this list a magnetic survey for pipeline inspection purposes. In addition, we discuss application of a novel absolute 3-component magnetometer POS-4 based on a principle of bias field switching method. The device was tested at several INTERMAGNET geomagnetic observatories. Due to high absolute accuracy and stability, there is a good prospect of implementing these magnetometers at observation points of long-term geomagnetic field secular variation and in autonomous magnetic observatories.