Magnetic Tensorial Gradiometer

Abstract

The vectorial gradiometry offers many advantages compared to scalar gradiometry in the exploration of the subsoil. The introduction of new differential quantities adds a new dimension for the identification of magnetic sources. The direct measurement of the differential tensor quantities in the process of inversion can significantly increase the quality of solutions and the ability to separate more effectively the various magnetic sources in the regions where the magnetic field is derivable from a simple scalar potential. This paper describes the development of a magnetic tensorial gradiometer system and its capabilities with emphasis on the design, testing and operation. The system has been constructed by employing two independent cubic coil sensors at a distance of 50cm. The system measures the nine tensor components Tij as well as the magnitude of the six magnetic components Bhk, in the range of +/-50000 nT with a bandwidth from DC to 10 Hz and a sensitivity of 10 pT/m. The sampling rate can be set from 1 Hz to 20 Hz. It has been shown that a gradiometer sensitivity of 10 pT/m is sufficient to detect even weak magnetic contrasts such as in archaeological applications.