The Experimental Study Of The Identification Of Ferromagnetic Target For Optical Pumping Magnetometer

Geomagnetic field of every location on the earth has certain intensity, direction anddistribution. Not only the carrier will affect the geomagnetic field in the measurement area;but the induced magnetic field magnetized by geomagnetic field of ferromagnetic objects willalso generate changes of spatial distributions of itself in the measurement area. The study ofthis paper was spread around the influence of ferromagnetic objects; the magnetic dipolemagnetic field distributing theory was applied to guide the elimination of magnetic fieldinterference. For high precision measurement of geomagnetic field, the induced magneticfield calculations for ferromagnetic objects have important academic and practicalsignificance when degaussing.This paper introduced the basic conceptions of geomagnetic measurements andgeomagnetic map firstly; give the brief analysis of geomagnetic field constitution; thenintroduced the classification and some main technical indexes of magnetometer particularly,since the instrument for geomagnetic field measurement experiments could be decided. Thispaper introduced working principle and processes of proton magnetometer, then analyzed theworking principle for optically pumped cesium magnetometer from the theories of the cesiumatomic basic nature and cesium atomic energy level structure. Then we measured regionalgeomagnetic field by optical pumping cesium magnetometer, considering the discrete data ofgeomagnetic field, this paper plotted successive isoline map of local magnetic field by usingKriging on the platform of surfer, the magnetic abnormal points was found caused by theferromagnetic material. The induced magnetic fields of ferromagnetic objects under a weakmagnetic field was calculated in this paper, the formula of magnetic induction in space anypoint was obtained based on far magnetic field theory of magnetic dipoles and the theory thatferromagnetic objects can be regarded as a combination of certain magnetic dipoles. The leastsquare is applied to calculate the magnetic moments of nail according to the experiment dataof induced magnetic field, and then calculate the induced magnetic field strength of theestablished model.In this paper, the influence of ferromagnetic objects on geomagnetic fieldwas studied form both modeling analysis and experimental measurement, the establishedmagnetic dipole models were well verified through measuring the space magnetic fieldsurrounding buried nails, which has some theoretical reference value, finally the error sources are analyzed. Magnetic dipole models can be used for detecting position of magnetic anomalypoint caused by ferromagnetic objects, and assessing the size of magnetic mineral, possesses avast range of application prospect.