Magnetic Research

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MAGNETIC SEARCH

Proton precession magnetometer is used in finding objects which are buried, submerged or hidden from view. An object can be found directly where it is itself magnetic, or where it may displace material which is otherwise uniformly magnetic. In some cases an object may be found indirectly when it produces a magnetic anomaly as a consequence of it being buried or emplaced. Objects of search may involve a man-made iron or steel objects, an archaeological feature such as a brick, pottery or tomb or an intentionally buried magnet used for relocation purposes.

DETERMINATION OF OBJECT MAGNETISM

It must first be determined whether the object of the search is truly magnetic before deciding whether the magnetometer will be useful in the search. Due to the presence of naturally occurring magnetite all rocks and soils are weakly magnetic. Increase in temperature increases the magnetism of a material. A magnetometer can detect magnets and coils carrying direct currents. Other materials that can be detected by a magnetometer include buried chambers, tombs, and other subsurface voids provided they occur at a shallow depth.

DETECTABILITY

The distance between the magnetometer and the object is one of the factors affecting detectability with a magnetometer. Most anomalies in a search vary inversely as the cube of this distance i.e. T=m/r3.Any effort made towards reducing this distance greatly increases the likelihood and one’s ability in finding the objects of search.

Another factor to be considered is the amount of ferromagnetic material associated with the object in contrast with the surrounding material. The effective magnetic mass (magnetic moment) of the object can be considered to be the degree of magnetism of the mate...

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...ally crossing it.In addition the signature varies inversely as the square of the distance instead of the cube of the distance as in the case of a dipole(pipelines are lines of dipoles and the anomaly amplitude thus remains large). To find one pipeline, pass a current through it for one reading and reverse the current for the next, taking two such readings at each point. The locations of the one anomaly can be as mapped as the difference in these values becomes larger as one is closer to the pipe.

Works Cited

APPLICATIONS MANUAL FOR PORTABLE MAGNETOMETERS

By S.BREINER

Geometrics,395 Java Drive

Sunnyvale,California 94086

U.S.A.

SOLID STATE PHYSICS

By S.O.PILAI.

Adapted from ES304 – Geophysical Prospecting, Earth Science Department

University of Melbourne, Australia.

By Dr.Kamar Shah Ariffin.

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