A Feasibility Study of the Use of SQUIDS for Scalar Field Magnetometry.

摘要

A single SQUID mounted on a platform subject to random motions in the earth's field will have large spurious components in its output. In order to recover the information of interest (changes in magnitude of the total magnetic field), it is necessary to combine the outputs of three mutually orthogonal sensors in an appropriate way. The coefficients characterizing this combination depend on the initial orientation of the platform relative to the earth's field, and thus must be determined dynamically. Several algorithms which deduce these coefficients from a sequence of SQUID output data have been studied. In general the noise in the ambient field and/or the sensor noise (input noise) results in errors in the computed coefficients; these errors in turn lead to an additional source of noise in the processed output (processing noise). Computer simulations have been used to study interactions relating the frequency spectrum of the processing noise to the spectra of the input noise and platform oscillations. A number of practical considerations involved in a realization of a mobile platform system have also been analyzed. These include (1) the possibility of achieving a digitized output from the SQUIDS with sufficient linearity, dynamic range, and slew rate; and (2) the maximum deviations of the sensors from perfect orthogonality and gain uniformity that can be tolerated for given magnitude of platform oscillations. (Author)