"Optimizing surface coils and the self-shielded gradiometer"
B. H. Suits and A. N. Garroway
Abstract
A computational method for optimizing both single- and two-layer
surface coils is presented that is relatively easy to implement
in practice using either a variational approach or through standard
numerical matrix diagonalization techniques. The technique is
applied, in particular, to develop a self-shielded gradiometer
that is relatively immune to radiofrequency (rf) interference
from distant sources with a minimal compromise to its ability to sense
rf from nearby sources, properties necessary for nuclear quadrupole
resonance detection of buried land mines. Results of the
optimization procedure are evaluated using finite-element numerical
techniques and measurements on prototype coils for a number of
configurations. These results show that practical coils can be
constructed that approximate the theoretically optimized coils
quite well. In addition, the trade off between the surface coil
sensitivity and noise immunity is presented for the self-shielded
gradiometer configuration.
Journal of Applied Physics 94, 4170-4178 (2003).
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