ONE-DIMENSIONAL AND 2-DIMENSIONAL PULSE SEQUENCES FOR DIFFUSION EXPERIMENTS IN THE FRINGE-FIELD OF SUPERCONDUCTING MAGNETS

The fringe field of superconducting magnets provides extremely strong and stable field gradients which can be used for diffusion experiments. A number of corresponding "supercon fringe-field" variants of the "pulsed-gradient spin-echo" method are presented. These include procedures and pulse sequences for the record of relaxation-independent diffusion decays, multislice excitation, and one- or two-dimensional Fourier-transform evaluation from the k to the z domain. Several test experiments are described. It is demonstrated that reliable diffusion decays are obtained. The one-dimensional z-domain evaluation produces grid patterns analogous to the optical "forced Rayleigh scattering" method. The two-dimensional experiments are suitable for the detection of spatially varying probability densities of diffusion or incoherent flow in heterogeneous media. As the resolution is particularly high, fluids can be studied close to solid surfaces. © 1994 by Academic Press, Inc.