Development of a 3-D, multi-nuclear continuous wave NMR imaging system

The development of a 3-D, multi-nuclear continuous wave NMR imaging (CW-NMRI) system is described and its imaging capability is demonstrated on a range of materials exhibiting extremely short T-2 relaxation values. A variety of radiofrequency resonators were constructed and incorporated into a new gradient and field offset coil assembly, while the overall system design was modified to minimise microphonic noise which was present in an earlier prototype system. The chemically combined Al-27 in a high temperature refractory cement was imaged, and the CW-NMRI system was found to be sensitive to small differences in Al-27 content in these samples. The penetration of Na-23 in salt water into samples of ordinary Portland cement (OPC) was investigated, with enhanced uptake observed for samples with larger pore size distributions. The solid C-13 component in a carbonated cement sample was also imaged, as were the Li-7 nuclei in a sample of powdered Li2CO3. A spatial resolution of 1 mm was measured in an image of a rigid polymeric material exhibiting a principal T-2(*), value of 16.3 mu s. Finally, a high-resolution 3-D image of this rigid polymer is presented. (c) 2005 Elsevier Inc. All rights reserved.