Experimental determination of three-dimensional RF magnetic field distribution of nmr coils

RF magnetic field homogeneity is an important consideraxion in all NMR experiments. In this work, an extension to an existing method is suggested for experimental evaluation of RF field homogeneity of NMR coils in three dimensions. The technique is founded on Fourier analysis of signal intensity modulation produced by variation of RF pulse length or amplitude. The frequency of signal modulation produced by RF pulse length variation is proportional to the strength of the local RF field. The three-dimensional spatial information is encoded by application of frequency- and phase-encoding magnetic field gradients. RF field profiles of commonly used coil configuration obtained using this technique are presented. The method was found to be more convenient and sensitive than other techniques currently used for generating RF field profiles.