Deuterium gradient shimming

Figure 3.50. Automatic deuterium gradient shimming. Spectrum (a) was acquired with all z-axis shims set to zero. After less than two minutes of gradient shimming of the z-z shims (3 iterations) spectrum (b) was obtained. The solvent was DMSO and one scan was acquired for each deuterium gradient echo collected via the probe lock coil. Automatic switching for deuterium observation was achieved with a home-built switching device.

The remarkable power of gradient shimming is illustrated in Fig. 3.50. The lower proton spectrum was recorded with the z-z shims all set to zero whilst the upper trace was the result of only 3 iterations of deuterium gradient shimming using the DMSO solvent resonance. The whole process took less than 2 minutes without operator intervention. Although a rather extreme example, the capabilities of this approach are clearly evident and it is likely to play a valuable role in automated spectroscopy, where irreproducible sample depths can lead to rather poor results with conventional simplex optimisation shim routines. The individual mapping of field errors within each and every sample overcomes these problems. 

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