Higher order shims

Table 3.6. Shim gradients found on high-resolution spectrometers. Lower field instruments (<500 MHz) may utihse only 20 or so gradients (such as those in the left panel), whilst higher field spectrometers may employ in excess of 30. Shims up to third order are those most likely to need periodic optimisation as part of longterm spectrometer maintenance for which the most significant interacting shims are Usted. Those shown in square brackets interact less strongly with the listed gradient whilst those that interact with Z° (the main field) may cause momentary disruption of the lock signal when adjusted...

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