Actively screened gradient coils for NMR microscopy

The ability to generate large magnetic field gradients is a prerequisite for the implementation of NMR microscopy. Large gradients are required to limit the broadening of the lineshape and the lowering of the signal to noise ratio in images. In order to reap the benefits of large gradients it is necessary to be able to rapidly switch them on and off without inducing eddy currents in the heat shields and cryostat walls of the magnet. It should also be possible to produce large gradients without excessive power dissipation in the gradient coils, which might significantly heat up the sample. These requirements have been fulfilled in the authors´ experiments by the use of gradient coils which have been designed using the ideas of active magnetic screening