Generation and application of ultra-high-intensity magnetic field gradient pulses for NMR spectroscopy

Two different concepts of gradient current power supplies are introduced, which are suitable for the generation of ultra-high intensity pulsed magnetic field gradients of alternating polarity. The first system consists of a directly binary coded current source (DBCCS). It yields current pulses of up to +/- 120 A and a maximum voltage across the gradient coil of +/- 400 V. The second system consists of two TECHRON 8606 power supplies in push-pull configuration (PSPPC). It yields current pulses of up to +/- 100 A and a maximum voltage across the gradient coil of +/- 300 V. In combination with actively shielded anti-Helmholtz gradient coils, both systems are used routinely in NMR diffusion studies with unipolar pulsed field gradients of up to 35 T/m. Until now, alternating pulsed field gradient experiments were successfully performed with gradient intensities of up to +/- 25 T/m (DBCCS) and +/- 35 T/m (PSPPC), respectively. Based on the observation of the NMR spin echo in the presence of a small read gradient, procedures to test the stability and the matching of such ultra-high pulsed field gradient intensities as well as an automated routine for the compensation of possible mismatches are introduced. The results of these procedures are reported for the PSPPC System. (C) 2001 Academic Press.