Coherence locking in a parallel NMR probe defends against gradient field spillover

Abstract. The implementation of parallel nuclear magnetic resonance detection aims to enhance measurement throughput in support of high throughput screening applications including, for example, drug discovery. In support of modern pulse sequences and solvent suppression methods, it is important that each detection site has independent pulsed field gradient capabilities. Hereby, a challenge is introduced, in which the local gradients applied in parallel detectors introduce field spillover in adjacent channels, leading to spin dephasing and hence to signal suppression. This study proposes a compensation scheme employing optimized pulses to achieve coherence locking during gradient pulse periods. The design of coherence-locking pulses utilizes optimal control to address gradient-induced field inhomogeneity. These pulses are applied in a PGSE experiment, and a parallel HSQC experiment, demonstrating their effectiveness in protecting the desired coherences from gradient field spillover. This compensation scheme presents a valuable solution for magnetic resonance probes equipped with parallel and independently switchable gradient coils.