EFFICIENT EXCITATION AND RINGING SUPPRESSION IN NUCLEAR QUADRUPOLE RESONANCE

Detection of materials using nuclear quadrupole resonance (NQR) is often hampered by interference from remote radio frequency sources such as radio stations, and from local sources such as piezoelectric and magnetoacoustic ringing. NQR pulse sequences have been devised that reduce or eliminate the ringing, but these pulse sequences also reduce the NQR signal. We show that the signal reduction is the result of destructive interference between spin echoes created by multiple echo formation pathways. The destructive interference can be greatly reduced using composite refocusing Pulses in the NQR pulse sequences to force the echoes into selected echo formation pathways.