Patent ID: 6291994
Filing Date: 2001-09-18
Classification: G01N,G01R

Abstract:
A quality factor damping (Q-damping) subsystem for use in a system for detecting substances in a specimen placed in a cavity of the system by means of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR), the subsystem comprising:a sequence controller having means for providing timing and programming pulses to the system;a variable frequency RF source to provide pulsed RF excitation at predetermined frequencies generally corresponding to resonant frequencies of the specimen;an RF coil shaped and configured to receive the specimen, the RF signal from the RF source being applied to the specimen through the RF coil, the RF coil also functioning as a pickup coil of NQR/NMR signals from the specimen and providing an output signal; andmeans for Q-damping the RF coil, which includes an isolated Q-damping coil that is controlled by the sequence controller, the sequence controller further including means for detecting a short spin-spin relaxation time (T.sub.2) of the specimen compared to the unmodified receiver dead-time, thereby maximizing RF coil sensitivity and minimizing dead time of the output signal for increasing the signal sampling averaging provided by the short-spin relaxation time.