Sensitivity improvement in NQR based detection methods

Sensitivity improvement in NQR based detection methods

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This article presents an approach to sensitivity improvement in a detection method based on nuclear quadrupole resonance (NQR); this technique is widely applied in, for example, the detection of explosives. We have an experimental pulsed NQR apparatus equipped with a 250 W pulse power rf amplifier with the working frequency range from 0.5 to approximately 50 MHz. This range can be employed in detecting the isotopes 14N and 35Cl. The article will describe certain improvements in the circuitry of the NQR system proposed by the authors and then experimentally verified on the existing system. These modifications lead to an increased signal-to-noise ratio (SNR), thus also increasing the sensitivity of the system during the detection of substances. The main improvements are in the rf blocking circuit, which prevents the power rf pulse from reaching the preamplifier of the receiver. In this position, some impedance transformers with switched coils have been tested. The appropriate quenching circuit further reduces the penetration of the excitation pulse to this sensitive preamplifier and thus shortens the recovery time.

This article presents an approach to sensitivity improvement in a detection method based on nuclear quadrupole resonance (NQR); this technique is widely applied in, for example, the detection of explosives. We have an experimental pulsed NQR apparatus equipped with a 250 W pulse power rf amplifier with the working frequency range from 0.5 to approximately 50 MHz. This range can be employed in detecting the isotopes 14N and 35Cl. The article will describe certain improvements in the circuitry of the NQR system proposed by the authors and then experimentally verified on the existing system. These modifications lead to an increased signal-to-noise ratio (SNR), thus also increasing the sensitivity of the system during the detection of substances. The main improvements are in the rf blocking circuit, which prevents the power rf pulse from reaching the preamplifier of the receiver. In this position, some impedance transformers with switched coils have been tested. The appropriate quenching circuit further reduces the penetration of the excitation pulse to this sensitive preamplifier and thus shortens the recovery time.

NQR, Nuclear Quadrupole Resonance, detection of chemical substances, spectroscopy

NQR, Nuclear Quadrupole Resonance, detection of chemical substances, spectroscopy

STEINBAUER, M.; SEGIŇÁK, J.; DOHNAL, P.

2015

30.09.2014

978-1-934142-28-8

Proceedings of PIERS 2014 in Guangzhou

1559-9450

Progress In Electromagnetics

Spojené státy americké

2360

2364

5