V. S. Grechishkin

Bio: V. S. Grechishkin is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

The Problem of Military TNT in NQR Mine Detector

Abstract: One of the most promising methods of demining is nuclear-quadrupole resonance (NQR) with nitrogen-14, which is contained in practically all mine explosives. In NQR the quadrupole moment of a nucleus interacts with the electric-field gradient of the surrounding molecule and crystal, and thus the energy-level differences are molecule- and crystal-specific. In pure NQR, no external magnetic field is needed. One may, however, combine nuclear magnetic resonance (NMR), e.g., of protons, with NQR to achieve selective excitation or better signal; in this case, a strong magnetic field has to be switched on and off.

Physics of magnetic phenomena use of the bohr principle for detecting nqr signals from mines

Abstract: Principles of message transfer in telecommunication systems are considered when a wide transmission band is required, which can result in tuning away from the transmitting station if the signal-to-noise ratio (SNR) is insufficiently high. Based on a solution of the Fokker−Planck−Kolmogorov equation, it is demonstrated that a signal below noise is broadened 20 times for SNR = 0.05. This makes signal accumulation difficult. The matrix pencil method of information theory is used to demonstrate that the broadening of a signal below noise and shift of its frequency detuning interfere with reliable signal detection for SNR ≤ 0.05. An analog of the Bohr complementarity principle is used to analyze the NQR detector. In addition, performance of the NQR-mine detector used to clear of mines territories of former military actions is examined.

Use of the Bohr Principle for Detecting NQR Signals from Mines

Abstract: Principles of message transfer in telecommunication systems are considered when a wide transmission band is required, which can result in tuning away from the transmitting station if the signal-to-noise ratio (SNR) is insufficiently high. Based on a solution of the Fokker-Planck-Kolmogorov equation, it is demonstrated that a signal below noise is broadened 20 times for SNR = 0.05. This makes signal accumulation difficult. The matrix pencil method of information theory is used to demonstrate that the broadening of a signal below noise and shift of its frequency detuning interfere with reliable signal detection for SNR ≤ 0.05. An analog of the Bohr complementarity principle is used to analyze the NQR detector. In addition, performance of the NQR-mine detector used to clear of mines territories of former military actions is examined.

Development of a Low-Cost, Portable NQR Spectrometer for RDX Explosives Detection

Abstract: Nuclear quadrupole resonance (NQR) technology is a promising approach to detect so-called “minimum metal” landmines, as it can look directly for their explosive content. Conventional commercially available NQR devices, however, are large and expensive, and they require a transmitter power amplifier with a power generator, which is not suitable for outdoor use and mass production. Here we present a small and inexpensive portable device developed for detecting landmines using NQR. The device uses a field-programmable gate array (FPGA) and low-impedance transmission and reception circuits that include a dual supply class-D power amplifier powered by conventional batteries to ensure sufficient magnetic field excitation for mine detection. The pulse width modulation signals that are fed into the power amplifier have been designed to protect the low impedance transmit-receive switch circuit from the high voltage. The system has been tested successfully in the laboratory with 100g of explosive RDX at a distance of 10cm from the antenna, corresponding to a plausible anti-personal (AP) mine scenario. Detection was achieved with a signal to noise ratio (SNR) ~2 in 2/3 of the time that a previous prototype required (120 sec). Moreover, the new device can detect RDX explosives with a measurement time and SNR comparable to mine detectors built with commercial-off-the-shelf (COTS) components, but at lower cost and smaller form factor.

Remote detection of double nuclear quadrupole resonance spectra

Abstract: Remote detection of the spectra of double nuclear quadrupole resonance of nitrogen-containing compounds is considered. A comparison is made of this technique with the cross-relaxation method.