Magnetic resonance detection (MRD) system for and methods of detecting and classifying multiple chemical substances
Inventors
Nichols, Todd • Gidcumb, Shaun M. • Ketterl, Thomas • Brauns, Gregory T. • Phillips, Eric
Assignees
Publication Number
US-11543477-B2
Publication Date
2023-01-03
Expiration Date
2040-04-15
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Abstract
A magnetic resonance detection (MRD) system for and methods of detecting and classifying multiple chemical substances is disclosed. In one example, the presently disclosed MRD system is a nuclear quadrupole resonance (NQR) detection system that provides multi-frequency operation for substantially full coverage of the explosive NQR spectrum using a broadband transmit/receive (T/R) switch (or duplexer) and a single multi-frequency radio frequency (RF) transducer. More particularly, the MRD system provides a frequency-agile system that can operate over a wide band of frequencies or wavelengths. Further, a method of detecting and classifying various chemical substances is provided that includes pulse sequencing with “frequency hopping,” phase cycling for reducing or substantially eliminating background noise, and/or a process of mitigating amplitude modulation (AM) radio interference.
Core Innovation
The invention discloses a magnetic resonance detection (MRD) system and associated methods for detecting and classifying multiple chemical substances, specifically using nuclear quadrupole resonance (NQR) technology. This MRD system offers multi-frequency, frequency-agile operation by incorporating a broadband transmit/receive (T/R) switch and a single multi-frequency radio frequency (RF) transducer, enabling wideband detection spanning significant portions of the NQR spectrum for substances such as explosives and narcotics.
The MRD system solves several issues of existing explosives detection systems, which are reported as bulky, heavy, complex, costly, and limited in substance detection capabilities. Traditional systems also perform poorly in standoff detection, particularly for substances buried underground or concealed in nonmetallic housings, and are typically limited to single-substance detection, requiring multiple systems for comprehensive coverage.
Key aspects of the invention include innovative pulse sequencing with frequency hopping for efficient multi-substance detection, phase cycling techniques to suppress background noise and improve signal-to-noise ratio, and processes for mitigating amplitude modulation (AM) radio interference. The MRD system integrates autotuning and automatching circuits in the transducer, advanced signal processing techniques, and modular, portable configurations, making it suitable for rapid, accurate classification and identification of multiple chemical substances in field and laboratory environments.
Claims Coverage
There are two independent claims in the patent: one for an apparatus and one for a method. The main inventive features focus on a broadband, frequency-agile magnetic resonance detection system and its advanced multi-phase, multi-frequency measurement method.
Broadband, frequency-tunable magnetic resonance detection apparatus
The apparatus includes: - A frequency-tunable transducer circuit comprising a coil and tuning network. - A transmit/receive switch circuit with a multi-octave operating bandwidth connected to the transducer. - A transmitter circuit with a power amplifier having a multi-octave operating bandwidth. - A digital quadrature receiver circuit with a multi-octave operating bandwidth. - A tunable frequency source with a multi-octave operating bandwidth connected to both transmitter and receiver. - A controller circuit configured to coordinate the frequency source, transmitter, and T/R switch to emit a series of RF pulses and to coordinate measurement of NQR responses after each pulse.
Multi-frequency, multi-phase magnetic resonance detection method
The method comprises: - Emitting a series of RF pulses that include a first phase group (with at least one pulse for each of a plurality of frequencies) and a second phase group at a different phase (with at least one pulse for each of the same frequencies). - Measuring nuclear quadrupole resonance (NQR) responses after each RF pulse. - For each frequency, coherently adding the measured NQR responses corresponding to the pulses for that frequency.
The independent claims protect a broadband, frequency-agile magnetic resonance detection apparatus and a method utilizing phase-cycled, frequency-hopped pulse sequences to efficiently detect and classify chemical substances based on their NQR responses.
Stated Advantages
The MRD system is portable, lightweight, and fully self-contained, overcoming the bulk and complexity of existing NQR/NMR devices.
It delivers multi-frequency, wideband operation without needing to swap single-frequency transducers, providing full coverage of the explosive NQR spectrum.
The system reduces detection dwell time and increases sensitivity by using advanced RF transducer technology, phase cycling, and Q-spoiling techniques.
It is capable of efficiently detecting and classifying a wide variety of chemical substances, including those buried or concealed, regardless of mixture formulations or impurities.
It is insensitive to the presence of metallic non-shielding clutter and operates in substantially all soil types, including high moisture soils.
Innovative self-tuning and automatching enhance system efficiency across the entire operating bandwidth.
Digital filtering and noise cancellation provide significant rejection of AM and impulse noise interference.
The modular arrangement enables adaptation to depot inspections, laboratory analysis, manual ground placement, and integration with other systems.
Documented Applications
Detection and classification of explosive substances, including solid nitrogen-based and oxygen-based explosives, for military and security applications.
Detection and classification of narcotics and other drugs, such as fentanyl, cocaine, morphine, heroin, methamphetamine, LSD, and paracetamol, for law enforcement and drug enforcement applications.
Detection and classification of kerogen for applications in the oil and gas industry, including assessment of hydrocarbon presence and production viability.
Quality control measurements for pharmaceutical development, including validation of molecule identity and chirality, potentially supplementing NMR techniques.
Deployment in diverse operational contexts, such as manual ground placement, robot payloads, tabletop analyzers, vehicles, prisons, schools, hospitals, mail facilities, and other public venues.
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