Frequency Modulated NQR Chemical Detection

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Solution Overview

Problem

Nuclear quadrupole resonance detection of chemicals is challenging due to the diffused nature of the response and the presence of ferromagnetic and piezoelectric materials, which can lead to false positives and increased difficulty in identifying specific chemicals like explosives and narcotics.

Innovation Solution

A system and method using frequency modulated nuclear quadrupole resonance signals, where an excitation pulse excites nuclei to an excited state, and a modulating magnetic field is applied to modulate the radiation emission, allowing for the detection of frequency modulation proportional to the time-varying magnetic field, thereby improving the detection of chemical nuclei.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If nuclear quadrupole resonance spectroscopy is used to detect chemicals, then chemical identification capability is improved, but detection reliability deteriorates due to diffused response and false positives from ferromagnetic and piezoelectric materials

Engineering Contradiction:

Improvechemical identification capabilityVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies a time-varying magnetic field to modulate the nuclear quadrupole resonance frequency dynamically. This dynamic modulation creates a time-dependent frequency signature that is characteristic of the target chemical, allowing discrimination between true chemical signals and static interference from ferromagnetic or piezoelectric materials. The dynamic nature of the measurement enables reliable detection despite the diffused response characteristic of NQR spectroscopy.

Inventive Principle:

Principle #15Dynamics

2Reliability

If ferromagnetic and piezoelectric materials are present in the sample, then false positives increase, but the ability to detect target chemicals remains necessary

Engineering Contradiction:

Improvefalse positive rateVSAvoidinterference from ferromagnetic and piezoelectric materials

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of ferromagnetic and piezoelectric materials into a beneficial discrimination mechanism. By applying a time-varying magnetic field, the system exploits the different magnetic response characteristics: target chemicals exhibit modulated NQR signals in response to the time-varying field, while ferromagnetic and piezoelectric materials produce static or differently characterized interference. This allows the harmful interference to be distinguished from true chemical signals, effectively converting the problem into a solution.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If a time-varying magnetic field is applied to modulate radiation emission, then frequency modulation detection accuracy is improved, but system complexity increases

Engineering Contradiction:

Improvefrequency modulation detection accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the magnetic field parameter from static to time-varying, specifically applying a magnetic field that varies sinusoidally or square-wave fashion at a defined frequency. This parameter change induces corresponding frequency modulation in the NQR signal, which can be detected and demodulated to extract chemical information. The approach achieves high detection accuracy by converting the static NQR frequency into a dynamically modulated signal that is easier to distinguish from background interference, while managing system complexity through straightforward field modulation techniques.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the detection of chemical nuclei by accurately measuring frequency modulation, reducing false positives and improving the identification of chemicals despite the presence of ferromagnetic and piezoelectric materials, leading to more reliable chemical detection.

Implementation Method 1

Nuclear quadrupole resonance spectroscopy may be used to directly identify explosives, narcotics, and other solid chemicals

Methodology Applied

Scientific EffectNuclear quadrupole resonance:

Implementation Method 2

The energy of which depends on the magnetic field in the sample. The magnetic field in the sample is modulated, after the end of the excitation pulse, while the nuclei of interest decay from the excited state, so that the radiation they emit is frequency modulated

Methodology Applied

Scientific EffectZeeman effect: Zeeman Effect

Data Source

PatentUS10649051B2System and method for detection of chemicals using frequency modulated nuclear quadrupole resonance signals

Publication Date: 2020.05.12 RAYTHEON CO

AI summary

A system and method for detecting a nucleus of interest in a chemical using a nuclear quadrupole resonance transition. An excitation pulse is used to excite one or more nuclei of interest, if they present in a sample, to an excited state, the energy of which depends on the magnetic field in the sample. The magnetic field in the sample is modulated, after the end of the excitation pulse, while the nuclei of interest decay from the excited state, so that the radiation they emit is frequency modulated. The frequency modulation is detected in the emitted radiation. In some embodiments a DC magnetic field is applied to the sample, during the application of the excitation pulse, to tune the frequency of the transition being excited.