Methods and systems for non-invasive measurement of soil chlorine and/or nitrogen content and for detecting sub-surface chlorine or nitrogen-containing objects
Inventors
Torbert, III, Henry A. • Prior, Stephen A. • KAVETSKIY, ALEKSANDR G. • YAKUBOVA, GALINA N.
Assignees
US Department of Agriculture USDA
Publication Number
US-10458930-B2
Publication Date
2019-10-29
Expiration Date
2037-04-24
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Abstract
The presence of chlorine and nitrogen are determined and measured using a non-invasive portable neutron-generating and gamma ray detecting system(s). Portable devices of the present invention can also be used to detect chlorine and/or nitrogen-containing underground objects rapidly and on-site. Devices and systems described herein can be operated remotely and pre-programmed with search patterns, guided by an operator remotely, or programmed to home in on high-chlorine and/or nitrogen concentration areas.
Core Innovation
The invention provides systems and methods for the non-invasive measurement of chlorine and nitrogen presence or amounts in or below a testable surface, particularly soil. It employs a neutron generator producing pulsed neutron beams, a moderator to convert fast neutrons to thermal neutrons, and a gamma ray detector to detect gamma ray emissions induced by neutron interaction with chlorine or nitrogen nuclei. The system acquires gamma spectra during and between neutron pulses, enabling separation of thermal neutron capture (TNC) gamma rays from background signals.
The problem solved is the difficulty, expense, and impracticality of current soil chlorine detection methods, which require soil sampling and laboratory chemical analysis. Conventional methods suffer from local sampling limitations, extensive sample preparation, and slow turnaround. Additionally, rapid, remote detection of chlorine or nitrogen-containing objects buried under soil is needed, such as for detection of hazardous chlorinated hydrocarbons or explosives, where current technologies do not allow for fast, on-site, non-destructive analysis.
Claims Coverage
The patent contains one independent claim directed to a detection system and one independent method claim for determining chlorine presence, covering key inventive features related to system components and functional operations.
Detection system with pulsed neutron beams and separated gamma spectra acquisition
The system comprises a neutron generator assembly producing pulsed neutron beams and a gamma ray detector processor/controller with split electronics processing that separates gamma spectra acquired during neutron pulses from spectra acquired between pulses, enabling collection of thermal neutron capture (TNC) gamma spectra data relevant for chlorine detection.
Use of moderator and gamma ray detector configured for thermal neutron capture spectroscopy
The system includes a moderator positioned between the neutron generator assembly and testable surface to convert fast neutrons to thermal neutrons, and a gamma ray detector (sodium iodate, NaI(Tl)) positioned to detect gamma ray response, facilitating identification of chlorine via a count rate peak near 1164 keV in TNC spectra.
System features controlling neutron beam energy and incorporating shielding and control electronics
The neutron generator assembly preferably comprises an accelerator tube and controller generating 14.1 MeV neutrons via a deuterium-tritium (D-T) source. The system optionally includes polyethylene moderator with optimal thickness between four and six centimeters, gamma ray shielding (e.g., lead) placed between neutron generator and detector, and a monitoring/controlling computer system such as a laptop for managing components and data acquisition.
Method for non-invasive detection of chlorine utilizing the described system
The claimed method involves providing the detection system, positioning it above a testable surface, generating pulsed neutron beams, detecting gamma ray spectra, collecting and processing gamma ray data, and determining chlorine presence based on a characteristic TNC gamma peak centroid at about 1164 keV.
The claims cover an integrated detection system employing a pulsed neutron source, moderator, gamma ray detection with split-spectrum acquisition enabling thermal neutron capture analysis, and a method for detecting chlorine presence non-invasively, with particular system configurations such as D-T neutron generation, polyethylene moderators, sodium iodate detectors, shielding, and computer-controlled operation.
Stated Advantages
Enables rapid, non-invasive measurement of chlorine or nitrogen content on or below surfaces without soil sampling or laboratory analysis.
Provides portable and remotely operable systems capable of detecting surface or buried chlorine and nitrogen-containing substances on-site.
Allows detection and quantification within short measurement times, as little as about one minute or less at multiple locations.
Offers enhanced sensitivity and selectivity through separated acquisition of gamma spectra during and between neutron pulses, improving signal-to-noise ratio.
Documented Applications
Detection and measurement of soil surface chlorine contamination and distribution for environmental monitoring.
Rapid on-site detection of buried chlorine-containing objects, including hazardous chlorinated hydrocarbons and explosive ordnances buried in soil.
Measurement of soil nitrogen content and carbon/nitrogen ratios in agricultural applications such as assessing nitrogen content in manures and compost.
Detection and identification of nitrogen-containing explosives, including unexploded ordnance, buried in soil, particularly for military training range management.
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