An all-digital associated particle imaging system for the 3D determination of isotopic distributions

Associated particle imaging (API) is a non-destructive nuclear technique for the 3D determination of isotopic distributions. By detecting the alpha particle associated with the emitted neutron in the deuterium-tritium fusion reaction with a position- and time-resolving detector, the direction of the 14.1 MeV neutron and its time of emission can be determined. Employing this method, isotope characteristic gamma rays emitted in inelastic neutron scattering events can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and characterized. The system was tested with common soil elements and shown to be sensitive to 12C, 16O, 28Si, 27Al, and 56Fe. New aspects of our approach are the use of a yttrium-aluminum-perovskite (YAP) scintillator, using a sapphire window instead of a fiber-optic faceplate for light transport to the photomultiplier, and the all-digital data acquisition system. We present a description of the system with simulations and experimental results that show a position resolution on the alpha detector of 1 mm, a depth resolution using a LaBr3 detector of 6.2 cm, and an angular resolution of 4.5 degrees. Additionally, we present single-element gamma response measurements for the elements mentioned above together with a comparison to Monte Carlo simulations (MCNP6)

An Associated Particle Imaging System for the Determination of 3D Isotopic Distributions

Associated Particle Imaging (API) is a nuclear technique that allows for the non-destructive determination of 3D isotopic distributions. The technique is based on the detection of the alpha particle associated with the neutron emitted in the deuterium-tritium (DT) fusion reaction, which provides information regarding the direction and time of emission of the 14 MeV neutron. Inelastic neutron scattering leads to characteristic gamma-ray emission from certain isotopes, which can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and tested at Lawrence Berkeley National Laboratory (LBNL) for the non-destructive quantification of 12C distribution in soils. Additionally, the system is also sensitive to other elements present in the soil such as O, Si, Al, Fe, etc. It is capable of quantifying 12C at the percent level with a resolution of 2 cm × 2 cm × 7 cm for an hour of measurement. The first half of the dissertation describes the design of the system (using the simulation packages MCNP6, SPICE, and COMSOL Multiphysics) and the characterization of its components including the neutron generator, the position-sensitive alpha detector (YAP), the lanthanum bromide (LaBr) and sodium iodide (NaI) gamma detectors, and the systems used to observe the alpha and gamma signal. The second half focuses on data analysis techniques and presents initial experimental data benchmarked against simulations

An Associated Particle Imaging System for the Determination of 3D Isotopic Distributions

Associated Particle Imaging (API) is a nuclear technique that allows for the non-destructive determination of 3D isotopic distributions. The technique is based on the detection of the alpha particle associated with the neutron emitted in the deuterium-tritium (DT) fusion reaction, which provides information regarding the direction and time of emission of the 14 MeV neutron. Inelastic neutron scattering leads to characteristic gamma-ray emission from certain isotopes, which can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and tested at Lawrence Berkeley National Laboratory (LBNL) for the non-destructive quantification of 12C distribution in soils. Additionally, the system is also sensitive to other elements present in the soil such as O, Si, Al, Fe, etc. It is capable of quantifying 12C at the percent level with a resolution of 2 cm x 2 cm x 7 cm for an hour of measurement. The first half of the dissertation describes the design of the system (using the simulation packages MCNP6, SPICE, and COMSOL Multiphysics) and the characterization of its components including the neutron generator, the position-sensitive alpha detector (YAP), the lanthanum bromide (LaBr) and sodium iodide (NaI) gamma detectors, and the systems used to observe the alpha and gamma signal. The second half focuses on data analysis techniques and presents initial experimental data benchmarked against simulations

An all-digital associated particle imaging system for the 3D determination of isotopic distributions.

Associated particle imaging (API) is a non-destructive nuclear technique for the 3D determination of isotopic distributions. By detecting the alpha particle associated with the emitted neutron in the deuterium-tritium fusion reaction with a position- and time-resolving detector, the direction of the 14.1 MeV neutron and its time of emission can be determined. Employing this method, isotope characteristic gamma rays emitted in inelastic neutron scattering events can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and characterized. The system was tested with common soil elements and shown to be sensitive to 12C, 16O, 28Si, 27Al, and 56Fe. New aspects of our approach are the use of a yttrium-aluminum-perovskite scintillator, using a sapphire window instead of a fiber-optic faceplate for light transport to the photomultiplier, and the all-digital data acquisition system. We present a description of the system with simulations and experimental results that show a position resolution on the alpha detector of 1 mm, a depth resolution using a LaBr3 detector of 6.2 cm, and an angular resolution of 4.5°. Additionally, we present single-element gamma response measurements for the elements mentioned above together with a comparison to Monte Carlo simulations (MCNP6)