The associated particle (AP) technique has recently been used with a high-purity germanium γ-ray spectrometer to assess its capability to improve field identification of recovered chemical warfare ...(CW) materiel through prompt gamma-ray neutron activation analysis (PGNAA) measurements. A particularly challenging pair of CW agents commonly found in recovered munitions are phosgene (CG) and cyanogen chloride (CK), which have two of three elements in common, i.e. chlorine and carbon, but differ in the third being either oxygen or nitrogen. The detection of both latter elements is complicated by high oxygen concentration in the field environment which interferes with the small signal produced from the chemical agents. The matter is further complicated by the precautionary field practice of overpacking recovered munitions with vermiculite in larger steel multiple round containers (MRCs), which places additional oxygen-rich material in contact with the munition while further attenuating an already weak signal emitted from the munition center. This work reports quantitative results from realistic field measurements of CG and CK simulants in mock 4.2-inch (11 cm) mortar rounds overpacked with vermiculite in a large MRC. Results obtained with the AP technique are compared to those obtained with the traditional PGNAA approach for both overpacked- and bare-munition measurements. The AP technique is shown to provide a much more confident discrimination between the two chemicals, particularly for the more challenging field-relevant overpacked measurements, where a significant gain in sensitivity to all the key elements (chlorine, carbon, nitrogen and oxygen) is achieved.
•Associated Particle (AP) technique allows better discrimination between phosgene and cyanogen chloride in recovered chemical munitions.•Improved prompt gamma-ray neutron activation analysis (PGNAA) sensitivity to key elements C, N, O, and Cl with AP technique.•Achieved success for field-relevant measurements of overpacked munitions in multiple round containers (MRCs).•Strong suppression of background oxygen enables better discriminability and sensitivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A new scintillator material for the detection of fast neutrons that consists of a methanol adduct of cerium trichloride with the composition CeCl 3 (CH 3 OH) 4 has been characterized using 14.1 MeV ...neutrons from a deuterium-tritium neutron generator and fast neutrons from a bare instrumented 252 Cf source. The timing resolution of the scintillator for fast neutrons was found to be 1~ ns. Neutron interactions in the CeCl 3 (CH 3 OH) 4 composition were simulated using the MCNP-PoliMi code. These simulations indicate that proton recoils account for most of the deposited energy in CeCl 3 (CH 3 OH) 4 . The crystalline molecular adduct CeCl 3 (CH 3 OH) 4 represents a rare-earth metal-organic scintillator that can be applied to both fast neutron and gamma-ray detection.
High-resolution prompt γ-ray neutron activation analysis (PGNAA) is performed using the associated particle (AP) technique with a deuterium–tritium neutron generator and high-purity germanium ...detector. Although the time resolution is inferior compared to similar systems employing fast scintillation γ-ray detectors, the strong background suppression combined with the high γ-ray energy resolution provides an important boost in sensitivity to certain key elements, especially relevant to field measurements of complex chemicals encased within thick layers of metal, such as in recovered chemical warfare (CW) munitions. Results for various CW and explosive simulants contained within mock munitions are presented and compared with results obtained from traditional PGNAA measurements without the aid of the AP technique. Significant improvements in identification and discrimination between certain chemicals are achieved with the high energy resolution AP technique.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Wood anatomical characteristics of twenty-nine 6-year-old Pinus radiata D. Don trees, selected to represent the extremes of intraring checking, were assessed with SilviScan. Derived ring-level ...summary variables were calculated from the SilviScan pith-to-bark wood property traces, based on ring means, standard deviations, and quantiles. Incidence of checking was assessed on discs that had been oven dried using a standardized method, and evidence for associations between wood characteristics and checking was evaluated at the tree and ring level using Bayesian statistical methods. Bayes factors of 39.1, 14.9, and 7.8 were obtained at the tree level, representing moderate to good evidence for associations between ring medians of wood density, tracheid radial diameter, and cell wall thickness, respectively. Increasing wood density, decreasing tracheid radial diameter, and increasing cell wall thickness were associated with reduced incidence of checking. These are parameters expected a priori to contribute to tracheid cells' resistance to collapse under drying stresses. A generalized linear model with radial diameter and cell wall thickness as independent variables had a concordance of 83% for predicting the checking status of trees.
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BF, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The design and performance of a pulseable neutron source utilizing a D-T neutron generator and a depleted uranium reflector are presented for use in a scanning system of improvised explosive devices. ...Approximately half the generator's 14 MeV neutron flux is used to produce a fission- like neutron spectrum similar to 252 Cf. For every 14 MeV neutron entering the reflector, more than one fission-like neutron is reflected back across the surface of the reflector. Because the delayed neutron production is more than two orders of magnitude below the prompt neutron production, the source takes full advantage of the generator's pulsed mode capability. Applications include all elemental characterization systems using neutron-induced gamma-ray spectroscopy. The source simultaneously emits 14 MeV neutrons optimal to excite fast neutron-induced gamma-ray signals, such as from carbon and oxygen, and fission-like neutrons optimal to induce neutron capture gamma-ray signals.
The design and performance of a pulseable neutron source utilizing a D–T neutron generator and a depleted uranium reflector are presented. Approximately half the generator's 14
MeV neutron flux is ...used to produce a fission-like neutron spectrum similar to
252Cf. For every 14
MeV neutron entering the reflector, more than one fission-like neutron is reflected back across the surface of the reflector. Because delayed neutron production is more than two orders of magnitude below the prompt neutron production, the source takes full advantage of the generator's pulsed mode capability. Applications include all elemental characterization systems using neutron-induced gamma-ray spectroscopy. The source simultaneously emits 14
MeV neutrons optimal to excite fast neutron-induced gamma-ray signals, such as from carbon and oxygen, and fission-like neutrons optimal to induce neutron capture gamma-ray signals, such as from hydrogen, nitrogen, and chlorine. Experiments were performed, which compare well to Monte Carlo simulations, showing that the uranium reflector enhances capture signals by up to a factor of 15 compared to the absence of a reflector.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
