Time-sensitive search for chemical agents in γ-ray spectra Cooper, J.C.; Kim, Y.E.; Koltick, D.S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2003, Letnik:
505, Številka:
1-2
Journal Article
Recenzirano
We have performed a search for Sarin, a chemical warfare agent, in luggage-sized sealed containers in order to illustrate how effectively and quickly a search could be conducted in a fixed ...installation at airports, embassies, government buildings, military installations, and other public areas. A portable neutron generator and a Californium source were used, generating up to 108 neutrons per second, that penetrate into a container and are capable of exciting a sample in a period of approximately 10s, to produce enough γ radiation that target elements within the sample can be identified. In the vast majority of cases, there is no chemical agent present, so the question becomes how long to search. We show results of tests for sensitivity of this technique as a function of time. We have also developed background or typical samples with no chemical agent present to estimate the false positive rate for this technique.
Associated Particle Neutron Elemental Imaging (APNEI) for in vivo and in vitro diagnostic analysis is a potential technology to measure elemental disease signatures. APNEI can produce elemental ...images with spatial resolution as small as ~ 1 mm. The use of APNEI technology for disease diagnoses is based on measured concentrations of many signature elements having large differences between normal and diseased tissues ranging up to more than 10 times. For cancer, anomalous elemental concentrations have been observed for breast, liver, colon, kidney, lung and prostate. In principle, in vivo observation of these anomalies would provide a diagnostic tool for disease presence. In vitro measurements may be useful in margin measurements for immediate surgical response. In addition, investigation into the pathways underlying these anomalous elemental concentrations may provide new understanding and possible novel therapeutic targets. To this end possible elemental concentration sensitivity and spatial resolution of APNEI technology for in vivo and in vitro disease diagnosis is presented.
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.
Liquid krypton has been used widely for electromagnetic calorimeters for charged particle and gamma ray detection above 100 MeV. Despite the significant price advantage of krypton over xenon, little ...work has been done with liquid krypton detectors for energies in the range 200 keV-12 MeV that is useful for applications involving neutron-induced gamma ray spectral analysis for isotope identification in elemental analysis. The presence of β decays arising from 85 Kr (10.76-year half-life) combined with the 80 ns decay time of the dominant component of krypton scintillation light generates pile-up and reduces the photopeak efficiency of liquid Kr detectors. We discuss detector performance expected after careful optimization of the detector dimensions and doping the Kr with Xe to improve its scintillation light decay time characteristics.
The Mu2e experiment at Fermilab will search for the neutrinoless μ−→e− conversion in the field of an aluminum nucleus. The Mu2e data-taking plan assumes two running periods, Run I and Run II, ...separated by an approximately two-year-long shutdown. This paper presents an estimate of the expected Mu2e Run I search sensitivity and includes a detailed discussion of the background sources, uncertainties of their prediction, analysis procedures, and the optimization of the experimental sensitivity. The expected Run I 5σ discovery sensitivity is Rμe=1.2×10−15, with a total expected background of 0.11±0.03 events. In the absence of a signal, the expected upper limit is Rμe<6.2×10−16 at 90% CL. This represents a three order of magnitude improvement over the current experimental limit of Rμe<7×10−13 at 90% CL set by the SINDRUM II experiment.
Monte Carlo simulations were used to model gamma ray interactions at 1 MeV and 11 MeV within liquid krypton to understand geometry effects and energy containment. Two Monte Carlo codes were used in ...this work: Geant4 and MCNP5. The agreement of the two codes was shown by the comparison of the calculated average energy deposition and fraction of incident gamma energy deposited as a function of chamber lengths and gamma ray offsets. Modeling shows that good energy containment for 1 MeV gamma rays occurs for chamber depths of 20 cm. For gamma rays entering parallel to the central axis of the detector, 1 MeV showers are well contained up to approximately 1 cm of the detectors' edge. For 11 MeV gamma rays the acceptance plateau occurs at a depth of 40 cm and 20 cm from the detectors' edge.
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.
The Mu2e experiment at Fermilab will search for the neutrinoless μ−→e− conversion in the field of an aluminum nucleus. The Mu2e data-taking plan assumes two running periods, Run I and Run II, ...separated by an approximately two-year-long shutdown. This paper presents an estimate of the expected Mu2e Run I search sensitivity and includes a detailed discussion of the background sources, uncertainties of their prediction, analysis procedures, and the optimization of the experimental sensitivity. The expected Run I 5σ discovery sensitivity is Rμe=1.2×10−15, with a total expected background of 0.11±0.03 events. In the absence of a signal, the expected upper limit is Rμe<6.2×10−16 at 90% CL. This represents a three order of magnitude improvement over the current experimental limit of Rμe<7×10−13 at 90% CL set by the SINDRUM II experiment.
