Gamma rays produced by scattering of 14MeV neutrons with detection of associated alpha particles were used for determination of object location in a shipping container. It is shown that is possible ...to locate an object’s position inside the container and, in some cases, also obtain some compositional information (at least carbon and oxygen in TNT). The movement of the peak in the time spectrum corresponds to the change of the object location in the container. Carbon was successfully identified together with its position in the container, even behind 5.1cm thick iron slabs which is impossible to be seen by an industrial 300keV X-ray radiographic system. Also, 7.5kg of TNT was successfully identified inside containers filled with soil.
Within the EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) project, the gamma-ray spectra produced in a series of materials by 14-MeV tagged-neutron beams have been collected in the ...inspection portal equipped with large volume NaI(Tl) detectors, in order to build a database of signatures for various elements: C, N, O, Na, Al, Si, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn, Pb. The measured spectra have been compared with prediction from Monte Carlo simulations to verify the consistency of the relevant nuclear data inputs. This library of measured 14-MeV neutron-induced gamma-ray spectra is currently used in a data processing algorithm to unfold the energy spectra of the transported goods into elementary contributions, thus allowing material identification.
The detection of illicit trafficking such as explosive materials inside large commercial payloads is today an important worldwide problem. Differently from the X- or γ-ray based systems, neutron ...interrogation allows the elemental composition of inspected materials to be measured. A container interrogation device based on the Tagged Neutron Inspection System (TNIS) has been developed within the EURITRACK (EURopean Illicit TRAfficking Countermeasures Kit) project of the 6th Framework Program of the European Union. A prototype of such system has been integrated at the Ruder Boskovic Institute (IRB) of Zagreb, Croatia, and performance tests have been carried out. A detailed simulation of the IRB experimental set-up has been performed. Comparison of the Monte Carlo predictions with collected experimental data is presented.
Measurements have been made of characteristic gamma rays spectra from A(n,n
′γ)A reactions induced by 14.1 MeV neutrons on bulk samples of different substances: C, H
2O, SiO
2, C
3H
6N
6 and samples ...of soil. Background radiation was reduced by the associated alpha particle technique.
Non-destructive inspections have been simulated in laboratory conditions by using our tagged neutron inspection system (TNIS), using YAP:Ce scintillators to tag the neutron beam and an array of BaF2 ...crystals to detect the γ-rays. The system has been operated up to 2×108neutron/s. Further developments of the TNIS concept are discussed in the light of our current projects for cargo container inspections.
The EURopean Illicit TRAfficing Countermeasures Kit (EURITRACK) Front-End and Data Acquisition System is a compact set of VME boards interfaced with a standard PC. The system is part of a cargo ...container inspection portal based on the tagged neutrons technique. The front-end processes all detector signals and checks coincidences between any of the 64 pixels of the alpha particle detector and any gamma-ray signals in 22 NaI(Tl) scintillators. The system is capable of handling the data flow at neutron flux up to the portal limiting value of 108neutrons/second. Some typical applications are presented.
The possibility of the detection of “dirty bomb” presence inside sea containers is evaluated. The method proposed for explosive and fissile material detection makes use of two sensors (X-rays and ...neutrons). A commercial imaging device based on the X-ray radiography performs a fast scan of the container, identifies a “suspect” region and provides its coordinates to the neutron based device for the final “confirmatory” inspection. In this two sensor system a 14MeV neutron beam defined by the detection of associated alpha particles is used for interrogation of only volume elements marked by X-ray sensor. The object’s nature is determined from passive and neutron induced, gamma energy spectra measurements. Experimental results (time-of-flight and gamma energy spectra) obtained for the irradiation 30kg of TNT, depleted uranium and other materials hidden inside the container are presented.
The new experimental setup TANGRA (Tagged Neutrons & Gamma Rays), for the investigation of neutron induced nuclear reactions, e.g. (n,xn’), (n,xn’γ), (n,γ), (n,f), on a number of important isotopes ...for nuclear science and engineering (235,238U, 237Np, 239Pu, 244,245,248Cm) is under construction and being tested at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in Dubna.
The TANGRA setup consists of: a portable neutron generator ING-27, with a 64-pixel Si charge-particle detector incorporated into its vacuum chamber for registering of α-particles formed in the T(d, n)4He reaction, as a source of 14.1 MeV steady-state neutrons radiation with an intensity of ∼5x107n/s; a combined iron (Fe), borated polyethylene (BPE) and lead (Pb) compact shielding-collimator; a reconfigurable multi-detector (neutron plus gamma ray detecting system); a fast computer with 2 (x16 channels) PCI-E 100 MHz ADC cards for data acquisition and hard disk storage; Linux ROOT data acquisition, visualization and analysis software. The signals from the α-particle detector are used to ‘tag’ the neutrons with the coincident α-particles. Counting the coincidences between the α-particle and the reaction-product detectors in a 20ns time-interval improves the effect/background-ratio by a factor of ∼200 as well as the accuracy in the neutron flux determination, which decreases noticeably the overall experimental data uncertainty.
The detection of landmines by using available technologies is a time consuming, expensive and extremely dangerous job, so that there is a need for a technological breakthrough in this field. Atomic ...and nuclear physics based sensors might offer new possibilities in de-mining. Among the available nuclear techniques, the neutron backscattering technique (NBT), based on the detection of the produced thermal neutrons, is thought to be the most promising for field applications. We discuss here two limitations of NBT, being related to the soil moisture. First, the critical value of the soil moisture, reached when the density of the hydrogen atoms in the landmine is equal to that in the background soil, defines a condition for which the detection is not possible. Critical values are small for some of the landmine types, thus suggesting the application of the method to arid countries, where the soil moisture is lower than 10%. Furthermore, small-scale variations of the soil moisture content, experimentally determined for different soil types, are found to be capable of generating false positive readings. To avoid this problem, the integration of the NBT with a second sensor, as the metal detector, is proposed.
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