Описаны характеристики прототипа детектора нейтронов с энергией 1–15 МэВ, представляющего собой детектор полного поглощения и состоящего из чередующихся сцинтилляторов из пластика и стекла с примесью 6Li. Попавший в детектор нейтрон теряет всю свою энергию в пластике, замедляется до тепловых энергий и регистрируется в литиевом стекле. Измеренное время полного замедления нейтрона составляет 60 мкс. Регистрация в этом временном интервале двух сигналов – от первого акта рассеяния нейтрона в пластике до акта поглощения нейтрона литием в стекле – обеспечивает эффективное подавление фоновых тепловых нейтронов и -квантов и, как следствие, детектирование малоинтенсивных источников нейтронов. Предлагаемая конструкция детектора дает возможность определения направления на источник нейтронов.

The characteristics of the detector prototype for 1–15 MeV neutrons are described. The prototype is a full absorption detector consisting of interlaced plastic scintillators and 6 Li doped glasses. A neutron incident on the detector deposits all its energy in the plastic scintillator, is moderated to thermal energies, and detected in the lithium glass. The measured time of complete neutron moderation is ∼60 μs. Recording two signals in this time interval from the first event of neutron scattering in the plastic scintillator and from the neutron absorption by a lithium atom in the glass, it is possible to effectively suppress background thermal neutrons and γ rays and, therefore, detect low-intensity neutron sources. Owing to the proposed detector design, the direction toward the neutron source can be determined.

A new low-background spectroscopic direction-sensitive neutron detector that would allow one to reduce the neutron background component in passive and active neutron detection techniques is proposed. The detector is based on thermal neutron detectors surrounded by a fast neutron scintillation detector, which serves at the same time as a neutron moderator. Direction sensitivity is achieved by coincidence/anticoincidence analysis between different parts of the scintillator. Results of mathematical modeling of several detector configurations are presented.

Experimental results in the detection of explosive and other hazardous materials by Nanosecond Neutron Analysis (NNA) technique are presented. The detecting device SENNA is based on a portable DT neutron generator with built-in segmented detector of associated α-particles, detectors of γ-rays, and fast data collection electronics. Experimental measurement of the response functions of NaI, BGO, and LaBr3-based γ-ray detectors to pure chemical elements is described. Examples of using SENNA to detect explosives in luggage and UXO on a conveyer belt and in the ground are discussed.

Device for detection of explosives, radioactive and heavily shielded nuclear materials in luggage and cargo containers based on Nanosecond Neutron Analysis / Associated Particles Technique (NNA/APT) is under construction. Detection module consists of a small neutron generator with built-in position-sensitive detector of associated alpha-particles, and several scintillator-based gamma-ray detectors. Explosives and other hazardous chemicals are detected by analyzing secondary high-energy gamma-rays from reactions of fast neutrons with materials insides container. The same gamma-ray detectors are used to detect unshielded radioactive and nuclear materials. An array of several neutron detectors is used to detect fast neutrons from induced fission of nuclear materials. Coincidence and timing analysis allows one to discriminate between fission neutrons and scattered probing neutrons. Mathematical modeling by MCNP5 and MCNP-PoliMi codes was used to estimate the sensitivity of the device and its optimal configuration. Comparison of the features of three gamma detector types based on BGO, Nat and LaBr3 crystals is presented.

Between 1505 and 1506 Leonardo Da Vinci painted his masterpiece, the Battle of Anghiari, in Palazzo Vecchio’s Hall of 500 in Florence. The unfinished mural remained visible until 1563, when architect Giorgio Vasari undertook a renovation of the Hall and all traces of the Battle of Anghiari were lost. However, scholarly interpretation and scientific evidence suggest that the mural could be on the eastern wall, hidden behind a brick wall built in 1563 by Vasari. This paper discusses the possibility of using NNA/APT (Nanosecond Neutron Analysis/Associated Particle Technique) to establish the presence of the masterpiece by identifying behind the Vasari’s wall chemical elements from the gesso preparation layer of the mural and possibly from its pigments. This paper reports on the experiments run with a simple NNA/APT system and the Monte Carlo simulations that have been carried out in order to outline the experimental setup of an advanced NNA/APT able to detect and locate the tiny amount of gesso and pigments.

Feasibility of Nanosecond Neutron Analysis/Associated Particle Technique for detection of explosive and flammable liquids has been experimentally demonstrated. Experimental results with imitators and real liquids are discussed.

Application of the nanosecond neutron analysis (NNA) to the detection of radiological dispersal devices (RDD) or 'dirty bombs' is considered. A prototype of the mobile device for detection of 'dirty bomb' is described. Results of preliminary tests are discussed.

Different methods of detection of liquid explosives and flammable agents are described. Feasibility and efficiency of different methods of detecting liquid explosives and flammable liquids in different scenarios are discussed.

A brief description of existing and prospective techniques for detection of improvised explosives (IE) and improvised explosive devices (IED) is presented.

A novel method of simultaneous detection of concealed explosive substances and heavily shielded nuclear materials is described. Experimental setup based on a portable DT neutron generator and detectors of neutrons and gamma-rays has been created and tested. Results of tests with real fissioning materials are presented.

Prototype portable device for detection of concealed explosive and other hazardous substances has been created on the basis of a neutron generator with built in position-sensitive detector of α-particles. Secondary γ-rays produced in the investigated volume by incident fast neutrons are detected in narrow (few nanoseconds) time interval counted from the moment of detection of the alpha particle, that had accompanied emission of neutron from the generator (Nanosecond Neutron Analysis / Associated Particles Technique NNA/APT). Analysis of the spectra of γ-rays allows one to determine elemental composition of the substances located in the investigated volume. Use of a position-sensitive tagging α-particle detector allows one to determine the flight direction of each neutron, and thus to divide the investigated volume into “voxels” producing its 3D “elemental” image.

Portable device for explosives' detection (SENNA) based on Nanosecond Neutron Analysis (NNA) / Associated Particles Technique (APT) has been created and tested. SENNA is a single suitcase weighting 35 kg; it is remotely controlled from any PC-compatible computer. Inside is an APT neutron generator with a 3x3 matrix of semiconductor detectors of associated alpha-particles, two BGO-based detectors of gamma-rays, fully-digital data acquisition electronics, data analysis and decision-making software, and batteries. Detection technology is based on determining chemical composition of the concealed substance by analyzing secondary gamma-rays from interaction of tagged fast neutrons with its material. A combination of position-sensitive alpha-detector and time-of-flight analysis allows one to determine the location of the detected material within the inspected volume and its approximate mass. Fully digital data acquisition electronics is capable of performing alpha-gamma coincidence analysis at very high counting rates, which leads to reduction of the detection time down to dozens of seconds. SENNA's scenario-driven automatic decision-making algorithm based of "fuzzy logic" mechanism allows one to detect not only standard military or industrial explosives, but also improvised explosives (including those containing no nitrogen), even if their chemical composition differs from that of standard explosives. SENNA can also be "trained" to detect other hazardous materials, such as chemical/toxic materials, if their chemical composition is in any way different from that of the surrounding materials.

Nanosecond Neutron Analysis (NNA) method with spatial selection of secondary gamma-radiation, proposed at V. G. Khlopin Radium Institute as a further development of the well-known Associated Particle Technique (APT), allows one to substantially (by two orders of magnitude) reduce the level of the background radiation, making possible creation of devices for detection of small amounts of hazardous materials. A prototype APT/NNA device is based on a DT neutron generator with built-in nine-segment semiconductor detector of accompanying alpha-particles. The prototype is the basis for further development of the NNA method in order to create devices for detection of explosives and other hazardous materials in luggage, sea cargo containers, etc. A concept of a device for detection of hazardous materials in sea cargo containers “3D NNA Scanner” has been developed. Results of numerical modeling suggest, that the device will be capable of detecting 30 kg of explosives hidden anywhere inside a 40-feet cargo container within a 12 minute-long inspection cycle.

The existing technical means of explosives detection are not efficient and reliable enough; therefore the development of new methods and equipment designed for this purpose is of prime importance.

Significant reduction of time needed to identify hidden explosives and other hazardous materials by the “neutron in, gamma out” method has been achieved by introducing timed (nanosecond) neutron sources—the so-called nanosecond neutron analysis technique. Prototype mobile device for explosives’ detection based on a timed (nanosecond) isotopic 252Cf neutron source has been created. The prototype is capable of identifying 400g of hidden explosives in 10min. Tests have been also made with a prototype device using timed (nanosecond) neutron source based on a portable D-T neutron generator with built-in segmented detector of accompanying α-particles. The presently achieved intensity of the neutron generator is 5×107n/s into 4π, with over 106 of these neutrons being correlated with α-particles detected by the built-in α-particle detector. Results of measurements with an anti-personnel landmine imitator are presented.

One of the most promising methods of detection of hidden explosives and other dangerous substances is the so-called, “neutron in, gamma out” technique. The main idea of this method consists in irradiation of suspicious object or volume with neutrons and measurement of secondary γ-radiation caused by interaction of neutrons with the material of the irradiated object. Different chemical elements produce different characteristic γ-radiation as a result of inelastic scattering or capture of neutrons. By decomposing measured γ-spectra into contributions from different chemical elements, one can obtain elemental composition of the explored object and thus determine whether it contains hazardous (e.g. explosive) material or not.

A new, graphical way of extracting important physical information from the total kinetic-energy—mass (TKE—M) distributions of the nuclear reaction products is presented. The resulting images indicate for the first time the presence of the Ni—Mo and Ge—Mo fission modes in the fission of Np nuclei at intermediate excitation energies.

Exotic Nuclei, pp. 158-166 (2002) No AccessLATEST RESULTS FROM HENDES COLLABORATION: FINE STRUCTURE IN FRAGMENT MASS-ENERGY DISTRIBUTIONW. H. TRZASKA, YU. V. PYATKOV, YU. E. PENIONZHKEVICH, V. A. MASLOV, O. I. OSETROV, A. A. ALEXANDROV, I. A. ALEXANDROVA, J. ÄYSTÖ, K. -TH. BRINKMANN, S. V. KHLEBNIKOV, V. F. KUSHNIRUK, A. V. KUZNETSOV, V. G. LYAPIN, M. MUTTERER, Z. RADIVOJEVICH, V. A. RUBCHENYA, YU. G. SOBOLEV, V. G. TISHCHENKO, G. P. TIOURINE and D. N. VAKHTINW. H. TRZASKADepartment of Physics of University of Jyväskylä, Finland, YU. V. PYATKOVMoscow Engineering Physics Institute, Russia, YU. E. PENIONZHKEVICHFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, V. A. MASLOVFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, O. I. OSETROVKhlopin Radium Institute, St. Petersburg, Russia, A. A. ALEXANDROVFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, I. A. ALEXANDROVAFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, J. ÄYSTÖDepartment of Physics of University of Jyväskylä, Finland, K. -TH. BRINKMANNTechnical University Dresden, Germany, S. V. KHLEBNIKOVKhlopin Radium Institute, St. Petersburg, Russia, V. F. KUSHNIRUKFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, A. V. KUZNETSOVKhlopin Radium Institute, St. Petersburg, Russia, V. G. LYAPINDepartment of Physics of University of Jyväskylä, Finland, M. MUTTERERTechnical University Darmstadt, Germany, Z. RADIVOJEVICHDepartment of Physics of University of Jyväskylä, Finland, V. A. RUBCHENYADepartment of Physics of University of Jyväskylä, FinlandKhlopin Radium Institute, St. Petersburg, Russia, YU. G. SOBOLEVFlerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, V. G. TISHCHENKOMoscow Engineering Physics Institute, Russia, G. P. TIOURINEDepartment of Physics of University of Jyväskylä, FinlandKhlopin Radium Institute, St. Petersburg, Russia and D. N. VAKHTINDepartment of Physics of University of Jyväskylä, FinlandKhlopin Radium Institute, St. Petersburg, Russiahttps://doi.org/10.1142/9789812777300_0012Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Existence of a new feature in fragment mass-energy distribution is reported. Careful analysis of the data obtained in the reaction 238U + 40Ar (275 MeV) shows that small but statistically significant ripples visible already in the gross mass spectrum come from extended and regular 2D patterns in the TKE vs. mass matrix. Intensity distributions of these patterns coincide with the location of heavy clusters such as 78Ni, 108Mo, or 132Sn. Presumably, the observed patterns show the dominant trajectories in the elongation vs. mass-asymmetry space of the decaying system. This information, unknown in the past, can shed a new light even on the previously well-studied reactions. FiguresReferencesRelatedDetails Exotic NucleiMetrics History PDF download