1,721,534 research outputs found
A proposal for an alternative use of prompt-Self Powered Neutron Detectors: Online spectral-deconvolution for monitoring high-intensity neutron flux in LFRs
No full textSelf-Powered Neutron Detectors (SPNDs) are currently used in reactors’ environment to sense the magnitude of neutron-fluxes, usually for spatial-distribution mapping of the fuel region as to optimize burn-up strategies. During the development of tailored instrumentation for Lead-cooled Fast Reactors, the possibility to perform online spectral deconvolution of fast neutron-fluxes was recognized. Seven geometrically similar SPNDs with different neutron-sensitive materials, have been characterized by the Monte Carlo transport code MCNPX. Thanks to a database of spectral sensitivities vs. neutrons’ energy, a mathematical deconvolution process from 7 electric current values virtually measured by SPNDs was started, retrieving spectral information, in terms of 7 energy windows, of the neutron-flux the detectors are subjected by. This paper describes the procedure that led to those results, prefiguring future development to improve proposed method. © 2017 Elsevier B.V
Radiative neutron capture as a counting technique at pulsed spallation neutron sources: A review of current progress
No full textNeutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources. © 2016 IOP Publishing Ltd
Calibration of a Poly Allyl Diglycol Carbonate (PADC) based track-etched dosimeter in thermal neutron fields
No full textThe purpose of this work was to study the response of a Poly Allyl Diglycol Carbonate (PADC) based neutron dosimeter in thermal fields. The dosimeter was irradiated in three different thermal piles, which are characterized by a homogeneous thermal field with a low proportion of fast neutrons. However, the dosimeter is highly sensitive to fast neutrons and, then, differences in the amount of fast neutrons arriving to the sensitive side of the dosimeter, which depends on the measurement point inside the pile and its orientation, can lead to differences in the response of the system. As an example, in one of the thermal piles, the response of the dosimeter ranged from (8.31 ± 0.44) × 10−6 tracks per neutron in a point with a 10% of fast neutrons to (2.27 ± 0.27) × 10−6 tracks per neutron in a point with an almost pure thermal field. This effect has the advantage that it is possible to choose conveniently a specific position inside the cavity where the neutron field spectrum is closest to the field where the dosimeter will be exposed, allowing to obtain the appropriate calibration factor. © 2018 Elsevier Lt
Study of the radiation damage of Silicon Photo-Multipliers at the GELINA facility
No full textIn this paper we present a study of the neutrons-induced damage in Silicon Photo-Multipliers. Twenty-six devices, produced by AdvanSiD, Hamamatsu and SensL, have been irradiated at the Geel Electron LINear Accelerator (GELINA) in Belgium with a nearly white neutron beam. The total 1 MeV equivalent integrated dose was 6.2 × 109 neq/cm2. Photodetector performances have been measured during the whole irradiation period and a gradual worsening of the detector properties, such as dark current and charge spectra, has been observed. An extensive comparison of the performances of all the tested devices will be presented. © 2014 IOP Publishing Ltd and Sissa Medialab srl
Comparison between silicon and single-crystal diamond photodiodes for localized pulsed fast neutron detection
No full textExperimental measurements are presented, devoted to the cross-comparison of two small-size fast neutron detection devices, namely Single-Crystal Diamond diode (SCDD) and Silicon Photodiode (SiPD). Neutron time-of-flight spectra are simultaneously recorded under the same experimental conditions, using an array composed of two SCDDs and two SiPDs placed in the incident beam of the ROTAX beam line at the ISIS spallation neutron source (UK). Experimental spectra are compared to calculated ones, obtained by taking into account material characteristics and the neutron spectrum. The SCDD detector features a higher time resolution with respect to the SiPD, likely related to the different neutron cross-sections and the electronic thresholds set during the measurements. © CopyrightEPLA, 2018
High-resolution wide-range dynamic neutron monochromators
No full textThis work proposes the concept of a high-resolution wide-range dynamic neutron monochromator able to operate up to a few eV, thus significantly extending the reliable operating neutron energy range of the state-of-the-art crystal-based devices, and to improve energy resolution in the epithermal range if compared to mechanical choppers. The proposed device is based on a radiation-hard aluminium nitride (AlN)/diamond heterostructure, operating as a super-high-frequency (> 3 GHz) high-speed (> 10000 m/s) acoustic resonator. The resulting surface acoustic wave (SAW) acts as a dynamic grating for the incoming neutrons: as long as neutron speed is lower than (or at least comparable to) SAW speed, diffraction angles are significantly enhanced, thus allowing for neutron beam monochromatization to be effective up to the eV energy range. SAW amplitude can be electrically tuned to increase first-order reflectivity, leading to an enhanced intensity of the monochromatized beam. Copyright © EPLA, 2015
Non-invasive characterisation of SIX Japanese hand-guards (tsuba)
No full textIn this work we present a systematic study of Japanese sword hand-guards (tsuba) carried out by means of non-invasive techniques using neutrons. Several tsuba from different periods, belonging to the Japanese Section of the Stibbert Museum, were analysed using an innovative approach to characterise the bulk of the samples, coupling two neutron techniques, namely Time of Flight Neutron Diffraction (ToF-ND) and Nuclear Resonance Capture Analysis (NRCA). The measurements were carried out on the same instrument: the INES beam-line at the ISIS spallation pulsed neutron source (UK). NRCA analysis allows identifying the elements present in the sample gauge volume, while neutron diffraction is exploited to quantify the phase distribution and other micro-structural parameters of the metal specimen. The results show that all samples are made of high-quality metal, either steel or copper alloy, with noticeable changes in composition and working techniques, depending on the place and time of manufacturing. © 2013 Springer-Verlag Berlin Heidelberg
Thermal neutron radiative capture on cadmium as a counting technique at the INES beam line at ISIS: A preliminary investigation of detector cross-talk
No full textExperimental tests are presented that assess the cross-talk level among three scintillation detectors used as neutron counters exploiting the thermal neutron radiative capture on Cd. The measurements were done at the INES diffractometer operating at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK). These tests follow a preliminary set of measurements performed on the same instrument to study the effectiveness of this thermal neutron counting strategy in neutron diffraction measurements, typically performed on INES using squashed 3He filled gas tubes. The experimental data were collected in two different geometrical configurations of the detectors and compared to results of Monte Carlo simulations, performed using the MCNP code. © 2017 Elsevier Lt
Silicon photo-multiplier radiation hardness tests with a white neutron beam
No full textWe report radiation hardness tests performed, with a white neutron beam, at the Geel Electron LINear Accelerator in Belgium on silicon Photo-Multipliers. These are semiconductor photon detectors made of a square matrix of Geiger-Mode Avalanche photo-diodes on a silicon substrate. Several samples from different manufacturers have been irradiated integrating up to about 6.2 × 10 9 1-MeV-equivalent neutrons per cm2. © 2013 IEEE
Simultaneous and integrated neutron-based techniques for material analysis of a metallic ancient flute
No full textA metallic 19th century flute was studied by means of integrated and simultaneous neutron-based techniques: neutron diffraction, neutron radiative capture analysis and neutron radiography. This experiment follows benchmark measurements devoted to assessing the effectiveness of a multitask beamline concept for neutron-based investigation on materials. The aim of this study is to show the potential application of the approach using multiple and integrated neutron-based techniques for musical instruments. Such samples, in the broad scenario of cultural heritage, represent an exciting research field. They may represent an interesting link between different disciplines such as nuclear physics, metallurgy and acoustics. © 2013 IOP Publishing Ltd
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