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Innovative techniques for non destructive analysis
Full text linkThis work describes the development of a radiometric mobile inspection system called SMANDRA (the Italian acronym stands for Sistema Mobile per Analisi Non Distruttive e RAdiometriche). SMANDRA is part of a large project called SLIMPORT, financed by the Italian Ministry for the Economic Development (MISE), dedicated to the development of an integrated toolbox forming a complete security system to monitor the flow of persons and merchandise in harbors.
The system has been conceived as a flexible and transportable tool, to be used in conjunction with fixed installation such as radiation portal monitors, x-ray scanners and large detector arrays. In particular, the aims of SMANDRA are to detect and identify sources of ionizing radiation or identify dangerous and/or illegal materials inside volumes previously tagged as “suspect” by conventional X-ray scanners.
The whole detector apparatus was designed minimizing volume and weight to be easily movable, mounted over forklifts or other light vehicles for inspections. In addition, it is possible to operate the entire system with batteries, making it completely independent from external power facilities.
The system is made of two pieces having a volume less than 0.1 m3 as follows:
1) A passive unit including two gamma-ray detectors (5”x5” NaI(Tl) and 2”x2” LaBr3(Ce)) and two neutron counters (5”x2” liquid scintillator NE-213 and 3He proportional counter for fast and slow neutrons). The unit hosts batteries, power supplies, front-end electronics and CPU.
2) An active unit including a portable sealed neutron generator based on the Tagged Neutron Inspection System (TNIS) technique.
The first unit can be used in standalone mode as a high efficiency spectroscopic radiometer for the detection of ionizing radiation such as gamma-rays, fast and thermal neutrons to search and identify radioactive material as well as Special Nuclear Material (SNM). It can also be used as detector package connected to the second unit for active interrogation of voxels inside a load by tagged neutron inelastic scattering imaging.
All detector used in the SMANDRA system have been fully characterized. Initial tests were done with traditional analog NIM electronics followed by the new digital electronics based on fast digitizers.
The detection and identification of standard radioactive sources (gamma ray and neutrons) has been tested successfully showing detection probability in order or even better with the requirements of this type of instrumentation.
The detection of special nuclear material has been tested using SMANDRA as a high sensitivity passive spectroscopic system or as a complete active inspection system using tagged neutrons. The detection of plutonium samples seems to be possible with passive interrogation even in case of small samples (few grams) due to the yield of gamma ray and neutrons.
As it is well known, detection of uranium samples poses more problems because of the low neutron yield that characterizes this material. The gamma ray yield of highly enriched U samples could be easily shielded. In this case active interrogation is needed.
Results show that it is possible to provide signature for the discrimination of uranium against heavy metals (as lead) by looking to the absolute gamma and neutron yield in coincidence with tagged neutrons or to correlations between detectors. It is worth mentioning that the SMANDRA system is a mobile multi-purpose spectrometric system not specifically designed to detect SNM. However the results reported might be implemented in future portable systems specifically designed to detect SNM in active mode.Questo lavoro descrive lo sviluppo di un sistema mobile per ispezioni radiometriche, chiamato SMANDRA (Sistema Mobile per Analisi Non Distruttive e Radiometriche). SMANDRA fa parte di un grande progetto chiamato SLIMPORT, finanziato dal Ministero Italiano dello sviluppo Economico (MISE), rivolto allo sviluppo di un sistema di sicurezza integrato per il monitoraggio del flusso di persone e merci nei porti.
Il sistema è stato progettato come uno strumento mobile e flessibile, da usare in combinazione con postazioni fisse come portali, scanners x-ray e grandi array di rivelatori. Più in particolare, lo scopo di SMANDRA è quello di identificare sorgenti radioattive e materiali illegali e/o pericolosi nascosti dentro container e bagagli segnalati come “sospetti” dai sistemi di sicurezza tradizionali.
L’intero apparato è stato disegnato per minimizzare il volume ed il peso in modo da essere facilmente trasportabile su un muletto o su altri veicoli leggeri per ispezioni mirate. In aggiunta il sistema può essere alimentato a batterie, rendendolo completamente indipendente dall’allacciamento elettrico.
Il sistema è composto di due unità che hanno un volume totale minore di 0.1 m3:
1) Un’unità passiva composta da due rivelatori di raggi gamma (5”x5” NaI(Tl) e 2”x2” LaBr3(Ce)) e due rivelatori di neutroni (scintillatore liquido NE-213 da 5”x2” e un contatore proporzionale ad 3He). L’unità contiene le batterie, l’alimentazione, l’elettronica digitale e la CPU per l’acquisizione ed analisi dati.
2) Un’unità passiva che include un generatore portatile di neutroni per l’identificazione dei materiali illeciti e/o pericolosi tramite la tecnica TNIS (Tagged Neutron Inspection System).
La prima unità può essere usata da sola come un radiometro spettroscopico ad alta efficienza per la rivelazione di radiazioni ionizzanti come raggi-gamma, neutroni veloci e neutroni termici e per identificare materiale radioattivo come ad esempio il Materiale Speciale Nucleare (SNM). Questa unità è poi usata insieme al generatore di neutroni per interrogazioni attive di specifiche porzioni di volume all’interno di container, grazie alla tecnica TNIS.
Tutti i rivelatori di SMANDRA sono stati totalmente caratterizzati: i test iniziali sono stati fatti con elettronica analogica NIM seguiti da quelli effettuati con la nuova elettronica digitale basata su digitizer veloci.
E’ stata dimostrata la possibilità di rivelare e identificare le sorgenti radioattive standard (raggi-gamma e neutroni) con un livello di confidenza migliore di quello richiesta dallo standard per questo tipo di strumentazione.
La rivelazione di materiale speciale nucleare è stata testata sia in modalità passiva con la prima unità sia in modalità attiva usando il generatore di neutroni.
Il riconoscimento di un campione di plutonio è possibile con la sola interrogazione passiva anche in caso di campioni molto piccoli (qualche grammo) grazie all’alta emissione di raggi-gamma e neutroni.
Come è noto, invece, la rivelazione di campioni di Uranio è più difficoltosa vista la bassa emissione di neutroni e la possibilità di schermare facilmente i pochi raggi-gamma; in questo caso è necessario intervenire con un’interrogazione attiva. I risultati dimostrano la possibilità di discriminare fra campioni di Uranio rispetto a metalli pesanti (come il piombo) guardando i conteggi assoluti di raggi-gamma e neutroni in coincidenza con l’emissione di un neutrone da parte del generatore o, in alternativa, guardando alla correlazione degli eventi fra due rivelatori (NaI(Tl) e NE-213). E’ importante sottolineare che SMANDRA è un sistema spettrometrico mobile multi-funzione, non disegnato specificamente per la rivelazione di materiale speciale nucleare. Tuttavia i risultati mostrano la possibilità in futuro di poter implementare sistemi portatili disegnati specificatamente per l’identificazione di Materiale Speciale Nucleare con l’ausilio di un generatore di neutroni
Neutron detection in a high gamma-ray background with EJ-301 and EJ-309 liquid scintillators
No full textUsing a fast digitizer, the neutron–gamma discrimination capability of the new liquid scintillator EJ-309 is compared with that obtained using standard EJ-301. Moreover the capability of both the scintillation detectors to identify a weak neutron source in a high gamma-ray background is demonstrated. The probability of neutron detection is PD=95% at 95% confidence level for a gamma-ray background corresponding to a dose rate of 100 uSv/h
Comparison of cosmic-ray neutron sensing and gamma-ray spectrometry for non-invasive soil moisture estimation over a large cropped field
No full textSoil moisture is a key variable for supporting agriculture and forest management. This variable, however, shows strong variability in space and time and its correct quantification is still difficult in many practical applications. In the present study we compare two innovative non-invasive sensors developed for the estimation of soil moisture over large area. The first one is a new sensor based on cosmic-ray neutron sensing approach. The second one is a new gamma-ray spectrometer specifically designed for this type of application. Data have been collected at a large, cropped field at Ceregnano, Italy in 2021. The results show that both sensors well capture the local hydrological conditions, and they can be considered reliable methods for soil moisture estimations. In both sensors, however, the signal shows to also be sensitive even if to a different degree to water in the biomass, highlighting the need of corrections when fast plant growth is expected
Experimental tests of the new plastic scintillator with pulse shape discrimination capabilities EJ-299-33
No full textWe have studied the prototype of a new plastic scintillator material (EJ-299-33) engineered for gamma-neutron discrimination. Energy and time resolutions as well as pulse shape discrimination capability have been compared with those of standard plastic and liquid scintillators. EJ-299-33 characteristics are somewhat poorer compared to standard scintillators. However, results obtained with the new plastic material suggest its possible use in basic research (time-of-flight measurements) as well as in Homeland Security applications (neutron/gamma monitoring device)
Neutron detection in a high gamma ray background with liquid scintillators
No full textThe capability of liquid scintillator (namely 2” x 2” cells of EJ301 and EJ309) of detecting neutrons in a very high gamma ray background is explored. A weak 252-Cf source has been detected in a high 137-Cs gamma ray background corresponding to a dose rate of 100 uSv/h with probability of detection in compliance with IEC requirements for hand held instruments. Tests were performed with new generation of CAEN digitizers, in particular the V1720 (8 Channel 12bit 250 MS/s) one
Digital front-end electronics for a tagged neutron inspection system
No full textIn this paper, we shall present a simple VME front-end system that employs the FADC CAEN V1720 8- channel 12-bit 250-MS/s digitizer. This system produces coincidence spectra between the trigger particle and other detectors and it replaces the traditional technique of chaining analog electronics. Tests have been performed using a pulser working at different frequencies as well as employing a 252Cf source in concert with an array of detectors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the combined use of static and mobile cosmic-ray neutron sensors for monitoring spatio-temporal variability of soil water content in cropped fields
No full textThe primary aim of precision agriculture is to optimize crop yield while minimizing the usage of production inputs (in particular water and energy). This entails understanding and effectively managing the spatial variability of soil moisture within agricultural fields. This study present the performance of a combinated system of static and mobile Cosmic Rays Neutron Sensing (CRNS) probes installed in site and mounted onto a tractor for monitoring the temporal variability and mapping the spatial distribution of soil moisture in a cropped field. The use of CRNS entails different benefits, firstly, it allows for the collection of valuable information regarding soil water content in depth, reaching tens of centimeters. Moreover, the large footprint coverage, spanning approximately 5 hectares, provides a comprehensive understanding of soil moisture distribution over a significant area. The installation of CRNS probes on tractor allows for an efficient coverage of a large area and capturing dynamic changes in soil moisture over time. In order to achieve a comprehensive understanding of the soil moisture distribution, a total of four field mappings were conducted at key agronomic intervention points during the growing season of a plot cropped with tobacco
A compact neutron–gamma spectrometer
No full textA compact neutron/gamma detector has been developed using a liquid scintillator cell coupled to a Flat Panel PMT; performances have been compared with a second cell coupled to a traditional linearly-focused 12 dynodes PMT. Energy resolution and pulse shape discrimination (PSD) measured by using a fast digitizer are very similar for the two detectors with the time resolution of the Flat Panel PMT slightly worse. The new detector results to be weakly affected by the influence of a moderate magnetic field while the traditional PMT exhibits strong pulse reduction. The compact size and the low power consumption obtained by using the Flat Panel PMT are very useful in portable neutron/gamma spectrometers
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