602 research outputs found
Hydrologic Conditions Leading to Debris-Flow Initiation in the Campanian Volcanoclastic soils
No full textThe GEMpix detector as new soft X-rays diagnostic tool for laser produced plasmas
No full textLaser produced plasmas lend to several interesting applications. The study of X-ray emission from this kind of plasmas is important not only to characterize plasmas itself but also to study the application of these particular plasmas as intense X-ray sources. In particular several emission configurations can be obtained using different kinds of targets and tuning the characteristics of the laser pulse delivered to the target. Typically, laser pulse duration ranges between a few tens of femtoseconds and tens of nanoseconds, with energies from few mJ to tens of kJ. X-ray photon emissions last for times comparable to the laser pulses and during this time a great number of photons can be emitted. The following paper presents a measure of the soft-X-ray emission on the ECLIPSE laser facility realized with a new triple-GEM gas detector (GEMpix). It is a hybrid gas detector with a C-MOS front-end electronics based on Medipix chips. In the present work, different targets have been used in order to test X-rays of different energies. In this paper, in particular, we present results obtained for copper and iron targets. GEMpix is able to realize a 2D imaging of the X-ray emission from plasma with a signal proportional to the energy released in the gas of the detector active volume. Then through a preliminary single photon equalization realized at the NIXT lab (ENEA), also the number of photons reaching the area of the detector has been estimated. © 2016 Author(s)
Informational entropy of fractal river networks
No full textInformational entropy of river networks, as defined by Fiorentino and Claps (1992), proved to be a useful tool in the interpretation of several properties exhibited by natural networks. In this paper, self-similar properties of river networks are taken as the starting point for investigating analogies and differences between natural networks and geometric fractal trees, comparing their variability entropy with parameters of both classes of networks. Attention is directed particularly to relations between entropy and Horton order and entropy and topological diameter of subnetworks. Comparisons of these relations for fractals and natural networks suggest that network entropy can contribute to clarify important points concerning self-similar properties of river networks. Moreover, the estimation of the fractal dimension of branching for natural networks can be considerably improved using the relation between entropy and Horton order throughout the network
GEM-based detectors for thermal and fast neutrons
No full textLately the problem of 3He replacement for neutron detection stimulated an intense activity research on alternative technologies based on alternative neutron converters. This paper presents briefly the results obtained with new GEM detectors optimized for fast and thermal neutrons. For thermal neutrons, we realized a side-on GEM detector based on a series of boron-coated alumina sheets placed perpendicularly to the incident neutron beam direction. This prototype has been tested at n@BTF photo-production neutron facilty in order to test its effectiveness under a very high flux gamma background. For fast neutrons, we developed new GEM detectors (called nGEM) for the CNESM diagnostic system of the SPIDER NBI prototype for ITER (RFX-Consortium, Italy) and as beam monitor for fast neutrons lines at spallation sources. The nGEM is a Triple GEM gaseous detector equipped with a polyethylene layer used to convert fast neutrons into recoil protons through the elastic scattering process. This paper describes the results obtained by testing a medium size (30 × 25 cm2 active area) nGEM detector at the ISIS spallation source on the VESUVIO beam line. © 2015, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg
Neutron diffraction measurements on a reference metallic sample with a high-efficiency GEM side-on 10B-based thermal neutron detector
No full textThe upgraded version of the GEM side-on thermal neutron detector was successfully tested in a neutron diffraction experiment on a reference sample using the INES diffractometer at the ISIS spallation neutron source, UK. The performance of the new 10B4C-based detector is compared to that of a standard 3He tube, operating at the instrument as a part of the detectors assembly. The results show that the upgraded detector has a better resolution and an efficiency of the same order of magnitude of a 3He-based detector. © 2018 EPLA
Dichiarazione Ambientale del Centro Ricerche ENEA Trisaia
No full textLa Dichiarazione Ambientale costituisce il documento con cui il Centro Ricerche Trisaia presenta periodicamente gli sviluppi delle performance del proprio sistema di gestione integrato Ambiente e Sicurezza e comunica al pubblico, attivamente e con trasparenza, le prestazioni ambientali delle proprie attività e i risultati raggiunti rispetto agli obiettivi fissati. Gli obiettivi di miglioramento stabiliti per gli aspetti ambientali diretti (consumo di energia, consumo risorse idriche, produzione rifiuti, impiego sostanze pericolose) e indiretti (rapporti con il territorio, con appaltatori e fornitori esterni ecc.) risultano ampiamente conseguiti. La dichiarazione ambientale oltre a contenere informazioni sull’organizzazione, sulla politica integrata Ambiente e Sicurezza e sul sistema di gestione, descrive il Centro, gli aspetti ambientali e di sicurezza e gli obiettivi di volta in volta prefissati. La validità della Dichiarazione è triennale e annualmente vengono predisposti gli aggiornamenti
Tomographic 2-D X-ray imaging of toroidal fusion plasma using a tangential pinhole camera with gas electron multiplier detector
No full textA tangential X-ray pinhole camera based on a gas electron multiplier (GEM) detector was installed on KSTAR to study high temperature plasmas emitting X-ray photons in the energy band of 4–15 keV. The camera system consists of a triple-GEM gas chamber with a readout printed circuit board and a pinhole to image the plasma in two dimensions (2-D). The advantages of this tangential camera system include its compactness, high efficiency, energy discrimination in bands, and selectivity of the photon energy range etc. This camera system allows a selection of the viewing area through a remote control of the entire setup. The Philips-Tikhonov algorithm for tangential reconstruction was used to visualize the poloidal cross-sectional images. Phantom tests were performed with synthetic D-shaped plasma images and a comparison with the magnetic equilibrium flux surfaces from the real-time EFIT code obtaining a good agreement between each other. The 2-D X-ray images of the KSTAR plasma were successfully acquired during sawtooth crash, electron cyclotron heating, vertical displacement event, and emissivity from the injected trace Ar impurity. © 2016 Elsevier B.V
Major results from the first plasma campaign of the Wendelstein 7-X stellarator
No full textAfter completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 1019 m-3, central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre. © 2017 Max-Planck-Institut fur Plasmaphysik
Aspetti idrologici della gestione operativa delle risorse idriche in uno schema interconnesso
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