The next generation of very-short-baseline reactor experiments will require compact detectors operating at surface level and close to a nuclear reactor. This paper presents a new detector concept ...based on a composite solid scintillator technology. The detector target uses cubes of polyvinyltoluene interleaved with 6LiF:ZnS(Ag) phosphor screens to detect the products of the inverse beta decay reaction. A multi-tonne detector system built from these individual cells can provide precise localisation of scintillation signals, making efficient use of the detector volume. Monte Carlo simulations indicate that a neutron capture efficiency of over 70 % is achievable with a sufficient number of 6LiF:ZnS(Ag) screens per cube and that an appropriate segmentation enables a measurement of the positron energy which is not limited by γ-ray leakage. First measurements of a single cell indicate that a very good neutron-gamma discrimination and high neutron detection efficiency can be obtained with adequate triggering techniques. The light yield from positron signals has been measured, showing that an energy resolution of 14%/√E(MeV) is achievable with high uniformity. A preliminary neutrino signal analysis has been developed, using selection criteria for pulse shape, energy, time structure and energy spatial distribution and showing that an antineutrino efficiency of 40% can be achieved. It also shows that the fine segmentation of the detector can be used to significantly decrease both correlated and accidental backgrounds.
Performance of prototypes for the ALICE electromagnetic calorimeter Allen, J.; Awes, T.; Badalá, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2010, Letnik:
615, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A
4
×
4
array of final design modules showed an energy ...resolution of about
11
%
/
E
(
GeV
)
⊕
1.7
%
with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100
GeV. The electromagnetic shower position resolution was found to be described by
1.5
mm
⊕
5.3
mm
/
E
(
GeV
)
. For an electron identification efficiency of 90% a hadron rejection factor of
>
600
was obtained.
Sterile neutrinos have been considered as a possible explanation for the recent reactor and Gallium anomalies arising from reanalysis of reactor flux and calibration data of previous neutrino ...experiments. A way to test this hypothesis is to look for distortions of the anti-neutrino energy caused by oscillation from active to sterile neutrino at close stand-off (∼6–8m) of a compact reactor core. Due to the low rate of anti-neutrino interactions the main challenge in such measurement is to control the high level of gamma rays and neutron background.
The SoLid experiment is a proposal to search for active-to-sterile anti-neutrino oscillation at very short baseline of the SCK•CEN BR2 research reactor.
This experiment uses a novel approach to detect anti-neutrino with a highly segmented detector based on Lithium-6. With the combination of high granularity, high neutron-gamma discrimination using 6LiF:ZnS(Ag) and precise localization of the Inverse Beta Decay products, a better experimental sensitivity can be achieved compared to other state-of-the-art technology. This compact system requires minimum passive shielding allowing for very close stand off to the reactor. The experimental set up of the SoLid experiment and the BR2 reactor will be presented. The new principle of neutrino detection and the detector design with expected performance will be described. The expected sensitivity to new oscillations of the SoLid detector as well as the first measurements made with the 8 kg prototype detector deployed at the BR2 reactor in 2013–2014 will be reported.
The ARRONAX cyclotron is fully operational since the end of 2010. It delivers projectiles (p, d, α) at high energy (up to 70 MeV for protons) and high intensity(2*375μA for protons). The main fields ...of application of ARRONAX are radionuclide production for nuclear medicine and irradiation of inert or living materials for radiolysis and radio-biology studies. A large part of the beam time will be used to produce radionuclides for targeted radionuclide therapy (copper-67, scandium-47 and astatine-211) as well as for PET imaging (scandium-44, copper-64, strontium-82 for rubidium-82 generators, and germanium-68 for gallium-68 generators). Since June 2012, large scale production of 82Sr has started with rubidium chloride (RbCl) targets. Several improvements are being explored which consist of changing the target material from RbCl to Rb metal and introducing an additional target behind the rubidium assembly. Thus, a target alloy of nickel/gallium for germanium-68 production has been developed. It is obtained by electroplating and exhibits a better thermal behavior than the natural gallium target used in most production facilities.
The next generation of very-short-baseline reactor experiments will require compact detectors operating at surface level and close to a nuclear reactor. This paper presents a new detector concept ...based on a composite solid scintillator technology. The detector target uses cubes of polyvinyltoluene interleaved with \(^6\)LiF:ZnS(Ag) phosphor screens to detect the products of the inverse beta decay reaction. A multi-tonne detector system built from these individual cells can provide precise localisation of scintillation signals, making efficient use of the detector volume. Monte Carlo simulations indicate that a neutron capture efficiency of over 70% is achievable with a sufficient number of \(^6\)LiF:ZnS(Ag) screens per cube and that an appropriate segmentation enables a measurement of the positron energy which is not limited by gamma-ray leakage. First measurements of a single cell indicate that a very good neutron-gamma discrimination and high neutron detection efficiency can be obtained with adequate triggering techniques. The light yield from positron signals has been measured, showing that an energy resolution of 14%/\(\sqrt{E({\mathrm{MeV}})}\) is achievable with high uniformity. A preliminary neutrino signal analysis has been developed, using selection criteria for pulse shape, energy, time structure and energy spatial distribution and showing that an antineutrino efficiency of 40% can be achieved. It also shows that the fine segmentation of the detector can be used to significantly decrease both correlated and accidental backgrounds.
The tracking system of the ALICE dimuon spectrometer Basciu, S.; Arba, M.; Atanassov, I. ...
2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515),
2003, Letnik:
1
Conference Proceeding
The ALICE Muon Spectrometer is mainly dedicated to the measurement of the production of the J//spl psi/, and Y families through their decay into muon pairs, in Pb-Pb collisions. In this paper we give ...a description of the dimuon tracking system, mainly concentrating on the modular CSC chambers which occupy the last three stations. The R&D phase is now almost over and the production of the final modules started. A description of the main performances of the detectors based on test beam results on prototypes will be given.
The aim of this paper was to evaluate the potential of chitosan nanoparticles as carriers for the anthracycline drug, doxorubicin (DOX). The challenge was to entrap a cationic, hydrophilic molecule ...into nanoparticles formed by ionic gelation of the positively charged polysaccharide chitosan. To achieve this objective, we attempted to mask the positive charge of DOX by complexing it with the polyanion, dextran sulfate. This modification doubled DOX encapsulation efficiency relative to controls and enabled real loadings up to 4.0 wt.% DOX. Separately, we investigated the possibility of forming a complex between chitosan and DOX prior to the formation of the particles. Despite the low complexation efficiency, no dissociation of the complex was observed upon formation of the nanoparticles. Fluorimetric analysis of the drug released in vitro showed an initial release phase, the intensity of which was dependent on the association mode, followed by a very slow release. The evaluation of the activity of DOX-loaded nanoparticles in cell cultures indicated that those containing dextran sulfate were able to maintain cytostatic activity relative to free DOX, while DOX complexed to chitosan before nanoparticle formation showed slightly decreased activity. Additionally, confocal studies showed that DOX was not released in the cell culture medium but entered the cells while remaining associated to the nanoparticles. In conclusion, these preliminary studies showed the feasibility of chitosan nanoparticles to entrap the basic drug DOX and to deliver it into the cells in its active form.
The distribution of nitrogen (N) and carbon (C) pools in 100-year-old sessile oaks was investigated in situ at four key periods of tree phenology. Leaves, twigs, trunk and roots were sampled, and ...total non-structural nitrogen compounds (TNNC) and total non-structural carbohydrates (TNC) were quantified. TNC concentrations decreased more than 50 % between February and May, especially in the above-ground parts. During the same period, TNNC concentrations drastically decreased especially in twigs (more than 55 % below the winter baseline). This indicates high sink strength of new organs at bud break. TNC concentrations increased in summer in all tree compartments highlighting the TNC storage. TNNC deposition for storage constitution began in autumn during leaf senescence. The first organs acting as a N store were coarse roots followed by twigs; whereas all oak tree compartments were potential C store organs except phloem tissue. Arginine and asparagine were the two prevailing amino acids involved in both storage and transport. Besides identifying the compounds involved in the storage and transportation of N, our results highlight that oak seasonal cycles of C and N are not in phase: after intensive use of C and N stores in spring, the replenishment of N stores lags behind that of C stores.
Salinity is one of the most severe environmental stresses limiting agricultural crop production worldwide. Photosynthesis is one of the main biochemical processes getting affected by such stress ...conditions. Here we investigated the stomatal and non-stomatal factors during photosynthesis in two Iranian melon genotypes “Ghobadlu” and “Suski-e-Sabz”, as well as the “Galia” F1 cultivar, with an insight into better understanding the physiological mechanisms involved in the response of melon plants to increasing salinity. After plants were established in the greenhouse, they were supplied with nutrient solutions containing three salinity levels (0, 50, or 100 mM NaCl) for 15 and 30 days. With increasing salinity, almost all of the measured traits (e.g. stomatal conductance, transpiration rate, internal to ambient CO2 concentration ratio (Ci/Ca), Rubisco and nitrate reductase activity, carbon isotope discrimination (Δ13C), chlorophyll content, relative water content (RWC), etc.) significantly decreased after 15 and 30 days of treatments. In contrast, the overall mean of water use efficiency (intrinsic and instantaneous WUE), leaf abscisic acid (ABA) and flavonol contents, as well as osmotic potential (ΨS), all increased remarkably with increasing stress, across all genotypes. In addition, notable correlations were found between Δ13C and leaf gas exchange parameters as well as most of the measured traits (e.g. leaf area, biomass, RWC, ΨS, etc.), encouraging the possibility of using Δ13C as an important proxy for indirect selection of melon genotypes with higher photosynthetic capacity and higher salinity tolerance. The overall results suggest that both stomatal and non-stomatal limitations play an important role in reduced photosynthesis rate in melon genotypes studied under NaCl stress. This conclusion is supported by the concurrently increased resistance to CO2 diffusion, and lower Rubisco activity under NaCl treatments at the two sampling dates, and this was revealed by the appearance of lower Ci/Ca ratios and lower Δ13C in the leaves of salt-treated plants.
•DUALEX, an optical sensor, could be applied to assess crop nitrogen status of melon genotypes under salinity condition.•Both the NR and Rubisco activities were significantly reduced under NaCl stress.•A significant positive relationship was observed between Δ13C and Ci/Ca measured by gas exchanges in all genotypes.•Δ13C was negatively correlated with WUE and WUEi in both sampling times.•Using Δ13C would be an important proxy for selection of melon genotypes with higher photosynthetic performance.
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