144 research outputs found
Novel Scintillating Materials Based on Phenyl-Polysiloxane for Neutron Detection and Monitoring
Neutron detectors are extensively used at many nuclear research facilities
across Europe. Their application range covers many topics in basic and applied
nuclear research: in nuclear structure and reaction dynamics (reaction
reconstruction and decay studies); in nuclear astrophysics (neutron emission
probabilities); in nuclear technology (nuclear data measurements and
in-core/off-core monitors); in nuclear medicine (radiation monitors,
dosimeters); in materials science (neutron imaging techniques); in homeland
security applications (fissile materials investigation and cargo inspection).
Liquid scintillators, widely used at present, have however some drawbacks given
by toxicity, flammability, volatility and sensitivity to oxygen that limit
their duration and quality. Even plastic scintillators are not satisfactory
because they have low radiation hardness and low thermal stability. Moreover
organic solvents may affect their optical properties due to crazing. In order
to overcome these problems, phenyl-polysiloxane based scintillators have been
recently developed at Legnaro National Laboratory. This new solution showed
very good chemical and thermal stability and high radiation hardness. The
results on the different samples performance will be presented, paying special
attention to a characterization comparison between synthesized phenyl
containing polysiloxane resins where a Pt catalyst has been used and a
scintillating material obtained by condensation reaction, where tin based
compounds are used as catalysts. Different structural arrangements as a result
of different substituents on the main chain have been investigated by High
Resolution X-Ray Diffraction, while the effect of improved optical
transmittance on the scintillation yield has been elucidated by a combination
of excitation/fluorescence measurements and scintillation yield under exposure
to alpha and {\gamma}-rays.Comment: InterM 2013 - International Multidisciplinary Microscopy Congres
Probing the statistical decay and alpha-clustering effects in 12c+12c and 14n+10b reactions
An experimental campaign has been undertaken at INFN Laboratori Nazionali di
Legnaro, Italy, in order to progress in our understanding of the statistical
properties of light nuclei at excitation energies above particle emission
threshold, by measuring exclusive data from fusion-evaporation reactions. A
first reaction 12C+12C at 7.9 AMeV beam energy has been measured, using the
GARFIELD+Ring Counter experimental setup. Fusion-evaporation events have been
exclusively selected. The comparison to a dedicated Hauser-Feshbach calculation
allows us to give constraints on the nuclear level density at high excitation
energy for light systems ranging from C up to Mg. Out-of-equilibrium emission
has been evidenced and attributed both to entrance channel effects favoured by
the cluster nature of reaction partners and, in more dissipative events, to the
persistence of cluster correlations well above the 24Mg threshold for 6 alphas
decay. The 24Mg compound nucleus has been studied with a new measurement 14N +
10B at 5.7 AMeV. The comparison between the two datasets would allow us to
further constrain the level density of light nuclei. Deviations from a
statistical behaviour can be analyzed to get information on nuclear clustering.Comment: 4 pages, 2 figures, Contribution to conference proceedings of the
25th International Nuclear Physics Conference (INPC 2013
A new study of Mg(,n)Si angular distributions at = 3 - 5 MeV
The observation of Al gives us the proof of active nucleosynthesis in
the Milky Way. However the identification of the main producers of Al is
still a matter of debate. Many sites have been proposed, but our poor knowledge
of the nuclear processes involved introduces high uncertainties. In particular,
the limited accuracy on the Mg(,n)Si reaction cross
section has been identified as the main source of nuclear uncertainty in the
production of Al in C/Ne explosive burning in massive stars, which has
been suggested to be the main source of Al in the Galaxy. We studied
this reaction through neutron spectroscopy at the CN Van de Graaff accelerator
of the Legnaro National Laboratories. Thanks to this technique we are able to
discriminate the (,n) events from possible contamination arising from
parasitic reactions. In particular, we measured the neutron angular
distributions at 5 different beam energies (between 3 and 5 MeV) in the
\ang{17.5}-\ang{106} laboratory system angular range. The presented results
disagree with the assumptions introduced in the analysis of a previous
experiment.Comment: 9 pages, 9 figures - accepted by EPJ
GARFIELD + RCo Digital Upgrade: a Modern Set-up for Mass and Charge Identification of Heavy Ion Reaction Products
An upgraded GARFIELD + Ring Counter (RCo) apparatus is presented with
improved performances as far as electronics and detectors are concerned. On one
side fast sampling digital read out has been extended to all detectors,
allowing for an important simplification of the signal processing chain
together with an enriched extracted information. On the other side a relevant
improvement has been made in the forward part of the setup (RCo): an increased
granularity of the CsI(Tl) crystals and a higher homogeneity in the silicon
detector resistivity. The renewed performances of the GARFIELD + RCo array make
it suitable for nuclear reaction measurements both with stable and with
Radioactive Ion Beams (RIB), like the ones foreseen for the SPES facility,
where the Physics of Isospin can be studied.Comment: 13 pages, 19 figures - paper submitted to Eur. Phys. J.
Status and performances of the FAZIA project
FAZIA is designed for detailed studies of the isospin degree of freedom,
extending to the limits the isotopic identification of charged products from
nuclear collisions when using silicon detectors and CsI(Tl) scintillators. We
show that the FAZIA telescopes give isotopic identification up to Z25
with a E-E technique. Digital Pulse Shape Analysis makes possible
elemental identification up to Z=55 and isotopic identification for Z=1-10 when
using the response of a single silicon detector. The project is now in the
phase of building a demonstrator comprising about 200 telescopes
Isospin transport in 84Kr + 112,124Sn collisions at Fermi energies
Isotopically resolved fragments with Z<=20 have been studied with high
resolution telescopes in a test run for the FAZIA collaboration. The fragments
were produced by the collision of a 84Kr beam at 35 MeV/nucleon with a n-rich
(124Sn) and a n-poor (112Sn) target. The fragments, detected close to the
grazing angle, are mainly emitted from the phase-space region of the
projectile. The fragment isotopic content clearly depends on the n-richness of
the target and it is a direct evidence of isospin diffusion between projectile
and target. The observed enhanced neutron richness of light fragments emitted
from the phase-space region close to the center of mass of the system can be
interpreted as an effect of isospin drift in the diluted neck region.Comment: 8 pages, 7 figure
N and Z odd-even staggering in Kr + Sn collisions at Fermi energies
The odd-even staggering of the yield of final reaction products has been
studied as a function of proton (Z) and neutron (N) numbers for the collisions
84 Kr+112 Sn and 84 Kr+124 Sn at 35 MeV/nucleon, in a wide range of elements
(up to Z ~ 20). The experimental data show that staggering effects rapidly
decrease with increasing size of the fragments. Moreover the staggering in N is
definitely larger than the one in Z. Similar general features are qualitatively
reproduced by the GEMINI code. Concerning the comparison of the two systems,
the staggering in N is in general rather similar, being slightly larger only
for the lightest fragments produced in the n-rich system. In contrast the
staggering in Z, although smaller than that in N, is sizably larger for the
n-poor system with respect to the n-rich one.Comment: 6 pages, 5 figures, Revtex forma
Charged particle decay of hot and rotating Mo nuclei in fusion-evaporation reactions
A study of fusion-evaporation and (partly) fusion-fission channels for the
Mo compound nucleus, produced at different excitation energies in the
reaction Ti + Ca at 300, 450 and 600 MeV beam energies, is
presented. Fusion-evaporation and fusion-fission cross sections have been
extracted and compared with the existing systematics. Experimental data
concerning light charged particles have been compared with the prediction of
the statistical model in its implementation in the Gemini++ code, well suited
even for high spin systems, in order to tune the main model parameters in a
mass region not abundantly covered by exclusive experimental data.
Multiplicities for light charged particles emitted in fusion evaporation events
are also presented. Some discrepancies with respect to the prediction of the
statistical model have been found for forward emitted -particles; they
may be due both to pre-equilibrium emission and to reaction channels (such as
Deep Inelastic Collisions, QuasiFission/QuasiFusion) different from the
compound nucleus formation.Comment: 14 pages, 14 figure
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