195 research outputs found
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
Progresses in FAZIA detection system and preliminary results from the ISO-FAZIA experiment
In this contribution the status of the FAZIA project is presented, with a particular focus on the first experiment (identified as ISO-FAZIA) after the R&D phase. In this experiment four complete FAZIA blocks in a fully operating configuration were used. They were mounted in a planar “belt” geometry, symmetrically positioned with respect to the beam axis, covering the polar angles between 2.5◦ and 17.4◦ degrees. The investigated systems were 84Kr + 48,40Ca at 35AMeV. The main goal of the experiment was the study of the isospin transport phenomena, extending a previous analysis. This contribution will report on the isotopic identification capability of the FAZIA detector as well as preliminary results concerning the average isospin of the quasi-projectile produced in semiperipheral collisions as a function of the isospin of the target
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.
Influence of Neutron Enrichment on Disintegration Modes of Compound Nuclei
Cross sections, kinetic energy and angular distributions of fragments with
charge 6Z28 emitted in 78,82Kr+40C at 5.5 MeV/A reactions were
measured at the GANIL facility using the INDRA apparatus. This experiment aims
to investigate the influence of the neutron enrichment on the decay mechanism
of excited nuclei. Data are discussed in comparison with predictions of
transition state and Hauser-Feshbach models.Comment: 8 pages, 1 figure, paper presented at the First Workshop on "State of
the Art in Nuclear Cluster Physics" 13-16 May, 2008, at Strasbourg, France
(SOTANCP2008) and accepted for publication at International Journal of Modern
Physics E (Special Issue), Proceedings of SOTANCP2008 (to be published
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
Energy measurement and fragment identification using digital signals from partially depleted Si detectors
A study of identification properties of a Si-Si DE-E telescope exploiting an
underdepleted residual-energy detector has been performed. Five different bias
voltages have been used, one corresponding to full depletion, the others
associated with a depleted layer ranging from 90% to 60% of the detector
thickness. Fragment identification has been performed using either the DE-E
technique or Pulse Shape Analysis (PSA). Both detectors are reverse mounted:
particles enter from the low field side, to enhance the PSA performance. The
achieved charge and mass resolution has been quantitatively expressed using a
Figure of Merit (FoM). Charge collection efficiency has been evaluated and the
possibility of energy calibration corrections has been considered. We find that
the DE-E performance is not affected by incomplete depletion even when only 60%
of the wafer is depleted. Isotopic separation capability improves at lower bias
voltages with respect to full depletion, though charge identification
thresholds are higher than at full depletion. Good isotopic identification via
PSA has been obtained from a partially depleted detector whose doping
uniformity is not good enough for isotopic identification at full depletion.Comment: 13 pages, 10 figures 5 tables; submitted to European Physical Journal
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
X-ray fluorescence from the element with atomic number Z = 120
Accepted for publication in Physical Review LettersAn atomic clock based on X-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238U + 64Ni at 6.6 MeV/A. Inner shell vacancies are created during the collisions in the electronic structure of the possibly formed Z=120 compound nuclei. The filling of these vacancies accompanied by X-ray emission with energies characteristic of Z=120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the X-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K X-rays from the element with Z = 120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time _f$ = 2.5×10−18s has been deduced for Z=120 from the measured X-ray multiplicity
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