552 research outputs found
Isoscaling and the symmetry energy in spectator fragmentation
Isoscaling and its relation to the symmetry energy in the fragmentation of
excited residues produced at relativistic energies were studied in two
experiments conducted at the GSI laboratory. The INDRA multidetector has been
used to detect and identify light particles and fragments with Z <= 5 in
collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per
nucleon. Isoscaling is observed, and the deduced parameters decrease with
increasing centrality. Symmetry term coefficients, deduced within the
statistical description of isotopic scaling, are near gamma = 25 MeV for
peripheral and gamma < 15 MeV for central collisions.
In a very recent experiment with the ALADIN spectrometer, the possibility of
using secondary beams for reaction studies at relativistic energies has been
explored. Beams of 107Sn, 124Sn, 124La, and 197Au were used to investigate the
mass and isospin dependence of projectile fragmentation at 600 MeV per nucleon.
The decrease of the isoscaling parameters is confirmed and extended over the
full fragmentation regime covered in these reactions.Comment: Proceedings of the IWM2005, Catania, Italy, Nov 200
18 Ne diproton decay
Two proton radioactivity studies have been performed on excited states of 18 Ne produced, among other fragments, by 20 Ne projectile fragmentation and excited via Coulomb excitation on a Pb target. Every incoming ion was tagged before interacting with the lead target on an event by event basis in order to discriminate the secondary reactions according to the projectile. Decay of 18 Ne levels has been studied by complete kinematical reconstruction. In spite of the low statistics a couple of events looks very promising for two proton correlated emission
Neutron Skins: Weak Elastic Scattering and Neutron Stars
The recently completed PREX-2 campaign - which measured the weak form factor
of lead at an optimal momentum transfer - has confirmed that the neutron skin
of lead is relatively large and has provided a precise determination of the
interior baryon density of a heavy nucleus. In turn, the measured form factor
can be related to various nuclear and neutron-star properties. Astrophysical
observations by the NICER mission have benefited from improvements in flux,
energy resolution, and notably, timing resolution. NICER has the capability to
measure pulse profile data, which enables simultaneous mass-radius
determinations. During the next decade, measurements in astrophysics,
gravitational wave astronomy, and nuclear physics are expected to provide a
wealth of more precise data. In this review we provide an overview of the
current state of neutron skin measurements and offer insights into the
prospects for the future.Comment: submitted to Annual Reviews of Nuclear and Particle Scienc
First experimental evidence of 2He decay from 18Ne excited states
Two-proton decay from 18Ne excited states has been studied by complete kinematical detection of the decay products. The 18Ne nucleus has been produced as a radioactive beam by 20Ne projectile fragmentation at 45 AMeV on a 9Be target, using the FRIBs in-flight facility of the LNS. The 18Ne at 33 AMeV incident energy has been excited via Coulomb excitation on a natPb target. The correlated 2p emission has been disentangled from the uncorrelated 2p emission using a high granularity particle detector setup allowing the reconstruction of momentum and angle correlations of the two emitted protons. The obtained results unambiguously show that the 6.15 MeV 18Ne state two-proton decay proceeds through 2He emission (31%) and democratic or virtual sequential decay (69%)
Light Ions Response of Silicon Carbide Detectors
Silicon carbide (SiC) Schottky diodes 21 mum thick with small surfaces and
high N-dopant concentration have been used to detect alpha particles and low
energy light ions. In particular 12C and 16O beams at incident energies between
5 and 18 MeV were used. The diode active-region depletion-thickness, the
linearity of the response, energy resolution and signal rise-time were measured
for different values of the applied reverse bias. Moreover the radiation damage
on SiC diodes irradiated with 53 MeV 16O beam has been explored. The data show
that SiC material is radiation harder than silicon but at least one order of
magnitude less hard than epitaxial silicon diodes. An inversion in the signal
was found at a fluence of 10^15 ions/cm^2.Comment: 20 pages, 16 figures, submitted for publication to Nuclear
Instruments and Methods in Physics Research
Past, present and future of radioactive ion beams produced In-Flight at LNS
The FRIBs@LNS facility produces Radioactive Ion Beams (RIBs)
at intermediate energies, by projectile fragmentation. The possibility of using the produced RIBs as secondary beams in nuclear physics experiments by applying the tagging technique, i.e. the identification, event-by-event, in charge, mass and energy of each ion of the RIBs cocktail selected by the fragment separator, before it interacts with the secondary target, has been demonstrated. In 2010 an upgrade of the facility has been performed. Status and perspectives of the FRIBs@LNS facility are discussed
Discriminant Analysis and Secondary-Beam Charge Recognition
The discriminant-analysis method has been applied to optimize the exotic-beam
charge recognition in a projectile fragmentation experiment. The experiment was
carried out at the GSI using the fragment separator (FRS) to produce and select
the relativistic secondary beams, and the ALADIN setup to measure their
fragmentation products following collisions with Sn target nuclei. The beams of
neutron poor isotopes around 124La and 107Sn were selected to study the isospin
dependence of the limiting temperature of heavy nuclei by comparing with
results for stable 124Sn projectiles. A dedicated detector to measure the
projectile charge upstream of the reaction target was not used, and alternative
methods had to be developed. The presented method, based on the multivariate
discriminant analysis, allowed to increase the efficacy of charge recognition
up to about 90%, which was about 20% more than achieved with the simple scalar
methods.Comment: 6 pages, 7 eps figures, elsart, submitted to Nucl. Instr. and Meth.
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