338 research outputs found
Solving the large discrepancy between inclusive and exclusive measurements of the reaction cross section at astrophysical energies
A solution of the large discrepancy existing between inclusive and exclusive
measurements of the reaction
cross section at MeV is evaluated. This problem has profound
astrophysical relevance for this reaction is of great interest in Big-Bang and
r-process nucleosynthesis. By means of a novel technique, a comprehensive study
of all existing cross section
data is carried out, setting up a consistent picture in which all the inclusive
measurements provide the reliable value of the cross section. New unambiguous
signatures of the strong branch pattern non-uniformities, near the threshold of
higher excited levels, are presented and their possible
origin, in terms of the cluster structure of the involved excited states of
and nuclei, is discussed.Comment: 5 pages, 4 figures, 1 tabl
EuroGammaS gamma characterisation system for ELI-NP-GBS: The nuclear resonance scattering technique
A Gamma Beam Characterisation System has been designed by the EuroGammaS association for thecommissioning and development of the Extreme Light Infrastructure-Nuclear Physics Gamma Beam System(ELI-NP-GBS) to be installed in Magurele, Romania. The characterisation system consists of four elements: aCompton spectrometer, a sampling calorimeter, a nuclear resonant scattering spectrometer (NRSS) and a beamprofile imager. In this paper, the nuclear resonant scattering spectrometer system, designed to perform anabsolute energy calibration for the gamma beam, will be describe
Papillary thyroid microcarcinomas: a comparative study of the characteristics and risk factors at presentation in two cancer registries.
The Bare Astrophysical S(E) Factor of the 7Li(p, α)α Reaction
The astrophysically important 7Li(p, α)α reaction has been studied via the Trojan horse method in the energy range E = 10-400 keV. A new theoretical description, based on the distorted-wave Born approximation approach, allows one to extract information on the bare astrophysical S-factor, Sb(E), with Sb(0) = 55 ± 3 keV barns. The results are compared with direct experimental data leading to a model-independent value of the electron screening potential energy, Ue = 330 ± 40 eV, much higher than the adiabatic limit Uad = 175 eV
A proton-recoil track imaging system for fast neutrons: the RIPTIDE detector
Fast neutron detection is often based on the neutron-proton elastic
scattering reaction: the ionization caused by recoil protons in a hydrogenous
material constitutes the basic information for the design and development of a
class of neutron detectors. Although experimental techniques have continuously
improved, proton-recoil track imaging remains still at the frontier of
n-detection systems, due to the high photon sensitivity required. Several
state-of-the-art approaches for neutron tracking by using n-p single and double
scattering - referred to as Recoil Proton Track Imaging (RPTI) - can be found
in the literature. So far, they have showed limits in terms of detection
efficiency, complexity, cost, and implementation. In order to address some of
these deficiencies, we have proposed RIPTIDE a novel recoil-proton track
imaging detector in which the light output produced by a fast scintillator is
used to perform a complete reconstruction in space and time of the interaction
events. The proposed idea is viable thanks to the dramatic advances in low
noise and single photon counting achieved in the last decade by new scientific
CMOS cameras as well as pixel sensors, like Timepix or MIMOSIS. In this
contribution, we report the advances on the RIPTIDE concept: Geant4 Monte Carlo
simulations, light collection tests as well as state-of-the-art approach to
image readout, processing and fast analysis.Comment: proceeding of the 23rd International Workshop on Radiation Imaging
Detectors, IWoRID 2022, 26-30 June 2022, Riva del Garda (TN), Ital
Probing Nuclear forces beyond the drip-line using the mirror nuclei N and F
Radioactive beams of O and O were used to populate the resonant
states 1/2, 5/2 and in the unbound F and F
nuclei respectively by means of proton elastic scattering reactions in inverse
kinematics. Based on their large proton spectroscopic factor values, the
resonant states in F can be viewed as a core of O plus a proton
in the 2s or 1d shell and a neutron in 1p. Experimental
energies were used to derive the strength of the 2s-1p and
1d-1p proton-neutron interactions. It is found that the former
changes by 40% compared with the mirror nucleus N, and the second by
10%. This apparent symmetry breaking of the nuclear force between mirror nuclei
finds explanation in the role of the large coupling to the continuum for the
states built on an proton configuration.Comment: 6 pages, 3 figures, 2 tables, accepted for publication as a regular
article in Physical Review
CaloCube: a novel calorimeter for high-energy cosmic rays in space
In order to extend the direct observation of high-energy cosmic rays up to
the PeV region, highly performing calorimeters with large geometrical
acceptance and high energy resolution are required. Within the constraint of
the total mass of the apparatus, crucial for a space mission, the calorimeters
must be optimized with respect to their geometrical acceptance, granularity and
absorption depth. CaloCube is a homogeneous calorimeter with cubic geometry, to
maximise the acceptance being sensitive to particles from every direction in
space; granularity is obtained by relying on small cubic scintillating crystals
as active elements. Different scintillating materials have been studied. The
crystal sizes and spacing among them have been optimized with respect to the
energy resolution. A prototype, based on CsI(Tl) cubic crystals, has been
constructed and tested with particle beams. Some results of tests with
different beams at CERN are presented.Comment: Seven pages, seven pictures. Proceedings of INSTR17 Novosibirs
Halo effects on fusion cross section in 4,6He+64Zn collision around and below the Coulomb barrier
The structure of the halo nuclei is expected to influence the fusion mechanism at energies around and below the Coulomb barrier. Here new data of 4He+64Zn at sub-barrier energies are presented which cover the same energy region of previous measurements of 6He+64Zn. The fusion cross section was measured by using an activation technique where the radioactive evaporation residues produced in the reaction were identified by the X-ray emission which follows their electron capture decay. By comparing the two system, we observe an enhancement on the fusion cross section in the reaction induced by 6He, at energy below the Coulomb barrier. It is shown that this enhancement seems to be due to static properties of halo 2n 6He nucleus
Quasielastic backscattering and barrier distributions for the 6, 7Li + 64Zn systems
Excitation functions of quasielastic scattering at backward angles were measured for the weakly bound 6Li and 7Li projectiles on a 64Zn target at energies around the Coulomb barrier. The corresponding barrier distributions were derived from the experimental cross sections. The experimental data were analyzed within the coupled-channel model using a double-folding potential as the bare potential. Inelastic excitations of the target, the 7Li first excited state, and 6Li, 7Li resonant state(s), corresponding to sequential breakup, were included in the calculations. The comparison between the data and coupled-channel predictions shows that the effects of channels not included in the calculations, such as direct breakup and transfers, are much larger for 6Li than for 7Li
Measuring total reaction cross-sections at energies near the coulomb barrier by the active target method
An experimental technique is described that is able to measure reaction cross-sections at energies around the Coulomb barrier by using low intensity beams and a Si detector as an active target. Set-up optimization was carefully investigated in terms of collimation, detector efficiency and pile-up rejection. The method has been tested by measuring the total reaction cross-section sigma(R)(E) for the (7)Li + (28)Si system in the energy range of E(lab) = 12-16 MeV. The deduced excitation function sigma(R)(E) agrees with the data obtained in a previous experiment. The presented technique can also be applied in order to determine total reaction cross-sections for low intensity radioactive beams at energies around the Coulomb barrier. (C) 2009 Elsevier B.V. All rights reserved. Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipmen
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