331 research outputs found
HEAVY RESIDUE PRODUCTION IN HEAVY ION INDUCED REACTIONS ON 124 Sn BETWEEN 10 AND 84 MeV/NUCLEON
Heavy residue velocity spectra of 12C, 20Ne, 40Ar + 124Sn reactions induced in the 10-84 MeV/nucleon energy range have been measured between 0° and 10°. Asymmetric incomplete fusion process calculations are in agreement with the data
Thermal Bremsstrahlung photons probing the nuclear caloric curve
Hard-photon (E 30 MeV) emission from second-chance
nucleon-nucleon Bremsstrahlung collisions in intermediate energy heavy-ion
reactions is studied employing a realistic thermal model. Photon spectra and
yields measured in several nucleus-nucleus reactions are consistent with an
emission from hot nuclear systems with temperatures 4 - 7 MeV. The
corresponding caloric curve in the region of excitation energies
3{\it A} - 8{\it A} MeV shows lower values of than
those expected for a Fermi fluid.Comment: 13 pages, 3 figures. To appear in Physics Letters
Prompt reactivity determination in a subcritical assembly through the response to a Dirac pulse
The full understanding of the kinetics of a subcritical assembly is a key issue for its online reactivity control. Point kinetics is not sufficient to determine the prompt reactivity of a subcritical assembly through the response to a dirac pulse, in particular in the cases of a large reflector, a small reactor, or a large subcriticality.Taking into account the distribution of intergeneration times, which appears as a robust characteristic of each type of reactor, helps to understand this behaviour.Eventually, a method is proposed for the determination of the prompt reactivity. It provides a decrease rate function depending on the prompt multiplication coefficient Keffp. Fitting a measured decrease rate with this function, calculated once for the reactor, gives the true value of keffp. The robustness of the method is tested. (Elsevier
HARD PHOTON PRODUCTION IN NUCLEUS-NUCLEUS COLLISIONS AT 30 MeV/u AND 44 MeV/u
Doubly differential cross-sections for Bremsstrahlung production have been measured in the reactions 40Ar + 197Au at 30 MeV/u and 86Kr +12C, AgNat and 197Au at 44 MeV/u. A qualitative analysis of the characteristics of the Îł-ray emission suggests strongly that the initial proton-neutron collisions are the main source of nuclear Bremsstrahlung
Proton-proton bremsstrahlung below and above pion-threshold: the influence of the -isobar
The proton-proton bremsstrahlung is investigated within a coupled-channel
model with the degree of freedom. The model is consistent with the
scattering up to 1 GeV and the vertex determined in the
study of pion photoproduction reactions. It is found that the
excitation can significantly improve the agreements with the at MeV. Predictions at and MeV are
presented for future experimental tests.Comment: 26 pages Revtex, 12 figures are available from the authors upon
request ([email protected]
Evidence for Thermal Equilibration in Multifragmentation Reactions probed with Bremsstrahlung Photons
The production of nuclear bremsstrahlung photons (E 30 MeV) has
been studied in inclusive and exclusive measurements in four heavy-ion
reactions at 60{\it A} MeV. The measured photon spectra, angular distributions
and multiplicities indicate that a significant part of the hard-photons are
emitted in secondary nucleon-nucleon collisions from a thermally equilibrated
system. The observation of the thermal component in multi-fragment
Ar+Au reactions suggests that the breakup of the thermalized
source produced in this system occurs on a rather long time-scale.Comment: Revised version, accepted for publication in Physical Review Letters.
4 pages, 4 fig
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