Elastic and inelastic scattering of 2.5 mev neutrons

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The effect of valence neutrons on spin-orbit splitting

We study the splitting of single-particle energies between spin-orbit partners (Is splitting) for the isotopic chains of some even-even closed shell nuclei in the Hartree-Fock-Bogolyubov framework. Z = 8, 20, 28 and 50 magic proton nuclei of stability valley and their even-even neighbours are selected and a limited systematic investigation is performed for the isotopic chains of C, O, Si, Ca, Ni, Sr, Sn, Te, and Ce isotopes. They are compared with existing data. The modification of proton spin-orbit partners energy splitting of those isotopes is investigated with valence neutron numbers extending to the neutron drip-line. Our calculation shows that the proton Is splitting in chosen nuclei becomes smaller with the increasing neutron number. This reduction is accounted for two different effects, namely, the effect of neutron diffuseness and tensor interaction. The neutron diffuseness values are also calculated for the nuclei under investigation. The deduced ls splitting reduction is compared for the nuclei with the same isospin number. The larger reduction is attributed to the tensor interaction assuming that the Is reduction due to the neutron surface thickness will be the same for the nuclei having the same neutron diffuseness parameter. The contribution from tensor interaction is mainly accounted for the interaction between the spin-orbit partner proton orbital and the neutron orbital having different angular momentum. Briefly, the effect of increased valence neutron number on proton effective single particle levels is discussed

Isomeric cross section ratio for the (n,2n) reaction on Sc-45 from 13.6 to 14.9 MeV

The isomeric cross section ratio sigma(m)/sigma(g) for the reaction Sc-45(n,2n) Sc-44(m,g) was measured in the neutron energy range of 13.6-14.9 MeV for six different neutron energies. The neutrons were produced by the H-3(d,n)He-4 reaction utilizing a SAMES T-400 neutron generator. Isomeric cross section ratios were determined by applying the method of least squares to the time behavior of the ground-state decay of isomeric pair. The absolute cross section for the formation of the metastable state was measured by the usual activation technique. The ground-state cross section was then obtained by using the absolute truss section of the metastable state and isomeric cross section ratio for each neutron energy. Experimental cross section values and isomeric cross section ratios were compared with those obtained by a statistical model calculation

Digital pulse-timing technique for the neutron detector array NEDA

International audienc

Design and Test of a High-speed Flash ADC Mezzanine Card for High-resolution and Timing Performance in Nuclear Structure Experiments

International audienceThis board will be part of the upgrade for the new electronics for the EXOGAM2 (HP-Ge detector array) and NEDA (BC501A-based neutron detector array), therefore it was necessary to deal with the problem of providing a sampling card with high resolution for new gamma spectroscopy experiments while sampling at very high rates, with a broad bandwidth in order to preserve the shape for further analysis. Pulse shape analysis is of paramount importance in neutron detectors, such as NEDA, based on scintillators that are sensitive to γ-rays as well. High resolution and high speed are often two parameters which conform a trade-off and it is hard to achieve both simultaneously. The aforementioned constraints and the urge of building new sampling electronics to improve the signal analysis in nuclear physics experiments, led to the development of this FADC mezzanine This involves sampling rates up to 250 Msps preserving a high resolution of 11.3 effective bits in order to satisfy the experiment demands. In this work is described the design and the test bench proposed for a proper high speed ADC characterization system and the results obtained up to now