arXiv subjects

D. Doré

Publications and source records attributed to D. Doré.

5 recordsLinked to original sources

arXiv2026

Results on $^{235}$U(n$_{\mathrm{th}}$,f) isotopic fission yields using prompt and delayed gamma rays at the FIPPS spectrometer of the ILL

We present preliminary results from a measurement campaign conducted with the FIPPS $γ$-ray spectrometer at the ILL using an active target made of $^{235}$U dissolved in a liquid scintillator. Prompt $γ$ rays were used to extract absolute, independent isotopic fission yields. We obtained yields for a selected set of well-produced even-even nuclei from the $^{235}$U(n$_{\mathrm{th}}$,f) reaction and compared them with JEFF-3.3 evaluated data. This included the doubly magic nucleus $^{132}$Sn, for which we observed a pronounced deficit (about a factor 7) with respect to JEFF-3.3. Using the FIFRELIN fission fragment de-excitation code, we interpreted this discrepancy as evidence that $^{132}$Sn is mainly produced in its ground state at scission or after neutron evaporation. Delayed $γ$ rays recorded in the same experiment were also analysed. No deviation was found in the beta decay of $^{132}$Sn compared to the nuclear database. However, an excess of about a 40% was found in the $β$ decay of $^{90}$Kr, which may originate from an overestimated ground-state feeding of $^{90}$Rb in the evaluated data.

nucl-ex↗

arXiv2026

Isotopic fission yields of ${}^{240}$Pu as a function of the excitation energy

Complete isotopic fission yields distributions of $^{240}$Pu have been measured as a function of the initial excitation energy. The $^{240}$Pu fissioning system was produced through a two-proton transfer reaction between a $^{238}$U beam and a $^{12}$C target. The reaction was measured in inverse kinematics at Coulomb barrier energies, allowing for the full distribution of fission fragments to be isotopically identified with the VAMOS++ Spectrometer. The excitation energy of the system was measured on an event-by-event basis by detecting the target-like recoil $^{10}$Be in a segmented silicon telescope. This manuscript reports on the evolution of the fission yields as a function of the excitation energy of the system between 8.2 to 11.9 MeV. The influence of the excitation energy is manifested in the damping of shell effects that feed the yields in the symmetry valley, as well as in a reduction of the neutron content of the fragments. This reduction, however, is observed only in the heavy fragment, while the neutron content of the light fragment remains unaffected. The comparison with previous measurements, models, and evaluations highlights the importance of correlated observables for improving fission models.

nucl-ex↗

arXiv2021

Stopping power of fission fragments in thin Mylar and nickel foils

The energy loss of heavy ions in thin Mylar and nickel foils was measured accurately using fission fragments from $^{239}Pu(n_{th},f)$, mass and energy separated by the Lohengrin separator at ILL. The detection setup, placed at the focal plane of the Lohengrin separator enabled to measure precisely the kinetic energy difference of selected fragments after passing through the sample. From these data, the stopping powers in Mylar and nickel layers were extracted and compared to calculations. Whereas large deviations are observed with SRIM-2013 for Mylar, fairly good agreements are obtained with the semi-empirical approach of Knyazheva et al. and the calculations contained within the DPASS database. In nickel, SRIM-2013 and Knyazheva model are in agreement with our data within about 10 %, while large deviations are observed with DPASS. We used our data to provide updated parameters for the Knyazheva et al. model and rescale DPASS database for nickel and Mylar.

nucl-ex↗

arXiv2013

Transfer reactions in inverse kinematics, an experimental approach for fission investigations

Inelastic and multi-nucleon transfer reactions between a $^{238}$U beam, accelerated at 6.14 MeV/u, and a $^{12}$C target were used for the production of neutron-rich, fissioning systems from U to Cm. A Si telescope, devoted to the detection of the target-like nuclei, provided a characterization of the fissioning systems in atomic and mass numbers, as well as in excitation energy. Cross-sections, angular and excitation-energy distributions were measured for the inelastic and transfer channels. Possible excitations of the target-like nuclei were experimentally investigated for the first time, by means of g -ray measurements. The decays from the first excited states of $^{12}$C, $^{11}$B and $^{10}$Be were observed with probabilities of 0.12 - 0.14, while no evidence for the population of higher-lying states was found. Moreover, the fission probabilities of $^{238}$U, $^{239}$Np and $^{240,241,242}$Pu and $^{244}$Cm were determined as a function of the excitation energy.

nucl-ex↗

arXiv2013

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.

astro-ph.IM↗