Browsing by Author "Tatischeff, V."

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De-excitation nuclear gamma-ray line emission from low-energy cosmic rays in the inner galaxy
(Institute of Physics Publishing, 2013) Benhabiles-Mezhoud, H.; Kiener, J.; Tatischeff, V.; Strong, A. W.
Recent observations of high ionization rates of molecular hydrogen in diffuse interstellar clouds point to a distinct low-energy cosmic-ray component. Supposing that this component is made of nuclei, two models for the origin of such particles are explored and low-energy cosmic-ray spectra are calculated, which, added to the standard cosmic-ray spectra, produce the observed ionization rates. The clearest evidence of the presence of such low-energy nuclei between a few MeV nucleon-1 and several hundred MeV nucleon-1 in the interstellar medium would be a detection of nuclear γ -ray line emission in the range Eγ ∼ 0.1-10 MeV, which is strongly produced in their collisions with the interstellar gas and dust. Using a recent γ -ray cross section compilation for nuclear collisions, γ -ray line emission spectra are calculated alongside the high-energy γ -ray emission due to π0 decay, the latter providing normalization of the absolute fluxes by comparison with Fermi-LAT observations of the diffuse emission above Eγ = 0.1 GeV. Our predicted fluxes of strong nuclear γ -ray lines from the inner Galaxy are well below the detection sensitivities of the International Gamma-Ray Astrophysics Laboratory, but a detection, especially of the 4.4MeV line, seems possible with new-generation γ -ray telescopes based on available technology.We also predict strong γ -ray continuum emission in the 1-8 MeV range, which, in a large part of our model space for low-energy cosmic rays, considerably exceeds the estimated instrument sensitivities of future telescopes
γ -ray emission in α -particle interactions with C, Mg, Si, and Fe at Eα=50-90 MeV
(American Physical Society, 2021) Kiener, J.; Bundesmann, J.; Deloncle I., I.; Denker, A.; Tatischeff, V.; Gostojic, A.; Hamadache, C.; Röhrich, J.; Benhabiles, H.; Bourgaoub, I.; Coc, A.; Hammache, F.; Mezhoud, R.; Peyré, J.
Nuclear deexcitation lines are regularly observed in the γ-ray emission spectra of strong solar flares. The most prominent lines are produced by interactions of protons and α particles, accelerated up to hundreds of MeV, with abundant nuclei of the solar atmosphere. Analysis and interpretation of these lines, which carry valuable information on the solar flare properties, need cross-section data for the γ-ray line emission in these interactions for a wide particle energy range. To this purpose, we measured the γ-ray emission in interactions of α-particle beams of Eα=50-90 MeV with target foils of C, Mg, Si, and Fe at the center for proton therapy of the Helmholtz-Zentrum Berlin. Setups of three high-purity Ge detectors and one LaBr3:Ce detector have been employed to detect the γ rays in two experiment campaigns. Relatively large distances of the detectors from the target and pulsed beams with sub-ns-wide pulses allowed the separation of beam-induced prompt γ-ray emission from the targets from other γ rays and neutron-induced background. γ-ray production cross sections for about 60 deexcitation lines from excited target nuclei or reaction products have been determined. For the strongest deexcitation lines from the major target isotopes, C12, Mg24, Si28, Fe56, there are now measured cross-section data from reaction threshold to Eα=90 MeV that can be directly used for astrophysical applications like solar flares. Comparison of the results with a cross-section compilation for strong γ-ray lines in solar flare emissions and the predictions of the talys nuclear reaction code were done. They underline the importance of cross-section determinations at accelerator laboratories for the establishment of an accurate cross-section data base in a wide projectile energy range
γ-ray production by proton and α-particle induced reactions on C12, O16, Mg24, and Fe
(Physical Review C - Nuclear Physics, 2007) Belhout, A.; Kiener, J.; Coc, A.; Duprat, J.; Engrand, C.; Fitoussi, C.; Gounelle, M.; Lefebvre-Schuhl, A.; De Séréville, N.; Tatischeff, V.; Thibaud, J.-P.; Chabot, M.; Hammache, F.; Benhabiles-Mezhoud, H.
γ-ray production cross sections for proton and α-particle interactions with C12, O16, Mg24, and Fe have been measured in the energy range 5-25 MeV with proton beams and 5-40 MeV with α-particle beams. Isotopically pure foils of Mg24 and foils of natural isotopical composition of C, MgO, and Fe have been used. γ-ray angular distributions were obtained with five high-purity Ge detectors with bismuth germanate Compton shields placed at angles of 45° to 157.5°. Cross sections for more than 50 different γ-ray transitions were extracted, and for many of them no data have been published before. Comparison of present data with data available in the literature shows mostly good to excellent agreement. In addition to the production cross sections, high-statistics, low-background line shapes of the 4.438 MeV C12 γ ray from inelastic scattering off C12 and spallation of O16 were obtained. Comparison with nuclear reaction calculations shows that these data place interesting constraints on nuclear reaction models. © 2007 The American Physical Society