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First measurement of the O-18(p, alpha)N-15 cross section at astrophysical energies
La Cognata, M. ; Spitaleri, C. ; Mukhamedzhanov, A. ; Tribble, R. E. ; Al-Abdullah, T. ; Banu, A. ; Cherubini, S. ; Coc, A. ; Crucilla, V. ; Goldberg, V. ; Gulino, M. ; Irgaziev, B. ; Kiss, G. G. ; Lamia, L. ; Mrázek, Jaromír ; Pizzone, R. G. ; Puglia, S. M. R. ; Rapisarda, G. G. ; Romano, S. ; Sergi, M. L. ; Tabacaru, G. ; Trache, L. ; Trzaska, W. ; Tudisco, S. ; Tumino, A.
The O-18(p, alpha)N-15 reaction rate has been deduced by means of the Trojan horse method. For the first time the contribution of the 20 keV resonance has been directly evaluated, giving a value about 35% larger than the one in the literature. Moreover, the present approach has allowed to improve the accuracy by a factor 8.5, as it is based on the measured strength instead of spectroscopic measurements. The contribution of the 90 keV resonance has been also determined, which turned out to be of negligible importance to astrophysics.
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Indirect Approach To The H-2(d,p)H-3 Reaction Study
Sparta, R. ; Pizzone, R. G. ; Spitaleri, C. ; Aliotta, M. ; Burjan, Václav ; Cherubini, S. ; Crucilla, V. ; Gulino, M. ; Hons, Zdeněk ; Kiss, G. G. ; Kroha, Václav ; La Cognata, M. ; Lamia, L. ; McCleskey, M. ; Mrázek, Jaromír ; Puglia, S. M. R. ; Rapisarda, G. G. ; Romano, S. ; Sergi, M. L. ; Trache, L. ; Tumino, A.
In order to understand primordial and stellar nucleosynthesis, we have studied H-2(d,p)H-3 reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The H-2(d,p)H-3 reaction has been studied through the Trojan Horse Method applied to the three-body reaction H-2(He-3,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another H-2(d,p)H-3 THM measurements, where a different spectator particle was employed.
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Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Pizzone, R. G. ; Lamia, L. ; Bertulani, C. A. ; Mukhamedzhanov, A. ; Spitaleri, C. ; Blokhinstev, L. ; Burjan, Václav ; Cherubini, S. ; Hons, Zdeněk ; Kiss, G. G. ; Kroha, Václav ; La Cognata, M. ; Li, C. ; Mrázek, Jaromír ; Piskoř, Štěpán ; Puglia, S. M. R. ; Rapisarda, G. G. ; Romano, S. ; Sergi, M. L. ; Tumino, A.
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even sometimes impossible. In such cases the use of indirect methods can give a substantial help. The Trojan Horse Method (THM) is based on the quasi-free break-up of a nucleus, which can be described in terms of a cluster structure. In such applications the independence of THM results with different break-up schemes, was tested using the quasi free(3)He(Li-6,alpha alpha)H and He-3(Li-7,alpha alpha)H-2 reactions. Results were then compared with the direct behaviours obtained from available data as well as with the cross sections extracted from previous indirect investigations of the same binary reactions using a different nuclide as a Trojan Horse nucleus.
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High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
La Cognata, M. ; Spitaleri, C. ; Mukhamedzhanov, A. ; Banu, A. ; Cherubini, S. ; Coc, A. ; Crucilla, V. ; Goldberg, V. ; Gulino, M. ; Irgaziev, B. ; Kiss, G. G. ; Lamia, L. ; Mrázek, Jaromír ; Pizzone, R. G. ; Puglia, S. M. R. ; Rapisarda, G. G. ; Romano, S. ; Sergi, M. L. ; Tabacaru, G. ; Trache, L. ; Tribble, R. E. ; Trzaska, W. ; Tumino, A.
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy O-18(p, alpha) N-15 reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2(+) resonance. Since Gamma similar to 100 - 300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T similar to 0.510(9) K based over our new improved determination of its resonance parameters.
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Features of Nuclear Reactions with Light Weakly Bond Nuclei at Energy near the Coulomb Barrier
Skobelev, N. K. ; Penionzhkevich, Y. E. ; Kroha, Václav ; Burjan, Václav ; Hons, Zdeněk ; Mrázek, Jaromír ; Piskoř, Štěpán ; Šimečková, Eva ; Voskoboynik, E. I.
In the experiments carried out by ion beam He-6 of the cyclotron complex DRIBs (JINR) and He-3 beam cyclotron U-120M of the NPI, Czech Academy of Sciences have been investigated reaction Sc-45+He-3, He-6 and Au-197+He-3, He-6 in the energy range near the Coulomb barrier. It were obtained the experimental values of the cross sections for complete fusion reactions and direct reactions for formation of the isotopes Sc-43, Sc-44 and Sc-46 also Au-196 and Au-198 as a function of the bombarding He-3 and He-6 energy. Despite the low binding energy of He-3 and the positive Q-values leading to the formation of isotopes Sc-44 and Sc-46 also Au-196 and Au-198, the behavior of the excitation functions with the formation of these isotopes is different from the excitation functions for d, He-6.
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The activation of W and Zr by deuterons at energies up to 20 MeV
Šimečková, Eva ; Štefánik, Milan ; Bém, Pavel ; Mrázek, Jaromír ; Novák, Jan
The proton and deuteron induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, target and beam stoppers. In order to investigate the important nuclides, we have carried up the irradiation experiments with the variable-energy cyclotron U-120 M of the NPI CAS ež. The production cross sections of the nuclides 179,181,182m,182,183,184m,184,186Re and 187W from reaction on natural W were investigated by deuteron beams of 20 MeV energy. A part of preliminary results of deuteron activation of natural Zr is also shown. The stacked-foil technique was utilized. The comparison of present results to data of other authors and to predictions of evaluated data libraries is discussed.
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Proton and deuteron activation measurements at the NPI and future plans in SPIRAL2/NFS
Šimečková, Eva ; Bém, Pavel ; Mrázek, Jaromír ; Štefánik, Milan ; Běhal, Radomír ; Glagolev, Vadim
The proton- and deuteron-induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, target and beam stoppers as well as isotope production for medicine. In the present work, the deuteron-induced reaction cross sections on zinc were investigated by stacked-foil activation technique with deuteron beam of 20 MeV energy from the cyclotron U-120M of NPI CAS ež. Also the proton activation cross section measurement of iron is presented. The comparison of present results to data of other authors and to predictions of evaluated data libraries is discussed. The investigation shall continue for higher proton and deuteron energy interval 20-35 MeV at SPIRAL2/NFS facility using a charged particle irradiation chamber with pneumatic transport system to measure isotopes and isomers with half-lives in minutes-regions.
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Trojan horse method with neutrons induced reactions: The 17O(n,alpha)14C reaction
Guardo, G. L. ; Spitaleri, C. ; Lamia, L. ; Gulino, M. ; Tang, X. ; Bucher, B. ; Burjan, Václav ; Couder, M. ; Davies, P. ; deBoer, R. ; Fang, X. ; Kroha, Václav ; La Cognata, M. ; Ma, C. ; Mrázek, Jaromír ; Mukhamedzhanov, A. ; Notani, M. ; O'Brien, S. ; Pizzone, R. G. ; Rapisarda, G. G. ; Roberson, D. ; Sergi, M. L. ; Tan, W. ; Wiescher, M.
The experimental study of the 17O(n,alpha)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To over-come the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested.
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Studies of nuclei by means of nuclear orientation at low temperatures and in-beam spectroscopy
Vénos, Drahoslav ; Srnka, Dušan ; Zákoucký, Dalibor ; Honusek, Milan ; Mrázek, Jaromír ; van Geert, A. ; Severijns, N. ; Schuurmans, P. ; Vereecke, B. ; Versyck, S. ; Špalek, Antonín ; Bielčík, J. ; Slívová, Jana ; Adam, Jindřich
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