Browsing by Author "Hammache, F."

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    Effectiveness of using a magnetic spectrograph with the Trojan Horse method
    (IOP Publishing, 2018) Manwell, S.; Parikh, A.; Chen, A. A.; De Sereville, N.; Adsley, P.; Irvine, D.; Hammache, F.; Stefan, I.; Longland, R. F.; Tomlinson, J.; Morfuace, P.; Le Crom, B.
    The Trojan Horse method relies on performing reactions in a specific kinematic phase space that maximizes contributions of a quasi-free reaction mechanism. The hallmark of this method is that the incident particle can be accelerated to high enough energies to overcome the Coulomb barrier of the target, but once inside the target nucleus the relative motion of the clustered nuclei allows the reaction of interest to proceed at energies below this Coulomb Barrier. This method allows the experimentalist to probe reactions that have significance in astrophysics at low reaction energies that would otherwise be impossible due to the vanishing cross section. Traditionally the Trojan Horse method has been applied with the use of silicon detectors to observe the reaction products. In this study we apply the Trojan Horse method to a well studied reaction to examine the potential benefits of using a splitpole magnetic spectrograph to detect one of the reaction products. We have measure the three body 7Li(d,αn)α reaction to constrain the energy 7Li(d,α)α cross section. Measurements were first made using two silicon detectors, and then by replacing one detector with the magnetic spectrograph. The experimental design, limitations, and early results are discussed.
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    High-resolution study of levels in the astrophysically important nucleus 26Mg and resulting updated level assignments
    (American Physical Society, 2018) Adsley, P.; Brummer, J. W.; Faestermann, T.; Faestermann, T.; Fox, S. P.; Hammache, F.; Hertenberger, R.; Meyer, A.; Neveling, R.; Seiler, D.; De Sereville, N.; Wirth, H. F.
    Background: The 22Ne(α,n)25Mg reaction is an important source of neutrons for the s-process. Direct measurement of this reaction and the competing 22Ne(α,γ)26Mg reaction are challenging due to the gaseous nature of both reactants, the low cross section and the experimental challenges of detecting neutrons and high-energy γ rays. Detailed knowledge of the resonance properties enables the rates to be constrained for s-process models. Purpose: Previous experimental studies have demonstrated a lack of agreement in both the number and excitation energy of levels in 26Mg. To try to resolve the disagreement between different experiments, proton and deuteron inelastic scattering from 26Mg have been used to identify excited states. Method: Proton and deuteron beams from the tandem accelerator at the Maier-Leibnitz Laboratorium at Garching, Munich, were incident upon enriched 26MgO targets. Scattered particles were momentum-analyzed in the Q3D magnetic spectrograph and detected at the focal plane. Results: Reassignments of states around Ex=10.8–10.83 MeV in 26Mg suggested in previous works have been confirmed. In addition, new states in 26Mg have been observed, two below and two above the neutron threshold. Up to six additional states above the neutron threshold may have been observed compared to experimental studies of neutron reactions on 25Mg, but some or all of these states may be due to 24Mg contamination in the target. Finally, inconsistencies between measured resonance strengths and some previously accepted Jπ assignments of excited 26Mg states have been noted. Conclusion: There are still a large number of nuclear properties in 26Mg that have yet to be determined and levels that are, at present, not included in calculations of the reaction rates. In addition, some inconsistencies between existing nuclear data exist that must be resolved in order for the reaction rates to be properly calculated.
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    Neutron-rich nuclei produced at zero degrees in damped collisions induced by a beam of ¹⁸O on a ²³⁸U target
    (Elsevier, 2018) Stefan, I.; Fornal, B.; Leoni, S.; Azaiez, F.; Portail, C.; Thomas, J. C.; Karpovi, A. V.; Ackermann, D.; Bednarczyk, P.; Blumenfeld, Y.; Calinescu, S.; Chbihi, A.; Ciemala, M.; Cieplicka-Orynczak, N.; Crespi, F. C. L.; Franchoo, S.; Hammache, F.; Iskr, L. W.; Jacquote, B.; Janssens, R. V. F.; Kamalou, O.; Lewitowicz, M.; Olivier, L.; Lukyanov, S. M.; Maccormick, M.; Maj, A.; Marini, P.; Matea, I; Naumenko, M. A.; De Oliveira Santos, F.; Petrone, C.; Penionzhkevich, Yu E.; Rotaru, F.; Savajols, H.; Sorline, O.; Stanoiu, M.; Szpak, B.; Tarasov, O. B.; Verney, D.
    Cross sections and corresponding momentum distributions have been measured for the first time at zero degrees for the exotic nuclei obtained from a beam of 18O at 8.5 MeV/A impinging on a 1 mg/cm2238U target. Sizable cross sections were found for the production of exotic species arising from the neutron transfer and proton removal from the projectile. Comparisons of experimental results with calculations based on deep-inelastic reaction models, taking into account the particle evaporation process, indicate that zero degree is a scattering angle at which the differential reaction cross section for production of exotic nuclei is at its maximum. This result is important in view of the new generation of zero degrees spectrometers under construction, such as the S3 separator at GANIL, for example.