Heine, Marcel (2015)
Measurement of (n,γ)-Rates of Light Neutron-Rich Nuclei for the r-Process Nucleosynthesis.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Exclusive neutron capture cross sections of 17C and associated stellar reaction rates have been derived from Coulomb dissociation of 18C using the R3B-LAND setup at GSI in Darmstadt (Germany). The secondary beam of relativistic 18C at approximately 430 AMeV was generated by fragmentation of primary 40Ar on a beryllium target. In the FRagment Separator (FRS) the nuclei of interest were selected and subsequently guided to the experimental setup at Cave C. There the ions were excited electromagnetically in the electric field of lead target nuclei and the de-excitation process was detected with the R3B-LAND setup. All reaction products of the one-neutron evaporation channel including gammas from de-exciting states of fragments were measured and the invariant mass was reconstructed. A similar measurement of 17C Coulomb dissociation served as a benchmark to validate the accuracy of the present results with respect to previously published data. The measured relative energy spectra of 18C Coulomb dissociation to the ground state of 17C as well as the first and second excited state in 17C qualitatively match theoretical calculations of the Coulomb- dissociation process in an independent-particle model. In particular, the shapes of experimental data are reproduced. The measured spectroscopic factors were compared to an exclusive one-neutron knockout measurement on 18C, which is consistent within the respective uncertainties. The energy differential cross sections were converted into photo-absorption cross sections 18C(γ,n)17C with virtual-photon theory. Subsequently, exclusive neutron-capture cross sections 17C(n,γ)18C to the ground state were derived using the detailed-balance theorem. The neutron-capture cross sections were used to calculate stellar reaction rates, where the neutron velocities follow a Maxwell-Boltzmann distribution. The results were compared to thermonuclear reaction rates from a statistical Hauser-Feshbach model (HF). The uncertainty of the experimental results is at maximum around 60% at T9 = 1 GK for neutron capture in the ground state of 17C. This is accompanied by an uncertainty of a factor of ten in the HF calculation.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2015 | ||||
Autor(en): | Heine, Marcel | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Measurement of (n,γ)-Rates of Light Neutron-Rich Nuclei for the r-Process Nucleosynthesis | ||||
Sprache: | Englisch | ||||
Referenten: | Aumann, Prof., Dr. Thomas ; Pietralla, Prof. Dr. Norbert | ||||
Publikationsjahr: | 12 Januar 2015 | ||||
Datum der mündlichen Prüfung: | 9 Juli 2014 | ||||
URL / URN: | http://tuprints.ulb.tu-darmstadt.de/4343 | ||||
Kurzbeschreibung (Abstract): | Exclusive neutron capture cross sections of 17C and associated stellar reaction rates have been derived from Coulomb dissociation of 18C using the R3B-LAND setup at GSI in Darmstadt (Germany). The secondary beam of relativistic 18C at approximately 430 AMeV was generated by fragmentation of primary 40Ar on a beryllium target. In the FRagment Separator (FRS) the nuclei of interest were selected and subsequently guided to the experimental setup at Cave C. There the ions were excited electromagnetically in the electric field of lead target nuclei and the de-excitation process was detected with the R3B-LAND setup. All reaction products of the one-neutron evaporation channel including gammas from de-exciting states of fragments were measured and the invariant mass was reconstructed. A similar measurement of 17C Coulomb dissociation served as a benchmark to validate the accuracy of the present results with respect to previously published data. The measured relative energy spectra of 18C Coulomb dissociation to the ground state of 17C as well as the first and second excited state in 17C qualitatively match theoretical calculations of the Coulomb- dissociation process in an independent-particle model. In particular, the shapes of experimental data are reproduced. The measured spectroscopic factors were compared to an exclusive one-neutron knockout measurement on 18C, which is consistent within the respective uncertainties. The energy differential cross sections were converted into photo-absorption cross sections 18C(γ,n)17C with virtual-photon theory. Subsequently, exclusive neutron-capture cross sections 17C(n,γ)18C to the ground state were derived using the detailed-balance theorem. The neutron-capture cross sections were used to calculate stellar reaction rates, where the neutron velocities follow a Maxwell-Boltzmann distribution. The results were compared to thermonuclear reaction rates from a statistical Hauser-Feshbach model (HF). The uncertainty of the experimental results is at maximum around 60% at T9 = 1 GK for neutron capture in the ground state of 17C. This is accompanied by an uncertainty of a factor of ten in the HF calculation. |
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URN: | urn:nbn:de:tuda-tuprints-43433 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik | ||||
Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik > Institut für Kernphysik 05 Fachbereich Physik |
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Hinterlegungsdatum: | 18 Jan 2015 20:55 | ||||
Letzte Änderung: | 18 Jan 2015 20:55 | ||||
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Referenten: | Aumann, Prof., Dr. Thomas ; Pietralla, Prof. Dr. Norbert | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 9 Juli 2014 | ||||
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