Coulomb dissociation of 31Cl and 32Ar - constraining the rp process

The subject of this thesis aimed at a better understanding of the spectacular X-ray
burst. The most likely astrophysical site is a very dense neutron star, which accretes
H/He-rich matter from a close companion. While 
The subject of this thesis aimed at a better understanding of the spectacular X-ray
burst. The most likely astrophysical site is a very dense neutron star, which accretes
H/He-rich matter from a close companion. While falling towards the neutron star, the
matter is heated up and a thermonuclear runaway is ignited. The exact description of
this process is dominated by the properties of a few proton-rich radioactive isotopes,
which have a low interaction probability, hence a high abundance.
The topic of this thesis was therefore an investigation of the short-lived, proton-rich
isotopes 31Cl and 32Ar. The Coulomb dissociation method is the modern technique of
choice. Excitations with energies up to 20 MeV can be induced by the Lorentz contracted
Coulomb field of a lead target. At the GSI Helmholtzzentrum für Schwerionenforschung
GmbH in Darmstadt, Germany, a Ar beam was accelerated to an energy of 825 AMeV
and fragmented in a beryllium target. The fragment separator was used to select the
desired isotopes with a remaining energy of 650 AMeV. They were subsequently directed
onto a 208 Pb target in the ALAND/LAND setup. The measurement was performed in
inverse kinematics. All reaction products were detected and inclusive and exclusive measurements of the respective Coulomb dissociation cross sections were possible.
During the analysis of the experiment, it was possible to extract the energy-differential
excitation spectrum of 31Cl, and to constrain astrophysically important parameters for
the time-reversed 30S(p,γ)31Cl reaction. A single resonance at 0.443(37) MeV dominates
the stellar reaction rate, which was also deduced and compared to previous calculations.
The integrated Coulomb dissociation cross section of this resonance was determined to
15(6) mb. The astrophysically important one- and two-proton emission channels were
analyzed for 32Ar and energy-differential excitation spectra could be derived. The integrated Coulomb dissociation cross section for two proton emission were determined
with two different techniques. The inclusive measurement yields a cross section of
214(29stat)(20sys) mb, whereas the exclusive reconstruction results in a cross section
of 226(14stat)(23sys) mb. Both results are in very good agreement. The Coulomb dissociation cross section for the one-proton emission channel is extracted solely from the
exclusive measurement and is 54(8stat)(6sys) mb.

Furthermore, the development of the Low Energy Neutron detector Array (LENA) for
the upcoming R3B setup is described. The detector will be utilized in charge-exchange
reactions to detect the low-energy recoil neutrons from (p,n)-type reactions. These reaction studies are of particular importance in the astrophysical context and can be used to
constrain half lifes under stellar conditions. In the frame of this work, prototypes of the detector were built and successfully commissioned in several international laboratories.
The analysis was supported by detailed simulations of the detection characteristics.
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Metadaten
Author:Christoph Langer
URN:urn:nbn:de:hebis:30:3-247944
Referee:René Reifarth, Thomas Aumann
Advisor:René Reifarth
Document Type:Doctoral Thesis
Language:English
Date of Publication (online):2012/07/05
Year of first Publication:2012
Publishing Institution:Univ.-Bibliothek Frankfurt am Main
Granting Institution:Johann Wolfgang Goethe-Univ.
Date of final exam:2012/05/02
Release Date:2012/05/15
Pagenumber:I, 141
HeBIS PPN:30099799X
Institutes:Physik
Dewey Decimal Classification:530 Physik
Sammlungen:Universitätspublikationen
Licence (German):License Logo Veröffentlichungsvertrag für Publikationen

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