Speaker
Solveig Hyldegaard
(Department of Physics and Astronomy, University of Aarhus)
Description
Experimental studies of the 12C nucleus are important to both nuclear
theory and astrophysics. Improved knowledge of states in 12C is
necessary for our understanding of the triple alpha reaction in
stars. Especially the Hoyle state at just 0.38 MeV above the triple
alpha threshold is vital for this process, but also a predicted 2+
state at 1.7 MeV above the triple alpha threshold in 12C has been
included in the NACRE reaction rate calculations, and its existence
needs to be verified experimentally.
The structure of the 12C nucleus is not fully
understood. Some properties are well described by cluster models and
others by mean field theory. New ab-initio calculations have been
published and the results are promising giving good agreement with
experimental data in the literature.
In a new experiment at KVI in Groningen, the Netherlands, 12C was
populated in beta-decay of 12B and 12N. Beams of 12B and 12N ions were
implanted in a 48 times 48 strip detector (DSSSD) and let
decay. Because of the segmentation of the DSSSD into very small pixels
the background of beta particles is significantly reduced and
essentially confined to low energies. The implanted ions and emitted
alpha particles are stopped in one pixel of the detector so very
precise absolute branching ratios and decay spectra can be
obtained. Measurements at very low energies are possible because
detector deadlayer effects are avoided in the implantation method, so
new information about the Hoyle state can be achieved. Results of the
analysis will be presented including new energy spectra, branching
ratios and comparisons to earlier work and theory.
Author
Solveig Hyldegaard
(Department of Physics and Astronomy, University of Aarhus)
