New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4
π
instrument. AGATA is a high-resolution
γ
-ray spectrometer, solely built from ...highly segmented high-purity Ge detectors, capable of measuring
γ
rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual
γ
-ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.
We present
12
C+
12
C direct fusion measurements with STELLA UKFATIMA, that reach into the region of astrophysics interest relevant to massive stars (
M
⊙
≈ 25) using self-supporting thin rotating ...carbon foils 1. We demonstrate that detecting gammas and light charged particles in coincidence with nanosecond timing is key for effective background reduction achieving reliable measurements in the sub-nanobarn range. We give details about core developments of the detection apparatus as well as the coincidence-analysis procedure of low count statistics. The present data largely follows the phenomenological hindrance interpolation and shows indication for resonant behaviour at the lowest energy explored.
Among the reactions driving stellar evolution during carbon burning, 12C + 12C fusion provides the key ingredients. This system reveals many resonances, but also regions with suppressed fusion ...cross-sections. The reaction was recently measured by the STELLA collaboration utilizing the gammaparticle coincidence technique for precise cross-section measurements reaching down to the Gamow window of massive stars. From the experimental data, reaction rates were determined by approximating a hindrance parametrization and by adding on top a resonance at the lowest measured energy. The impact of these reaction rates on the evolution of massive stars was explored with models of 12 and 25 M⊙ using the stellar evolution code GENEC, and a detailed study of the resulting nucleosynthesis with a 1454 elements network was performed. The sensitivity of the STELLA experimental cross-sections on the temperature range for C-burning for the stellar models studied were presented. The final abundances and their impacts on stellar evolution were discussed.
A first performance test of the Coulomb excitation multipolarimetry (
Coulex-multipolarimetry
) method is presented. It is based on a
85
Br
π
p
3
/
2
→
π
p
1
/
2
spin-flip experiment performed as ...part of the PreSPEC-AGATA campaign at the GSI Helmholtzzentrum für Schwerionenforschung (GSI). Via determination of background levels around the expected
85
Br
excitations as well as measured
197
Au
excitations, an upper limit for the
M
1 transition strength of the
1
/
2
1
-
→
3
/
2
g.s.
-
transition in
85
Br
and a lower beam time limit for upcoming experimental campaigns utilizing
Coulex-multipolarimetry
have been inferred. The impact of the use of AGATA in its anticipated
1
π
configuration on these estimates is deduced via
Geant4
simulations.
The Rare ISotopes INvestigation at GSI project combines the former EUROBALL Ge-Cluster detectors, the MINIBALL Ge detectors, BaF
2-HECTOR detectors, and the fragment separator at GSI for ...high-resolution in-beam
γ
-ray spectroscopy measurements with radioactive beams. These secondary beams produced at relativistic energies are used for Coulomb excitation or secondary fragmentation experiments in order to explore the nuclear structure of the projectiles or projectile like nuclei by measuring de-excitation photons. The newly designed detector array is described and the performance characteristics are given. Moreover, particularities of the experimental technique are discussed.
Shape evolution and magnetic rotation in 141Nd Zerrouki, T.; Petrache, C. M.; Leguillon, R. ...
The European physical journal. A, Hadrons and nuclei,
04/2015, Letnik:
51, Številka:
4
Journal Article
Recenzirano
The high-spin states in
141
Nd were investigated using the
96
Zr(
48
Ca, 3n) reaction and the EUROBALL array. The level scheme has been extended up to an excitation energy of around 16MeV and spin ...81/2. Two new bands of dipole transitions and three bands presumably of quadrupole transitions were identified and their connections to low-lying states were established. Cranked Nilsson-Strutinsky and tilted axis cranking calculations are combined in the interpretation of the observed dipole bands. The high-spin bands with assigned quadrupole transitions are interpreted as triaxial bands, while the dipole bands appear in the calculations to exhibit a shape evolution from low-deformation triaxial to spherical shape. They can be classified as magnetic rotation, with transition probabilities that show the characteristic decrease with angular momentum caused by the shears mechanism.
The Clover: a new generation of composite Ge detectors Duchêne, G.; Beck, F.A.; Twin, P.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/1999, Letnik:
432, Številka:
1
Journal Article
Recenzirano
This paper presents the characteristics of a new generation of composite germanium detectors: the Clover detector. Its development was based on simulation calculations performed with the code GEANT3. ...An extensive study of its main characteristics involving the photopeak detection efficiency, the energy resolution and the timing performed with sources and in-beam experiments have been measured. A simple Doppler broadening correction procedure is proposed to improve the in-beam energy resolution of the Clover detector. An other important property, the sensitivity to the linear polarisation of γ-rays has been measured. The performances obtained with the associated BGO suppression shield are also reported. All these results compare very well with the initial simulation calculations.
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