Relatore
Sig.
Christian Stahl
(IKP, TU Darmstadt)
Descrizione
The Doppler-shift attenuation method (DSAM) is a well-established technique for the determination of sub-picosecond nuclear level lifetimes. It is based on analyzing the characteristic shape of Doppler-broadened photo-peaks from nuclear transitions observed at specific observation angles in in-flight γ-ray spectroscopy experiments, when the de-excitation of a nuclear level occurs while the emitting nucleus is being decelerated in a thick target.
We have extended the method in order to exploit the possibilities arising from state-of-the-art position sensitive HPGe detector arrays by analyzing the Doppler-broadened peaks not only as a function of the Doppler-shifted γ-ray energy, but also as a continuous function of the polar angle of γ-ray detection with respect to the incident beam direction. This approach significantly boosts the sensitivity and applicability of the method. The corresponding two-dimensional fit algorithm in the energy – polar detection angle (Eγ, θγ) space is also applicable to conventional HPGe detector arrays without intrinsic position-sensitivity. We have furthermore extended this new technique to experiments with relativistic ion beams, where we analyze Doppler-corrected, two-dimensional γ-ray spectra in the (Eγ, θγ) space without stopping the beam ions in the target. This is especially useful for experiments with radioactive and/or cocktail beams, because it avoids the accumulation of radioactivity at the target position and makes ion identification behind the reaction target possible. With this “differential” DSAM technique, a second sensitivity region for level lifetimes in the range of 100ns arises from geometric effects.
Autore principale
Sig.
Christian Stahl
(IKP, TU Darmstadt)
Coautore
Sig.
Marc Lettmann
(IKP, TU Darmstadt)
Prof.
Norbert Pietralla
(TU Darmstadt)
