New methods for the γ-ray spectroscopy with position-sensitive detector systems

• Main Author: Stahl, Christian
• Format: Others
• Language: German; en
• Published: 2015
• Online Access: http://tuprints.ulb.tu-darmstadt.de/4955/13/Thesis_Stahl_online.pdf; Stahl, Christian <http://tuprints.ulb.tu-darmstadt.de/view/person/Stahl=3AChristian=3A=3A.html> : New methods for the γ-ray spectroscopy with position-sensitive detector systems. Technische Universität, Darmstadt [Ph.D. Thesis], (2015)

This doctoral thesis describes two new experimental techniques for in-beam γ-ray spectroscopy that exploit the position-sensitivity of the latest generation of high-purity Germanium detectors, so-called γ-ray tracking detectors. These detectors allow to determine the interaction points of γ-ray quanta within the detector material with unrivaled accuracy. The continuous-angle Doppler-Shift Attenuation Method extends the well-known DSA Method for the measurement of nuclear level lifetimes by providing a complete description of the observed characteristic, Doppler-broadened γ-ray lineshapes as a function of the energy and detection polar angle of the γ-rays. The method’s power is demonstrated by the precise lifetime determination of the 2+1 and 3−1 state of 136 Xe from data taken with the AGATA demonstrator. The method of Coulex-Multipolarimetry with relativistic heavy-ion beams allows for the measurement of electromagnetic multipole-mixing ratios of γ-radiation. The core of the method is the determination of velocity-dependent Coulomb excitation cross sections at two different relativistic ion energies. These can be determined in one single measurement by distinguishing excitations in two spatially separated targets via different observed Doppler-shifts that can be reliably separated in γ-ray tracking detectors. This method was employed during the PreSPEC-AGATA campaign in the experiment S426 at GSI’s FRS in 2014.