The Electron-Gamma Coincidence Setup DAGOBERT

Abstract

The QCLAM electron spectrometer at the S-DALINAC electron accelerator at Technische Universit\"at Darmstadt has been extended by the DAGOBERT $\gamma$-detector array consisting of fast timing and high efficiency LaBr$_3$:Ce detectors to perform electron-gamma coincidence measurements. The functionality of the setup and data acquisition system was demonstrated in a commissioning measurement on $^{12}\textrm{C}$ observing the $4.44\,$MeV and $15.11\,$MeV states. A medium-heavy nucleus, $^{96}\textrm{Ru}$, has been studied for the first time up to excitation energies of $15\,$MeV using the $(e,e'\gamma)$ reaction. In particular, the angular distribution of the $2_1^+$ state and the $\gamma$-decay branching ratios of the mixed-symmetric $2_3^+$ state were observed. DAGOBERT@QCLAM is a new and worldwide unique setup for nuclear structure studies of excitation and decay using purely electromagnetic probes, with a significantly improved sensitivity compared to previous experiments.