Speaker
Description
The all-electromagnetic $(e,e^\prime\gamma)$ reaction provides an exclusive access to nuclear properties. It had first been used for nuclear structure measurements in the 1980s [1]. Since then, very few experiments were based on this reaction. One of its challenges lies in the coincident bremsstrahlung, which - apart from the angular distribution - cannot be distinguished from the $\gamma$-radiation of nuclei decaying to their ground state after excitation by inelastic electron scattering.
Over the last years, first successful $(e,e^\prime\gamma)$ measurements with unprecedented performance were conducted at the S-DALINAC (Superconducting DArmstadt electron LINear ACcelerator) of Technische Universität Darmstadt, Germany. The resolution of electron energy, gamma energy and coincidence time were improved by two orders of magnitude as compared to previous setups [2]. The scattered electrons were registered with the QCLAM magnetic spectrometer. The $\gamma$-radiation was detected by DAGOBERT (Darmstadt Array for coincident Gamma-ray OBservation in Electron scattering ReacTions) consisting of LaBr$_3$:Ce detectors. DAGOBERT@QCLAM is a worldwide unique device for high-resolution electron-gamma coincidence experiments. Recent upgrades for the experimental setup enhanced the performance for upcoming experimental campaigns.
Measurements on $^{12}\textrm{C}$, $^{96}\textrm{Ru}$ and $^{140}\textrm{Ce}$ targets were performed and demonstrated the superior performance of the new facility over previous attempts to study $(e,e^\prime\gamma)$ reactions. The measurement on $^{96}\textrm{Ru}$ is the first electron-gamma coincidence experiment of a medium-heavy open-shell nucleus.
The performance of the set-up will be reported and scientific results on the $\gamma$-decay behaviour and angular distributions will be presented.
This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 279384907 - SFB 1245 and Project-ID 499256822 – GRK 2891 “Nuclear Photonics”. It was supported by the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006).
[1] C. N. Papanicolas et al., Phys. Rev. Lett. 54, 26 (1985).
[2] B. Hesbacher et al., Nucl. Instrum. Methods Phys. Res. A 1078, 170574 (2025).
| Contribution category | Experiment |
|---|---|
| Presenter status | Student |