First in-beam experiment with the ELIADE detectors: a spectroscopic study of ¹³⁰La

Abstract

The new facility, Extreme Light Infrastructure – Nuclear Physics (ELI-NP), is a combined laser-gamma nuclear physics research facility currently undergoing its final implementation stages in Măgurele near Bucharest, Romania. It already hosts two fully-operational 10 PW laser arms and, by 2023, it will also house a γ-beam system based on laser Compton backscattering, capable of delivering a high-brilliance, low-energy beam at E γ ≲ 19.5 MeV. Owing to this unique laser-gamma instrumentation combination, several types of experiments will be possible at ELI-NP, including high precision nuclear resonance fluorescence (NRF) experiments. In this case, the main γ-beam detection system for performing NRF studies at ELI-NP is represented by the ELI Array of DEtectors (ELIADE), featuring eight high-purity germanium (HPGe) segmented clover detectors. The current work presents the characteristics of two of the ELIADE detectors, including their photopeak detection efficiency, energy resolution, and peak-to-total ratio measured using γ-ray sources, as well as the timing performance obtained via in-beam measurements. For these latter detector tests, 130La was populated via the fusion evaporation reaction 121Sb(12C,3n)130La using a beam energy of 53 MeV at the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), also located in Măgurele. Herein, we report on the results of the ^130La linear polarization measurements taken using the ELIADE detectors as Compton polarimeters. The results obtained from the in-beam experiment were compared to several already published works and we present new information on the transition multipolarity in 130La.

The annealing setup and associated monitoring system of the ELIADE HPGe clover detectors at ELI-NP

“…for two of the ELIADE HPGe clover detectors were reported in ref. [11]. A similar measurement procedure was used for the post-annealing testing of the other six segmented clover detectors, as well.…”

“…Therefore, in order to restore these characteristics back to their optimal values, HPGe detectors need to be annealed through a controlled heating process for a specific duration of time, all the while maintaining a high degree of vacuum inside the detectors throughout both the heating and cooling (back to room temperature) cycles of the crystals therein. To this end, we have set up a dedicated annealing station at Extreme Light Infrastructure -Nuclear Physics (ELI-NP) [4,5] for the annealing of the HPGe segmented clover detectors (4 × 60 × 90 SEG32 type [6,7]) of the ELI-NP Array of DEtectors (ELIADE) 𝛾-ray spectrometer [8][9][10][11]. ELIADE represents a state-of-the-art, multi-detector 𝛾-ray spectrometer dedicated to nuclear physics research utilizing the Nuclear Resonance Fluorescence (NRF) technique [12][13][14], also employed by the gamma-beam industrial applications [15] team at ELI-NP researching industrial radiography and tomography.…”

Nuclear astrophysics studies with γ-ray beams: What do we expect to learn from them?

“…Thus, it will be possible to extract from the measured spectra the γ-ray branching ratios, the γ-ray multipolarities and mixing ratios, the level energies, the spins, parities, and the K quantum numbers of the levels, their partial and total decay widths, the transition and excitation strength, and the integrated (γ,γʹ) cross-section. The performance of the ELIADE detectors was tested in-beam and the results meet the requirements for highprecision NRF experiments [13]. The family of ELI-NP Gamma Above the Neutron Threshold (ELIGANT) instruments will be used to study (γ,γʹ), (γ,n), (γ,γʹn) and (γ,νn), ν = 1,2,3 reactions.…”

“…On the nuclear physics side, there is a strong need for good quality photonuclear reaction data for most of the light nuclei of astrophysical interest below iron. The situation is further complicated by the non-availability of reliable theoretical means for required photo-nuclear cross sections since the prediction of mean-field theories and statistical models do not agree well with measured values in this region, as illustrated in Figure 3 for 13 C. These measurements would lead to new insights into the effect of clustering, shell structure, and NN correlations on the photonuclear response of these nuclei.…”

“…The existing data for the 13 C(γ,n) reaction in inverse kinematics, as a function of 13 C kinetic energy where the cosmic microwave background serves as a target. The three facilities together will cover the full energy region of the shown data.…”