arXiv subjects

T. Petruse

Publications and source records attributed to T. Petruse.

7 recordsLinked to original sources

arXiv2025

Precise measurement of the $γ$-decay probability of the Hoyle state with a new triple coincidence-detection method

We measured the $γ$-decay probability of the Hoyle state with a new method of triple coincidence detection of a scattered $α$ particle, a recoil $\rm ^{12}C$ nucleus, and a $γ$ ray in inelastic alpha scattering on $\rm ^{12}C$. This method successfully enabled a low-background measurement and a precise determination of the $γ$-decay probability of the Hoyle state as $Γ_\mathrmγ/Γ=[4.00 \pm 0.22 \mathrm{(sta.)} \pm 0.18 \mathrm{(sys.)}]\times10^{-4}$, which is consistent with the previous literature value. Therefore, we concluded that the literature value can be reliably used in the study of nucleosynthesis in the universe.

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arXiv2025

ELIGANT-TN -- ELI Gamma Above Neutron Threshold: The Thermal Neutron setup

Here we present the thermal neutron counter from the ELI Gamma Above Neutron Threshold setup at the Extreme Light Infrastructure - Nuclear Physics. We describe the mechanical design of the setup, the properties of the ${}^{3}$He gas counters, and the hardware data-acquisition electronics and software digital signal processing. The performance of the complete detector array is demonstrated via Geant4 and MCNP simulations, and measurements with typical neutron sources. The analysis procedure for experimental measurements are outlined with a in-beam test experiment with an $\alpha$ beam to measure the ${}^{13}\mathrm{C}(\alpha,\mathrm{n}_{0}){}^{16}\mathrm{O}$ cross-section branching ratios.

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arXiv2025

Nuclear level density of ${}^{128}$Te from $(\mathrm{p},\mathrm{p}'γ)$ scattering and complementary photonuclear data

We have extracted the nuclear level density of ${}^{128}$Te from a $(\mathrm{p},\mathrm{p} 'γ)$ scattering experiment using the large-volume \labr\ and \cebr\ detectors from ELI-NP at the 9~MV Tandem facilities at IFIN-HH. The decay data were normalised using photonuclear data, resulting in nuclear level densities without intrinsic model dependencies from the constant temperature or Fermi gas models. The deduced nuclear level density follows in between the expectations from these two models, but we observe a clear divergence from a microscopic model based on the Skyrme force.

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arXiv2025

Statistical properties and photon strength functions of the ${}^{112,114}$Sn isotopes below the neutron separation threshold

Here, we report on the measurements of the $γ$-ray strength functions and nuclear level densities of ${}^{112,114}$Sn performed for the first time at the 9~MV Tandem accelerator facilities at IFIN-HH using the Oslo method. We extract thermodynamic properties and gross and fine properties of the pygmy dipole resonance for systematic comparison in the chain of Sn isotopes. The results are compared with microscopic models implemented in the TALYS reaction code and the fully microscopic quasiparticle-phonon model for the underlying nuclear structure of the dipole strength in ${}^{112,114}$Sn. The quasiparticle-phonon model results show the importance of complex configurations to the low-energy dipole response in the pygmy dipole resonance energy region. The experimental data are further included in the cross-section and reaction rate calculations for the $(\mathrm{n},γ)$ reaction of the $p$-process nuclei ${}^{112,114}$Sn showing a significant increase in reaction rates at high temperatures compared to existing nuclear databases.

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arXiv2022

PANDORA project: photo-nuclear reactions below $A=60$

Photo-nuclear reactions of light nuclei below a mass of $A=60$ are studied experimentally and theoretically by the PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project. Two experimental methods, virtual-photon excitation by proton scattering and real-photo absorption by a high-brilliance gamma-ray beam produced by laser Compton scattering, will be applied to measure the photo-absorption cross sections and the decay branching ratio of each decay channel as a function of the photon energy. Several nuclear models, e.g. anti-symmetrized molecular dynamics, mean-field type models, a large-scale shell model, and ab initio models, will be employed to predict the photo-nuclear reactions. The uncertainty in the model predictions will be evaluated from the discrepancies between the model predictions and the experimental data. The data and the predictions will be implemented in a general reaction calculation code TALYS . The results will be applied to the simulation of the photo-disintegration process of ultra-high-energy cosmic rays in inter-galactic propagation.

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arXiv2020

Electromagnetic character of the competitive $γγ/γ$-decay from $^{137\mathrm{m}}$Ba

Second-order processes in physics is a research topic focusing attention from several fields worldwide including, for example, non-linear quantum electrodynamics with high-power lasers, neutrinoless double-$β$ decay, and stimulated atomic two-photon transitions. For the electromagnetic nuclear interaction, the observation of the competitive double-$γ$ decay from $^{137\mathrm{m}}$Ba has opened up the nuclear structure field for detailed investigation of second-order processes through the manifestation of off-diagonal nuclear polarizability. Here we confirm this observation with an $8.7σ$ significance, and an improved value on the double-photon versus single-photon branching ratio as $2.62\times10^{-6}(30)$. Our results, however, contradict the conclusions from the original experiment, where the decay was interpreted to be dominated by a quadrupole-quadrupole component. Here, we find a substantial enhancement in the energy distribution consistent with a dominating octupole-dipole character and a rather small quadrupole-quadrupole element in the decay, hindered due to an evolution of the internal nuclear structure. The implied strongly hindered double-photon branching in $^{137\mathrm{m}}$Ba opens up the possibility of the double-photon branching as a feasible tool for nuclear-structure studies on off-diagonal polarizability in nuclei where this hindrance is not present.

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arXiv2019

Unfolding of sparse high-energy $γ$-ray spectra from LaBr$_{3}$:Ce detectors

Here we report on the characterization of one of the large-volume LaBr$_{3}$:Ce detectors for the ELIGANT project at ELI-NP. The main focus of this work is the response function for high-energy $γ$ rays of such detectors. In particular, we compare a selection of unfolding methods to resolve small structures in $γ$-ray spectra with high-energies. Three methods have been compared using $γ$-ray spectra with energies up to 12 MeV obtained in an experiment at the 3 MV Tandetron\texttrademark\ facility at IFIN-HH. The results show that the iterative unfolding approach gives the best qualitative reproduction of the emitted $γ$-ray spectrum. Furthermore, the correlation fluctuations in high-energy regime from the iterative method are two orders of magnitude smaller than when using the matrix inversion approach with second derivative regularization. In addition, the iterative method is computationally faster as it does not contain large matrix inversions. The matrix inversion method does, however, give more consistent results over the full energy range and in the low-statistics limit. Our conclusion is that the performance of the iterative approach makes it well suitable for semi-online analysis of experimental data. These results will be important, both for experiments with the ELIGANT setup, and for on-line diagnostics of the energy spread of the $γ$-ray beam which is under implementation at ELI-NP.

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