|
|
AGATA Collaboration(Siciliano, M. et al), Gadea, A., Perez-Vidal, R. M., & Domingo-Pardo, C. (2020). Pairing-quadrupole interplay in the neutron-deficient tin nuclei: First lifetime measurements of low-lying states in Sn-106,Sn-108. Phys. Lett. B, 806, 135474–7pp.
Abstract: The lifetimes of the low-lying excited states 2(+) and 4(+) have been directly measured in the neutron-deficient Sn-106,Sn-108 isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted gamma rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the B(E2; 2(1)(+) -> 0(g.s)(+)) values and it describes well the experimental pattern for Sn104-114 ; the B(E2;(+)(4) -> 2(1)(+)) values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in Sn-108.
|
|
|
|
AGATA Collaboration(Avigo, R. et al), Domingo-Pardo, C., Gadea, A., & Gonzalez, V. (2020). Low-lying electric dipole gamma-continuum for the unstable Fe-62(,)64 nuclei: Strength evolution with neutron number. Phys. Lett. B, 811, 135951–6pp.
Abstract: The gamma-ray emission from the nuclei Fe-62,Fe-64 following Coulomb excitation at bombarding energy of 400-440 AMeV was measured with special focus on E1 transitions in the energy region 4-8 MeV. The unstable neutron-rich nuclei Fe-62,Fe-64 were produced at the FAIR-GSI laboratories and selected with the FRS spectrometer. The gamma decay was detected with AGATA. From the measured gamma-ray spectra the summed E1 strength is extracted and compared to microscopic quasi-particle phonon model calculations. The trend of the E1 strength with increasing neutron number is found to be fairly well reproduced with calculations that assume a rather complex structure of the 1(-) states (three-phonon states) inducing a strong fragmentation of the E1 nuclear response below the neutron binding energy.
|
|
|
|
Pasqualato, G. et al, Gadea, A., & Jurado, M. (2023). An alternative viewpoint on the nuclear structure towards 100Sn: Lifetime measurements in 105Sn. Phys. Lett. B, 845, 138148–7pp.
Abstract: This work aims at presenting an alternative approach to the long standing problem of the B(E2) values in Sn isotopes in the vicinity of the N=Z double-magic nucleus Sn-100, until now predominantly measured with relativistic and intermediate-energy Coulomb excitation reactions. The direct measurement of the lifetime of low-lying excited states in odd-even Sn isotopes provides a new and precise guidance for the theoretical description of the nuclear structure in this region. Lifetime measurements have been performed in Sn-105 for the first time with the coincidence Recoil Distance Doppler Shift technique. The lifetime results for the 7/2(1)(+) first excited state and the 11/2(1)(+) state, 2(+)(Sn-104) circle times nu 1g(7/2) multiplet member, are discussed in comparison with state-of-the-art shell model and mean field calculations, highlighting the crucial contribution of proton excitation across the core of Sn-100. The reduced transition probability B(E2) of the 11/2(1)(+) core-coupled state points out an enhanced staggering with respect to the B(E2; 2(1)(+) -> 0(1)(+)) in the even-mass Sn-104 and Sn-106 isotopes.
|
|
|
|
Ljungvall, J., Perez-Vidal, R. M., Lopez-Martens, A., Michelagnoli, C., Clement, E., Dudouet, J., et al. (2020). Performance of the Advanced GAmma Tracking Array at GANIL. Nucl. Instrum. Methods Phys. Res. A, 955, 163297–13pp.
Abstract: The performance of the Advanced GAmma Tracking Array (AGATA) at GANIL is discussed, on the basis of the analysis of source and in-beam data taken with up to 30 segmented crystals. Data processing is described in detail. The performance of individual detectors are shown. The efficiency of the individual detectors as well as the efficiency after gamma-ray tracking are discussed. Recent developments of gamma-ray tracking are also presented. The experimentally achieved peak-to-total is compared with simulations showing the impact of back-scattered gamma rays on the peak-to-total in a gamma-ray tracking array. An estimate of the achieved position resolution using the Doppler broadening of in-beam data is also given. Angular correlations from source measurements are shown together with different methods to take into account the effects of gamma-ray tracking on the normalization of the angular correlations.
|
|
|
|
Azevedo, C. D. R., Baeza, A., Chauveau, E., Corbacho, J. A., Diaz, J., Domange, J., et al. (2020). Simulation results of a real-time in water tritium monitor. Nucl. Instrum. Methods Phys. Res. A, 982, 164555–7pp.
Abstract: In this work we present simulation results for a modular tritium in-water real-time monitor. The system allows for scalability in order to achieve the required sensitivity. The modules are composed by 340 uncladed scintillating fibers immersed in water and 2 photosensors in coincidence for light readout. Light yield and Birks' coefficient uncertainties for low energy beta particles is discussed. A study of the detection efficiency according to the fiber length is presented. Discussion on the system requirements and background mitigation for a device with sensitivity of 100 Bq/L, required to comply with the European directive 2013/51/Euratom, is presented. Due to the low energetic beta emission from tritium a detection efficiency close to 3.3% was calculated for a single 2 mm round fiber.
|
|
