Pasqualato, G. et al, Domingo-Pardo, C., & Gadea, A. (2023). Shape evolution in even-mass 98-104Zr isotopes via lifetime measurements using the γ γ-coincidence technique. Eur. Phys. J. A, 59(11), 276–13pp.
Abstract: The Zirconium (Z = 40) isotopic chain has attracted interest for more than four decades. The abrupt lowering of the energy of the first 2(+) state and the increase in the transition strength B(E2; 2(1)(+) -> 0(1)(+) ) going from Zr-98 to Zr-100 has been the first example of “quantum phase transition” in nuclear shapes, which has few equivalents in the nuclear chart. Although a multitude of experiments have been performed to measure nuclear properties related to nuclear shapes and collectivity in the region, none of the measured lifetimes were obtained using the Recoil Distance Doppler Shift method in the gamma gamma-coincidence mode where a gate on the direct feeding transition of the state of interest allows a strict control of systematical errors. This work reports the results of lifetime measurements for the first yrast excited states in Zr98-104 carried out to extract reduced transition probabilities. The new lifetime values in gamma gamma-coincidence and gamma-single mode are compared with the results of former experiments. Recent predictions of the Interacting Boson Model with Configuration Mixing, the Symmetry Conserving Configuration Mixing model based on the Hartree-Fock- Bogoliubov approach and the Monte Carlo Shell Model are presented and compared with the experimental data.
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Pajtler, M. V., Szilner, S., Corradi, L., de Angelis, G., Fioretto, E., Gadea, A., et al. (2015). Selective properties of neutron transfer reactions in the Zr-90+Pb-208 system for the population of excited states in zirconium isotopes. Nucl. Phys. A, 941, 273–292.
Abstract: Nuclei produced via multineutron transfer channels have been studied in Zr-90 + Pb-208 close to the Coulomb barrier energy in a fragment-gamma coincident measurement employing the PRISMA magnetic spectrometer coupled to the CLARA gamma-array. The selective properties of the reaction mechanism have been discussed in terms of states and their strength excited in the neutron transfer channels leading to Zr89-94 isotopes. A strong population of yrast states, with energies up to similar to 7.5 MeV has been observed.
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Lalovic, N., Louchart, C., Michelagnoli, C., Perez-Vidal, R. M., Ralet, D., Gerl, J., et al. (2016). Performance of the AGATA gamma-ray spectrometer in the PreSPEC set-up at GSI. Nucl. Instrum. Methods Phys. Res. A, 806, 258–266.
Abstract: In contemporary nuclear physics, the European Advanced GAmma Tracking Array (AGATA) represents a crucial detection system for cutting-edge nuclear structure studies. AGATA consists of highly segmented high-purity germanium crystals and uses the pulse-shape analysis technique to determine both the position and the energy of the y-ray interaction points in the crystals. It is the tracking algorithms that deploy this information and enable insight into the sequence of interactions, providing information on the full or partial absorption of the 7 ray. A series of dedicated performance measurements for an AGATA set-up comprising 21 crystals is described. This set-up was used within the recent PreSPEC-AGATA experimental campaign at the GSI Helmholtzzentrum fur Schwerionenforschung. Using the radioactive sources Co-56, Co-60 and Eu-152, absolute and normalized efficiencies and the peak-to-total of the array were measured. These quantities are discussed using different data analysis procedures. The quality of the pulse-shape analysis and the tracking algorithm are evaluated. The agreement between the experimental data and the Geant4 simulations is also investigated.
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Mengoni, D., Duenas, J. A., Assie, M., Boiano, C., John, P. R., Aliaga, R. J., et al. (2014). Digital pulse-shape analysis with a TRACE early silicon prototype. Nucl. Instrum. Methods Phys. Res. A, 764, 241–246.
Abstract: A highly segmented silicon-pad detector prototype has been tested to explore the performance of the digital pulse shape analysis in the discrimination of the particles reaching the silicon detector. For the first time a 200 tun thin silicon detector, grown using an ordinary floating zone technique, has been shown to exhibit a level discrimination thanks to the fine segmentation. Light-charged particles down to few MeV have been separated, including their punch-through. A coaxial HPGe detector in time coincidence has further confirmed the quality of the particle discrimination.
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Soderstrom, P. A. et al, Agramunt, J., Egea, J., Gadea, A., & Huyuk, T. (2019). Neutron detection and gamma-ray suppression using artificial neural networks with the liquid scintillators BC-501A and BC-537. Nucl. Instrum. Methods Phys. Res. A, 916, 238–245.
Abstract: In this work we present a comparison between the two liquid scintillators BC-501A and BC-537 in terms of their performance regarding the pulse-shape discrimination between neutrons and gamma rays. Special emphasis is put on the application of artificial neural networks. The results show a systematically higher gamma-ray rejection ratio for BC-501A compared to BC-537 applying the commonly used charge comparison method. Using the artificial neural network approach the discrimination quality was improved to more than 95% rejection efficiency of gamma rays over the energy range 150 to 1000 keV for both BC-501A and BC-537. However, due to the larger light output of BC-501A compared to BC-537, neutrons could be identified in BC-501A using artificial neural networks down to a recoil proton energy of 800 keV compared to a recoil deuteron energy of 1200 keV for BC-537. We conclude that using artificial neural networks it is possible to obtain the same gamma-ray rejection quality from both BC-501A and BC-537 for neutrons above a low-energy threshold. This threshold is, however, lower for BC-501A, which is important for nuclear structure spectroscopy experiments of rare reaction channels where low-energy interactions dominates.
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