|
|
Guadilla, V. et al, Tain, J. L., Algora, A., Agramunt, J., Jordan, D., Monserrate, M., et al. (2019). Total absorption gamma-ray spectroscopy of the beta-delayed neutron emitters I-137 and Rb-95. Phys. Rev. C, 100(4), 044305–17pp.
Abstract: The decays of the beta-delayed neutron emitters( 137)I and Rb-95 have been studied with the total absorption gamma-ray spectroscopy technique. The purity of the beams provided by the JYFLTRAP Penning trap at the ion guide isotope separator on-line facility in Jyvaskyla allowed us to carry out a campaign of isotopically pure measurements with the decay total absorption gamma-ray spectrometer, a segmented detector composed of 18 NaI(T1) modules. The contamination coming from the interaction of neutrons with the spectrometer has been carefully studied, and we have tested the use of time differences between prompt gamma rays and delayed neutron interactions to eliminate this source of contamination. Due to the sensitivity of our spectrometer, we have found a significant amount of beta intensity to states above the neutron separation energy that deexcite by gamma rays, comparable to the neutron emission probability. The competition between gamma deexcitation and neutron emission has been compared with Hauser-Feshbach calculations, and it can be understood as a nuclear structure effect. In addition, we have studied the impact of the beta-intensity distributions determined in this work on reactor decay heat and reactor antineutrino spectrum summation calculations. The robustness of our results is demonstrated by a thorough study of uncertainties and with the reproduction of the spectra of the individual modules and the module-multiplicity gated spectra. This work represents the state-of-the-art of our analysis methodology for segmented total absorption spectrometers.
|
|
|
|
Guadilla, V. et al, Tain, J. L., Algora, A., Agramunt, J., Jordan, D., Monserrate, M., et al. (2020). Determination of beta-decay ground state feeding of nuclei of importance for reactor applications. Phys. Rev. C, 102(6), 064304–12pp.
Abstract: In beta-decay studies the determination of the decay probability to the ground state (g.s.) of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed gamma-ray emission. In this work we revisit the 4 pi gamma – beta method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the beta-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large g.s. branches. The method is relevant for nuclear structure studies as well. Pertinent formulas are revised and extended to the special case of beta-delayed neutron emitters, and the robustness of the method is demonstrated with synthetic data. We apply it to a number of measured decays that serve as test cases and discuss the features of the method. Finally, we obtain g.s. feeding intensities with reduced uncertainty for four relevant decays that will allow future improvements in antineutrino spectrum and decay heat calculations using the summation method.
|
|
|
|
Orrigo, S. E. A. et al, Rubio, B., Gelletly, W., Aguilera, P., Algora, A., Morales, A. I., et al. (2021). beta decay of the very neutron-deficient Ge-60 and Ge-62 nuclei. Phys. Rev. C, 103(1), 014324–12pp.
Abstract: We report here the results of a study of the beta decay of the proton-rich Ge isotopes, Ge-60 and Ge-62, produced in an experiment at the RIKEN Nishina Center. We have improved our knowledge of the half-lives of Ge-62 [73.5(1) ms] and Ge-60 [25.0(3) ms] and its daughter nucleus, Ga-60 [69.4(2) ms]. We measured individual beta-delayed proton and gamma emissions and their related branching ratios. Decay schemes and absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. A total beta-delayed proton-emission branching ratio of 67(3)% has been obtained for Ge-60. New information has been obtained on the energy levels populated in Ga-60 and on the 1/2(-) excited state in the beta p daughter Zn-59. We extracted a ground state-to-ground state feeding of 85.3(3)% for the decay of Ge-62. Eight new y lines have been added to the deexcitation of levels populated in the Ga-62 daughter.
|
|
|
|
Algora, A., Ganioglu, E., Sarriguren, P., Guadilla, V., Fraile, L. M., Nacher, E., et al. (2021). Total absorption gamma-ray spectroscopy study of the beta-decay of Hg-186. Phys. Lett. B, 819, 136438–7pp.
Abstract: The Gamow-Teller strength distribution of the decay of Hg-186 into Au-186 has been determined for the first time using the total absorption gamma spectroscopy technique and has been compared with theoretical QRPA calculations using the SLy4 Skyrme force. The measured Gamow-Teller strength distribution and the half-life are described by mixing oblate and prolate configurations independently in the parent and daughter nuclei. In this theoretical framework the best description of the experimental beta strength is obtained with dominantly prolate components for both parent Hg-186 and daughter Au-186. The approach also allowed us to determine an upper limit of the oblate component in the parent state. The complexity of the analysis required the development of a new approach in the analysis of the X-ray gated total absorption spectrum.
|
|
|
|
Mistry, A. K. et al, Tain, J. L., Agramunt, J., Algora, A., Guadilla, V., Morales, A. I., et al. (2022). The DESPEC setup for GSI and FAIR. Nucl. Instrum. Methods Phys. Res. A, 1033, 166662–18pp.
Abstract: The DEcay SPECtroscopy (DESPEC) setup for nuclear structure investigations was developed and commissioned at GSI, Germany in preparation for a full campaign of experiments at the FRS and Super-FRS. In this paper, we report on the first employment of the setup in the hybrid configuration with the AIDA implanter coupled to the FATIMA LaBr3(Ce) fast-timing array, and high-purity germanium detectors. Initial results are shown from the first experiments carried out with the setup. An overview of the setup and function is discussed, including technical advancements along the path.
|
|
