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Agramunt, J. et al, Algora, A., Domingo-Pardo, C., Jordan, D., Rubio, B., Tain, J. L., et al. (2014). New Beta-delayed Neutron Measurements in the Light-mass Fission Group. Nucl. Data Sheets, 120, 74–77.
Abstract: A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4 pi neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for Br-91, As-86, As-85, and Ge-85 nuclei.
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Martinez, T. et al, Agramunt, J., Algora, A., Domingo-Pardo, C., Jordan, M. D., Rubio, B., et al. (2014). MONSTER: a TOF Spectrometer for beta-delayed Neutron Spectroscopy. Nucl. Data Sheets, 120, 78–80.
Abstract: beta-delayed neutron (DN) data, including emission probabilities, P-n, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.
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Nichols, A. L., Dimitriou, P., Algora, A., Fallot, M., Giot, L., Kondev, F. G., et al. (2023). Improving fission-product decay data for reactor applications: part I-decay heat. Eur. Phys. J. A, 59(4), 78–78pp.
Abstract: Effort has been expended to assess the relative merits of undertaking further decay-data measurements of the main fission-product contributors to the decay heat of neutron-irradiated fissionable fuel and related actinides by means of Total Absorption Gamma-ray Spectroscopy (TAGS – sometimes abbreviated to TAS) and Discrete Gamma-ray Spectroscopy (DGS). This review has been carried out following similar work performed under the auspices of OECD/WPEC-Subgroup 25 (2005-2007) and the International Atomic Energy Agency (2009, 2014), and various highly relevant TAGS measurements completed as a consequence of such assessments. We present our recommendations for new decay-data evaluations, along with possible requirements for total absorption and discrete high-resolution gamma-ray spectroscopy studies that cover approximately 120 fission products and various isomeric states.
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n_TOF Collaboration(Tarrio, D. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2014). Measurement of the angular distribution of fission fragments using a PPAC assembly at CERN n_TOF. Nucl. Instrum. Methods Phys. Res. A, 743, 79–85.
Abstract: A fission reaction chamber based on Parallel Plate Avalanche Counters (PPACs) was built for measuring angular distributions of fragments emitted in neutron-induced fission of actinides at the neutron beam available at the Neutron Time-Of-Flight (n_TOF) facility at CERN. The detectors and the samples were tilted 45 degrees with respect to the neutron beam direction to cover all the possible values of the emission angle of the fission fragments. The main features of this setup are discussed and results on the fission fragment angular distribution are provided for the Th-232(n,f) reaction around the fission threshold. The results are compared with the available data in the literature, demonstrating the good capabilities of this setup.
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Rasco, B. C., Brewer, N. T., Yokoyama, R., Grzywacz, R., Rykaczewski, K. P., Tolosa-Delgado, A., et al. (2018). The ORNL analysis technique for extracting beta-delayed multi-neutron branching ratios with BRIKEN. Nucl. Instrum. Methods Phys. Res. A, 911, 79–86.
Abstract: Many choices are available in order to evaluate large radioactive decay networks. There are many parameters that influence the calculated beta-decay delayed single and multi-neutron emission branching fractions. We describe assumptions about the decay model, background, and other parameters and their influence on beta-decay delayed multi-neutron emission analysis. An analysis technique, the ORNL BRIKEN analysis procedure, for determining beta-delayed multi-neutron branching ratios in beta-neutron precursors produced by means of heavy-ion fragmentation is presented. The technique is based on estimating the initial activities of zero, one, and two neutrons occurring in coincidence with an ion-implant and beta trigger. The technique allows one to extract beta-delayed multi-neutron decay branching ratios measured with the He-3 BRIKEN neutron counter. As an example, two analyses of the beta-neutron emitter Cu-77 based on different a priori assumptions are presented along with comparisons to literature values.
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Guadilla, V. et al, Tain, J. L., Algora, A., Agramunt, J., Gelletly, W., Jordan, D., et al. (2018). Characterization and performance of the DTAS detector. Nucl. Instrum. Methods Phys. Res. A, 910, 79–89.
Abstract: DTAS is a segmented total absorption y-ray spectrometer developed for the DESPEC experiment at FAIR. It is composed of up to eighteen NaI(Tl) crystals. In this work we study the performance of this detector with laboratory sources and also under real experimental conditions. We present a procedure to reconstruct offline the sum of the energy deposited in all the crystals of the spectrometer, which is complicated by the effect of NaI(Tl) light-yield non-proportionality. The use of a system to correct for time variations of the gain in individual detector modules, based on a light pulse generator, is demonstrated. We describe also an event-based method to evaluate the summing-pileup electronic distortion in segmented spectrometers. All of this allows a careful characterization of the detector with Monte Carlo simulations that is needed to calculate the response function for the analysis of total absorption gamma-ray spectroscopy data. Special attention was paid to the interaction of neutrons with the spectrometer, since they are a source of contamination in studies of beta-delayed neutron emitting nuclei.
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Caballero-Folch, R. et al, Domingo-Pardo, C., Tain, J. L., Agramunt, J., Algora, A., & Rubio, B. (2014). beta-decay and beta-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis. Nucl. Data Sheets, 120, 81–83.
Abstract: New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and beta-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Ti, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them (Hg208-211, Tl211-215, Pb214-218) were implanted with enough statistics to determine their half-lives. About half of them are expected to be neutron emitters, in such cases it will become possible to obtain the neutron emission probabilities, P-n.
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Algora, A., Tain, J. L., Rubio, B., Fallot, M., & Gelletly, W. (2021). Beta-decay studies for applied and basic nuclear physics. Eur. Phys. J. A, 57(3), 85–28pp.
Abstract: In this reviewwe will present the results of recent beta-decay studies using the total absorption technique that cover topics of interest for applications, nuclear structure and astrophysics. The decays studied were selected primarily because they have a large impact on the prediction of (a) the decay heat in reactors, important for the safety of present and future reactors and (b) the reactor electron anti-neutrino spectrum, of interest for particle/nuclear physics and reactor monitoring. For these studies the total absorption technique was chosen, since it is the only method that allows one to obtain beta-decay probabilities free from a systematic error called the Pandemonium effect. The total absorption technique is based on the detection of the. cascades that follow the initial beta decay. For this reason the technique requires the use of calorimeters with very high. detection efficiency. The measurements presented and discussed here were performed mainly at the IGISOL facility of the University of Jyvaskyla (Finland) using isotopically pure beams provided by the JYFLTRAP Penning trap. Examples are presented to show that the results of our measurements on selected nuclei have had a large impact on predictions of both the decay heat and the anti-neutrino spectrum from reactors. Some of the cases involve beta-delayed neutron emission thus one can study the competition between gamma – and neutron-emission from states above the neutron separation energy. The gamma-to-neutron emission ratios can be used to constrain neutron capture (n, gamma) cross sections for unstable nuclei of interest in astrophysics. The information obtained from the measurements can also be used to test nuclear model predictions of half-lives and Pn values for decays of interest in astrophysical network calculations. These comparisons also provide insights into aspects of nuclear structure in particular regions of the nuclear chart.
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n_TOF Collaboration(Weiss, C. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2015). The new vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance. Nucl. Instrum. Methods Phys. Res. A, 799, 90–98.
Abstract: At the neutron Lime-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beam line and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds.
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Yokoyama, R., Singh, M., Grzywacz, R., Keeler, A., King, T. T., Agramunt, J., et al. (2019). Segmented YSO scintillation detectors as a new beta-implant detection tool for decay spectroscopy in fragmentation facilities. Nucl. Instrum. Methods Phys. Res. A, 937, 93–97.
Abstract: A newly developed segmented YSO scintillator detector was implemented for the first time at the RI-beam Factory at RIKEN Nishina Center as an implantation-decay counter. The results from the experiment demonstrate that the detector is a viable alternative to conventional silicon-strip detectors with its good timing resolution and high detection efficiency for beta particles. A Position-Sensitive Photo-Multiplier Tube (PSPMT) is coupled with a 48 x 48 segmented YSO crystal. To demonstrate its capabilities, a known short-lived isomer in Ni-76 and the beta decay of Co-74 were measured by implanting those ions into the YSO detector. The half-lives and gamma-rays observed in this work are consistent with the known values. The beta-ray detection efficiency is more than 80 % for the decay of Co-74.
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