Precision mass measurements of neutron-rich Y, Nb, Mo, Tc, Ru, Rh, and Pd isotopes.

Direct mass measurements with typical uncertainties of 1–10 keV have been performed for the first time for ten neutron-rich isotopes 102,103 Y, 108 Nb, 111 Mo, 113,114 Tc, 116 Ru, 119 Rh, and 121,122 Pd. The obtained mass data compared with the 2003 atomic-mass evaluation shows systematic overestimation of binding energies far from stability. The relationship between two-neutron separation energies, nuclear structure and shape changes has been investigated by comparing the experimental data with a theoretical calculation based on the Hartree-Fock-Bogoliubov approximation using modern energy density functionals.This work has been supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2000–2005 (Nuclear and Condensed Matter Physics Programme at JYFL) and the Finnish Centre of Excellence Programme 2006–2011 (Nuclear and Accelerator Based Physics Programme at JYFL).Peer Reviewe

Precision half-life and Q-value measurement of the super-allowed beta emitter (30)S

The b \beta -decay half-life and the ground-state-to-ground-state Q EC -value of 30S were measured with a relative precision of 14 and 2 parts in 104, respectively. The half-life measurement yields a value of 1175.9(17)ms which is in agreement with previous measurements but has a precision that is better by a factor of three. The new super-allowed Q EC -value 5464.32(20)keV is 20 times more precise and slightly larger than the previously adopted value. The experiment was performed at the IGISOL facility at the Accelerator Laboratory of the University of Jyväskylä.This work was supported in part by the Conseil Regional d’Aquitaine. We also acknowledge support from the Academy of Finland under the Finnish Center of Excellence Programme 2006-2011 (Project No. 213503, Nuclear and Accelerator Based Physics Programme at JYFL).Peer Reviewe

Characterization of the DTAS detector and first measurements

V. Guadilla et al.; EMIS 2015, Grand Rapids, Michigan, in the United States, May 11 through May 15, 2015A new Total Absorption Gamma-Ray Spectrometer for beta-decay studies (DTAS) has been developed within the DESPEC experiment of the NUSTAR collaboration [1]. The instrument has been designed [2] to determine accurately the beta-decay intensity distribution for exotic nuclei produced in high-energy reactions, which will be separated and identified by means of the Super Fragment Separator at the future FAIR facility. DTAS has a modular construction with up to 18 large NaI(Tl) detector modules (module dimension: 25cmx15cmx15cm) which can be assembled in a 4pi geometry with little dead material around the AIDA implantation detector, a stack of double sided Si strip-detectors [2]. We have recently performed the first experiment with this setup at the upgraded IGISOL IV (Jyväskylä, Finland) facility. The low energy radioactive beams have been further purified with the JYFLTRAP Penning trap [3]. The experiment aimed to study fission products of relevance in neutrino physics and reactor decay heat time evolution. The measurements allowed us to perform a careful characterization of the detector and to study the overall performance of the setup. The results of this work will be presented, including the performance of the gain stabilization system, the correction of electronic pulse pileup, the sensitivity to neutrons and the calibration of the response of the spectrometer to decay radiation by means of Geant4 Monte Carlo simulations.Peer Reviewe

Total absorption γ-ray spectroscopy of beta delayed neutron emitters

International audiencePreliminary results of the data analysis of the beta decay of 94 Rb using a novel —segmented— total absorption spectrometer are shown in this contribution. This result is part ofa systematic study of important contributors to the decay heat problem in nuclear reactors. In thisparticular case the goal is to determine the beta intensity distribution below the neutron separationenergy and the gamma/beta competition above

Gamma/neutron competition above the neutron separation energy in delayed neutron emitters

International audienceTo study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyväskylä in Finland) using Total Absorption γ-ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn

Total Absorption Study of Beta Decays Relevant for Nuclear Applications and Nuclear Structure

An overview is given of our activities related to the study of the beta decay of neutron rich nuclei relevant for nuclear applications. Recent results of the study of the beta decay of 87,88Br using a new segmented total absorption spectrometer are presented. The measurements were performed at the IGISOL facility using trap-assisted total absorption spectroscopy

Gamma/neutron competition above the neutron separation energy in delayed neutron emitters

To study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyväskylä in Finland) using Total Absorption -ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn. © Owned by the authors, published by EDP Sciences, 2014

Total absorption γ-ray spectroscopy of beta delayed neutron emitters

Preliminary results of the data analysis of the beta decay of 94Rb using a novel - segmented- total absorption spectrometer are shown in this contribution. This result is part of a systematic study of important contributors to the decay heat problem in nuclear reactors. In this particular case the goal is to determine the beta intensity distribution below the neutron separation energy and the gamma/beta competition above. © 2013 AIP Publishing LLC

Measurement of fission products β decay properties using a total absorption spectrometer

In a nuclear reactor, the decay of fission fragments is at the origin of decay heat and antineutrino flux. These quantities are not well known while they are very important for reactor safety and for our understanding of neutrino physics. One reason for the discrepancies observed in the estimation of the decay heat and antineutrinos flux coming from reactors could be linked with the Pandemonium effect. New measurements have been performed at the JYFL facility of Jyväskylä with a Total Absorption Spectrometer (TAS) in order to circumvent this effect. An overview of the TAS technique and first results from the 2009 measurement campaign will be presented. © Owned by the authors, published by EDP Sciences, 2013