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Total absorption spectroscopy is a technique that helps obtain reliable β-feeding patterns of complex decays important for nuclear structure and astrophysics modeling as well as decay heat analysis in nuclear reactors. The need for improved measurements of β-feeding patterns from fission decay products has come to the forefront of experiments that use nuclear reactors as a source of antineutrinos. Here we present more detailed results, in particular the β-decay measurements of 96gsY, and demonstrate the impact of the β-delayed γ multiplicity on the overall efficiency of Modular Total Absorption Spectrometer used at Oak Ridge National Laboratory to study the decays of fission products abundant during a nuclear fuel cycle. [ABSTRACT FROM AUTHOR]

A Modular Total Absorption Spectrometer (MTAS) has been recently constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at the Oak Ridge National Laboratory (ORNL). The main goal of MTAS is to determine the true beta-decay feeding and following gamma radiation pattern for the decays of fission products. In this contribution, we would like to present the results of the measurement of 86Br. The preliminary analysis yields an average energy of emitted γ-radiation of about 4110 keV. It represents an increase of over 26% (850 keV), when compared to the average EM energies deduced using the ENSDF database. [ABSTRACT FROM AUTHOR]

Recently, a unique detector system for beta-delayed neutron spectroscopy, Hybrid-3Hen, was constructed and used in an experiment. This detector is a modification of the neutron detector 3Hen array, which uses ³He-filled tubes at 10 atm and high density polyethylene moderator. In Hybrid-3Hen the gamma-ray detection capability was implemented by adding two large HPGe clover-type detectors from the CLARION/CARDS array. This modification of 3Hen enabled efficient studies of beta-delayed neutron emission by using neutron-gamma coincidences. The system is equipped with full-digital readout for easy implementation of the slow and fast coincidences between various parts of the entire detection system. This new array was used in measurements at the Holifield Radioactive Ion Beam Facility and proven to be an essential tool to measure the large beta delayed two neutron emission branching ratio from the exotic isotope 86Ga. [ABSTRACT FROM AUTHOR]

The β-decay properties of neutron-rich fission fragments of Cu, Zn, and Ga isotopes were studied at the Holifield Radioactive Ion Beam Facility. Beams of 75-79Cu, 79-81Zn, and 83-85Ga were formed and delivered to two new end-stations at the facility. The Low-energy Radioactive Ion Beam Spectroscopy Station is a traditional on-line low energy (200 keV) beam line with 4 clover Ge detectors, two half-cylindrical plastic β-detectors, and a moving tape collector. In addition, many of the beams were accelerated to above 2 MeV/u and delivered to a micro-channel plate and transmission ion chamber located just in front of the same detector setup. In both cases, fine adjustment of an isobar separator was used to enhance the isotope of interest. Excited levels in the daughters and β-delayed neutron branching ratios were measured and used to confirm isotope identification. The decays from 79Cu and 85Ga were observed for the first time as was the 84Ge 2+1 level populated by β and βn decay channels. [ABSTRACT FROM AUTHOR]

The properties of β-γ and β-delayed neutron emission from 76-79Cu and 83-85Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed. [ABSTRACT FROM AUTHOR]

Precision measurement of the β-decay half-life, Q-value, and branching ratio between nuclear analog states of Jπ = 0+ and T = 1 can provide critical and fundamental tests of the Standard Model's description of electroweak interactions. A program has been initiated at TRIUMF-ISAC to measure the ft values of these superallowed beta transitions. Two Tz = 0, A > 60 cases, 74Rb and 62Ga, are presented. These are particularly relevant because they can provide critical tests of the calculated nuclear structure and isospin-symmetry breaking corrections that are predicted to be larger for heavier nuclei, and because they demonstrate the advance in the experimental precision on ft at TRIUMF-ISAC from 0.26% for 74Rb in 2002 to 0.05% for 62Ga in 2006. The high precision world data on experimental ft and corrected Ft values are discussed and shown to be consistent with CVC at the 10-4 level, yielding an average Ft = 3073.70(74) s. This Ft leads to Vud = 0.9737(4) for the up-down element of the Standard Model's CKM matrix. With this value and the Particle Data Group's 2006 values for Vus and Vub, the unitarity condition for the CKM matrix is met. Additional measurements and calculations are needed, however, to reduce the uncertainties in that evaluation. That objective is the focus of the continuing program on superallowed-beta decay at TRIUMF-ISAC. [ABSTRACT FROM AUTHOR]