[en] Historically, γ-γ and γ-γ-γ coincidence spectra were utilized to build nuclear level schemes. With the development of large detector arrays, it has became possible to analyze higher fold coincidence data sets. This paper briefly reports on software to analyze 4-fold coincidence data sets that allows creation of 4-fold histograms (hypercubes) of at least 1024 channels per side (corresponding to a 43 gigachannel data space) that will fit onto a few gigabytes of disk space, and extraction of triple-gated spectra in a few seconds. Future detector arrays may have even higher efficiencies, and detect an many as 15 or 20 γ rays simultaneously; such data will require very different algorithms for storage and analysis. Difficulties inherent in the analysis of such data are discussed, and two possible new solutions are presented, namely adaptive list-mode systems and list-list-mode storage

No abstract available

[en] Optimal sensitivity in large HPGe γ-ray spectrometers such as Gammasphere and Euroball is achieved with 4-fold γ-ray coincidences or higher. Analysis of coincidence data at these folds is difficult as storage constraints make histogram-based techniques impractical. To address the problem of efficient storage of and access to high-fold coincidence data we have developed Blue, a specialized database program. Each coincidence event in this database is stored in its native fold eliminating statistical artifacts which can be introduced by unfolding a high-fold event to several lower-fold events. Partition of the dataset is based on the density distribution of coincidence events which makes data access efficient. A simple yet flexible query system is implemented by using a tree-like index for these partitions. This program is capable of executing a variety of queries, such as taking gates on a multi-fold database, at timescales which are interactive (s) or near-interactive (min). Simple compression techniques are employed so that databases with sizes of 10⁹ coincidences can easily be stored in a space of 10 Gb or less

[en] The GRETINA spectrometer is a first generation, gamma-ray tracking spectrometer capable of determining the Compton scattering path of gamma-rays incident on the detector volume. This ability allows the Ge detectors to be close packed allowing the detector to be scaled to high efficiencies while maintaining good peak-to-total. GRETINA currently consists of 7 4-detector modules giving approximately 1π solid angle coverage with a calorimetric efficiency of 6.3% and tracked efficiency of 4.7% at 1.3 MeV. The array's sensitivity to the position of the gamma ray's first interaction point enables precision event-by-event Doppler correction which allows one to achieve 1% energy resolution even for sources moving at a large fraction of the speed of light such as those encountered at fragmentation facilities such as NSCL and the future FRIB. (paper)

No abstract available

[en] In a mixture of three Yb nuclei, we find the rotational damping widths vary from 180 keV at 1.1 MeV γ-ray energy to 290 keV at 1.5 MeV, and the average compound damping widths (or spreading widths) vary from 40 keV at 1.1 MeV γ-ray energy to 60 keV at 1.3 MeV. The simulations also suggest extensive motional narrowing

[en] The purpose of this paper is to show that recent data on the ground-state band and excited states based on the 0₂⁺ level in ¹⁵Nd and ¹⁵²Sm, especially the measured B(E2) values, can be well described by including a ΔK = 0 coupling between rotational bands. This is contrary to recent statements in the literature. The experimental data are compared with models which have supported the widely differing interpretations of these transitional nuclei. These interpretations include describing excited states as rotational excitations of single-phonon states, the multiphonon ''phase coexistence'' picture, and the X(5) critical-point description

No abstract available

[en] Lifetimes of states in the triaxial strongly deformed bands of ¹⁶³Lu have been measured in a Gammasphere experiment using the Doppler-shift attenuation method. The bands are interpreted as wobbling-phonon excitations from the characteristic electromagnetic properties of the transitions connecting the bands. Quadrupole moments were extracted for the 0-phonon yrast band and, for the first time, for the 1-phonon wobbling band. The very similar results found for both bands suggest a similar intrinsic structure confirming the wobbling interpretation. While the in-band quadrupole moments for the bands show a decreasing trend towards higher spin, the strength of the inter-band transitions remains constant. Both features can be understood by a small increase in triaxiality towards higher spin. Such a change in triaxiality is also found in cranking calculations, to which the experimental results are compared

[en] The binding energies of even-even and odd-odd N = Z nuclei are compared. After correcting for the symmetry energy we find that the lowest T = 1 state in odd-odd N = Z nuclei is as bound as the ground state in the neighboring even-even nucleus, thus providing evidence for isovector np pairing. However, T = 0 states in odd-odd N = Z nuclei are several MeV less bound than the even-even ground states. We associate this difference with the T = 1 pair gap and conclude from the analysis of binding energy differences and blocking arguments that there is no evidence for an isoscalar (deuteronlike) pair condensate in N = Z nuclei