The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer

This is an accepted version of a paper published in Nature. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the published paper: Hinke, C., Boehmer, M., Boutachkov, P., Faestermann, T., Geissel, H. et al. (2012) "Superallowed Gamow-Teller decay of the doubly magic nucleus 100 Sn" Nature, 486 (7403): [341][342][343][344][345] Access to the published version may require subscription.

The NEutron Detector Array (NEDA) project aims at the construction of a new highefficiency compact neutron detector array to be coupled with large γ-ray arrays such as AGATA. The application of NEDA ranges from its use as selective neutron multiplicity filter for fusionevaporation reaction to a large solid angle neutron tagging device. In the present work, possible configurations for the NEDA coupled with the Neutron Wall for the early implementation with AGATA has been simulated, using Monte Carlo techniques, in order to evaluate their performance figures. The goal of this early NEDA implementation is to improve, with respect to previous instruments, efficiency and capability to select multiplicity for fusion-evaporation reaction channels in which 1, 2 or 3 neutrons are emitted. Each NEDA detector unit has the shape of a regular hexagonal prism with a volume of about 3.23 litres and it is filled with the EJ301 liquid scintillator, that presents good neutron-γ discrimination properties. The simulations have been performed using a fusion-evaporation event generator that has been validated with a set of experimental data obtained in the 58 Ni + 56 Fe reaction measured with the Neutron Wall detector array.

The K hindrance to the γ decay is studied in the warm rotating 174 W nucleus, focusing on the weakening of the selection rules of the K quantum number with increasing excitation energy. 174 W was populated by the fusion reaction of 50 Ti (at 217 MeV) on a 128 Te target, and its γ decay was detected by the AGATA Demonstrator array coupled to a BaF 2 multiplicity filter at Laboratori Nazionali di Legnaro of INFN. A fluctuation analysis of γ coincidence matrices gives a similar number of low-K and high-K discrete excited bands. The results are compared to simulations of the γ -decay flow based on a microscopic cranked shell model at finite temperature in which the K mixing is governed by the interplay of Coriolis force with the residual interaction. Agreement between simulations and experiment is obtained only by hindering the E1 decay between low-K and high-K bands by an amount compatible with that determined by spectroscopic studies of K isomers in the same mass region, with a similar trend with excitation energy. The work indicates that K mixing due to temperature effects may play a leading role for the entire body of discrete excited bands, which probes the onset region of K weakening.

A second γ -decaying high-spin isomeric state, with a half-life of 197 (22)ns, has been identified in the N = Z + 2 nuclide 94 Pd as part of a stopped-beam Rare Isotope Spectroscopic INvestigation at GSI (RISING) experiment. Weisskopf estimates were used to establish a tentative spin/parity of 19 − , corresponding to the maximum possible spin of a negative parity state in the restricted (p 1/2 , g 9/2 ) model space of empirical shell model calculations. The reproduction of the E3 decay properties of the isomer required an extension of the model space to include the f 5/2 and p 3/2 orbitals using the CD-Bonn potential. This is the first time that such an extension has been required for a high-spin isomer in the vicinity of 100 Sn and reveals the importance of such orbits for understanding the decay properties of high-spin isomers in this region. However, despite the need for the extended model space for the E3 decay, the dominant configuration for the 19 − state remains (πp −1 1/2 g −3 9/2 ) 11 ⊗(νg −2 9/2 ) 8 . The half-life of the known, 14 + , isomer was remeasured and yielded a value of 499 (13) The N ≈ Z nuclei just below 100 Sn are of particular interest in contemporary nuclear structure studies. As well as lying on the pathway for rp-process nucleosynthesis in x-ray burster scenarios [1], these nuclei also provide significant information in relation to shell structure close to the last doubly magic N = Z nuclide [2] and constitute a key region for testing the reliability of the shell model (SM) and SM interactions [3]. The region is generally well described by the SM in a minimum space comprising p 1/2 and g 9/2 protons and neutrons [3][4][5]. Exploration of the limits of this approach with respect to inclusion of the p 3/2 and f 5/2 orbitals and excitations across the N = Z = 50 shell closure is a challenge both to the SM and experimental techniques.This region is also remarkable for an abundance of isomeric states [6]. Particularly interesting is the occurrence of high-spin isomers which can provide an ideal testing ground for the study of neutron-proton interactions near the N = Z line [6]. One of the most striking cases is the (21 + ) level in 94 Ag, with recent papers reporting evidence for a variety of particle decay channels: β [7,8], βp [9], p [10], and 2p [11]. The latter of these is the subject of much debate in the literature [12][13][14][15][16].The T z = 1 nuclide 94 Pd has been studied in a number of experiments [7,8,[17][18][19][20][21] and has a known 14 + isomer that decays through γ decay and internal conversion (IC). The half-life of this state has been measured previously, yielding values of 800 (200) [7,8]. The current work presents data from a Rare Isotope Spectroscopic INvestigation at GSI (RISING) experiment showing clear evidence of a second isomeric state that feeds the 14 + level through some of these transitions. The reproduction of the decay properties of this isomer in shellmodel calculations requires the inclusion of the negative-parity p 3/2 and f 5/2 orbitals. 94 Pd and ...