The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-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 gamma 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 gamma-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. (C) 2011 Elsevier B.V. All rights reserved.AGATA and this work is supported by the European funding bodies and the EU Contract RII3-CT-2004-506065, the German BMBF under Grants 06K-167 and 06KY205I, the Swedish Research Council and the Knut and Alice Wallenberg Foundation, UK EPSRC Engineering and Physical Sciences Research Council, UK STFC Science and Technology Facilities Council, AWE plc, Scientific and Technological Research Council of Turkey (Proj. nr. 106T055) and Ankara University (BAP Proj. nr. 05B4240002), the Polish Ministry of Science and Higher Education under Grant DPN/N190/AGATA/2009, the Spanish MICINN under grants FPA2008-06419 and FPA2009-13377-C02-02, the Spanish Consolider-Ingenio 2010 Programme CPAN (contract number CSD2007-00042) the Generalitat Valenciana under Grant PROMETEO/2010/101, and research performed in the frame of the GSI-IN2P3 collaboration agreement number 02-42. MICINN, Spain, and INFN, Italy, through the AIC10-D-000568 bilateral action.Peer Reviewe

Absolute cross sections for isotopically identified products formed in multinucleon transfer in the ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt}$ system at $\sim 8\mathrm{MeV}/\mathrm{nucleon}$ are reported. The isotopic distributions obtained using a large acceptance spectrometer demonstrated the production of the “hard-to-reach” neutron-rich isotopes for $Z<78$ around the $N=126$ shell closure far from stability. The main contribution to the formation of these exotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The present experimental finding corroborates for the first time recent predictions that multinucleon transfer reactions would be the optimum method to populate and characterize neutron-rich isotopes around $N=126$ which are crucial for understanding both astrophysically relevant processes and the evolution of “magic” numbers far from stability.

A new isomeric $0^{+}$ state was identified as the first excited state in the self-conjugate ($N=Z$) nucleus ${}^{\mathrm{72}}\mathrm{K}\mathrm{r}$. By combining for the first time conversion-electron and gamma-ray spectroscopy with the production of metastable states in high-energy fragmentation, the electric-monopole decay of the new isomer to the ground state was established. The new $0^{+}$ state is understood as the band head of the known prolate rotational structure, which strongly supports the interpretation that ${}^{\mathrm{72}}\mathrm{K}\mathrm{r}$ is one of the rare nuclei having an oblate-deformed ground state. This observation gives in fact the first evidence for a shape isomer in a $N=Z$ nucleus.