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

The nucleus ${}^{163}\mathrm{Lu}$ has been populated through the fusion-evaporation reaction ${}^{139}\mathrm{La}{(}^{29}\mathrm{Si},5n{)}^{163}\mathrm{Lu}$ with a beam energy of 152 MeV. The electromagnetic properties of several connecting transitions between two presumably triaxial, strongly deformed (TSD) bands have been studied. Evidence is presented for the assignment of the excited TSD band as a wobbling mode built on the yrast TSD band, based on comparisons to new calculations in which an aligned particle is coupled to a strongly deformed triaxial rotor. The wobbling mode is uniquely related to triaxiality in nuclei.

The $\gamma$ decay from Coulomb excitation of ${}^{68}\mathrm{Ni}$ at $600\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a Au target was measured using the RISING setup at the fragment separator of GSI. The ${}^{68}\mathrm{Ni}$ beam was produced by a fragmentation reaction of ${}^{86}\mathrm{Kr}$ at $900\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a ${}^9\mathrm{Be}$ target and selected by the fragment separator. The $\gamma$ rays produced at the Au target were measured with HPGe detectors at forward angles and with ${\mathrm{BaF}}_2$ scintillators at backward angles. The measured spectra show a peak centered at approximately 11 MeV, whose intensity can be explained in terms of an enhanced strength of the dipole response function (pygmy resonance). Such pygmy structure has been predicted in this unstable neutron-rich nucleus by theory.

The nucleus ${}^{\mathrm{163}}\mathrm{L}\mathrm{u}$ has been populated through the reaction ${}^{\mathrm{139}}\mathrm{L}\mathrm{a}({}^{\mathrm{29}}\mathrm{S}\mathrm{i},5n)$ with a beam energy of 157 MeV. Three triaxial, strongly deformed (TSD) bands have been observed with very similar rotational properties. The first excited TSD band has earlier been assigned as a one-phonon wobbling excitation built on the lowest-lying (yrast) TSD band. The large $B(E2{)}_{\mathrm{o}\mathrm{u}\mathrm{t}}/B(E2{)}_{\mathrm{i}\mathrm{n}}$ value obtainable for one of four observed transitions between the second and first excited TSD bands is in good agreement with particle-rotor calculations for a two-phonon wobbling excitation.