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

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Picosecond lifetimes in 46 V and 46 Ti were determined using the recoil distance Doppler-shift technique with a plunger device coupled to a setup of five HP Ge detectors enhanced by one EUROBALL CLUSTER detector. The experiment was carried out using the 32 S( 16 O,pn) reaction at 38 MeV at the Cologne FN TANDEM facility. The differential decay curve method in coincidence mode was employed to derive lifetimes for five excited states in each nucleus. The resulting E2 transition probabilities are compared with existing shell model calculations and a comparison within the Tϭ1 isospin triplet is given. Absolute E1 strengths of the 2 Ϫ decay in 46 V are discussed.The investigation of NϭZ nuclei is an exciting topic in nuclear structure physics, to which a lot of experimental and theoretical work has been devoted recently. Self-conjugate nuclei are symmetric with respect to the isospin degree of freedom and allow a sensitive testing of the isospin symmetry. This symmetry leads to selection rules, e.g., E1 transitions between low lying states with Tϭ0 character are strictly forbidden. The only way to enhance E1 strengths between such states is to assume an admixture of Tϭ1 components of the wave function, caused by the Coulomb interaction or by isospin violating parts of the strong interaction.The determination of isospin mixing matrix elements via lifetime measurements is of special interest in odd-odd N ϭZ nuclei with valence particles in the f 7/2 shell. In 46 V, much interesting data have been accumulated recently ͓1-6͔. A very peculiar finding was the isospin forbidden 2 Ϫ →1 ϩ transition with a relative E1 strength six times stronger than the strength of a competing allowed one with ⌬Tϭ1 ͓1͔. In order to achieve a better comparison between allowed and forbidden E1 transitions, it is important to determine ͑more and͒ absolute transition probabilities in this nucleus. The present work reports on the decay properties of the 2 1 Ϫ ,T ϭ0 state and explains the observed relative E1 strengths.Aside from this, a comparison with 46 Ti, the isobaric analog partner of 46 V, is presented. In the Tϭ1 triplet the reduced E2 matrix elements have a linear dependence upon T z , which follows from general arguments based on the ideas of isospin symmetry ͓7͔, provided that isospin is a good quantum number. Precise B(E2;2 1 ϩ →0 ϩ ) values provide a stringent test to this theoretical relation. The new data are in better agreement with the theoretical description than a previous value.In 46 V recent model calculations in the full p f shell without any truncation for the positive parity states describe the experimental level order and branching ratios well ͓1͔. Nevertheless, reliable data on transition probabilities are necessary for an overall comparison of experimental data with shell model calculations. Despite its relevance such information is still scarce.We performed a recoil distance Doppler-shift ͑RDDS͒ experiment with the Köln coincidence plunger device ͓8͔ at the FN TANDEM facility at the University of Cologne. Excited states ...

Lifetime measurements in 154 Gd were performed by means of the recoil distance Doppler-shift method. Excited states of 154 Gd were populated via Coulomb excitation with a 32 S beam at 110 MeV delivered by the FN tandem accelerator of the University of Cologne. The determined transition probabilities as well as the low-spin level scheme of 154 Gd demonstrate a good agreement with the predictions of the critical point symmetry X(5). Comparison of specific experimental observables for the N = 90 rare earth isotones with the calculations of the X(5) model clearly show that 154 Gd is one of the good examples of the realization of the X(5) dynamical symmetry. In addition, the experimental data are compared to fits in the framework of the IBA and the general collective model.

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