Abstract: 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.

Abstract: A scheme is proposed for hardware estimation of the location of zero crossings of sampled signals with subsample resolution for timing applications, which consists of interpolating the signal with a cubic spline near the zero crossing and then finding the root of the resulting polynomial. An iterative algorithm based on the bisection method is presented that obtains one bit of the result per step and admits an efficient digital implementation using fixed-point representation. In particular, the root estimation iteration involves only two additions, and the initial values can be obtained from finite impulse response (FIR) filters with certain symmetry properties. It is shown that this allows online real-time estimation of timestamps in free-running sampling detector systems with improved accuracy with respect to the more common linear interpolation. The method is evaluated with simulations using ideal and real timing signals, and estimates are given for the resource usage and speed of its implementation.

Abstract: We have characterized a detector equipped with an undoped LaCl3 truncated cone crystal with dimensions of 22.5 mm in the largest diameter, 16 mm in the smallest diameter, and 16 mm in height, coupled to a fast Photonis XP2020/URQ photomultiplier tube (PMT). Its time response at 511 keV (Na-22) and Co-60 photon energies has been measured against a reference detector using a fast digitizer module by digital signal processing methods based on a genetic algorithm. The time resolution was optimized by the choice of the photomultiplier bias voltage and the fine-tuning of the digital parameters of the time pickup algorithm. The de-convoluted full width at half maximum (FWHM) time resolution is found to be 250 +/- 10 ps at Co-60 energies, and 444 +/- 8 ps using positron annihilation gamma-rays from 22Na, providing good prospects for the use of the crystal in applications requiring a fast time response.