The AGATA array, is the European forefront instrument based on semiconductor Germanium detectors, for high-resolution g-ray spectroscopy. It is used in the nuclear research facilities operating presently in Europe and will be especially important for the experimental conditions expected at the facilities, presently under construction, for intense radioactive ion beams as well as for high-intensity stable ion beams.
The European experimental γ-ray spectroscopy community has a long-standing tradition of coordinated efforts to build large scale high-energy resolution arrays. Since the early nineties, the community has worked together to build instruments with the highest possible sensitivity, e.g. the escape-suppressed spectrometer EUROBALL (1995-2004). The escape-suppression technique provides excellent peak-to-total (signal to background) ratios but limits the solid angle covered by the Ge detectors, thus limiting the sensitivity of the arrays.
AGATA is the result of the early European Commission financed initiative, the TMR network ‘Development of g-ray tracking detectors’ (1996 and 2001), encouraging the development of the highly segmented position sensitive Germanium detector technology in Europe.
The successful inception of the Ge position sensitive detectors technology has opened the possibility to build arrays of detectors based on the γ-ray tracking concept, providing an unprecedented level of sensitivity and efficiency. Only two arrays with such technology are being built in the world, the European implementation of the tracking array is realized in the AGATA project. The second one, as well under construction in the U.S., is the GRETA array.
AGATA is being built in a collaborative effort of more than 40 institutes in 12 countries. The conceptual design of AGATA foresees a 4π array with 60 triple clusters summing up to 180 Ge encapsulated detectors. The construction is being done in phases, presently followed by an international review process. In 2020 the Phase 1 of AGATA is finishing with a new Phase 2, aiming to complete 3p of the array solid angle, starting in 2021. The Phase 2 of AGATA requires improvements in several sub-systems and data processing algorithms.
The groups participating to this coordinated project are directly involved in developments of pre-processing electronics and on the characterization of the position sensitive Ge detectors with scanning tables, fundamental step to determine the response function of the detectors to be able to perform efficiently the Pulse Shape Analysis procedure. The instrumentation activities of the groups have produced already 3 PhD thesis along with all the associated know how attainment.
Along the way to the final configuration, smaller sub arrays of AGATA have been implemented. First, the AGATA Demonstrator, as a prove of concept for a tracking array at INFN-LNL, and later to prove the potential of AGATA in different experimental conditions as well as to profit from the scientific possibilities provided by the early AGATA implementations.
Since 2012 AGATA sub-arrays have been installed at the FAIR/NUSTAR-precursor PRESPEC set-up, placed at the focal plane of the FRS Fragment Separator in GSI, where experiments with in-flight highly relativistic exotic beams were performed, and at GANIL and SPIRAL where experiments with high-intensity stable beams and reaccelerated ISOL radioactive beams will be performed till mid 2021. From 2022, AGATA with a solid angle coverage beyond 1p, will be installed at INFN-LNL, coupled to the magnetic spectrometer PRISMA, to perform experimental nuclear structure activity with the high-intensity stable beams and ISOL radioactive beams from the SPES accelerator complex being built at INFN-LNL.