It is built from large crystals of hyper-pure germanium that is electrically segmented. This permits to reconstruct the path of the detected gamma rays by using the recently developed concept of tracking. Up to 48 crystals covering about 1/3 of the solid angle are mounted in the array.

GRETINA is a gamma-ray detector array capable of reconstructing the energy and spatial positions of gamma-ray interactions within the germanium crystals. It is used to study the structure and stability of nuclei under various conditions. The new capabilities provided by gamma-ray tracking give large gains in sensitivity for a large number of experiments, particularly those aimed at nuclei far from beta stability.

GRETINA was located at ATLAS for three experimental campaign of approximately 18 months each. We expect GRETINA back one last time in 2024 before it will transition to the larger array GRETA. In the past, ATLAS delivered a variety of stable beams, long-lived rare isotopes and radioactive beams from CARIBU and RAISOR. For the next visit, beams from nuCARIBU will be available.

Usually more than 50% of the available beamtime is dedicated to GRETINA during its stay. The rest of the time is needed to change between ancillary setups like the charged-particle arrays CHICO-II, ORRUBA or coupling GRETINA to the Fragment Mass Analyzer (FMA).