In-beam test and imaging capabilities of the AGATA prototype detector

High-resolution gamma-ray spectroscopy is one of the most powerful and sensitive tools to investigate Nuclear Structure. Significant progress in this field was achieved through the use of arrays of Compton-suppressed high purity germanium detectors, leading for instance to the discovery of phenomena such as nuclear superdeformation. However, it is apparent that the present generation devices are not suited to the expected experimental conditions at the planned and under construction radioactive ion beam facilities. Devices with higher efficiency and sensitivity should be developed. The solution which has been proposed since the mid-nineties relies on the possibility to determine the position and the energy deposition of the individual interaction points of a photon within a germanium crystal, and on the capability to reconstruct the photon scattering sequence through powerful signal analysis algorithms. The results of Monte Carlo simulations suggest that indeed an array of germanium detectors using such techniques, which are known as Pulse Shape Analysis and gamma-ray tracking, will reach the performance required to operate effectively at the future radioactive ion beam facilities. Presently, two major projects aim at the construction of an array of germanium detectors based on the pulse shape analysis and gamma ’–ray tracking techniques, namely GRETA in the USA and AGATA in Europe. The present work describes the results obtained during the first in-beam test performed with the prototype detector of AGATA. The goal of the experiment was essentially to measure the precision on the position of the individual interaction points extracted with pulse shape analysis algorithms. Such a precision plays an essential role in determining the overall performance of the array. Chapter 1 deals briefly with the most actual topics in Nuclear Structure studies, pointing to the necessity to develop new generation radioactive ion beam facilities, as well as new detection systems such as AGATA. The status of the AGATA project is reviewed in Chapter 2, together with a short introduction to the principles of gamma-ray tracking and of pulse shape analysis. The results from the in-beam test with the AGATA prototype detector are presented in Chapter 3, where the data analysis procedure is described in detail. Finally, in Chapter 4 a possible technique to extract the position resolution of the AGATA detectors through Compton imaging techniques is presented, together with some preliminary results.