The Advanced GAmma Tracking Array (AGATA) is a next-generation gamma-ray spectrometer for nuclear
physics being developed as part of a Europe-wide collaboration. AGATA aims to vastly improve upon the
sensitivity of today's arrays by removing the BGO shields used to suppress the Compton background and
instead, tracking gamma rays through a complete 4π shell of Germanium using Gamma Ray Tracking (GRT).
In order to facilitate this, Pulse Shape Analysis (PSA) must be used to accurately locate the position of each
gamma-ray interaction within each detector.
The preferred approach to PSA relies on the generation of a database of typical pulse shapes produced by
interactions at each position on a grid throughout the detector. This paper details current progress at the
University of Liverpool toward validating the electric field simulation, which will be used to generate the pulse
shape database, with experimental data from an asymmetric AGATA detector. The field simulation is discussed
and some comparisons are made between this and a two dimensional raster scan of the detector with a highly
The Advanced GAmma Tracking Array (AGATA) is a European project that is aiming to construct a complete 4π High
Purity Germanium (HPGe) gamma-ray spectrometer for nuclear structure studies at future Radioactive Ion Beam (RIB)
Facilities. The proposed array will utilise digital electronics, Pulse Shape Analysis (PSA) and Gamma-Ray Tracking
(GRT) algorithms, to overcome the limited efficiencies encountered by current Escape Suppressed Spectrometers (ESS),
whilst maintaining the high Peak-to-Total ratio.
Two AGATA symmetrical segmented Canberra Eurisys (CE) prototype HPGe detectors have been tested at the
University of Liverpool. A highly collimated Cs-137 (662keV) beam was raster scanned across each detector and data
were collected in both singles and coincidence modes. The charge sensitive preamplifier output pulse shapes from all 37
channels (one for each of the 36 segments and one for the centre contact) were digitised and stored for offline analysis.
The shapes of the real charge and image charge pulses have been studied to give detailed information on the position
dependent response of each detector. 1mm position sensitivity has been achieved with the parameterisation of average
pulse shapes, calculated from data collected with each of the detectors. The coincidence data has also been utilised to
validate the electric field simulation code Multi Geometry Simulation (MGS). The precisely determined 3D interaction
positions allow the comparison of experimental pulse shapes from single site interactions with those generated by the
simulation. It is intended that the validated software will be used to calculate a basis data set of pulse shapes for the
array, from which any interaction site can be determined through a χ<sup>2</sup> minimisation of the digitized pulse with linear
combinations of basis pulseshapes. The results from this partial validation, along with those from the investigation into
the position sensitivity of each detector are presented.