Study of the performance of tracking algorithms for the DESPEC planar setup

DESPEC is one of the experiments of the low-energy branch project of the future installations at FAIR (GSI). The main goal of this experiment is to study the decay properties of exotic nuclei. The basic instrumentation of this setup includes a set of implantation detectors, a Ge array and neutron detectors. Presently the collaboration is considering two possible setups for the Ge array. One possibility is to use an array of stacks of planar Ge detectors specifically designed for DESPEC. The other alternative is to use standard segmented Ge detectors of EXOGAM [1] or TIGRESS [2] type. The R&D phase requires the realization of Monte Carlo (MC) simulations to determine the optimal setup for the future facility. In this annual report we present a preliminary study of the application of tracking techniques to the results of the simulations. The idea is to apply the recent developments for the tracking array AGATA to exploit maximally the possibilities of the new array for DESPEC. To perform this study a new MC code was developed which generates a list-mode output that can be used in combination with the tracking programs and algorithms developed for AGATA. This output resembles the ones obtained in a real experiment after using the pulse shape technique and contains information on the position of the interactions and the deposited energy in the sensitive parts of the array after the interaction with radiation. The results obtained for the planar setup are presented here. This setup consists on an array of 24 composite planar detectors. Each detector unit is formed by a stack of three planar Ge detectors with dimensions 72 × 72× 22 mm with an active Ge volume of 68 × 68 × 22 mm. The distance between the planars is 3 mm and the stack is encapsulated in an Al capsule of 1.5 mm thickness. The composite detectors are positioned around a focal plane of 240 × 80 mm. The described geometry has been implemented using the MC code GEANT4 [3]. In this work the tracking code MGT developed by D. Bazzacco was used [4]. The MGT code has several ingredients: first a preprocessing of the interaction points is done in order to take into account the effects of a non-ideal pulse shape analysis, next the interaction points are clustered and a reconstruction process is applied (forward tracking) and finally the results of the reconstruction process are accepted or rejected according to a validation criteria. The results, presented in Table 1, correspond to the application of the MGT code to simulation data of centered, point-like monoenergetic gamma sources. The first column