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This work describes the development of a gamma detector based on silicon drift detectors (SDDs) to read out large \LaBr_3:\Ce scintillators for gamma-ray astronomy applications, within an activity supported by the European Space Agency (ESA). SDDs, characterized by high quantum efficiency and low electronic noise, when coupled with a scintillator are good candidates for gamma-ray spectroscopy applications in a wide energy range, e.g., from 150 keV to 15 MeV. The gamma-ray detector prototype presented here is composed of a 2^\prime^\prime\times2^\prime^\prime \LaBr_3:\Ce scintillator coupled with four SDD arrays arranged in a 2 \times 2 format (a total of 36 SDDs). This detection system is operated with custom readout application specific integrated circuits (ASICs) and a data acquisition (DAQ) system. With this prototype gamma-camera, an energy resolution of 3.4% FWHM at 662 keV has been measured. Spectroscopy measurements have been carried out between 300 keV and 1800 keV and the achieved results are consistent with the electronic noise of the SDD technology. In this work, we report on the SDD based detection head’s design, its X-ray characterization, readout electronics, experimental setups and gamma-ray spectroscopy results. Finally, perspectives with the possible use of an improved SDD technology are discussed. [ABSTRACT FROM AUTHOR]

In this work, we report on a new development of Silicon Drift Detectors (SDDs) for gamma-ray spectroscopy with space science applications. The research is supported by the European Space Agency through the Technology Research Programme (TRP). The final goal of the development is the realization of monolithic arrays of SDDs which will be assembled to readout large (2” and 3”) LaBr3(Ce) scintillators. We present here the results of the development of a single SDD prototype, with 8 \times 8~mm^2 active area, produced at Fondazione Bruno Kessler (FBK) semiconductor laboratories. We discuss the design issues related to the specific use of this device as a photo-detector for scintillators. Then, we focus on the read-out electronics. Since this SDD does not include a front-end transistor on the silicon chip, we have adopted a CMOS charge preamplifier (CUBE) recently developed at Politecnico di Milano. This preamplifier has allowed the achievement of state-of-the-art noise performance using a SDD technology process without the integration of the FET (Field Effect Transistor) on the detector chip. A quantum efficiency of about 80% has been measured for the SDD at the emission wavelength band of LaBr3 (360–380 nm). First experimental measurements consisting of direct ^55 Fe irradiation of the SDD without scintillator, have demonstrated energy resolution of 140 eV and 129 eV at -20^\circC and -43^\circC respectively. By coupling the SDD with a LaBr3(Ce) scintillator (9 mm diameter), we have measured energy resolution of 5.6% FWHM and 2.6% FWHM at 122 keV and 662 keV respectively. [ABSTRACT FROM PUBLISHER]

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28×28×20 mm 3 (length×breadth × thickness) LaBr 3 :Ce crystal, a 25×25×20 mm 3 CeBr 3 crystal and a 25×25×10 mm 3 CeBr 3 crystal. Each crystal was encapsulated and coupled to an array of 4×4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133 Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr 3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z -coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr 3 :Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical interface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr 3 :Ce and 5.5% for CeBr 3 . The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively. [ABSTRACT FROM AUTHOR]