Digital Signal Processing for segmented HPGe Detectors: Preprocessing Algorithms and Pulse Shape Analysis

MINIBALL is an versatile spectrometer consisting of 24 longitudinally six-fold segmented HPGe detectors, build for the efficient detection of rare decays in nuclear reactions of radioactive ion beams. MINIBALL was the first spec- trometer equipped with digital electronics. Pulse shape analysis algorithms to determine the interaction position of -rays were implemented on a Digital Signal Processor and validated in an experiment using a collimated -ray source. Emphasis was placed on the properties of the different digital signal processing algorithms, the consequences for the implementation and the applicability for position determination. The next generation of -ray spectrometers will consist of highly segmented HPGe detectors equipped with digital electronics, resulting in a more than ten-fold increase in complexity compared to current spectrometers. To enable the construction of a -ray tracking spectrometer, new and powerful digital elec- tronics will be developed. Preprocessing algorithms, giving the -ray energy and generating event triggers, were implemented on a VME module equipped with fast A/D converters and tested with different detectors and sources. Emphasis was placed on the detailed simulation and understanding of the algorithms as well as the influence of electronics and detector onto the energy resolution.