Influence of crystal-orientation effects on pulse-shape-based identification of heavy-ions stopped in silicon detectors

Current and charge signals have been collected for Se ions at 408 MeV, S at 160 MeV and Ni at 703 MeV, all stopped in silicon detectors. Some detectors were cut 0∘0∘ off the 〈111〉 axis and some off the 〈100〉 axis. Important effects on the shape of the silicon current and charge signals have been observed, depending on the orientation of the impinging ion relative to the crystal axes and planes.A degradation of the energy and risetime resolution of about a factor ∼3∼3 with respect to the measured optimal values (for example 7∘7∘ off-axis orientation) is observed for ion impinging directions close to crystal axes and/or planes, i.e. the common scenario for normal incidence on 0∘0∘ cut detectors.For Pulse Shape Analysis applications, the necessity of using such “random” oriented silicon detectors is demonstrated.