Particle Identification In Solid-State Detectors By Exploiting Pulse Shape Information

The pulse shapes of current signals were investigated for various silicon detectors of 450 to 2000 mum thickness irradiated with reaction products from S-32 (795 MeV) + Au and C-12 (380 MeV) + Ho. Particle information was found to be present not only in the rise time, but also in the pulse length and in the ratio of charge samples taken at different times. By integrating the whole current signal as well as a defined pulse fraction by means of two QDC channels with different (long and short) integration gates we were able to obtain simultaneously energy and particle information. This simple and cheap technique of signal processing which has already been used for large phoswich arrays has proved to be well suited for the 4pi solid-state multidetector ("Silicon Ball") which is presently under construction at the Hahn-Meitner-Institut. Charge numbers up to Z = 16 are resolved for fast intermediate-mass fragments.