A combined module for detecting charged particles in a wide dynamic range

The construction of a modular detector system is described, which is based on a set of detectors with different stopping powers covering a wide dynamic range (1-500). Each module is composed of a position-sensitive avalanche counter, an ionization chamber of the Bragg type, and a CsI(Tl) scintillation crystal detector array. A system of 30 modules forms a 4 pi PHOBOS setup (Laboratory of Nuclear Reactions, JINR) capable of studying nuclear reactions involving heavy nuclei with energies up to 100 MeV/nucleon. The intrinsic time resolution of an avalanche counter is 0.2 ns, and its coordinate resolution is 2 mm; the energy resolution of the Bragg chamber is 1%, and the accuracy of charge determination corresponds to Z/dZ = 65 for Al. The CsI(Tl) scintillation counters ensure the stopping of light charged particles with energies up to 65 MeV/nucleon. An analysis of the shape of light pulses allows light particles with Z < 3 to be identified. The combined detector modules have been successfully employed in experiments on the PHOBOS setup since 1993.