Design, instrumentation and response characteristics of a 2π multi-detector of CsI(Tl) scintillators mounted inside the Plastic Ball spectrometer

A 2π hemispherical detector consisting of 64 CsI(Tl) scintillator modules covering the angular range of 80o-160o has been constructed. This detector is employed as the Inner Shell of the Plastic Ball detector and was used in two experimental programs concerning the study of pionic fusion in light-ion systems. The geometry and construction are presented. The improved response of the combined detectors for photons are discussed. An energy calibration method using high energy cosmic muons for the Inner Shell and the Plastic Ball has been developed and the calibration results are compared to the results of the same method in the Monte-Carlo simulation. The improved acceptance of the combined detectors for the π0 detection in the 6Li(4He, π0)10B* experiment are presented and discussed.