Dwarf Ball and Dwarf Wall: Design, instrumentation, and response characteristics of a 4 π CsI(Tl) plastic phoswich multidetector system for light charged particle and intermediate mass fragment spectrometry

Abstract

A 4 π multidetector intermediate mass fragment and charged particle spectrometer is described. It consists of the Dwarf Ball section with 65 CsI(Tl) plastic scintillator phoswiches closely packed to cover the angular range of 32°–168°, and the Dwarf Wall section, with 40 CsI(Tl) plastic phoswiches covering the angular range of 4°–32°. For each detector that fires, three regions of the photomultiplier anode current are separately integrated; one at early times for the fast plastic ΔE, another at intermediate times for the bulk of the signal from the CsI(Tl), and a third in the tail region of the CsI(Tl) signal. In addition, the times are recorded for each detector that fires. From this information, 1,2,3H, 3,4He and the elements from Li to Mn can be identified and their energies measured over a large dynamic range. The geometry, construction, energy calibration, gain stability, associated electronics, and an approximate light charged particle identification procedure are discussed. Examples of the performance of the spectrometer from heavy-ion induced reaction experiments are given. The capabilities of this device as a channel selecting device in conjunction with the spin spectrometer are also discussed.