“The microball” Design, instrumentation and response characteristics of a 4π-multidetector exit channel-selection device for spectroscopic and reaction mechanism studies with Gammasphere

Role of 4π charged-particle detector arrays in lifetime measurements by Doppler-shift attenuation methods: the Microball

“…Furthermore, it is difficult in the offline analysis to distinguish low-energy protons from low-energy α particles. One should also recall that there are absorbers placed in front of the CsI detectors [3]. These absorbers stop the large amounts of δ-ray electrons produced in the reaction, and prevent scattered beam from entering the detectors at the forward angles.…”

“…5(a), the energies of protons in experiment GSFMA8 measured in a ring-2 detector of the Microball (at 21 • ) are plotted versus the ratio of the charges integrated over the fast and slow gates on the CsI signal (the so-called PID ratio, see Ref. [3] for details). The measured proton energies increase until they reach a maximum value E max , indicated by the dashed line on Fig.…”

“…Equivalently, one could count the events in the punchthrough region directly, although, due to PID resolution loss at high counting rates (refer to Ref. [3]), it may be difficult to separate these from the normal events in the region near E max .…”

“…7 and 8 in Ref. [3]), in a typical fusion-evaporation reaction only protons and α particles are measured. If deuteron-like signals appear in the spectra, they can be assumed to be a pair of double-hit protons and these events can be recovered.…”

“…The capabilities of these devices, however, can be greatly improved by the addition of auxiliary detectors. One particularly successful addition to Gammasphere is the Microball [3], a 4π array of 95 CsI(Tl) detectors. The Microball can be used to identify the charged particles emitted by compound nuclei, affording the opportunity to select, or gate on, the reaction channel of interest and exclude other channels.…”