D. G. Sarantites

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

A 4π 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.

Large deformation in A ~ 170 nuclei at high excitation energies

Abstract The γ -ray decay of the giant dipole resonance was measured in coincidence with fission fragments following the fusion reaction 16 O+ 159 Tb forming 175 Ta at 123.4 MeV excitation energy. A large splitting of the giant dipole resonance (GDR) energies in the compound system was observed corresponding to a large deformation of β =0.55.

Time scale for proton emission from highly excited projectiles

Abstract Highly fragmented exit channels produced by the decay of excited 24Mg projectiles were detected. The longitudinal velocity spectra of protons and alpha particles from such channels are offset. This offset is consistent with post-breakup Coulomb accelerations from the 197Au target nuclei implying that the protons were emitted within 3 X 10−22 s after the target-projectile separation.

“The tube”: a simple 4π detector for enhancing channels in γ-ray spectroscopy experiments

Abstract A simple 4 π charged-particle sensitive detector useful for γ-ray spectroscopy is described. The detector is a plastic scintillator tube, which surrounds the target. The tube is segmented into four optically isolated cylindrical arcs. The tube is an efficient charge particle hit detector with a very small photon interaction probability.