RoSiB - a 4 pi silicon ball for charged-particle detection in EUROBALL

Pausch, G Prade, H Sobiella, M Schnare, H Schwengner, R Kaubler, L Borcan, C Ortlepp, HG Oehmichen, U Grawe, H Schubart, R Gerl, J Cederkall, J Johnson, A Kerek, A Klamra, W Moszynski, M Wolski, D Kapusta, M Axelsson, A Weiszflog, M Hartlein, T Pansegrau, D de Angelis, G Ashrafi, S Likar, A Lipoglavsek, M

G. Pausch et al., RoSiB - a 4 pi silicon ball for charged-particle detection in EUROBALL, NUCL INST A, 443(2-3), 2000, pp. 304-318

20

INGLESE

Article

Spectroscopy /Instrumentation/Analytical Sciences","Instrumentation & Measurement

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT

0168-9002 → ACNP

443

2-3

2000

304 - 318

ISI

0168-9002(20000401)443:2-3<304:R-A4PS>2.0.ZU;2-G

A 4 pi silicon bail for detection and identification of light charged parti cles in large multidetector gamma-arrays as EUROBALL is presented. The desi gn is based on a N = 42 ball with 12 pentagons and 30 hexagons as used in t he GASP array. The absorptive material for gamma-rays is minimized to the d etector thickness of 300 or 500 mu m and a 0.63 mm ceramic backing. The geo metrical coverage is designed for about 90% of 4 pi. A pulse shape discrimi nation method with totally depleted detectors working in the reverse mount allows identifying protons and alpha-particles above an energy threshold of about 2 MeV. The performances of the ball were rested at the tandem - boos ter accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228 MeV Ni-58 + Ti-46 and the low-recoil reacti on of 95 MeV O-16 + Ni-58. The two-dimensional spectra of zero-crossing (ZC ) versus energy confirmed an excellent discrimination of protons and alpha- particles in all the detectors at different angles. The energy spectra of p rotons and alpha-particles measured in the experiments are presented. too. The gamma-spectra measured in coincidence with various combinations of emit ted particles showed a high selectivity of the ball. The reduced total effi ciency for protons of 59% and 55% and alpha-particles of 44% and 32% measur ed in a nuclear spectroscopy application is analyzed in a Monte-Carlo simul ation (GEANT). It is due to a combined influence of a thick target needed t o stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extr apolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channel s with heavy ions. (C) 2000 Elsevier Science B.V. All rights reserved.