Abstract-- The capability of digital pulse shape technique to acquire data from CHIMERA detection cells (Si-CsI(Tl) telescopes) has been evidenced in our previous works. ∆E-E scatter plots to obtain charge identification for the detected reaction products and Fast-Slow scatter plots from the CsI(Tl) light pulses for light charged product identification have been carefully reconstructed. We have now applied this technique to the charge discrimination of the products which stop in the silicon detectors, by using large area totally depleted CHIMERA silicon detectors (300 µm thick, 5 x 5 cm 2 area) in reverse mount. In preliminary tests full charge identification for the reaction products up to Z=11 have been obtained for products both crossing the silicon detector (∆E-E technique) and stopping in it, using a 21.1 MeV/u 20 Ne beam at the LNS Superconducting Cyclotron in Catania. The quality of the obtained results clearly indicates that the digital signal processing approach is able to give excellent results in this application, too. I. INTRODUCTION T is well known that the pulse shape of solid state detectors depends on the density and the spatial distribution of charge carriers generated by the detected ions. The sensitivity of the pulse shape to length and density of ionization tracks – and thus to mass, charge, and energy of the detected ions – depends essentially on plasma and charge- carrier-drifting effects. By using charge-sensitive Manuscript received October 7, 2004. This work was supported in part by the Italian Ministry for University and Research (MIUR) under contract COFIN2002. M. Alderighi, and G. R. Sechi are with Istituto Nazionale di Fisica Nucleare and Istituto di Astrofisica Spaziale e Fisica Cosmica CNR, via Bassini 15, I- 20133 Milano, Italy (telephone: +39-0223699333). F.Amorini, A. Anzalone, S.Cavallaro, E. Laguidara, G. Lanzalone, C.Maiolino, F.Rizzo, F. Porto are with Università di Catania – Dipartimento di Fisica and Laboratorio Nazionale del Sud, via Santa Sofia 44, I-95123 Catania, Italy (telephone: +39-095542111). G. Cardella, E. De Filippo, G. Lanzanò, A. Pagano, M. Papa, S. Pirrone, G. Politi, G. Saccà, are with Istituto Nazionale di Fisica Nucleare and Università di Catania – Dipartimento di Fisica e Astronomia, Via S. Sofia 64, I-95123 Catania, Italy (telephone: +39-0953785111). R. Bassini, C. Boiano, P. Guazzoni, S. Russo, M. Sassi and L. Zetta are with Università degli Studi di Milano - Dipartimento di Fisica dell’Università and Istituto Nazionale di Fisica Nucleare, via Celoria 16, I-20133 Milano, Italy (telephone: +39-0250317249; e-mail: Paolo.Guazzoni@mi.infn.it). preamplifiers, the total charge-collection time (plasma erosion- time plus charge carriers drift-time) corresponds to the rise time of the output signals. In 1963, Ammerlaan et al. [1] have shown that the shape of signals from silicon solid state detectors, following the interaction of an ionizing particle can be employed for particle identification, due to its strong dependence on the nuclear charge Z. In fact the pulse shape depends on the density and spatial distribution of space carriers (electron and holes) produced by the charged particle, because of plasma effects [2] and finite drift time of charge carriers [1]. A careful analysis of experimental data [3], by means of numerical simulation [4], and experimental investigations, performed by Pausch et al. [5,6], exploited the dependence of the plasma erosion time and charge carrier drift time effects on the electric field distribution inside the detector and on the density and length of the ionizing track, i.e. on the mass, charge and energy of the detected ion. When the range of the incident particle is comparable with the thickness of the detector, clear Z-discrimination is obtained via the measurement of the risetime of the signals collected from totally depleted silicon detectors. When, however, the range is small in comparison with the thickness of the detector, the measured risetimes coalesce into a broad band. The Z-separation for this second ensemble of particles can be enhanced by allowing them to enter from the rear side (n-side) of the totally depleted detector. This is due to the lower electric field in the entrance region and the lower velocity of the holes which are mainly responsible for the signal formation [4,7]. Moreover this method takes advantage of the rising field profile with penetration depth which minimize the plasma erosion effect at the Bragg maximum near the end of the trace. The big advantage of the Z-discrimination obtained with this technique is that it takes place in a single detector. When the technique is combined with a simultaneous time-of-flight measurement using a pulsed beam, complete identification of the ions stopped in the detector is possible. Consequently the shape of the signals, and in particular their rise-time and height, can be used for particle identification [3] Digital Pulse-Shape Technique for Charge Discrimination in Reversed CHIMERA Silicon Detectors M.Alderighi, F.Amorini, A.Anzalone, R.Bassini, C.Boiano, G.Cardella, S.Cavallaro, E.DeFilippo, P.Guazzoni, E.Laguidara, G.Lanzanò, G.Lanzalone, C.Maiolino, A.Pagano, M.Papa, S.Pirrone, G.Politi, F.Porto, F.Rizzo, S.Russo, G.Saccà, M.Sassi, G.Sechi, L.Zetta. I 0-7803-8701-5/04/$20.00 (C) 2004 IEEE