A modular NIM electronics for Pulse Shape method with the large area n-planar silicon detectors of the 4π CHIMERA

A new modular NIM electronics has been developed for pulse shape discrimination (PSD) of the signals produced in silicon (Si) detectors. The main purpose in design the module was the possibility to achieve Z-identification of light nuclear fragments (Z < 15) which are stopped in the active region of a silicon detector, with a charge resolution as good as that one commonly obtained with an energy loss ΔE - E method requiring a two-stage telescopes. In the present study, a simple PSD method based on the rise time measurement of the charge signal is proposed. The method was developed for the silicon detectors of the 4π array CHIMERA and, consequently, it was implemented in a compact NIM module. This implementation allows for charge discrimination of fragments with charge Z < 15 and energy threshold as low as 4.5 MeV/nucleon (for Z = 6). This result is the natural follow on of a previous work recently done for the large area planar silicon detectors of CHIMERA, where the silicon detectors were used in both direct and reverse injection. The good performance of the constant fraction discrimination (CFD) required to trigger a start signal allowed to use this signal for time of flight (TOF) methods.