Search

Abstract: The next generation of detector arrays for heavy ion studies will largely use Pulse Shape Analysis to push the performance of silicon detectors with respect to ion identification. Energy resolution and pulse shape identification capabilities of silicon detectors under prolonged irradiation by energetic heavy ions have thus become a major issue. In this framework, we have studied the effects of irradiation by energetic heavy ions on the response of neutron transmutation doped (nTD) silicon detectors. Sizeable effects on the amplitude and the risetime of the charge signal have been found for detectors irradiated with large fluences of stopped heavy ions, while much weaker effects were observed by punching-through ions. The robustness of ion identification based on digital pulse shape techniques has been evaluated. [Copyright &y& Elsevier]

Abstract: The response of silicon–silicon–CsI(Tl) telescopes, developed within the FAZIA collaboration, to fragments produced in nuclear reactions 84Kr+120-124Sn at 35AMeV, has been used to study ion identification methods. Two techniques are considered for the identification of the nuclear products in the silicon stages. The standard one requires signals induced in two detection layers by ions punching through the first one. Conversely, the digital Pulse Shape Analysis (PSA) allows the identification of ions stopped in the first silicon layer. The capabilities of these two identification methods have been compared for different mountings of the silicons, i.e. rear (particles entering through the low electric field side) or front (particles entering through the high electric field side) side injection. The identification method gives exactly the same results in both configurations. At variance, the pulse shape discrimination is very sensitive to the detector mounting. In case of rear side injection, the identification with the “energy vs. charge rise time” PSA method presents energy thresholds which are significantly lower than in the case of front side injection. [Copyright &y& Elsevier]

Abstract: The response of silicon–silicon–CsI(Tl) and silicon–CsI(Tl) telescopes to fragments produced in nuclear interactions has been studied. The telescopes were developed within the FAZIA collaboration. The capabilities of two methods are compared: (a) the standard technique and (b) the digital Pulse Shape Analysis technique (for identification of nuclear fragments stopped in a single Si-layer). In a test setup, nuclear fragments covering a large range in nuclear charge, mass and energy were detected. They were produced in nuclear reactions induced by a 35A MeV beam of 129Xe impinging on various targets. It was found that the correlations allow the identification of all isotopes up to . With the digital Pulse Shape Analysis it is possible to fully distinguish the charge of stopped nuclei up to the maximum available Z (slightly over that of the beam, Z=54). [Copyright &y& Elsevier]

Abstract: In the last few years the FAZIA collaboration has been investigating the properties of silicon detectors – in particular the crystal orientation and resistivity non-uniformity – in order to better pin down the detector characteristics that influence their performances for particle identification using and Pulse Shape Analysis (PSA) techniques. In this paper we present the first particle identification results obtained with detectors selected for good resistivity uniformity and using a “non-channeled” configuration. A new digital electronics was also designed for the R&D phase of FAZIA and was tested under beam for the first time. A quantitative procedure to measure the observed performances is applied in order to quantify the particle identification thresholds. Particle identification thresholds of for have been reached with the studied reaction. [Copyright &y& Elsevier]

Abstract: Current pulses induced in a silicon detector by 10 different heavy ion species at known energies around 10AMeV have been sampled in time at high frequency. Their individual average shapes are quite well reproduced by a fit procedure based on our recent charge carrier collection treatment which considers the progressive extraction of the electrons and holes from the high carrier density zone along the ionizing particle track. This region is assumed to present a supplementary dielectric polarization and consequently a disturbed electric field. The influence of the nature of the heavy ion on the values of the three fit parameters is analyzed. [Copyright &y& Elsevier]

Abstract: Current and charge signals have been collected for Se ions at 408MeV, S at 160MeV and Ni at 703MeV, all stopped in silicon detectors. Some detectors were cut off the axis and some off the axis. Important effects on the shape of the silicon current and charge signals have been observed, depending on the orientation of the impinging ion relative to the crystal axes and planes. A degradation of the energy and risetime resolution of about a factor with respect to the measured optimal values (for example off-axis orientation) is observed for ion impinging directions close to crystal axes and/or planes, i.e. the common scenario for normal incidence on cut detectors. For Pulse Shape Analysis applications, the necessity of using such “random” oriented silicon detectors is demonstrated. [Copyright &y& Elsevier]

New charge- and current-sensitive preamplifiers coupled to silicon detectors and devoted to studies in nuclear structure and dynamics have been developed and tested. For the first time shapes of current pulses from light charged particles and carbon ions are presented. Capabilities for pulse shape discrimination techniques are demonstrated. [Copyright &y& Elsevier]