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GALILEO, a new 4 π high-resolution γ -detection array, based on HPGe detectors, has been developed and installed at the Legnaro National Laboratories. The GALILEO array greatly benefits from a fully-digital read-out chain, customized DAQ, and a variety of complementary detectors to improve the resolving power by the detection of particles, ions or high-energy γ -ray transitions. In this work, a full description of the array, including electronics and DAQ, is presented together with its complementary instrumentation.

The GALILEO γ -ray spectrometer has been constructed at the Legnaro National Laboratory of INFN (LNL-INFN). It can be coupled to advanced ancillary devices which allows nuclear structure studies employing the variety of in-beam γ -ray spectroscopy methods. Such studies benefit from reactions induced by the intense stable beams delivered by the Tandem-ALPI-PIAVE accelerator complex and by the radioactive beams which will be provided by the SPES facility. In this paper we outline two experiments performed within the experimental campaign at GALILEO coupled to the EUCLIDES Si-ball and the Neutron Wall array. The first one was aimed at spectroscopic studies in A=31 mirror nuclei and the second one at measurements of lifetimes of excited states in nuclei in the vicinity of 100 Sn.

FARCOS is a modular detection system intended to boost the capacity of 4π detectors towards correlation measurements. The final FARCOS system will be composed of 20 telescopes, each formed by two Si layers of 32-ch orthogonal Double Sided Silicon Strip Detectors and one calorimeter stage composed by 4 CsI(Tl) tronco-pyramidal scintillator crystals readout by a Si photodiode. The paper focuses on the first application of the FARCOS detection array in the present configuration of 10 telescopes in a real experiment, the CHIFAR experiment and discusses the main instrumental features relevant for the experiments.

The FARCOS (Femtoscope ARray for Correlation and Spectroscopy) collaboration is finally going to instrument the first batch of 10-12 telescopes. They are capable of reconstructing the particle’s momentum with a high degree of precision and of performing correlation measurements of Light Charged Particles (LCPs) and of LCPs and Intermediate Mass Fragments thanks to the very good energy and angular and resolution. Each telescope features a sensitive area of 6.4 × 6.4 cm2 and is composed of three detection stages: two Si layers and a CsI(Tl) calorimeter. The FARCOS cluster modularity allows the arrangement in different configurations, depending on the physics case one wants to address. The final system will be a modular assembly of 20 telescopes. The total number of readout channels for the final FARCOS system is 2560 channels for the silicon layers and 80 channels for the scintillators. In this paper, we focus on the FARCOS basic module and system architecture and illustrate its performance as assessed in test beams in true experimental conditions.

The position sensitivity of a thick, cylindrical and continuous 3” x 3” (7.62 cm x 7.62 cm) LaBr3:Ce crystal was studied using a 1 mm collimated beam of 662 keV gamma rays from a 400 MBq intense 137Cs source and a spectroscopic photomultiplier (PMT) (HAMAMATSU R6233-100SEL). The PMT entrance window was covered by black absorber except for a small window 1 cm x 1 cm wide. A complete scan of the detector over a 0.5 cm step grid was performed for three positions of the 1 cm x 1 cm window. For each configuration the energy spectrum was measured and the peak centroid, the FWHM, the area and peak asymmetry of the 662 keV gamma transition were analyzed. The data show that, even in a 3” thick LaBr3:Ce crystal with diffusive surfaces the position of the full energy peak centroid depends on the source position. We verified that, on average, the position of the full energy peak centroids measured in the three 1 cm x 1 cm window configurations is sufficient for the correct identification of the collimated gamma source position.

The EXPADES (EXotic PArticle DEtection System) detector array consists of 16 Double Side Silicon Strip Detectors (DSSSD) with active areas of 64 × 64 mm 2 , arranged in 8 ΔE (40/50 μm)–E (300 μm) telescopes. All detector faces are segmented into 32 × 2-mm wide strips, ensuring a 2 × 2 mm 2 pixel configuration. Eight ionization chambers can be alternatively used as ΔE stages or, if needed, as an additional third layer for more complex triple telescopes. The signals from silicon ΔE layers and from ionization chambers are read by standard electronics, while innovative 32-channel ASIC chips are employed for the readout of the E stages. The results of off-line tests with alpha sources and from the first in-beam experiment with a 17 O beam are presented.

Few years ago we proposed a novel detection system textbf- named FARCOS (Femtoscopy ARray for COrrelations andSpectroscopy) – to target different open cases in nuclear physics. The basic cluster unit of the FARCOS array is a telescope structure with an active area of $6.4 \times 6.4$ cm$^{\mathbf {2}}$ composed of three detection stages. The first two detection layers are DC-coupled Double-Sided Silicon Strip Detectors (DSSSDs), 300 $\mu \textbf{m}$ thick and 1500 $\mu \textbf{m}$ thick, featuring $32 \times 32$ orthogonal strips. The third stage, acting as calorimeter, is composed of four truncated pyramids of CsI(Tl) crystals with an active area of $3.2 \times 3.2$ cm$^{\mathbf {2\, }}$textbfand an absorption length of 6 cm arranged in window configuration. The final system will be a modular assembly of 20 telescopes.A key feature of FARCOS is the identification of the particles stopping even in the first detection layer, relying on pulse shape analysis techniques. The FARCOS frontend electronics features a full scale energy range up to 2 GeV with 5 different selectable ranges and an energy resolution down to 10 keV FWHM with a power budget of about 10 mW/channel in the case of the lower full scale energy range. Its core is a custom multichannel charge preamplifier VLSI chip.The system performance has been extensively qualified on few workhorses in view of the assembly of the final telescopes foreseen for 2018.

The 16-channel fast stretcher BaFPro module, originally developed for processing signals of Barium Fluoride scintillators, has been modified to make a high performing analog pulse-shape analysis of signals from the NE213 liquid scintillators of the EDEN neutron detector array. The module produces two Gaussian signals, whose amplitudes are proportional to the height of the fast component of the output light and to the total energy deposited into the scintillator, respectively. An in-beam test has been performed at INFN-LNS (Italy) demonstrating a low detection threshold, a good pulse-shape discrimination even at low energies and a wide dynamic range for the measurement of the neutrons energy.

Silicon Photomultipliers (SiPMs) are excellent devices to detect the faint and short Cherenkov light emitted in high energy atmospheric showers, and therefore suitable for use in imaging air Cherenkov Telescopes. The high density Near Ultraviolet Violet SiPMs (NUV-HD3) produced by Fondazione Bruno Kessler (FBK) in collaboration with INFN were used to equip optical modules for a possible upgrade of the Schwarzschild-Couder Telescope camera prototype, in the framework of the Cherenkov Telescope Array project. SiPMs are 6×6 mm2 devices based on 40×40 μm2 microcells optimized for photo-detection at the NUV wavelengths. More than 40 optical modules, each composed by a 4×4 array of SiPMs, were assembled. In this contribution we report on the development and on the assembly of the optical modules, their validation and integration in the camera.

We show the results of some test beams performed on a new monolithic strip silicon detector telescope developed in collaboration with the INFN and ST-microelectronics. Using an appropriate design, the induction on the ΔE stages, generated by the charge released in the E stage, was used to obtain the position of the detected particle. The position measurement, together with the low threshold for particle charge identification, allows the new detector to be used for a large variety of applications due to its sensitivity of only a few microns measured in both directions.

The position sensitivity of a large LaBr 3 :Ce crystal was investigated with the aim of correcting for the Doppler broadening in nuclear physics experiments. The crystal was cylindrical, 3 in×3 in (7.62 cm x 7.62 cm) and with diffusive surfaces as typically used in nuclear physics basic research to measure medium or high energy gamma rays (0.5 MeV γ

We describe the experimental set-up of the Radioactive Ion Beam (RIB) in-flight facility EXOTIC consisting of: (a) two position-sensitive Parallel Plate Avalanche Counters (PPACs), dedicated to the event-by-event tracking of the produced RIBs and to time of flight measurements and (b) the new high-granularity compact telescope array EXPADES (EXotic PArticle DEtection System), designed for nuclear physics and nuclear astrophysics experiments employing low-energy light RIBs. EXPADES consists of eight Δ E – E res telescopes arranged in a cylindrical configuration around the target. Each telescope is made up of two Double Sided Silicon Strip Detectors (DSSSDs) with a thickness of 40/60 μm and 300 μm for the Δ E and Eres layer, respectively. Additionally, eight ionization chambers were constructed to be used as an alternative Δ E stage or, in conjunction with the entire DSSSD array, to build up more complex triple telescopes. New low-noise multi-channel charge-sensitive preamplifiers and spectroscopy amplifiers, associated with constant fraction discriminators, peak-and-hold and Time to Amplitude Converter circuits were developed for the electronic readout of the Δ E stage. Application Specific Integrated Circuit-based electronics was employed for the treatment of the Eres signals. An 8-channel, 12-bit multi-sampling 50 MHz Analog to Digital Converter, a Trigger Supervisor Board for handling the trigger signals of the whole experimental set-up and an ad hoc data acquisition system were also developed. The performance of the PPACs, EXPADES and of the associated electronics was obtained offline with standard α calibration sources and in-beam by measuring the scattering process for the systems 17O+58Ni and 17O+208Pb at incident energies around their respective Coulomb barriers and, successively, during the first experimental runs with the RIBs of the EXOTIC facility.

The response of a cylindrical continuous 3″ × 3″ LaBr3:Ce crystal coupled to four Position Sensitive photomultipliers (PSPMT) was studied using a 1 mm collimated beam of 662 keV gamma rays.

Fast scintillation detectors based on Lanthanum Bromide (LaBr 3 ) crystals are nowadays used in nuclear physics experiments, mainly to measure γ-ray energy and time information. The Milano group has developed a 10 large volume (3.5″×8″) LaBr 3 detector array (HECTOR+) and collaborates to a a γ-calorimeter based on tens of LaBr 3 -NaI phoswich detectors (PARIS). A dedicated 16 channels NIM analog module handling these photomultiplier detector signals has been developed in order to satisfy the experimental requests of both detector arrays. Each channel of the module provides two shaped signals, the “Slow Out” proportional to the total energy of the γ ray and the “Fast Out” proportional to the fast negative peak of the signal. For phoswich (LaBr 3 -NaI) detectors, the analysis of the two dimensional spectrum (fast versus slow) allows to disentangle the interactions in different part of the detector. If used with a pure LaBr 3 detector, the Fast output can be switched as a second energy output. An independent gain control of this second output allows to have a wide energy range. For each channel there is also a constant fraction discriminator (CFD) which generates the time information. Slow control of the module parameters such as gain, CFD thresholds, width of logic signals, etc. is possible through a RS485 serial line.

A fast gateless pulse stretcher has been developed for an easy acquisition of pulse-shape information of BaF/sub 2/ scintillator signals. Commonly, this information is obtained by the use of two QDCs with different integration windows. This technique becomes complex and rather inconvenient when signals need to be delayed. The developed circuit uses a fast-stretcher technique to generate pulse-shape information, which requires no delay lines or gate signals. The outputs consist of two Gaussian signals whose amplitudes are proportional to the height of the BaF/sub 2/ fast component and to the total energy deposited into the scintillator. These outputs are easily acquired with a standard peak ADC with no gate-timing problems. An excellent Fast-Slow separation has been obtained even with small input signals of only few millivolts. This technology is general purpose and can be used with any other scintillator whose light emission is characterized by two components with different lifetimes.

We suggest that some key physical parameters of high-purity germanium (HPGe) segmented detectors, including segment capacitance and leakage current, can be derived from standard noise measurements. These parameters are relevant when designing and optimizing the front-end electronics.

In this paper, we propose a new add-on circuit structure that swiftly desaturates a digitized charge preamplifier for ionizing-radiation detectors when an energetic event occurs, or when a burst of piled up events puts it into saturation. The amplitude of the energetic event can even be reconstructed with a time-over-threshold (TOT) measurement of the fast-reset transient. With an analog-to-digital converter (ADC) range of 10 MeV, we were able to measure events of up to 100 MeV. The circuit is conceived for experiments where a spurious background of energetic particles and photons exists, such those with exotic beams in the new generation of nuclear-physics research facilities.

The position sensitivity of a thick, cylindrical and continuous 3" × 3" (7.62 cm × 7.62 cm) LaBr3:Ce crystal with diffusive surfaces was investigated. Nuclear physics basic research uses thick LaBr3:Ce crystals (> 3cm) to measure medium or high energy gamma rays (0.5 MeV < Eγ< 20 MeV). In the first measurement the PMT photocathode entrance window was covered by black absorber except for a small window 1 cm × 1cm wide. A complete scan of the detector over a 0.5 cm step grid was performed. The data show that even in a 3" thick LaBr3:Ce crystal with diffusive surfaces the position of the full energy peak centroid depends on the source position. The position of the full energy peak centroids are sufficient to identify the collimated gamma source position. The crystal was then coupled to four Position Sensitive Photomultipliers (PSPMT). We acquired the signals from the 256 segments of the four PSPMTs grouping them into 16 elements. An event by event analysis shows a positon resolution of the order of 2 cm.

Two-point charge division is a typical technique for position measurements in linear multi electrode detectors (microstrips, multiwire proportional counters, silicon drift-detector arrays, and scintillators coupled to photodetectors). Only two preamplifiers, located at the right and the left ends of the detection array, are used, each of which receives a fraction of the charge produced by the ionizing event. Position is reconstructed comparing these charge fractions. In principle, either a resistive or a capacitive divider may be used to split the charge. The choice between such two different setups is not obvious. In fact, each of them shows advantages and disadvantages in terms of noise, signal propagation, and linearity. In this paper, we present a unified treatment for the capacitive and the resistive mechanisms of charge division that addresses the issues of this choice. As an example, the realistic setup of the multiwire position-sensitive proportional counter to be used in the TP-MUSIC III chamber of the ALADiN experiment at GSI is considered.

A new detection apparatus, named EXPADES (EXotic PArticle DEtection System), has been expressly designed to be used in nuclear physics experiments involving exotic beams and devoted to the study of nuclear reactions (scattering, direct reactions, breakup…) at energies around the Coulomb barrier. It consists of double-side segmented silicon detectors arranged in a compact configuration around the target. A very large solid angle, a wide angular range, high granularity and a highly miniaturized readout electronics, based on a new production commercial ASIC chipset, are the main features of the system.

Heavy ion studies with stable and exotic beams require the identification of nuclear frag- ments in a broad range of mass and atomic numbers. Recent progresses of the Pulse Shape Discrimination (PSD) method applied to the current signals of silicon detectors have en- couraged new studies in this field. The aim of our experimental study was to progress in this technique by applying PSD to charge signals produced in planar silicon detectors of large capacitance (1nF). A new electronic design based on a double constant-fraction discrimination of timing signals, was applied to some of the CHIMERA Si detectors, by using Tandem and Cyclotron beams delivered by the LNS in Catania. We obtained charge identification with energy threshold of about 4 AMeV from Z=1 up to fluorine and with good timing performances (direct injection mode). Our recent results strongly encourage for further application to 4π detection systems in the field of exotic beams.

[EN] A highly segmented silicon-pad detector prototype has been tested to explore the performance of the digital pulse shape analysis in the discrimination of the particles reaching the silicon detector. For the first time a 200 tun thin silicon detector, grown using an ordinary floating zone technique, has been shown to exhibit a level discrimination thanks to the fine segmentation. Light-charged particles down to few MeV have been separated, including their punch-through. A coaxial HPGe detector in time coincidence has further confirmed the quality of the particle discrimination. K.; 2014 Elsevier B.V. All rights reserved, This work has been supported by the Italian Ministry of Education, University and Research (MIUR) under the project FIRB/08-RBFR08RDKZ and partially supported by the Spanish Ministry of Science and Innovation (MICINN) under projects FPA2007-63074 (FINURA) and INGENIO-2010 (CPAN). The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under Grant Agreement no. 262010 ENSAR. One of the authors (V.V. P.) acknowledges the financial support through the INSPIRE faculty program, Department of Science and Technology, Government of India, in carrying out these investigations. The authors would like to extend appreciation to the technical staff of LNL Tandem for their assistance during the experiment and the local members of the EXOTIC project for their support in the preparation of the experimental setup

A selection of the properties of large volume, cylindrical 3.5” x 8” LaBr 3 :Ce scintillation detectors coupled to a 3.5” PMT (model R10233-1000SEL from HAMAMATSU) and a special designed Voltage Divider (LABRVD) will be discussed. A number of 10 of such detectors constitute the HECTOR + array which, in fall 2012, measured at GSI coupled to the AGATA DEMOSTRATOR at the PRESPEC experimental setup. These crystals are among the largest ever produced and needed to be characterized. We have performed several tests and here we discuss, in particular, the energy resolution measured using monochromatic γ −ray sources and in-beam reactions producing γ −rays up to 22.6 MeV. As already measured in two previous works a saturation in the energy resolution was observed in case of high energy gamma rays. Crystal non-homogeneities and PMT gain drifts can affect the resolution of measurements especially in case of high energy γ −rays.

The position sensitivity of a cylindrical continuous 3″ × 3″ (7.62 cm × 7.62 cm) LaBr 3 :Ce crystal was studied using a collimated beam of 662 keV gamma rays and a spectroscopic shielded PMT (HAMAMATSU R6233-100SEL) with standard passive voltage divider (HAMAMATSU E1198-26). The used crystal is sealed in a capsule and has diffusive/reflective surfaces to optimize the energy resolution. A complete scan of the crystal was performed with a 5 mm step grid. The data show that, in average, the image, produced by the scintillation light on the photocathode, changes with the source position. By using the measured full energy peak position using three different windows on the PMT it was possible to identify the position of the interaction of the incident gamma ray.

We investigated the merits of different event parameters in the identification of Light Charged Particles (LCPs) with CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). This investigation is made possible by digital signal processing the output signals. As in the conventional analogue case, the digitized signals allow the discrimination of light charged particles by computing the fast and slow components. In addition other identification parameters as the rise time of the output pulses of the CsI(Tl) come out nearly for free. Aim of this paper is the investigation of novel identification plots and the probe of their merits, in particular at relativistic energies. When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punch-through energies provide a complete set of data for the energy calibration of the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies the energy vs. rise time computation provide an efficient figure for the discrimination in charge and mass of LCPs.

The facility EXOTIC for the in-flight production of light weakly-bound Radioactive Ion Beams (RIBs) has been operating at INFN-LNL since 2004. RIBs are produced via two-body reactions induced by high intensity heavy-ion beams impinging on light gas targets and selected by means of a 30°-dipole bending magnet and a 1-m long Wien filter. The facility has been recently upgraded (i) by developing a cryogenic gas target, (ii) by replacing the power supplies of the middle lenses of the two quadrupole triplets, (iii) by installing two y-steerers and (iv) by placing two Parallel Plate Avalanche Counters upstream the secondary target to provide an event-by-event reconstruction of the position hit on the target. So far, RIBs of 7Be, 8B and 17F in the energy range 3–5 MeV/u have been produced with intensities about 3 × 105, 1.6 × 103 and 105 pps, respectively. Possible light RIBs (up to Z = 10) deliverable by the facility EXOTIC are also reviewed.

We are currently developing a novel detection system, named FARCOS (Femtoscope Array for Correlation and Spectroscopy) and featuring high angular and energy resolution and able to reconstruct particle's momentum at high precision for different physical cases in multi-fragmentation nuclear physics experiments. Performing a Pulse Shape Analysis on signals coming from the ΔE stages -Double Sided Silicon Strip Detectors (DSSSDs) - we aim at identifying in charge and mass even particles stopping in the first detection layer. In the framework of the full characterization of the DSSSD response in terms of both the linearity of the amplitude response and of the efficiency and collection properties as a function of the point of incidence, we got evidences of significant alterations of the signals shape in case of particle injection in the inter-strip region. Such an effect, which depends also on the type and energy of the impinging particle, cannot be ascribed only to a mere charge division, especially in case of signals with “wrong” polarity, but to more complex phenomena - for instance charge induction on neighbor strips. In this work we present the results of the qualification campaign carried out exploiting the monochromatic pulsed proton beam facility available at LaBeC of INFN - Sezione di Firenze, focusing the attention on the aforementioned “inter-strip effect”. We interpreted the measurements also with the aid of dedicated 3D simulations performed with a custom semi-analytical code, which gives a better insight on the physics occurring in the device. The impact of the “inter-strip effect” on particle identification scatter plots is also discussed.

The Farcos project (Femtoscope Array for Correlations and Spectroscopy) is discussed in this contribution. It consists of a new detector array designed and constructed by Exochim-Chimera group at INFN of Catania and Laboratori Nazionali del Sud. The array is described in its design and scientific goals to address. Some of the first preliminary tests with radioactive sources and beams are also discussed, together with some highlights of future perspectives.

We present a new highly integrated 16-channels pulse shape amplifier, suitable for processing signals from a variety of radiation detectors: its processing capabilities range from the relatively slow signals of charge sensitive preamplifier, up to the very fast signals typical of scintillation detectors coupled to photo-multiplier tubes (PMT). The amplifier provides the pulse shape analysis using the double constant fraction discriminator technique 131 and for each channel is also present a stretcher circuit and a time to amplitude converter (TAC) section, which allow sequential readout of time and energy parameters.

An experimental technique is described in the present work capable to identify pileup events and to reconstruct the hidden energy information. The procedure is based on the pulse shape analysis of digitized signals with the help of a high frequency, fast and sensitive flash ADC. The CAEN module V1729A, operating at a maximum sampling rate of 2 GHz has been successfully used in a recent experiment performed at the INFN-LNL EXOTIC facility, Padova, with an incident 8B beam near barrier energies (EL=25-40 MeV) on a three stage Si telescope. The nature of the unstable beam nucleus, which decays in 8Be and consequently in two alphas, necessitates the usage of appropriate pileup rejection techniques. The proposed offline algorithmic approach has efficiently identified all the recorded pileup events and in most cases has successfully reconstructed the energy information of the overlapping signals. Details of the applied technique with energy reconstruction examples for normal and pileup events are discussed in the present work.

International audience; We are currently developing a novel detection system featuring high angular and energy resolution and able to reconstruct the particles momentum at high precision for different physical cases in multi-fragmentation nuclear physics experiments, based on Double Sided Silicon Strip Detectors as ΔE stages aimed at performing also pulse shape analysis for fragments stopping therein. We carried out a detailed qualification of the performance of the strip detectors. In order to provide the detector response matrix we used a pulsed monoenergetic proton beam. The paper reviews the pulsed proton beam facility of the LaBeC of INFN - Sezione di Firenze and present the results of the characterization of the DSSSD prototypes with the pulsed proton beam. In particular we will discuss the amplitude and time response mapping and we will present the analysis of the dependence of the signal shape as a function of the position of interaction.

New materials with very high light yield and short scintillation decay time have been developed in the past few years: e.g. Cerium doped Lanthanum Bromide (LaBr 3 :Ce), Europium doped Strontium Iodide (SrI 2 : Eu).

In the framework of multi-fragmentation experiments the evolution towards two- (or more) particle correlations with stable and radioactive beams calls for the development of a novel detection system featuring high angular and energy resolution and able to reconstruct the particles momentum at high precision. The proposed detection system, named FARCOS (Femtoscopy ARray for COrrelations and Spectroscopy) will be beneficial for different physical cases. To this aim we are building a prototype detection system featuring four telescopes. Each telescope features an active area of 6.4 cm × 6.4 cm and is composed of three detection stages. The first ΔE stage is a Double Sided Silicon Strip Detector (DSSSD), 300 μm thick, featuring 32 × 32 strips. The second ΔE stage is again a DSSSD, 1500 μm thick, featuring 32 × 32 strips. The third stage, acting as calorimeter, is composed by four CsI(Tl) crystals with an active area of 3.2 cm × 3.2 cm and an absorption length of 6 cm forming a 2 × 2 matrix. The scintillators are readout by a Silicon photodiode 300 μm thick. The paper presents the relevant features of FARCOS and the expected performance of the silicon detection layers, with a special focus on the requirements of the frontend electronics for the DSSSD and the qualification of the DSSSD. In addition we report the first results of the preliminary on-beam tests. © 2012 IEEE.

The design of modern multi-detector arrays for Intermediate Energy Nuclear Physics experiments has to face the problem of the improvement of the Charge and Mass Identification of Heavy and Light Charged Products. Most of the detector arrays developed for the identification of mass and atomic number of the emitted fragments, use detection units composed by thin silicon detectors and by thick scintillator crystals read-out by photodiodes. The light output of the CsI(TI) crystal can be modeled - at least in a given energy range - with a combination of two exponential functions with different time constants. The possibility of storing the digitized waveforms allows performing further off-line analyses. In the present work we determine - by direct least-square fitting of the base-line subtracted output waveforms - the four-vector defining the light output ( τ ƒ , τ s , h ƒ , h s ). In this way it is possible to provide an experimental determination of the scintillator parameters for a wide energy range and for different particle types. The proposed method has been applied to the waveforms acquired with the CHIMERA 4π detector array during runs at the INFN Laboratori Nazionali del Sud Superconducting Cyclotron in Catania, Italy with different beam/target pairs. In this paper we present the results obtained with a 21.5 MeV/u 20Ne beam bombarding a 12C target.

We report the results obtained by applying digital pulse shape acquisition and digital signal processing to the signals from CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). The digitized signals allows the discrimination of light charged particles by computing the Fast and Slow components and the Rise Time of the output pulses of the CsI(Tl). When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punching-through points are used as energy calibration points for the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies it is possible to perform efficient discrimination in charge and mass of light charged particles by using the energy vs. rise time computation. © 2011 IEEE.

Lanthanum bromide scintillation detectors produce very high light outputs (∼60,000 ph/MeV) within a very short decay time (typically ∼20 ns) which means that high instantaneous currents can be generated in the photocathode and dynode chain of the photomultiplier tube (PMT) used for the scintillation readout. The net result is that signal saturation can occur long before the recommended PMT biasing conditions can be reached. In search of an optimized light readout system for LaBr3, we have tested and compared two different PMT configurations for detection of gamma-rays up to 15 MeV. This range was chosen as being appropriate for gamma-ray remote sensing and medium energy nuclear physics applications. The experiments were conducted at two facilities: the Laboratori Nazionali del Sud (LNS) in Catania, Italy [1] and the High Intensity Gamma-ray Source (HIγS) at Triangle University Nuclear Laboratory, in Durham, North Carolina, USA [2] . The PMT configurations we have tested are (1) a standard dynode chain operated under-biased; (2) a 4-stage reduced chain operated at nominal inter-dynode bias. The results are that shortening the number of active stages, as in configuration (2), has advantages in preserving energy resolution and avoiding PMT saturation over a large energy range. However, the use of an under-biased PMT, configuration (1), can still be considered a satisfactory solution, at least in the case of PMTs manufactured by Photonis. The results of this study will be used in support of the Mercury Gamma-ray and Neutron Spectrometer (MGNS) on board of BepiColombo, the joint ESA/JAXA mission to Mercury, scheduled for launch in 2014.

The 16-channel module (BaFPro) that we have originally developed for processing signals of Barium Fluoride scintillators has been recently adopted to made a pulse shape analysis with signals of Lanthanum Bromide scintillators. Our idea is to use the precision of the fast analog stretcher circuit present in the BaFPro module, to capture in precise way the amplitude peak of the LaBr 3 signals. Since in the peak area are concentrate the difference from alfa particle and gamma rays signal shape this type of analysis evidence a clear separation between these two kind of radiation. We report the scatter plot, peak amplitude (Fast) versus total energy (Slow) of the internal activity of LaBr 3 made with our stretcher circuit.

The huge amount of optical photons emitted in burst by Cerium doped Lanthanum bromide scintillators poses a severe constraint on the specifications of photomultipliers, namely they must operate at very large instantaneous current values with minimum saturation of output pulse signals. Acquisition in shape and processing of photomultipliers output pulses by means of high-speed free-running analog to digital converters and processing devices allows specific correction for pulse saturation and distortion effects, due to high-gain tubes operated at relatively high power supply voltage. We analyze the effects of output signal saturation in photomultiplier tubes as a function of the high voltage level and the amount of energy released in the scintillator crystal, proposing a simple model to characterize this complex phenomenon. According to the proposed model, a preliminary first-order correction is calculated and applied to the energy estimations obtained by a traditional analog spectroscopy system, for energies up to 9 MeV, reducing the maximum estimation error by almost an order of magnitude.

The position sensitivity in a 3”×3” LaBr 3 :Ce crystal has been simulated using collimated beams of medium and high energy γ-rays. The simulations have been done using the GEANT4 libraries which allow to follow both the gamma ray interaction in the detector and the scintillation light up to the photocathode. In the simulations the crystal has been coupled to an ideal PSPMT and/or a shielded PMT. The results indicate that in the 3” × 3” crystal with darkened surfaces it should be possible to localize the first interaction point of a 662 keV gamma ray within 1 cm, in the case of diffusive surfaces the position sensitivity deteriorates but it is not destroyed. As expected, the position sensitivity improves as the γ-ray energy increases. The measurements generally confirm the results given by simulations.

New monolithic silicon telescopes act as high performance and versatile devices to detect and identify charged particles. Their features allow their use also as position sensitive detectors.

The position sensitivity of two large volume (1” × 1” and 3” × 3”) LaBr 3 :Ce crystals has been measured using collimated beams of 662 keV γ-rays. The crystals have been coupled to a Position Sensitive Photo Multiplier Tube (PSPMT) and/or shielded phototube. The results indicate that, in the case of 662 keV γ -rays, both crystals should allow identification of the the position of the γ-ray first interaction with a 1-2 cm resolution. Similar tests have been done in the past using 140 keV γ-rays and no sensitivity was found. Using GEANT4 simulations we confirmed these results.

We show the possibility to use a new kind of monolithic silicon telescope as position sensitive detector.

In order to simplify the electronic chain with respect to the traditional one, we decided to apply Digital Pulse Shape Acquisition (DPSA) to collect signals from the ΔE and E stages of a monolithic silicon detector telescope, directly from the preamplifier. The collected pulse shapes are digitally processed in order to obtain the physical observables. To verify the device capability of position measurement we have bombarded the 16 strips in different points along the vertical position as well as in some points from the centre of the strip. The position information has been deduced from the signal induced on different strips by the charge collected in the E stage of the telescope. In order to explain the behavior of the induction signals, a basic model of charge generation in the monolithic telescope and of the induction for different irradiation is presented.

We applied the digital pulse shape acquisition to the read out of the anode pads of the focal plane detector of the MAGNEX spectrometer in order to measure the position coordinates using digital signal processing.

We have realized a mixed continuous-pulsed reset preamplifier suitable for multi-channel gamma-ray sensors. The continuous-reset mode is used for typical signal amplitudes within the ADC input range, or 1 V. The pulsed-reset mode works on larger signal amplitudes, either caused by individual events or by bursts of piled-up events. Such operation mode maximizes the live time in the typical energy range and minimizes the dead time caused by ADC saturation on large individual signals or at high count rates. The amplitude of large individual signals can also be estimated from the reset time still achieving a high resolution. Using this technique and a bulky high purity germanium detector we got a "continuous-reset" range of 2 MeV with a resolution of 2.02 keV fwhm at 1.408 MeV, and an extended "pulsed-reset" range of 27 MeV, with a typical resolution of 0.3% at 27 MeV.

We present a fast low-noise hybrid charge-sensitive preamplifier for germanium position-sensitive /spl gamma/-ray detectors. In conjunction with a bulky 36-fold segmented detector it provided a record resolution of 1.71/1.77 keV fwhm on the 1.17/1.33 MeV /sup 60/Co lines. The preamplifier rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 23 pF and with a 5 m 50 /spl Omega/ twisted-pair cable connected at its output. The dynamic range of the preamplifier input stage is as large as 92 dB, ranging from 0.275 fC to 9.9 pC, i.e. from 5 keV to 180 MeV in terms of photon energy. On signals larger than 2 MeV a fast reset (/spl sim/10 MeV//spl mu/s) is enforced to reduce the system dead time. An estimate of the amplitude of such large signals can be derived from the reset time, still obtaining a high resolution. Using this technique we achieved an energy resolution of 0.3% at 16.7 MeV.

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. We have now applied this technique to the charge discrimination of the products stopped in the silicon detectors. Large area totally depleted CHIMERA planar silicon detectors (5 cmtimes5 cm area, 300 mum thick) in both rear and front side injection have been used. In preliminary tests full charge identification for the reaction products up to Z=11 have been obtained for products both crossing (DeltaE-E technique) and stopping in the silicon detector, using a 21 MeV/u 20Ne 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

Two-point charge division is a typical technique for position measurements in linear multi-element detectors (microstrip detectors, multi-wire proportional chambers, silicon drift detectors, scintillator arrays coupled to photodetectors). This technique makes use of only two preamplifiers connected at the right and the left ends of the detection array, each of which receives a fraction of the total charge delivered by the event. The position of the event along the array is related to such fractions. In principle both resistor or capacitance dividers may be used to split the charge towards the two measurement points. The choice among such two possible setups is not obvious. In fact each of them shows advantages and disadvantages in terms of noise, signal propagation, linearity, which may vary depending upon the constraints dictated by the detection system. In this paper we present a comparative analysis which addresses the issues of this choice, considering as an example the realistic setup of the multiwire position-sensitive proportional counter to be used in the TP-MUSIC III chamber of the ALADiN experiment at GSI.

Mass and atomic-number identification (ID) of reaction products is a fundamental requirement of any nuclear reaction study. An effective particle-ID method is demonstrated, based on pulse shape analysis/discrimination (PSD) applied to large-area, single-element silicon detectors. This technique uses commercial electronic modules and achieves atomic number resolution rivaling that typically obtained with multi-element (/spl Delta/E-E) detector telescopes. The method is applied to the CHIMERA detector system without compromising its time-of-flight (TOF) resolution. In-beam tests of the PSD method have been performed with large-area, 300-/spl mu/m thick CHIMERA silicon detectors, measuring particles from the /sup 19/F+/sup 12/C reaction at Tandem energies. Performance of a simple PSD set up is discussed, for front and rear particle injection.