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An investigation of the influence of the isospin (N/Z ratio) on the thermometric characteristics, in the reactions 78Kr+40Ca and 86Kr+48Ca at 10 AMeV is presented. The experiment was performed at the INFN Laboratori Nazionali del Sud in Catania by using the beams delivered by the Superconductive Cyclotron and the 4π multidetector CHIMERA. The isospin effects on the decay modes of the two produced composite systems and on the competition between statistical and dynamical break-up of the projectile have been studied. The thermal evaporation from both compound nucleus (CN) and Quasi-Projectile Like Fragment (PLF) has been investigated by extracting the temperature with two different thermometric methods, namely the slope thermometer, with the alpha particles as probe, and the double isotope yields ratio thermometer. The results of the analysis suggest the influence of the N/Z ratio on the system (CN or PLF) temperature, regardless of the nature of the method used for its determination.

In this contribution the connection between the Dipolar degree of freedom excited in Heavy Ion Collisions through pre-equilibrium dipolar modes and the Isospin-equilibration processes is discussed. The connection leads to the definition of a new observable the so called “dipolar signal”, able to describe the equilibration process in the momentum space related to the final fragmentation produced by the HIC. Preliminary results on this observable measured on the system 48Ca +27 Al at 40 MeV/nucleon and corresponding to different degrees of dissipation/centrality are presented. The beam was accelerated through the Superconductor Cyclotron at the Laboratori Nazionali del Sud di Catania (Italy) and fragments were detected and identified with the 4π multi-detector CHIMERA.

We describe the search of the Efimov state in 12C performed by analysing a large set of 3-α particles coincidence data measured at the LNS laboratories with the CHIMERA detector. The data are compatible with the presence of an Efimov state at the excitation energy of 7.485 MeV, with an excitation probability smaller than 0.3% of the population probability of the Hoyle state. The Efimov state gamma decay probability should be around 30%, much larger than the one of the Hoyle state. The population of this level is compatible with the Suda limit for the 3-α reaction rate in stars because its population should be possible only through direct 3-α reaction. More investigations improving the detector angular resolution are needed to confirm these preliminary observations.

Radioactive Ion Beams (RIBs) of large intensity (106 pps or higher) are at the frontier in nuclear physics. We designed a novel detection system for RIBs diagnostics and tagging based on Silicon Carbide detectors and on custom frontend electronics ready to be coupled with a Real Data Management Unit. The full detection system is designed to measure the spatial distribution of the beam intensity and trajectory with sufficient spatial resolution (of the order of 1-2 mm). In addition, the detection system has to determine the RIB composition that can be obtained from the joint measurement of the energy loss (>E) of the ions passing through the sensors and the time of flight between two sensors or with respect to a given reference signal as the RadioFrequency signal of a Cyclotron. In this paper we present the full design of the proposed system together with the results of the first experimental qualification of the first mini-prototype. The paper also shows the steps towards the final detection system, housed in a DN160 spherical cross and able to cover an active area of 30 mm × 60 mm.

In this work, we present a recent study concerning the break-up of the Projectile-Like (PLF) into two fragments, following more violent deep-inelastic collisions in the reactions 78Kr + 40Ca and 86Kr + 48Ca at 10 A MeV, realized at INFN-Laboratori Nazionali del Sud by using the 4π multi detector CHIMERA. For these systems, we have already analyzed the fusion-evaporation and fission-like processes. A selection method has been developed, in order to discriminate PLF break up events from those due to other mechanisms which populate the same region of the phase- space. A preference for PLF aligned break-up, along the direction of the PLF-TLF separation axis with the light fragment emitted in the backward part, has been put in light, suggesting the presence of dynamical effects. Also a comparison between the neutron-rich 86Kr + 48Ca and neutron-poor 78Kr + 40Ca systems is presented, to put in evidence the isospin role in these processes.

The study of nuclei properties and of collision dynamics is a very active research field whose result have implications in different domains as for example astrophysics. The present and future facilities delivering radioactive ion beams with high intensity allow to extend these studies in the region far from the stability valley. New insight has thus been found on the effects of neutron richness on reaction mechanisms as well as on nuclear structure and nuclear matter properties, as for instance, the role of symmetry energy term of the nuclear Equation of State. The presence of diverse reaction products demands for highly performing and very specialized devices, also able to disentangle among different mechanisms, from fast dynamical processes to statistical emission from equilibrated sources. Numerous studies of the effects of N/Z ratio on fusion and associated processes can be found at different energies, together with many examples of the influence of neutron richness on the reaction time scale and the competition between equilibrated and prompt processes. A survey of very recent findings obtained with the CHIMERA and FARCOS devices is presented.

We present a new method for the measurement of very small Γγ partial width that is important for the synthesis of elements in astrophysics. The method is based on the simultaneous detection of scattered beam, residual nucleus and decay γ rays. This method is optimized for the use of the CHIMERA detector at LNS. Experimental details are described.

This paper is concerned with the automatic analysis of data coming from the multidetector array CHIMERA, used in nuclear physics at intermediate energies. Each of Chimera's detection cells is a telescope made of a [DELTA]E silicon detector and a CsI(Tl) crystal, thick enough to stop all the charged light particles. The signals produced in the CsI(Tl) scintillators can be subdivided into two components--Fast and Slow. These data are collected in the form of bi-dimensional matrices (Fast-Slow matrices), particularly important for light particle identification. The proposed approach consists in applying image processing techniques. In particular, Grossberg's pre-attentive neural networks are used as a first step in order to isolate the regions of physical interest in the matrices and to roughly identify the directions depicted by the most intense lines; a successive step of filtering based on Markov random fields is then performed. Index Terms--Clustering methods, image processing, nuclear measurements, visualization.

We have built and tested a computational unit for on-line processing of special algorithms to be embedded in the central processing unit VERSAmodule Eurocard (CPU VME)-crate of the CHIMERA data acquisition system. The computational unit consists of a number of VME digital signal processor (DSP)-based commercial boards delivering 720 MFlops/board. Index Terms--Data acquisition (DAQ), digital signal processor (DSP), on-line computation.

The CHIMERA 4[pi] detector trigger system is described. The trigger decisions are based on a combination of geometrical multiplicity of detected particles and other logic signals. The trigger can manage the buffer memory of the used analog to digital converters. This allows performance of parallel data conversion and readout and substantial improvement of the acquisition system dead-time performances. The trigger module generates all the necessary gate signals for the converters and the control signals necessary to synchronize the readout. It also allows the remote control of the whole system. Index Terms--4[pi] detector, data acquisition, dead time, parallel readout, trigger system.

The kinematical coincidence method is used to extract angular distribution of elastic scattering and transfer reactions. The detected light particle energy spectra are used to extract the angular distribution with around 1° resolution in the Center of Mass (CM) system. Examples with 10Be beam are presented. In the case of proton scattering, γ-ray coincidences are used to discriminate excited levels population from elastic scattering.

In nuclear physics at intermediate energies, the use of multidetector arrays consisting of thousands of detectors is customary. This paper presents a novel approach to the automatic classification of data collected by the 4[Pi] detector CHIMERA, constituted by 1192 telescopes of a thin silicon transparent detector coupled to a thick CsI(TI) scintillator. The method is based on spatial density data processing and produces frequency distributions of the most significant physical parameters. These one-dimensional spectra can be more easily analyzed than the standard two-dimensional scatter plots. With respect to manual or semiautomatic procedures, presently used for data analysis, our method offers the advantages of drastic time reduction and unbiased criteria for cluster identification. The proposed method can be successfully used in both off-line data analysis and multidetector stability control. Index Terms--Clustering methods, image processing, nuclear measurements, visualization.

Presents a novel approach to the automatic classification of data collection by the CHIMERA detector. Importance of data classification to nuclear physics measurement; Details on the semiautomatic system; Conclusion.