A multi-layer trigger system, based on programmable logic devices hosted on VME boards, has been implemented. It is completely scalable and suitable for handling from a few up to a few hundred ...channels. Custom software for monitoring and controlling the trigger system has been developed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A theoretical approach was developed to describe secondary particle emission in heavy ion collisions, with special regards to pre-equilibrium alpha -particle production. The probabilities of neutron, ...proton and alpha -particle emission have been evaluated for both the equilibrium and pre-equilibrium stages of the process. Effects due the possible cluster structure of the projectile which has been excited during the collisions have been experimentally evidenced studying the double differential cross sections of p and alpha -particles emitted in the E=250MeV super(16)O + super(116)Sn reaction. Calculations within the present model with different clusterization probabilities have been compared to the experimental data.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Fiasco multidetector is a low-threshold apparatus, optimized for the investigation of peripheral to semi-central collisions in heavy ion reactions at Fermi energies. It consists of three types of ...detectors. The first detector layer is a shell of 24 position-sensitive Parallel Plate Avalanche Detectors (PPADs), covering about 70% of the forward hemisphere, which measure the velocity vectors of the heavy (Z≳10) reaction products. Below and around the grazing angle, behind the most forward PPADs, there are 96 ΔE–E silicon telescopes (with thickness of 200 and 500μm, respectively); they are mainly used to measure the energy of the projectile-like fragment and to identify its charge and, via the time-of-flight of the PPADs, also its mass. Finally, behind most of the PPADs there are 158 (or 182, depending on the configuration) scintillation detectors, mostly of the phoswich type, which cover 25–30% of the forward hemisphere; they identify both light charged particles (Z=1,2) and intermediate mass fragments (3⩽Z≲20), measuring also their time-of-flight.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An estimate of the average freeze-out volume for multifragmentation events is presented. Values of volumes are obtained by means of a simulation using the experimental charged product partitions ...measured by the 4π multidetector INDRA for 129Xe central collisions on natSn at 32 AMeV incident energy. The input parameters of the simulation are tuned by means of the comparison between the experimental and simulated velocity (or energy) spectra of particles and fragments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The decay of highly excited states of 24Mg is studied in fusion evaporation events completely detected in charge in the reactions 12C+12C and 14N+10B at 95 and 80 MeV incident energy respectively. ...The comparison of light charged particles measured spectra with statistical model predictions suggests that the dominant reaction mechanism is compound nucleus (CN) formation and decay. However, in both reactions, a discrepancy with statistical expectations is found for α particles detected in coincidence with Carbon, Oxigen and Neon residues. The comparison between the two reactions shows that this discrepancy is only partly explained by an entrance channel effect. Evidence for cluster correlations in excited 24Mg CN is suggested by the comparison between the measured and calculated branching ratios for the channels involving α particles.
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Peripheral and semiperipheral collisions have been studied in the system 93Nb+93Nb at 38A MeV. The evaporative and midvelocity components of the light charged particle and intermediate mass fragment ...emissions have been carefully disentangled. In this way it was possible to obtain the average amount not only of charge and mass, but also of energy, pertaining to the midvelocity emission, as a function of an impact parameter estimator. This emission has a very important role in the overall balance of the reaction, as it accounts for a large fraction of the emitted mass and for more than half of the dissipated energy. As such, it may give precious clues on the microscopic mechanism of energy transport from the interaction zone toward the target and projectile remnants.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
An annular detector (Ring Counter, RCo) is presented, which has been designed and built to detect and identify in mass and charge light charged particles and fragments with very low energy thresholds ...and high energy resolution. It complements the GARFIELD apparatus, operating at INFN Laboratori Nazionali di Legnaro, to detect the forward emitted products of nuclear heavy ion reactions. It consists of eight sectors of a three-stage telescope, each one formed by an ionization chamber followed by eight strips of a silicon detector and by two CsI(Tl) scintillators. Construction features and performances are described and discussed in details.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central 129Xe + natSn collisions have been used to deduce event by event freeze-out properties on ...the thermal excitation energy range 4–12 AMeV. From such properties, information on constrained caloric curves has been derived. At constant average volumes caloric curves exhibit a monotonous behavior whereas for constrained pressures backbending is observed. Such results support the existence of a first order phase transition for hot nuclei.
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