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.
Ion beams supplied by the 3MV Tandem accelerator of LABEC laboratory (INFN-Firenze), have been used to study the feasibility of irradiating materials with ion fluences reproducible to about 1%. Test ...measurements have been made with 7.5 MeV
7
Li
2+
beams of different intensities. The fluence control is based on counting ions contained in short bursts generated by chopping the continuous beam with an electrostatic deflector followed by a couple of adjustable slits. Ions are counted by means of a micro-channel plate (MCP) detecting the electrons emitted from a thin layer of Al inserted along the beam path in between the pulse defining slits and the target. Calibration of the MCP electron detector is obtained by comparison with the response of a Si detector.
The emission pattern in the v(perp)-v(par) plane of intermediate mass fragments with Z = 3--7 (IMF) has been studied in the collision 116Sn+ 93Nb at 29.5A MeV as a function of the total kinetic ...energy loss of the reaction. This pattern shows that for peripheral reactions most IMF's are emitted at velocities intermediate between those of the projectile- and target-like products. Coulomb trajectory calculations show that these IMF's are produced in the interaction zone in a short time interval at the end of the target-projectile interaction.
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.
The response of a CdWO4 crystal scintillator to protons, α particles, Li, C, O and Ti ions with energies in the range 1–10MeV was measured. The non-proportionality of CdWO4 for low energy electrons ...(4–110keV) was studied with the Compton Coincidence Technique. The energy dependence of the quenching factors for ions and the relative light yield for low energy electrons was calculated using a semi-empirical approach. Pulse-shape discrimination ability between γ quanta, protons, α particles and ions was investigated.
Experimental data concerning binary events in peripheral collisions for the systems 93Nb+93Nb and 93Nb+116Sn at 38 MeV/nucleon, collected with the Fiasco setup, are compared with calculations ...performed with the dynamic code AMD, coupled with the statistical code Gemini used as an afterburner. The comparison focuses on the properties of the quasiprojectile (QP) and on the total multiplicities of the emitted light charged particles. A good reproduction of the average mass ratio, charge Z and c.m. angle of the QP is obtained in the examined impact parameter range (b~7-12 fm). Concerning the light charged particles, a general agreement is found for the total emitted charge, while some discrepancy remains for the multiplicities of the various species, especially for the protons which are always overestimated by the calculations.
The design and implementation of linear electronics based on small-size, low-power charge preamplifiers and shaping amplifiers, used in connection with Si-detector telescopes employed in heavy ion ...experiments, are presented. Bench tests and “under beam” performances are discussed. In particular, the energy calibration and the linearity test of the overall system (Si-detector and linear and digital conversion electronics) has been performed with a procedure which avoids the pulse height defect problems connected with the detection of heavy ions. The procedure, basically, consists of using bursts of MeV protons, releasing up to GeV energies inside the detector, with low ionization density.
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