.
In the Fermi energy domain, the temperature of hot nuclei can be determined using the energy spectra of evaporated light charged particles. But this method of measurement is not without ...difficulties both theoretical and experimental. The present study aims to disentangle the respective influences of different factors on the quality of this measurement: the physics, the detection (a
4
π
detector array such as INDRA) and the experimental procedure. This analysis demonstrates the possibility of determining from an energy spectrum, with an accuracy of about 10%, the true apparent temperature felt by a given type of particle emitted from a hot nucleus. This temperature allows to deduce the initial temperature using an appropriate method. However, three conditions are necessary: a perfect particle detector, important statistics and very weak secondary emissions. According to the GEMINI event generator, for hot intermediate mass nuclei, only deuterons and tritons could meet these conditions. In this case the determination may be better than 15%. With a realistic experimental device, insufficient angular resolution and topological distortions, caused by detection, can distort spectra to the point where it is very difficult to determine the apparent temperature correctly. Experimental reconstruction of the moving frame of the hot nucleus can also be responsible for this deterioration.
The FAZIA project in Europe: R&D phase Bougault, R.; Poggi, G.; Barlini, S. ...
The European physical journal. A, Hadrons and nuclei,
2014/2, Letnik:
50, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The goal of the FAZIA Collaboration is the design of a new-generation 4
π
detector array for heavy-ion collisions with radioactive beams. This article summarizes the main results of the R&D phase, ...devoted to the search for significant improvements of the techniques for charge and mass identification of reaction products. This was obtained by means of a systematic study of the basic detection module, consisting of two transmission-mounted silicon detectors followed by a CsI(Tl) scintillator. Significant improvements in
ΔE
-
E
and pulse-shape techniques were obtained by controlling the doping homogeneity and the cutting angles of silicon and by putting severe constraints on thickness uniformity. Purposely designed digital electronics contributed to identification quality. The issue of possible degradation related to radiation damage of silicon was also addressed. The experimental activity was accompanied by studies on the physics governing signal evolution in silicon. The good identification quality obtained with the prototypes during the R&D phase, allowed us to investigate also some aspects of isospin physics, namely isospin transport and odd-even staggering. Now, after the conclusion of the R&D period, the FAZIA Collaboration has entered the demonstrator phase, with the aim of verifying the applicability of the devised solutions for the realization of a larger-scale experimental set-up.
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 ΔE−E 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 ΔE−E 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.
Recent results from INDRA Chbihi, A.; Frankland, J.D.; Lopez, O. ...
EPJ Web of Conferences,
01/2015, Letnik:
88
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Recent results of the INDRA collaboration are presented in this contribution. They concern the evolution of reaction dynamics from the first stage of the collision to the production of fragments. ...Different probes are used to evidence the stopping/transparency, collective flow and the symmetry energy term of the nuclear equation of state.
The characterization of hot quasi-projectiles produced in symmetric or quasi-symmetric reactions (Au + Au, Xe + Sn, Ni + Ni, Ar + KCl) at different incident energies are estimated by means of two ...different procedures. The advantages and disadvantages of each method are analyzed on the basis of simulations using events produced by two slightly different models: HIPSE and ELIE.
Lors de réactions nucléaires dissipatives, un transfert important d'énergie se produit entre le projectile et la cible. Une partie de l'énergie mécanique initiale est emmagasinée sous forme d'énergie ...thermique dans les noyaux en interaction. Afin de suivre l'évolution de leur comportement lorsque cette énergie augmente, deux techniques de calorimétrie ont été utilisées : l'une dite " calorimétrie 3D " validée et optimisée au cours de cette thèse ; l'autre dite " calorimétrie standard ", déjà très utilisée par la communauté scientifique. Celles-ci ont permis de reconstruire les caractéristiques de Quasi-Projectiles chauds, produits lors de réactions entre systèmes symétriques ou quasi-symétriques. Les avantages et les inconvénients de chacune d'elles ont été étudiés grâce à deux générateurs d'événements, HIPSE et ELIE, modélisant les processus physiques intervenant lors de ces collisions mais qui diffèrent par le scénario de formation du noyau chaud. Cette étude systématique a permis de déterminer pour quelle température et quelle énergie d'excitation par nucléon, des noyaux de masse intermédiaire passent d'un état de liquide nucléaire chaud à un état de gaz nucléaire. Les informations obtenues par la " calorimétrie 3D " ont permis aussi d'isoler en partie la composante dite de prééquilibre. Ce résultat a été confirmé expérimentalement par une nouvelle utilisation du degré de liberté d'isospin (rapport neutron/proton), comme 'marqueur' dans l'espace des vitesses.
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