The FAZIA project in Europe: R&D phase Bougault, R.; Poggi, G.; Barlini, S. ...
European physical journal. A, Hadrons and nuclei,
2014/2, Volume:
50, Issue:
2
Journal Article
Peer reviewed
Open access
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.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A completely exclusive experiment was performed by the INDRA collaboration to study the isospin dependence of the level density parameter. Over a large N/Z range, the fusion-evaporation charged ...products of 34,36,40Ar+58,60,64Ni reactions were measured and identified both in charge and mass by coupling INDRA and VAMOS spectrometer. Preliminary results obtained by combining data of both detectors are presented for the 36Ar+58Ni at 13.3 A MeV. The analysis method of relevant observables for such an ambitious investigation are discussed and the progress of the data analysis are reviewed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A study of identification properties of a Si-Si
ΔE
-
E
telescope exploiting an underdepleted residual-energy detector has been performed. Five different bias voltages have been used, one ...corresponding to full depletion, the others associated with a depleted layer ranging from 90% to 60% of the detector thickness. Fragment identification has been performed using either the
ΔE
-
E
technique or the Pulse Shape Analysis (PSA). Both detectors are reverse mounted: particles enter from the low field side, to enhance the PSA performance. The achieved charge and mass resolution has been quantitatively expressed using a Figure of Merit (FoM). Charge collection efficiency has been evaluated and the possibility of energy calibration corrections has been considered. We find that the
ΔE
-
E
performance is not affected by incomplete depletion even when only 60% of the wafer is depleted. Isotopic separation capability improves at lower bias voltages with respect to full depletion, though charge identification thresholds are higher than at full depletion. Good isotopic identification via PSA has been obtained from a partially depleted detector, whose doping uniformity is not good enough for isotopic identification at full depletion.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
FAZIA applications Piantelli, S.; Casini, G.; Maurenzig, P.R. ...
EPJ Web of Conferences,
01/2016, Volume:
117
Journal Article, Conference Proceeding
Peer reviewed
Open access
The present status and the perspectives of the FAZIA project are presented. The main achievements in terms of identification thresholds and isotopic resolution are discussed, together with the ...adopted technical solutions. The detector is particularly well suited for the investigation of isospin transport phenomena at intermediate beam energies; perspectives to reduce the identification thresholds to cope with lower energy ISOL beams are briefly introduced. Some experimental results concerning isospin transport effects obtained with a test telescope are presented. The study of isospin transport phenomena can give information on the symmetry energy term of the nuclear equation of state by comparing the experimental results on isospin related observables with the predictions of transport codes.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Experimental results concerning isospin transport phenomena and odd-even staggering in Z and N distributions are presented. Data refer to 84Kr+112,124Sn collisions at 35AMeV and they were collected ...with a high resolution FAZIA telescope, able to isotopically resolve ions up to Z ∼ 20. Evidences of isospin diffusion and drift obtained from the < N > /Z behaviour of the detected fragments are discussed. The odd-even staggering both in Z and N is compared with experimental data available in literature, finding that it shows a common trend in different reaction types.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Isospin transport phenomena in dissipative heavy ion collisions have been investigated at Fermi energies with a beam of 84Kr at 35AMeV. A comparison of the 〈N〉/Z of light and medium products ...forward-emitted in the centre of mass frame when the beam impinges on two different targets, the n-poor 112Sn and the n-rich 124Sn, is presented. Data were collected by means of a three-layer telescope with very good performances in terms of mass identification (full isotopic resolution up to Z ~ 20 for ions punching through the first detector layer) built by the FAZIA Collaboration and located just beyond the grazing angle for both reactions. The 〈N〉/Z of the products detected when the n-rich target is used is always higher than that associated to the n-poor one; since the detector was able to measure only fragments coming from the QuasiProjectile decay and/or neck emission, the observed behaviour can be ascribed to the isospin diffusion process, driven by the isospin gradient between QuasiProjectile and QuasiTarget. Moreover, for light fragments the 〈N〉/Z as a function of the lab velocity of the fragment is observed to increase when we move from the QuasiProjectile velocity to the centre of mass (neck zone). This effect can be interpreted as an evidence of isospin drift driven by the density gradient between the QuasiProjectile zone (at normal density) and the more diluted neck zone.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A new technique of large-area thin ion implanted silicon detectors has been developed within the R&D performed by the FAZIA Collaboration. The essence of the technique is the application of a ...low-temperature baking process instead of high-temperature annealing. This thermal treatment is performed after B
+
ion implantation and Al evaporation of detector contacts, made by using a single adjusted Al mask. Extremely thin silicon pads can be therefore obtained. The thickness distribution along the
X
and
Y
directions was measured for a prototype chip by the energy loss of
α
-particles from
241
Am (〈
E
α
〉 = 5.5 MeV). Preliminary tests on the first thin detector (area ≈ 20 × 20 mm
2
) were performed at the INFN-LNS cyclotron in Catania (Italy) using products emitted in the heavy-ion reaction
84
Kr (
E
= 35
A
MeV) +
112
Sn. The
ΔE
−
E
ion identification plot was obtained using a telescope consisting of our thin
ΔE
detector (21
μ
m thick) followed by a typical FAZIA 510
μ
m E detector of the same active area. The charge distribution of measured ions is presented together with a quantitative evaluation of the quality of the
Z
resolution. The threshold is lower than 2
A
MeV depending on the ion charge.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A study of the identification properties and of the energy response of a Si-Si-CsI(Tl) ΔE-E telescope exploiting a partially depleted second Si stage has been performed. Five different bias voltages ...have been applied to the second stage of the telescope, one corresponding to full depletion, the others associated with a depleted layer ranging from 60% to 90% of the detector thickness. Fragment identification has been obtained using either the ΔE-E technique or the Pulse Shape Analysis (PSA). Charge collection efficiency has been evaluated. The ΔE-E performance is not affected by incomplete depletion. Isotopic separation capability improves at lower bias voltages with respect to full depletion, though charge identification thresholds increase.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The european Fazia collaboration aims at building a new modular array for charged product identification to be employed for heavy-ion studies. The elementary module of the array is a ...Silicon-Silicon-CsI telescope, optimized for ion identification including pulse shape analysis, too. The achievement of top performances imposes specific electronics which has been developed by the FAZIA collaboration and includes high quality charge and current preamplifiers, coupled to fully digital front-end. During the initial R&D phase, original and novel solutions have been tested in prototypes, obtaining unprecedented ion identification capabilities. FAZIA is now constructing a demonstrator array consisting of about two hundreds telescopes arranged in a compact and transportable configuration. In this contribution, we mainly summarize some aspects studied by FAZIA to improve the ion identification. Then we will briefly discuss the FAZIA program focused on experiments to be done with the demonstrator. First results on the isospin dynamics obtained with a reduced set-up demonstrate well the performance of the telescope and represent a good starting point towards future investigations with both stable and exotic beams.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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