The experimental set-up of the RIB in-flight facility EXOTIC Pierroutsakou, D.; Boiano, A.; Boiano, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2016, Letnik:
834
Journal Article
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We describe the experimental set-up of the Radioactive Ion Beam (RIB) in-flight facility EXOTIC consisting of: (a) two position-sensitive Parallel Plate Avalanche Counters (PPACs), dedicated to the ...event-by-event tracking of the produced RIBs and to time of flight measurements and (b) the new high-granularity compact telescope array EXPADES (EXotic PArticle DEtection System), designed for nuclear physics and nuclear astrophysics experiments employing low-energy light RIBs. EXPADES consists of eight ΔE–Eres telescopes arranged in a cylindrical configuration around the target. Each telescope is made up of two Double Sided Silicon Strip Detectors (DSSSDs) with a thickness of 40/60μm and 300μm for the ΔE and Eres layer, respectively. Additionally, eight ionization chambers were constructed to be used as an alternative ΔE stage or, in conjunction with the entire DSSSD array, to build up more complex triple telescopes. New low-noise multi-channel charge-sensitive preamplifiers and spectroscopy amplifiers, associated with constant fraction discriminators, peak-and-hold and Time to Amplitude Converter circuits were developed for the electronic readout of the ΔE stage. Application Specific Integrated Circuit-based electronics was employed for the treatment of the Eres signals. An 8-channel, 12-bit multi-sampling 50MHz Analog to Digital Converter, a Trigger Supervisor Board for handling the trigger signals of the whole experimental set-up and an ad hoc data acquisition system were also developed. The performance of the PPACs, EXPADES and of the associated electronics was obtained offline with standard α calibration sources and in-beam by measuring the scattering process for the systems 17O+58Ni and 17O+208Pb at incident energies around their respective Coulomb barriers and, successively, during the first experimental runs with the RIBs of the EXOTIC facility.
The elastic scattering in the reaction
7
Li+
208
Pb was investigated in the bombarding energy range from 25 to 39 MeV. The real and imaginary parts of the optical potential were analyzed by using a ...phenomenological potential. A dispersion relation analysis is presented in order to investigate the threshold anomaly effect. It is concluded that
7
Li has an intermediate behavior between the tightly bound nuclei such as
16
O and the loosely bound nuclei such as
6
Li where the lack of the threshold anomaly is unambiguously observed. Reaction cross sections are also extracted from the elastic scattering data and its comparison with the ones of other systems has been performed to draw hints on the effect of the breakup channel.
•We realized a detection array for Exotic Radioactive Ion Beams.•High granularity (32×32 pixels 2×2mm wide for 8 telescopes).•High solid angle (8 telescopes 64×64mm wide in a cylindrical ...configuration covering up to 2.6sr).•We tested each component of the array by both alpha particles and in-beam environment.•We measured the angular distribution for 17O elastic scattering on a 58Ni target.
The EXPADES (EXotic PArticle DEtection System) detector array consists of 16 Double Side Silicon Strip Detectors (DSSSD) with active areas of 64×64mm2, arranged in 8 ΔE (40/50μm)–E (300μm) telescopes. All detector faces are segmented into 32×2-mm wide strips, ensuring a 2×2mm2 pixel configuration. Eight ionization chambers can be alternatively used as ΔE stages or, if needed, as an additional third layer for more complex triple telescopes. The signals from silicon ΔE layers and from ionization chambers are read by standard electronics, while innovative 32-channel ASIC chips are employed for the readout of the E stages. The results of off-line tests with alpha sources and from the first in-beam experiment with a 17O beam are presented.
•Production of in-flight Radioactive Ion Beams via two-body reactions.•Development of a cryogenic gas target.•Event-by-event tracking via Parallel Plate Avalanche Counters (PPACs).
The facility ...EXOTIC for the in-flight production of light weakly-bound Radioactive Ion Beams (RIBs) has been operating at INFN-LNL since 2004. RIBs are produced via two-body reactions induced by high intensity heavy-ion beams impinging on light gas targets and selected by means of a 30°-dipole bending magnet and a 1-m long Wien filter. The facility has been recently upgraded (i) by developing a cryogenic gas target, (ii) by replacing the power supplies of the middle lenses of the two quadrupole triplets, (iii) by installing two y-steerers and (iv) by placing two Parallel Plate Avalanche Counters upstream the secondary target to provide an event-by-event reconstruction of the position hit on the target. So far, RIBs of 7Be, 8B and 17F in the energy range 3–5MeV/u have been produced with intensities about 3×105, 1.6×103 and 105pps, respectively. Possible light RIBs (up to Z=10) deliverable by the facility EXOTIC are also reviewed.
The EXOTIC facility, installed at the INFN-Laboratori Nazionali di Legnaro (LNL), is devoted to the in-flight production of light Radioactive Ion Beams (RIBs) in the energy range between 3-5 ...MeV/nucleon. The research field accessible using the EXOTIC RIBs is the investigation of reaction mechanisms and nuclear structure, resonant scattering measurements and measurements of nuclear reaction cross sections of astrophysical interest.
The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first time in the formation of a heavy composite system in the A∼190 mass region, in fusion-evaporation and ...fission events. The composite system was formed at identical conditions of excitation energy and spin from two reactions with different charge asymmetry: the charge asymmetric 40Ca + 152Sm and the nearly charge symmetric 48Ca + 144Sm at Elab=11 and 10.1 MeV/nucleon, respectively. In this paper, we report the results on fusion evaporation events and the preliminary analysis on fission channel.
The scattering process of weakly-bound nuclei at Coulomb barrier energies provides deep insights on the reaction dynamics induced by exotic nuclei. Within this framework, we measured for the first ...time the scattering process of the short-lived Radioactive Ion Beam (RIB) 8B (Sp = 0.1375 MeV) from a 208Pb target at 50 MeV beam energy. The 8B RIB was produced by means of the in-flight facility CRIB (RIKEN, Japan) with an average intensity on target of 10 kHz and a purity about 25%. Elastically scattering ions were detected in the angular range θc.m. = 10°-160° by means of the detector array EXPADES. A preliminary optical model analysis indicates a total reaction cross section of about 1 b, a value, once reduced, 2-3 times larger than those obtained for the reactions induced by the stable weakly-bound projectiles 6,7Li on a 208Pb target in the energy range around the Coulomb barrier.
In this work we give evidence for the first time of the Dynamical Dipole mode in a heavy system in the A∼190 mass region, in both fusion-evaporation and fission events. The 40,48Ca + 152,144Sm ...reactions at Elab=11(10.1) MeV/nucleon were employed. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.
The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first time in the formation of a heavy compound nucleus in the A~190 mass region. The compound nucleus was ...formed at identical conditions of excitation energy and spin from two entrance channels having different charge asymmetry: the charge asymmetric 40Ca + 152Sm and the nearly charge symmetric 48Ca + 144Sm at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion–evaporation and fission events were studied simultaneously for the first time. The Dynamical Dipole mode excitation in the charge asymmetric channel was evidenced, in a model-independent way, by comparing the γ-ray multiplicity spectra and angular distributions of the two entrance channels with each other.
.
Total reaction cross sections for the radioactive nucleus
8
Li on
90
Zr are reported at the near-barrier energies of 18.5 and 21.5MeV, derived from quasi-elastic scattering measurements. An ...analysis of the quasi-elastic scattering results is performed within an optical model framework using the BDM3Y1 interaction and total reaction cross sections are deduced. These quantities, appropriately reduced, are compared with previous data obtained in elastic scattering measurements with well and weakly bound projectiles on various targets and a formula for predicting total reaction cross sections with an uncertainty of
% is obtained. Further on, the ratios of direct to total reaction cross sections are estimated for
6,8
Li on various targets and are compared with CDCC or CRC calculations. The energy dependence of the optical potential is also discussed.
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